Ground-and satellite-based evidence of the biophysical mechanisms behind the greening Sahel

DEFF Research Database (Denmark)

Brandt, Martin Stefan; Mbow, Cheikh; Diouf, Abdoul A.

2015-01-01

After a dry period with prolonged droughts in the 1970s and 1980s, recent scientific outcome suggests that the decades of abnormally dry conditions in the Sahel have been reversed by positive anomalies in rainfall. Various remote sensing studies observed a positive trend in vegetation greenness...... over the last decades which is known as the re-greening of the Sahel. However, little investment has been made in including long-term ground-based data collections to evaluate and better understand the biophysical mechanisms behind these findings. Thus, deductions on a possible increment in biomass...... remain speculative. Our aim is to bridge these gaps and give specifics on the biophysical background factors of the re-greening Sahel. Therefore, a trend analysis was applied on long time series (1987-2013) of satellite-based vegetation and rainfall data, as well as on ground-observations of leaf biomass...

Analysis of teleconnections between AVHRR-based sea surface temperature and vegetation productivity in the semi-arid Sahel

DEFF Research Database (Denmark)

Huber Gharib, Silvia; Fensholt, Rasmus

2011-01-01

Vegetation Index (NDVI) in the Sahel, however with different magnitudes in terms of strength for the western, central and eastern Sahel. Also the correlations based on NDVI and global SST anomalies revealed the same East–West gradient, with a stronger association for the western than the eastern Sahel......, we achieved high correlations for SSTs of oceanic basins which are geographically associated to the climate indices yet by far not always these patterns were coherent. The detected SST–NDVI patterns could provide the basis to develop new means for improved forecasts in particular of the western...

Water for a Thirsty Sahel

International Nuclear Information System (INIS)

Quevenco, Rodolfo

2013-01-01

In 2012, the IAEA launched a large scale, four-year, technical cooperation project to promote the integrated management and development of shared groundwater resources in the Sahel region. The project supports the use of isotope techniques in hydrological studies to map underground water, and to identify and understand the root causes of the main threats to the five transboundary aquifers. Isotope hydrology techniques can also provide useful information about the quality and availability of water hidden underground, and can be used to investigate the impact of climate change on water resources

Ponds' water balance and runoff of endorheic watersheds in the Sahel

Science.gov (United States)

Gal, Laetitia; Grippa, Manuela; Kergoat, Laurent; Hiernaux, Pierre; Mougin, Eric; Peugeot, Christophe

2015-04-01

The Sahel has been characterized by a severe rainfall deficit since the mid-twentieth century, with extreme droughts in the early seventies and again in the early eighties. These droughts have strongly impacted ecosystems, water availability, fodder resources, and populations living in these areas. However, an increase of surface runoff has been observed during the same period, such as higher "summer discharge" of Sahelian's rivers generating local floods, and a general increase in pond's surface in pastoral areas of central and northern Sahel. This behavior, less rain but more surface runoff is generally referred to as the "Sahelian paradox". Various hypotheses have been put forward to explain this paradoxical situation. The leading role of increase in cropped areas, often cited for cultivated Sahel, does not hold for pastoral areas in central and northern Sahel. Processes such as degradation of vegetation subsequent to the most severe drought events, soils erosion and runoff concentration on shallow soils, which generate most of the water ending up in ponds, seem to play an important role. This still needs to be fully understood and quantified. Our study focuses on a model-based approach to better understand the hydrological changes that affected the Agoufou watershed (Gourma, Mali), typical of the central, non-cultivated Sahel. Like most of the Sahelian basins, the Agoufou watershed is ungauged. Therefore we used indirect data to provide the information required to validate a rainfall-runoff model approach. The pond volume was calculated by combining in-situ water level measurements with pond's surface estimations derived by remote sensing. Using the pond's water balance equation, the variations of pond volume combined to estimates of open water bodies' evaporation and infiltration determined an estimation for the runoff supplying the pond. This estimation highlights a spectacular runoff increase over the last sixty years on the Agoufou watershed. The runoff

Characterization of Heat Waves in the Sahel and associated mechanisms

Science.gov (United States)

Oueslati, Boutheina; Pohl, Benjamin; Moron, Vincent; Rome, Sandra

2016-04-01

Large efforts are made to investigate the heat waves (HW) in developed countries because of their devastating impacts on society, economy and environment. This interest increased after the intense event over Europe during summer 2003. However, HWs are still understudied over developing countries. This is particularly true in West Africa, and especially in the Sahel, where temperatures recurrently reach critical values, such as during the 2010 HW event. Understanding the Sahelian HWs and associated health risks constitute the main objective of ACASIS, a 4-year project funded by the French Agence Nationale de la Recherche. Our work contributes to this project and aims at characterizing the Sahelian HWs and understanding the mechanisms associated with such extreme events. There is no universal definition of a HW event, since it is highly dependent on the sector (human health, agriculture, transport...) and region of interest. In our case, a HW is defined when the heat index of the day and of the night exceeds the 90th percentile for at least 3 consecutive days (Rome et al. 2016, in preparation). This index combines temperature and relative humidity in order to determine the human-perceived equivalent temperature (definition adapted from Steadman, 1979). Intrinsic properties of Sahelian HW are analyzed from the Global Summary of the Day (GSOD) synoptic observations and ERA-interim reanalyses over 1979-2014 during boreal spring seasons (April-May-June), the warmest period of the year in the Central Sahel. ERA-interim captures well the observed interannual variability and seasonal cycle at the regional scale, as well as the 1979-2014 increasing linear trend of springtime HW occurrences in the Sahel. Reanalyses, however, overestimate the duration, spatial extent of HW, and underestimate their intensity. For both GSOD and ERA-interim, we show that, over the last three decades, Sahelian HWs tend to become more frequent, last longer, cover larger areas and reach higher

Desertification, resilience, and re-greening in the African Sahel - a matter of the observation period?

Science.gov (United States)

Kusserow, Hannelore

2017-12-01

Since the turn of the millennium various scientific publications have been discussing a re-greening of the Sahel after the 1980s drought mainly based on coarse-resolution satellite data. However, the author's own field studies suggest that the situation is far more complex and that both paradigms, the encroaching Sahara and the re-greening Sahel, need to be questioned.This paper discusses the concepts of desertification, resilience, and re-greening by addressing four main aspects: (i) the relevance of edaphic factors for a vegetation re-greening, (ii-iii) the importance of the selected observation period in the debate on Sahel greening or browning, and (iv) modifications in the vegetation pattern as possible indicators of ecosystem changes (shift from originally diffuse to contracted vegetation patterns).The data referred to in this paper cover a time period of more than 150 years and include the author's own research results from the early 1980s until today. A special emphasis, apart from fieldwork data and remote sensing data, is laid on the historical documents.The key findings summarised at the end show the following: (i) vegetation recovery predominantly depends on soil types; (ii) when discussing Sahel greening vs. Sahel browning, the majority of research papers only focus on post-drought conditions. Taking pre-drought conditions (before the 1980s) into account, however, is essential to fully understand the situation. Botanical investigations and remote-sensing-based time series clearly show a substantial decline in woody species diversity and cover density compared to pre-drought conditions; (iii) the self-organised patchiness of vegetation is considered to be an important indicator of ecosystem changes.

Technical Guide for conservation of wood fuel: Experiences from Sahel

International Nuclear Information System (INIS)

Jorez, J.P.

1992-03-01

The guide gives technical information in design of energy efficient cooking stoves for the wood depleted countries in sub-saharan Africa. Knowledge and experiences of the Sahel region have been used to design the stoves discussed. As an introduction, the causes and consequences of the wood fuel crises are reviewed. The main models of improved stoves that are spread in Sahel are then described, together with data on performance and design considerations. Strategies for distribution of the improved stoves are analyzed, and ways to follow-up and evaluate their use are suggested. Results of campaigns to distribute the stoves in West African countries are given and methods to improve the distribution are proposed, in particular to promote the ceramic stoves. Finally, complementary wood fuel conservation campaigns are suggested for activities other than household cooking. 22 refs, 14 figs, 5 tabs and photos

Inventory and surveillance of natural resources as a contribution to land utilization planning in the Sahel

Energy Technology Data Exchange (ETDEWEB)

Panzer, K F

1980-09-01

The destructive land-use practices observed in large parts of the Sahel of West-Africa as a consequence of increasing population pressure must be replaced by sustained-yield management, e.g., by agro-sylvo-pastoral land-use systems. Information and planning aids required can only be obtained through the inventory and subsequent monitoring of the natural, renewable resources, i.e. water, range- and wood lands. Because of the extent and inaccessibility of the Sahel, an inventory design combining clustered fieldplots and large-scale aerial photography is being considered as most efficient in statistical and economical terms. Evidently, an inventory cannot solve the serious problems in the Sahel, but its results can contribute essentially towards defining better land-use policies and towards more effective management of the natural resource base.

The Re-Greening of the Sahel: Natural Cyclicity or Human-Induced Change?

Directory of Open Access Journals (Sweden)

Issa Ouedraogo

2014-09-01

Full Text Available The Sahel has been the focus of scientific interest in environmental-human dynamics and interactions. The objective of the present study is to contribute to the recent debate on the re-greening of Sahel. The paper examines the dynamics of barren land in the Sahel of Burkina Faso through analysis of remotely-sensed and rainfall data from 1975–2011. Discussions with farmers and land management staff have helped to understand the anthropogenic efforts toward soil restoration to enable the subsistence farming agriculture. Results showed that area of barren land has been fluctuating during the study period with approximately 10-year cyclicity. Similarly, rainfall, both at national and local levels has followed the same trends. The trends of the area of barren land and rainfall variability suggest that when rainfall increases, the area of barren land decreases and barren land increases when rainfall decreases. This implies that rainfall is one of the main factors driving the change in area of barren land. In addition, humans have contributed positively and negatively to the change by restoring barren lands for agriculture using locally known techniques and by accelerating land degradation through intensive and inappropriate land use practices.

Hacia un nuevo y diferente “Flanco Sur” en el Gran Magreb-Sahel

Directory of Open Access Journals (Sweden)

Raquel Barras

2015-10-01

Full Text Available La unión de espacios subgobernados, la corrupción, el crimen organizado y terrorismo es la amenaza a la que se enfrenta la UE y sus estados miembros en el Gran Magreb, el cual está recreando un nuevo y diferente Flanco Sur al que existía durante la Guerra Fría. El aumento de la actividad extremista en la región del Sahel-Sáhara a partir de 2005 ha ido en paralelo con el crecimiento de las redes de crimen organizado transnacional a través del área. Aunque hay un intenso debate sobre su relación, intensidad e impacto, es una dinámica innegable en el área. La UE no tiene realmente una política unificada Magreb-Sahel y en términos de crimen organizado y terrorismo, el Sahel no se puede separar del Magreb. Hay una comprensión limitada y parcial del problema tanto en términos de amenazas como en soluciones viables, ampliado irremediablemente por la acción de Boko Haram y desbordando la visión, proyección y estrategia de la UE. A pesar del "Sahel Regional Action Plan 2015-2020", las medidas tomadas son reducidas, muy recientes y probablemente insuficientes y tardías desde el punto de vista de la dinámica y sinergia entre terrorismo-crimen organizado en un contexto de corrupción. La UE sigue manteniendo un enfoque seguridad-desarrollo, básicamente en una concepción de seguridad humana, a pesar de que este enfoque es altamente discutible para enfrentarse a este tipo de amenazas.

Women's Right to Water for Agricultural Use in the Sahel (Mauritanie ...

International Development Research Centre (IDRC) Digital Library (Canada)

Women's Right to Water for Agricultural Use in the Sahel (Mauritanie, Niger, ... access of women to agricultural water resources in the three countries under study. ... long-term climate action to reduce social inequality, promote greater gender ...

Farm survey design in the Sahel : Experiences from Burkina Faso

NARCIS (Netherlands)

Graaff, de J.; Mijl, van der J.P.; Nibbering, J.W.

1999-01-01

In designing farm household surveys in the Sahel in West Africa much attention should be paid to various specific features of the farming systems. These features relate in particular to the social organisation of the farming communities. Within households, kinship relations have a strong bearing on

Extensive Admixture and Selective Pressure Across the Sahel Belt

Czech Academy of Sciences Publication Activity Database

Triska, P.; Soares, P.; Patin, E.; Fernandes, V.; Černý, Viktor; Pereira, L.

2015-01-01

Roč. 7, č. 12 (2015), s. 3484-3495 ISSN 1759-6653 R&D Projects: GA ČR GA13-37998S Institutional support: RVO:67985912 Keywords : genome-wide diversity * admixture * selection * Sahel Subject RIV: AC - Archeology, Anthropology, Ethnology Impact factor: 4.098, year: 2015 http://gbe.oxfordjournals.org/content/7/12/3484.full.pdf+html

Aspects of the Hematology and Serum Biochemistry of Sahel and ...

African Journals Online (AJOL)

This study was conducted to investigate effects of year, age, season and breeds on aspects of the hematology and serum biochemical indices of Sahel and Sokoto red bucks in Mubi, Adamawa state, Nigeria. Blood and serum samples were used to determine PCV, Hb, RBC and WBC, and while serum protein (BSP) and ...

Spatial and temporal variations in net carbon flux during HAPEX-Sahel.

NARCIS (Netherlands)

Moncrieff, J.B.; Monteny, B.; Verhoef, A.; Friborg, Th.; Elbers, J.; Kabat, P.; DeBruin, H.; Soegaard, H.; Jarvis, P.G.; Taupin, J.D.

1997-01-01

Micrometeorological measurements of the surface flux of carbon dioxide were made at a number of spatially separate sites within the HAPEX-Sahel experimental area. Differences in the timing of plant development caused by differences in rainfall (both quantity and frequency) over the experimental area

Using Relative Humidity Forecasts to Manage Meningitis in the Sahel

Science.gov (United States)

Pandya, R. E.; Adams-Forgor, A.; Akweogno, P.; Awine, T.; Dalaba, M.; Dukic, V.; Dumont, A.; Hayden, M.; Hodgson, A.; Hopson, T. M.; Hugonnet, S.; Yoksas, T. C.

2012-12-01

Meningitis epidemics in the Sahel occur quasi-regularly and with devastating impact. In 2008, for example, eighty-eight thousand people contracted meningitis and over five thousand died. Until very recently, the protection provided by the only available vaccine was so limited and short-lived that the only practical strategy for vaccination was reactive: waiting until an epidemic occurred in the region and then vaccinating in that region to prevent the epidemic's further growth. Even with that strategy, there were still times when demand outpaced available vaccine. While a new vaccine has recently been developed that is effective and inexpensive enough to be used more broadly and proactively, it is only effective against the strain of bacteria that causes the most common kind of bacterial meningitis. As a result, there will likely be continued need for reactive vaccination strategies. It is widely known that meningitis epidemics in the Sahel occur only in the dry season. Our project investigated this relationship, and several independent lines of evidence demonstrate a robust relationship between the onset of the rainy season, as marked by weekly average relative humidity above 40%, and the end of meningitis epidemics. These lines of evidence include statistical analysis of two years of weekly meningitis and weather data across the Sahel, cross-correlation of ten years of meningitis and weather data in the Upper East region of northern Ghana, and high-resolution weather simulations of past meningitis seasons to interpolate available weather data. We also adapted two techniques that have been successfully used in public health studies: generalized additive models, which have been used to relate air quality and health, and a linearized version of the compartmental epidemics model that has been used to understand MRSA. Based on these multiple lines of evidence, average weekly relative humidity forecast two weeks in advance appears consistently and strongly related to

Trend in land degradation has been the most contended issue in the Sahel. Trends documented have not been consistent across authors and science disciplines, hence little agreement has been gained on the magnitude and direction of land degradation in the Sahel. Differentiated science outputs are related to methods and data used at various scales.

Science.gov (United States)

Mbow, C.; Brandt, M.; Fensholt, R.; Ouedraogo, I.; Tagesson, T.

2015-12-01

Thematic gaps in land degradation trends in the SahelTrend in land degradation has been the most contended issue for arid and semi-arid regions. In the Sahel, depending to scale of analysis and methods and data used, the trend documented have not been consistent across authors and science disciplines. The assessment of land degradation and the quantification of its effects on land productivity have been assessed for many decades, but little agreement has been gained on the magnitude and direction in the Sahel. This lack of consistency amid science outputs can be related to many methodological underpinnings and data used for various scales of analysis. Assessing biophysical trends on the ground requires long-term ground-based data collection to evaluate and better understand the mechanisms behind land dynamics. The Sahel is seen as greening by many authors? Is that greening geographically consistent? These questions enquire the importance of scale analysis and related drivers. The questions addressed are not only factors explaining loss of tree cover but also regeneration of degraded land. The picture used is the heuristic cycle model to assess loss and damages vs gain and improvements of various land use practices. The presentation will address the following aspects - How much we know from satellite data after 40 years of remote sensing analysis over the Sahel? That section discuss agreement and divergences of evidences and differentiated interpretation of land degradation in the Sahel. - The biophysical factors that are relevant for tracking land degradation in the Sahel. Aspects such detangling human to climate factors and biophysical factors behind land dynamics will be presented - Introduce some specific cases of driver of land architecture transition under the combined influence of climate and human factor. - Based on the above we will conclude with some key recommendations on how to improve land degradation assessment in the Arid region of the Sahel.

Role of Surface Wind and Vegetation Cover in Multi-decadal Variations of Dust Emission in the Sahara and Sahel

Science.gov (United States)

Kim, Dong; Chin, Mian; Remer, Lorraine A.; Diehl, Thomas L.; Bian, Huisheng; Yu, Hongbin; Brown, Molly E.; Stockwell, William R.

2016-01-01

North Africa, the world's largest dust source, is non-uniform, consisting of a permanently arid region (Sahara), a semi-arid region (Sahel), and a relatively moist vegetated region (Savanna), each with very different rainfall patterns and surface conditions. This study aims to better understand the controlling factors that determine the variation of dust emission in North Africa over a 27-year period from 1982 to 2008, using observational data and model simulations. The results show that the model-derived Saharan dust emission is only correlated with the 10-m winds (W10m) obtained from reanalysis data, but the model-derived Sahel dust emission is correlated with both W10m and the Normalized Difference Vegetation Index (NDVI) that is obtained from satellite. While the Saharan dust accounts for 82 of the continental North Africa dust emission (1340-1570 Tg year(exp -1) in the 27-year average, the Sahel accounts for 17 with a larger seasonal and inter-annual variation (230-380 Tg year(exp -1), contributing about a quarter of the transatlantic dust transported to the northern part of South America. The decreasing dust emission trend over the 27-year period is highly correlated with W10m over the Sahara (R equals 0.92). Over the Sahel, the dust emission is correlated with W10m (R 0.69) but is also anti-correlated with the trend of NDVI (R equals 0.65). W10m is decreasing over both the Sahara and the Sahel between 1982 and 2008, and the trends are correlated (R equals 0.53), suggesting that Saharan Sahelian surface winds are a coupled system, driving the inter-annual variation of dust emission.

Genetic Structure of Pastoral and Farmer Populations in the African Sahel

Czech Academy of Sciences Publication Activity Database

Černý, Viktor; Pereira, L.; Musilová, E.; Kujanová, M.; Vašíková, A.; Blasi, P.; Garofalo, L.; Soares, P.; Diallo, I.; Brdička, R.; Novelletto, A.

2011-01-01

Roč. 28, č. 9 (2011), s. 2491-2500 ISSN 0737-4038 R&D Projects: GA ČR GA206/08/1587 Institutional research plan: CEZ:AV0Z80020508 Keywords : African Sahel * pastoralism * archaeogenetics Subject RIV: AC - Archeology, Anthropology, Ethnology Impact factor: 5.550, year: 2011 http://mbe.oxfordjournals.org/content/28/9/2491

Variations in selected physical proprieties of the soils of the sahel ...

African Journals Online (AJOL)

Infiltration rate, water content and textural properties of soils in the Sahel region of Nigeria as they are affected by shelterbelts were studied. The study was conducted on three measurement positions (60, 120 and 180 m) within the shelterbelt and the control was the unsheltered area. The site was situated on the southern ...

Political Reform, Socio-Religious Change, and Stability in the African Sahel

Science.gov (United States)

2016-12-08

research project This project proposed to analyze the socio- political factors affecting stability and instability in a set of six African countries...AFRL-AFOSR-VA-TR-2016-0360 Political Reform, Socio-Religious Change, and Stability in the African Sahel Leonard Villalon UNIVERSITY OF FLORIDA...STATEMENT DISTRIBUTION A: Distribution approved for public release. 13. SUPPLEMENTARY NOTES 14. ABSTRACT 15. SUBJECT TERMS Political stability

USSOF OPERATIONS IN AFRICA: PROSPECTS FOR FUTURE ENGAGEMENTS IN THE SAHEL

Science.gov (United States)

2017-04-03

counterterrorism operations in Somalia, Yemen , Afghanistan, Pakistan, and Syria.3 Absent the operational capability of terrorists to function in these...action by USSOF comes with some challenges. A fundamental challenge to USSOF operations outside the US, as evinced in the USSOF raid in Yakla- Yemen , is...assets. 8 Additionally, poor infrastructural facilities in the Sahel exacerbate the problem of poor logistics to support USSOF operations in

Services financiers et déploiement d'innovations agricoles au Sahel ...

International Development Research Centre (IDRC) Digital Library (Canada)

Services financiers et déploiement d'innovations agricoles au Sahel. Au cours des vingt dernières années, plusieurs innovations visant à améliorer les rendements des cultures vivrières ont été développées dans les centres de recherche agronomique d'Afrique de l'Ouest et par les chercheurs de la communauté ...

Alu insertion polymorphisms in the African Sahel and the origin of Fulani pastoralists

Czech Academy of Sciences Publication Activity Database

Čížková, M.; Hofmanová, Z.; Mokhtar, M. G.; Janoušek, V.; Diallo, I.; Munclinger, P.; Černý, Viktor

2017-01-01

Roč. 44, č. 6 (2017), s. 537-545 ISSN 0301-4460 R&D Projects: GA ČR GA13-37998S Institutional support: RVO:67985912 Keywords : Alu insertions * Fulani nomads * Western African pastoralism * African Sahel Subject RIV: AC - Archeology, Anthropology, Ethnology OBOR OECD: Archaeology Impact factor: 1.240, year: 2016

Summary of questionnaires completed by participating countries: for the project on the management of water resources in the Sahel region, using isotopic techniques

International Nuclear Information System (INIS)

Ito, Mari

2012-07-01

This presentation was carried out as part of the project on water resources management in the Sahel region, using isotope techniques. It summarizes the two sets of questionnaires made, highlights the basins (aquifers) selected for the Sahel project which are the Lullemen Basin, Taoudeni Basin, Lake Chad Basin and Liptako Gourma. Also, as well as the number of questionnaires completed by the participating countries.

The impacts of the dust radiative effect on vegetation growth in the Sahel

Science.gov (United States)

Evans, S. M.; Shevliakova, E.; Malyshev, S.; Ginoux, P. A.

2017-12-01

Many studies have been conducted on the effects of dust on rainfall in the Sahel, and generally show that African dust weakens the West African Monsoon, drying the region. This drying is often assumed to reduce vegetation cover for the region, providing a positive feedback with dust emission. There are, however, other competing effects of dust that are also important to plant growth, including a reduction in surface temperature, a reduction in downwelling solar radiation, and an increase in the diffuse fraction of that solar radiation. Using the NOAA/GFDL CM3 model coupled to the dynamic vegetation model LM3, we demonstrate that the combined effect of all these processes is to decrease the vegetation coverage and productivity of the Sahel and West Africa. We accomplish this by comparing experiments with radiatively active dust to experiments with radiatively invisible dust. We find that in modern conditions, the dust radiative effect reduces the net primary productivity of West Africa and the Sahel by up to 30% locally, and when summed over the region accounts for a difference of approximately 0.4 GtC per year. Experiments where the vegetation experiences preindustrial rather than modern CO2 levels show that without carbon fertilization, this loss of productivity would be approximately 10% stronger. In contrast, during preindustrial conditions the vegetation response is less than half as strong, despite the dust induced rainfall and temperature anomalies being similar. We interpret this as the vegetation being less susceptible to drought in a less evaporative climate. These changes in vegetation create the possibility of a dust-vegetation feedback loop whose strength varies with the mean state of the climate, and which may grow stronger in the future.

Impacts of the seasonal distribution of rainfall on vegetation productivity across the Sahel

Science.gov (United States)

Zhang, Wenmin; Brandt, Martin; Tong, Xiaoye; Tian, Qingjiu; Fensholt, Rasmus

2018-01-01

Climate change in drylands has caused alterations in the seasonal distribution of rainfall including increased heavy-rainfall events, longer dry spells, and a shifted timing of the wet season. Yet the aboveground net primary productivity (ANPP) in drylands is usually explained by annual-rainfall sums, disregarding the influence of the seasonal distribution of rainfall. This study tested the importance of rainfall metrics in the wet season (onset and cessation of the wet season, number of rainy days, rainfall intensity, number of consecutive dry days, and heavy-rainfall events) for growing season ANPP. We focused on the Sahel and northern Sudanian region (100-800 mm yr-1) and applied daily satellite-based rainfall estimates (CHIRPS v2.0) and growing-season-integrated normalized difference vegetation index (NDVI; MODIS) as a proxy for ANPP over the study period: 2001-2015. Growing season ANPP in the arid zone (100-300 mm yr-1) was found to be rather insensitive to variations in the seasonal-rainfall metrics, whereas vegetation in the semi-arid zone (300-700 mm yr-1) was significantly impacted by most metrics, especially by the number of rainy days and timing (onset and cessation) of the wet season. We analysed critical breakpoints for all metrics to test if vegetation response to changes in a given rainfall metric surpasses a threshold beyond which vegetation functioning is significantly altered. It was shown that growing season ANPP was particularly negatively impacted after > 14 consecutive dry days and that a rainfall intensity of ˜ 13 mm day-1 was detected for optimum growing season ANPP. We conclude that the number of rainy days and the timing of the wet season are seasonal-rainfall metrics that are decisive for favourable vegetation growth in the semi-arid Sahel and need to be considered when modelling primary productivity from rainfall in the drylands of the Sahel and elsewhere.

Energy needs, tasks and resources in the Sahel: Relevance to woodstoves programmes

Energy Technology Data Exchange (ETDEWEB)

Cecelski, E

1983-01-01

This article reviews the wood fuels situation in the Sahel and the findings of various needs assessment methodologies, especially as these are relevant to the numerous programmes to introduce improved cooking technologies in the region. Most people in West Africa, especially in poor and rural areas, rely primarily on wood fuels and crop wastes for energy needs, with devastating environmental consequences. Most wood is used in cooking. The quantity of fuel used depends on the type of fireplace, utensils used, how and when food is prepared, food preparation methods, types of fuels, how fuelwood is collected, and special customs surrounding the family fire - all of which are intimately associated with the economic, cultural and social fabric of Sahelian societies. Conventional fuel consumption and resource surveys have yielded useful information about quantitative energy needs in the Sahel, but increasingly sociocultural studies are being used to ensure that stove designs will meet the needs of the end-user. Economic analysis is also necessary to establish the dimensions of wood scarcity, to assess the financial attractiveness to consumers of alternative fuels and stoves, and in evaluating the costs and benefits to society of proposed national woodstoves programmes.

Spatiotemporal variability in carbon exchange fluxes across the Sahel

DEFF Research Database (Denmark)

Tagesson, Håkan Torbern; Fensholt, Rasmus; Cappelaere, Bernard

2016-01-01

for semi-arid ecosystems. We have synthesized data on the land-atmosphere exchange of CO2 measured with the eddy covariance technique from the six existing sites across the Sahel, one of the largest semi-arid regions in the world. The overall aim of the study is to analyse and quantify the spatiotemporal...... variability in these fluxes and to analyse to which degree spatiotemporal variation can be explained by hydrological, climatic, edaphic and vegetation variables. All ecosystems were C sinks (average ± total error -162 ± 48 g C m-2 y-1), but were smaller when strongly impacted by anthropogenic influences...

Mesoscale modeling of smoke radiative feedback over the Sahel region

Science.gov (United States)

Yang, Z.; Wang, J.; Ichoku, C. M.; Ellison, L.; Zhang, F.; Yue, Y.

2013-12-01

This study employs satellite observations and a fully-coupled meteorology-chemistry-aerosol model, Weather Research and Forecasting model with Chemistry (WRF-Chem) to study the smoke radative feedback on surface energy budget, boundary layer processes, and atmospheric lapse rate in February 2008 over the Sahel region. The smoke emission inventories we use come from various sources, including but not limited to the Fire Locating and Modeling of Burning Emissions (FLAMBE) developed by NRL and the Fire Energetic and Emissions Research (FEER) developed by NASA GSFC. Model performance is evaluated using numerous satellite and ground-based datasets: MODIS true color images, ground-based Aerosol Optical Depth (AOD) measurements from AERONET, MODIS AOD retrievals, and Cloud-Aerosol Lidar data with Orthogonal Polarization (CALIOP) atmospheric backscattering and extinction products. Specification of smoke injection height of 650 m in WRF-Chem yields aerosol vertical profiles that are most consistent with CALIOP observations of aerosol layer height. Statistically, 5% of the CALIPSO valid measurements of aerosols in February 2008 show aerosol layers either above the clouds or between the clouds, reinforcing the importance of the aerosol vertical distribution for quantifying aerosol impact on climate in the Sahel region. The results further show that the smoke radiative feedbacks are sensitive to assumptions of black carbon and organic carbon ratio in the particle emission inventory. Also investigated is the smoke semi-direct effect as a function of cloud fraction.

Scenarios on future land changes in the West African Sahel

DEFF Research Database (Denmark)

Lambin, Eric; D'haen, Sarah Ann Lise; Mertz, Ole

2014-01-01

by the Millennium Ecosystem Assessment: (1) ‘downward spiral’ characterized by rapid climate change, expansion of agriculture and chaotic urban growth; (2) ‘integrated economy’ with integrated land management, food production for local markets and rural–urban exchanges; (3) ‘open doors’ characterized by large......-scale out-migrations, land grabbing by foreign companies and development aid and (4) ‘climate change mitigation’ with an increase in biofuel crops, land management for carbon capture and development of off-farm activities. We conclude that the Sahel region is most likely moving away from being a highly...

A model of tree-crop competition for windbreaks systems in the Sahel : description and evaluation

NARCIS (Netherlands)

Mayus, M.; Keulen, van H.; Stroosnijder, L.

1999-01-01

A model was developed to simulate the effects of competition for soil water and radiation between windbreaks and pearl millet crops in the Sahel. These effects on millet (Pennisetum glaucum (L.) R. Br.) growth were simultaneously simulated for each millet row parallel to the windbreak with small

Fine-scale spatial distribution of plants and resources on a sandy soil in the Sahel

NARCIS (Netherlands)

Rietkerk, M.G.; Ouedraogo, T.; Kumar, L.; Sanou, S.; Langevelde, F. van; Kiema, A.; Koppel, J. van de; Andel, J. van; Hearne, J.; Skidmore, A.K.; Ridder, N. de; Stroosnijder, L.; Prins, H.H.T.

2002-01-01

We studied fine-scale spatial plant distribution in relation to the spatial distribution of erodible soil particles, organic matter, nutrients and soil water on a sandy to sandy loam soil in the Sahel. We hypothesized that the distribution of annual plants would be highly spatially autocorrelated

Household possession, use and non-use of treated or untreated mosquito nets in two ecologically diverse regions of Nigeria – Niger Delta and Sahel Savannah

Directory of Open Access Journals (Sweden)

Otsemobor Peju

2009-02-01

Full Text Available Abstract Background Current use of treated mosquito nets for the prevention of malaria falls short of what is expected in sub-Saharan Africa (SSA, though research within the continent has indicated that the use of these commodities can reduce malaria morbidity by 50% and malaria mortality by 20%. Governments in sub-Sahara Africa are investing substantially in scaling-up treated mosquito net coverage for impact. However, certain significant factors still prevent the use of the treated mosquito nets, even among those who possess them. This survey examines household ownership as well as use and non-use of treated mosquito nets in Sahel Savannah and Niger Delta regions of Nigeria. Methodology This survey employed cross-sectional survey to collect data from households on coverage and use of mosquito nets, whether treated or not. Fever episodes in previous two weeks among children under the age of five were also recorded. The study took place in August 1 – 14 2007, just five months after the March distribution of treated mosquito nets, coinciding with the second raining period of the year and a time of high malaria transmission during the wet season. EPI INFO version 2003 was used in data analysis. Results The survey covered 439 households with 2,521 persons including 739 under-fives, 585 women in reproductive age and 78 pregnant women in Niger Delta Region and Sahel Savannah Region. Of the 439 HHs, 232 had any mosquito nets. Significantly higher proportion of households in the Niger Delta Region had any treated or untreated mosquito nets than those in the Sahel Savannah Region. In the Niger Delta Region, the proportion of under-fives that had slept under treated nets the night before the survey exceeded those that slept under treated nets in the Sahel Savannah Region. Children under the age of five years in the Niger Delta Region were four times more likely to sleep under treated nets than those in the Sahel Savannah Region. Conclusion This study

Isotope hydrology in the Sahel zone

International Nuclear Information System (INIS)

1974-01-01

Northern Africa has recently experienced an exceptional period of severe drought. Practically no precipitation has been received during two or three years by large regions in the so-called Sahel zone, which extends over all Africa from West to East at a latitude between 10 and 20 degrees North in the following countries: Senegal, Mauritania, Mali, Upper Volta, Niger, Nigeria, Chad, Sudan and Ethiopia. Although precipitation is scarce even in normal years, important groundwater resources are present in the Sahei zone. However, groundwater is exploited mainly by dug wells, reaching only the upper part of the phreatic aquifer, which is also the one immediately affected by droughts (lowering of the water table). Deep groundwater is exploited only by a limited number of drilled wells. In recent years several hydrogeological projects have been financed by the United Nations through UNDP in the Sahel countries, with the purpose of locating and evaluating groundwater resources and of developing their exploitation. The International Atomic Energy Agency has taken or takes part in many of these projects by providing isotopic analyses of groundwater. Some of the most difficult questions to be answered in groundwater research in arid zones are: Is the recharge of a given aquifer also taking place at present? If so, from where does the major contribution to groundwater recharge come? What is the age of groundwater? Often it is not possible to answer these questions with the classical hydrogeological and geophysical methods above, but the techniques based on the so-called environmental isotopes ( 18 O and 2 H, 3 H and 14 C) may provide an answer. The information provided by isotope techniques is in many cases extremely valuable for a better understanding of groundwater resources and a better planning of their exploitation, despite the problems which always occur in actual cases. In fact, natural processes, like mixing or interaction with the aquifer material, or practical

Impact of soil-vegetation-atmosphere interactions on the spatial rainfall distribution in the Central Sahel

Directory of Open Access Journals (Sweden)

Marcus Breil

2017-10-01

Full Text Available In a Regional Climate Model (RCM the interactions between the land surface and the atmosphere are described by a Soil-Vegetation-Atmosphere-Transfer Model (SVAT. In the presented study two SVATs of different complexity (TERRA-ML and VEG3D are coupled to the RCM COSMO-CLM (CCLM to investigate the impact of different representations of soil-vegetation-atmosphere interactions on the West African Monsoon (WAM system. In contrast to TERRA-ML, VEG3D comprises a more detailed description of the land-atmosphere coupling by including a vegetation layer in its structural design, changing the treatment of radiation and turbulent fluxes. With these two different model systems (CCLM-TERRA-ML and CCLM-VEG3D climate simulations are performed for West Africa and analyzed. The study reveals that the simulated spatial distribution of rainfall in the Sahel region is substantially affected by the chosen SVAT. Compared to CCLM-TERRA-ML, the application of CCLM-VEG3D results in higher near surface temperatures in the Sahel region during the rainy season. This implies a southward expansion of the Saharian heat-low. Consequently, the mean position of the African Easterly Jet (AEJ is also shifted to the south, leading to a southward displacement of tracks for Mesoscale Convective Systems (MCS, developing in connection with the AEJ. As a result, less precipitation is produced in the Sahel region, increasing the agreement with observations. These analyses indicate that soil-vegetation-atmosphere interactions impact the West African Monsoon system and highlight the benefit of using a more complex SVAT to simulate its dynamics.

Using Case Studies to Teach About Global Issues, The Sahel: The "Shore" of Disaster

Science.gov (United States)

Hall, Susan J.

1974-01-01

Sahel is the Arabic word for "shore" and is applied to the Southern belt of the Sahara Desert now undergoing a severe drought. This article describes the lifestyle of a Tuareg herder as he and his family fight for survival. Discussion questions and possible solution to the problems are provided in the case study. (Author/DE)

Future supply and demand of net primary production in the Sahel

Science.gov (United States)

Sallaba, Florian; Olin, Stefan; Engström, Kerstin; Abdi, Abdulhakim M.; Boke-Olén, Niklas; Lehsten, Veiko; Ardö, Jonas; Seaquist, Jonathan W.

2017-12-01

In the 21st century, climate change in combination with increasing demand, mainly from population growth, will exert greater pressure on the ecosystems of the Sahel to supply food and feed resources. The balance between supply and demand, defined as the annual biomass required for human consumption, serves as a key metric for quantifying basic resource shortfalls over broad regions.Here we apply an exploratory modelling framework to analyse the variations in the timing and geography of different NPP (net primary production) supply-demand scenarios, with distinct assumptions determining supply and demand, for the 21st century Sahel. We achieve this by coupling a simple NPP supply model forced with projections from four representative concentration pathways with a global, reduced-complexity demand model driven by socio-economic data and assumptions derived from five shared socio-economic pathways.For the scenario that deviates least from current socio-economic and climate trends, we find that per capita NPP begins to outstrip supply in the 2040s, while by 2050 half the countries in the Sahel experience NPP shortfalls. We also find that despite variations in the timing of the onset of NPP shortfalls, demand cannot consistently be met across the majority of scenarios. Moreover, large between-country variations are shown across the scenarios, in which by the year 2050 some countries consistently experience shortage or surplus, while others shift from surplus to shortage. At the local level (i.e. grid cell), hotspots of total NPP shortfall consistently occur in the same locations across all scenarios but vary in size and magnitude. These hotspots are linked to population density and high demand. For all scenarios, total simulated NPP supply doubles by 2050 but is outpaced by increasing demand due to a combination of population growth and the adoption of diets rich in animal products. Finally, variations in the timing of the onset and end of supply shortfalls stem from

Do state-of-the-art CMIP5 ESMs accurately represent observed vegetation-rainfall feedbacks? Focus on the Sahel

Science.gov (United States)

Notaro, M.; Wang, F.; Yu, Y.; Mao, J.; Shi, X.; Wei, Y.

2017-12-01

The semi-arid Sahel ecoregion is an established hotspot of land-atmosphere coupling. Ocean-land-atmosphere interactions received considerable attention by modeling studies in response to the devastating 1970s-90s Sahel drought, which models suggest was driven by sea-surface temperature (SST) anomalies and amplified by local vegetation-atmosphere feedbacks. Vegetation affects the atmosphere through biophysical feedbacks by altering the albedo, roughness, and transpiration and thereby modifying exchanges of energy, momentum, and moisture with the atmosphere. The current understanding of these potentially competing processes is primarily based on modeling studies, with biophysical feedbacks serving as a key uncertainty source in regional climate change projections among Earth System Models (ESMs). In order to reduce this uncertainty, it is critical to rigorously evaluate the representation of vegetation feedbacks in ESMs against an observational benchmark in order to diagnose systematic biases and their sources. However, it is challenging to successfully isolate vegetation's feedbacks on the atmosphere, since the atmospheric control on vegetation growth dominates the atmospheric feedback response to vegetation anomalies and the atmosphere is simultaneously influenced by oceanic and terrestrial anomalies. In response to this challenge, a model-validated multivariate statistical method, Stepwise Generalized Equilibrium Feedback Assessment (SGEFA), is developed, which extracts the forcing of a slowly-evolving environmental variable [e.g. SST or leaf area index (LAI)] on the rapidly-evolving atmosphere. By applying SGEFA to observational and remotely-sensed data, an observational benchmark is established for Sahel vegetation feedbacks. In this work, the simulated responses in key atmospheric variables, including evapotranspiration, albedo, wind speed, vertical motion, temperature, stability, and rainfall, to Sahel LAI anomalies are statistically assessed in Coupled Model

PVO / NGO initiatives. The Global Dialogues Trust -- "Scenarios from the Sahel".

Science.gov (United States)

1997-01-01

Scenarios from the Sahel is an HIV/AIDS prevention project for adolescents and young adults in Senegal, Mali, Burkina Faso, and Niger, organized by the Global Dialogues Trust and launched in January 1997. The project invites people aged 24 years and younger to engage in a competition in which they write scenarios for a 1-5 minute video on HIV/AIDS. Those 30 scenarios judged to be the most valuable to the HIV/AIDS prevention effort in the Sahel will be developed into video spots by the region's film-makers and screened at cinemas and broadcast on television stations in West Africa. The spots will also be collected upon a compilation video available for use by local nongovernmental organizations in their HIV/AIDS prevention activities in the region. The compilation video will be dubbed from French into local languages and English to facilitate its broad dissemination in the 4 participating countries and their neighbors. The video together with an education pack will also be distributed to local organizations and schools. The project, to be conducted in close partnership with local people and their organizations, will end with its evaluation in June 1998. Global Dialogues Trust is a charitable trust based in the UK dedicated to advance the education of the public throughout the world in all matters concerning the prevention of HIV/AIDS. The organization's main priority is to develop local capacity to fight HIV/AIDS through preventive education.

[Migration and urbanization in the Sahel. Consequences of the Sahelian migrations].

Science.gov (United States)

Traore, S

1997-10-01

The consequences of Sahelian migration are multiple and diverse. In rural areas there may be a loss of income in the short run and a reduced possibility of development in the long run. Apart from its implications for urban growth, Sahelian migration may have four series of consequences in the places of origin. In detaching peasants from their lands, migration may contribute to loss of appreciation and reverence for the lands. Attachment to the lands of the ancestors loses its meaning as soon as questions of survival or economic rationality are raised. Migration contributes to the restructuring of the societies of origin. Increasing monetarization of market relations and introduction of new needs create new norms that favor stronger integration into the world economy. Migration may cause a decline in production because of the loss of the most active population, and it changes the age and sex distribution of households and usually increases their dependency burden. The effects on fertility and mortality are less clear. The effects of migration on the zones of arrival in the Sahel depend on the type of area. Conflicts between natives and in-migrants are common in rural-rural migration. Degradation of land may result from the increased demands placed upon it. Migrants to cities in Africa, and especially in the Sahel, appear to conserve their cultural values and to transplant and reinterpret their village rules of solidarity.

Climatic information of Western Sahel (1535-1793 AD) in original documentary sources

Science.gov (United States)

Millán, V.; Rodrigo, F. S.

2014-09-01

The Sahel is the semi-arid transition zone between arid Sahara and humid tropical Africa, extending approximately 10-20° N from Mauritania in the West to Sudan in the East. The African continent, one of the most vulnerable regions to climate change, is subject to frequent droughts and famine. One climate challenge research is to isolate those aspects of climate variability that are natural from those that are related to human influences. Therefore, the study of climatic conditions before mid-19th century, when anthropogenic influence was of minor importance, is very interesting. In this work the frequency of extreme events, such as droughts and floods, in Western Sahel from the 16th to 18th centuries is investigated using documentary data. Original manuscripts with historical chronicles from Walata and Nema (Mauritania), Timbuktu and Arawan (Mali), and Agadez (Niger) have been analyzed. Information on droughts, intense rainfall, storms and floods, as well as socioeconomic aspects (famines, pests, scarcity, prosperity) has been codified in an ordinal scale ranging from -2 (drought and famines) to +2 (floods) to obtain a numerical index of the annual rainfall in the region. Results show wet conditions in the 17th century, as well as dry conditions in the 18th century (interrupted by a short wet period in the 1730s decade).

Determination of stable and radioactive isotopes in rain water for the equatorial and Sahel zones

International Nuclear Information System (INIS)

Baudet, J.; Lesne, H.

1975-01-01

The extension of desert zones to detriment of Sahel zones lead to look for the circuit followed by water vapor between its principal source, i.e. the Guinea Gulf, and the place where it is changed in precipitation. Samples of rainwater have been collected in Abidjan, Ouagadougou, and Niamey when the Intertropical Front was beginning its moving down towards the South, i.e. at the end of the rainy season for the Sahel zone, and at the beginning of the small rainy season for the equatorial zone. The analysis of these tritium, deuterium and oxygen-18 contents show that: the rains collected in Abidjan comes mainly from Ocean; the rains collected in Ouagadougou and Niamey have followed a long journey above the continent, as shown by the tritium content. The water evaporated in the Guinea Gulf is condensed in the convergence zone above Cameroon, and mixed with re-evaporated continental water. The content of one of the Ouagadougou sample shows that the rain issued from a local cumulonimbus has drawn a part of its water from the stratosphere [fr

Hydrodynamic behaviour of crusted soils in the Sahel: a possible cause for runoff increase?

Science.gov (United States)

Malam Abdou, M.; Vandervaere, J.-P.; Bouzou Moussa, I.; Descroix, L.

2012-04-01

Crusted soils are in extension in the Sahel. As rainfall has decreased over the past decades (it is now increasing again in the central Sahel) and no significant change was observed in rainfall intensity and in its time and space distribution, it is supposed that land use management is the main cause for crusts cover increase. Fallow shortening, lack of manure, and land overexploitation (wood harvesting, overgrazing) are frequently cited as main factors of soil degradation. Based on field measurements in some small catchments of Western Niger, the hydrodynamics behaviour of the newly crusted soils of this area is described, mostly constituted by erosion crusts. A strong fall in soil saturated conductivity and in the active porosity as well as a rise in bulk density all lead to a quick onset of runoff production. Results are shown from field experiments in sedimentary and basement areas leading to similar conclusions. In both contexts, runoff plot production was measured at the rain event scale from 10-m2 parcels as well as at the catchment outlet. Soil saturated conductivity was reduced by one order of magnitude when crusting occurs, leading to a sharp runoff coefficient increase, from 4% in a weeded millet field and 10% in an old fallow to more than 60% in a erosion-crusted topsoil at the plot scale. At the experimental catchment scale, runoff coefficient has doubled in less than 20 years. In pure Sahelian basins, this resulted in endorheism breaching, and in a widespread river discharge increase. For some right bank tributaries of the Niger River, discharge is three times higher now than before the drought years, in spite of the remaining rainfall deficit. On the other hand, a general increase in flooding hazard frequency is observed in the whole Sahelian stripe. The role of surface crusts in the Sahel is discussed leading to the implementation of new experiments in the future.

The effect of irrigated rice cropping on the alkalinity of two alkaline rice soils in the Sahel

NARCIS (Netherlands)

Asten, van P.J.A.; Zelfde, van 't J.A.; Zee, van der S.E.A.T.M.; Hammecker, C.

2004-01-01

Irrigated rice cropping is practiced to reclaim alkaline-sodic soils in many parts of the world. This practice is in apparent contrast with earlier studies in the Sahel, which suggests that irrigated rice cropping may lead to the formation of alkaline-sodic soils. Soil column experiments were done

Developing a Shuffled Complex-Self Adaptive Hybrid Evolution (SC-SAHEL) Framework for Water Resources Management and Water-Energy System Optimization

Science.gov (United States)

Rahnamay Naeini, M.; Sadegh, M.; AghaKouchak, A.; Hsu, K. L.; Sorooshian, S.; Yang, T.

2017-12-01

Meta-Heuristic optimization algorithms have gained a great deal of attention in a wide variety of fields. Simplicity and flexibility of these algorithms, along with their robustness, make them attractive tools for solving optimization problems. Different optimization methods, however, hold algorithm-specific strengths and limitations. Performance of each individual algorithm obeys the "No-Free-Lunch" theorem, which means a single algorithm cannot consistently outperform all possible optimization problems over a variety of problems. From users' perspective, it is a tedious process to compare, validate, and select the best-performing algorithm for a specific problem or a set of test cases. In this study, we introduce a new hybrid optimization framework, entitled Shuffled Complex-Self Adaptive Hybrid EvoLution (SC-SAHEL), which combines the strengths of different evolutionary algorithms (EAs) in a parallel computing scheme, and allows users to select the most suitable algorithm tailored to the problem at hand. The concept of SC-SAHEL is to execute different EAs as separate parallel search cores, and let all participating EAs to compete during the course of the search. The newly developed SC-SAHEL algorithm is designed to automatically select, the best performing algorithm for the given optimization problem. This algorithm is rigorously effective in finding the global optimum for several strenuous benchmark test functions, and computationally efficient as compared to individual EAs. We benchmark the proposed SC-SAHEL algorithm over 29 conceptual test functions, and two real-world case studies - one hydropower reservoir model and one hydrological model (SAC-SMA). Results show that the proposed framework outperforms individual EAs in an absolute majority of the test problems, and can provide competitive results to the fittest EA algorithm with more comprehensive information during the search. The proposed framework is also flexible for merging additional EAs, boundary

Assessing the long-term effects of the Sahel drought on ponds and semi-arid hydrology.

Science.gov (United States)

Gal, L.; Grippa, M.; Kergoat, L.; Hiernaux, P.; Peugeot, C.; Mougin, E.

2015-12-01

The Sahel underwent a severe rainfall deficit in the late 20th century, with extreme droughts in the early 70s and early 80s. This drought is the strongest multidecadal drought of the 20th century, globally. It has strongly impacted ecosystems, water availability, and populations. However, an increase of surface water has been observed during the same period: higher discharge of Sahelian rivers, and a general increase in pond's surface. This phenomenon, "less rain but more surface runoff", is referred to as the "Sahelian paradox". The causes of this paradox are still debated. The role of the significant increase in cropped areas, often cited for cultivated Sahel, does not hold for pastoral areas in central and northern Sahel. Degradation of vegetation as a result of the drought, soils erosion, may also play an important role. Most Sahelian watersheds are still poorly gauged or ungauged, which makes it difficult to quantify surface runoff and its determinants. A method is developed to estimate runoff over ungauged ponds watersheds. It is tested for the Agoufou pond in the Gourma region in Mali, where in situ data are available for 2007-2014. A 3D model is first developed to relate water volume to height surface. This model is combined with daily evaporation and precipitation, to estimate the water supply to the pond which is a proxy for runoff over the watershed. This model highlights a spectacular increase of the runoff coefficient over the last 60 years. The method is then applied to two ungauged Sahelian watersheds in Mauritania and Niger, where pond surfaces by remote sensing are the only information. The runoff coefficients also increased in the last 60 years over these watersheds. The runoff derived for the Agoufou pond is used to evaluate simulations with the KINEROS2 model. We discuss to what extent the changes in rain intensity, soil hydrological properties and land-use land cover are able to cause the observed change in runoff over the last 60 years.

The significance of drinking water for population migration in the Sahel zone of the Republic of Sudan.

Science.gov (United States)

Ruppert, H

1991-01-01

This study examines how the availability of water supplies affects migration in the Sahel region of Sudan. More particularly, the author shows that "through the development of watering-places and the opening-up of new water resources, the government influences considerably processes of population migration and regional concentrations of population groups." excerpt

Advances in monitoring vegetation and land use dynamics in the Sahel

DEFF Research Database (Denmark)

Mbow, Cheikh; Fensholt, Rasmus; Nielsen, Thomas Theis

2014-01-01

of CO2 in the atmosphere, grazing pressure, bush fires and agricultural expansion or contraction. The use of satellite data in combination with field data played a major role in the monitoring of vegetation dynamics and land use in the Sahel, since the mega drought of the 1970s and the 1980s. This paper...... briefly reviews the advance of satellite-based monitoring of vegetation dynamics over these 40 years. We discuss the promises of current and likely future data sources and analysis tools, as well as the need to strengthen in situ data collection to support and validate satellite-based vegetation and land...

Water, energy and CO2 exchange over a seasonally flooded forest in the Sahel.

Science.gov (United States)

Kergoat, L.; Le Dantec, V.; Timouk, F.; Hiernaux, P.; Mougin, E.; Manuela, G.; Diawara, M.

2014-12-01

In semi-arid areas like the Sahel, perennial water bodies and temporary-flooded lowlands are critical for a number of activities. In some cases, their existence is simply a necessary condition for human societies to establish. They also play an important role in the water and carbon cycle and have strong ecological values. As a result of the strong multi-decadal drought that impacted the Sahel in the 70' to 90', a paradoxical increase of ponds and surface runoff has been observed ("Less rain, more water in the ponds", Gardelle 2010). In spite of this, there are excessively few data documenting the consequence of such a paradox on the water and carbon cycle. Here we present 2 years of eddy covariance data collected over the Kelma flooded Acacia forest in the Sahel (15.50 °N), in the frame of the AMMA project. The flooded forest is compared to the other major component of this Sahelian landscape: a grassland and a rocky outcrop sites. All sites are involved in the ALMIP2 data/LSM model comparison. The seasonal cycle of the flooded forest strongly departs from the surroundings grassland and bare soil sites. Before the rain season, the forest displays the strongest net radiation and sensible heat flux. Air temperature within the canopy reaches extremely high values. During the flood, it turns to the lowest sensible heat flux. In fact, due to an oasis effect, this flux is negative during the late flood. Water fluxes turn from almost zero in the dry season to strong evaporation during the flood, since it uses additional energy provided by negative sensible heat flux. The eddy covariance fluxes are consistent with sap flow data, showing that the flood greatly increases the length of the growing season. CO2 fluxes over the forest were twice as large as over the grassland, and the growing season was also longer, giving a much larger annual photosynthesis. In view of these data and data over surroundings grasslands and bare soil, as well as data from a long-term ecological

Revisiting historical climatic signals to better explore the future: prospects of water cycle changes in Central Sahel

Science.gov (United States)

Leauthaud, C.; Demarty, J.; Cappelaere, B.; Grippa, M.; Kergoat, L.; Velluet, C.; Guichard, F.; Mougin, E.; Chelbi, S.; Sultan, B.

2015-06-01

Rainfall and climatic conditions are the main drivers of natural and cultivated vegetation productivity in the semiarid region of Central Sahel. In a context of decreasing cultivable area per capita, understanding and predicting changes in the water cycle are crucial. Yet, it remains challenging to project future climatic conditions in West Africa since there is no consensus on the sign of future precipitation changes in simulations coming from climate models. The Sahel region has experienced severe climatic changes in the past 60 years that can provide a first basis to understand the response of the water cycle to non-stationary conditions in this part of the world. The objective of this study was to better understand the response of the water cycle to highly variable climatic regimes in Central Sahel using historical climate records and the coupling of a land surface energy and water model with a vegetation model that, when combined, simulated the Sahelian water, energy and vegetation cycles. To do so, we relied on a reconstructed long-term climate series in Niamey, Republic of Niger, in which three precipitation regimes can be distinguished with a relative deficit exceeding 25% for the driest period compared to the wettest period. Two temperature scenarios (+2 and +4 °C) consistent with future warming scenarios were superimposed to this climatic signal to generate six virtual future 20-year climate time series. Simulations by the two coupled models forced by these virtual scenarios showed a strong response of the water budget and its components to temperature and precipitation changes, including decreases in transpiration, runoff and drainage for all scenarios but those with highest precipitation. Such climatic changes also strongly impacted soil temperature and moisture. This study illustrates the potential of using the strong climatic variations recorded in the past decades to better understand potential future climate variations.

Rebuilding resilience in the Sahel: Regreening in the Maradi and Zinder regions of Niger

OpenAIRE

Sendzimir, J.; Reij, C.P.; Magnuszewski, P.

2011-01-01

The societies and ecosystems of the Nigerien Sahel appeared increasingly vulnerable to climatic and economic uncertainty in the late twentieth century. Severe episodes of drought and famine drove massive livestock losses and human migration and mortality. Soil erosion and tree loss reduced a woodland to a scrub steppe and fed a myth of the Sahara desert relentlessly advancing southward. Over the past two decades this myth has been shattered by the dramatic reforestation of more than 5 million...

A unifying view of climate change in the Sahel linking intra-seasonal, interannual and longer time scales

International Nuclear Information System (INIS)

Giannini, A; Salack, S; Gaye, A T; Lodoun, T; Ali, A; Ndiaye, O

2013-01-01

We propose a re-interpretation of the oceanic influence on the climate of the African Sahel that is consistent across observations, 20th century simulations and 21st century projections, and that resolves the uncertainty in projections of precipitation change in this region: continued warming of the global tropical oceans increases the threshold for convection, potentially drying tropical land, but this ‘upped ante’ can be met if sufficient moisture is supplied in monsoon flow. In this framework, the reversal to warming of the subtropical North Atlantic, which is now out-pacing warming of the global tropical oceans, provides that moisture, and explains the partial recovery in precipitation since persistent drought in the 1970s and 1980s. We find this recovery to result from increases in daily rainfall intensity, rather than in frequency, most evidently so in Senegal, the westernmost among the three Sahelian countries analyzed. Continuation of these observed trends is consistent with projections for an overall wetter Sahel, but more variable precipitation on all time scales, from intra-seasonal to multi-decadal. (letter)

The Crop Risk Zones Monitoring System for resilience to drought in the Sahel

Science.gov (United States)

Vignaroli, Patrizio; Rocchi, Leandro; De Filippis, Tiziana; Tarchiani, Vieri; Bacci, Maurizio; Toscano, Piero; Pasqui, Massimiliano; Rapisardi, Elena

2016-04-01

Food security is still one of the major concerns that Sahelian populations have to face. In the Sahel, agriculture is primarily based on rainfed crops and it is often structurally inadequate to manage the climatic variability. The predominantly rainfed cropping system of Sahel region is dependent on season quality on a year-to-year basis, and susceptible to weather extremes of droughts and extreme temperatures. Low water-storage capacity and high dependence on rainfed agriculture leave the agriculture sector even more vulnerable to climate risks. Crop yields may suffer significantly with either a late onset or early cessation of the rainy season, as well as with a high frequency of damaging dry spells. Early rains at the beginning of the season are frequently followed by dry spells which may last a week or longer. As the amount of water stored in the soil at this time of the year is negligible, early planted crops can suffer water shortage stresses during a prolonged dry spell. Therefore, the choice of the sowing date is of fundamental importance for farmers. The ability to estimate effectively the onset of the season and potentially dangerous dry spells becomes therefore vital for planning rainfed agriculture practices aiming to minimize risks and maximize yields. In this context, advices to farmers are key drivers for prevention allowing a better adaptation of traditional crop calendar to climatic variability. In the Sahel, particularly in CILSS (Permanent Interstates Committee for Drought Control in the Sahel) countries, national Early Warning System (EWS) for food security are underpinned by Multidisciplinary Working Groups (MWGs) lead by National Meteorological Services (NMS). The EWSs are mainly based on tools and models utilizing numeric forecasts and satellite data to outlook and monitor the growing season. This approach is focused on the early identification of risks and on the production of information within the prescribed time period for decision

Price and quality of livestock feeds in suburban markets of West Africa’s Sahel: Case study from Bamako, Mali

Directory of Open Access Journals (Sweden)

A. A. Ayantunde

2014-07-01

Full Text Available In West African Sahel cities, livestock husbandry such as smallholder dairy production and livestock (cattle, sheep and goat fattening has become popular among livestock owners to meet food needs for the household, and for income generation. The increasing importance of urban and suburban agriculture, particularly livestock husbandry in the region, has led to a rapid increase in livestock populations in most of the cities. As a result of this increase and the associated growth in the demand for feeds, feed markets have sprung up in many cities and towns of West Africa’s Sahel. A survey of livestock feed markets was conducted in five markets in Bamako, Mali. Prices of livestock feeds were monitored monthly from January to December 2010. In addition, feed samples were collected from the markets for laboratory analysis to determine their nutritional quality. Results showed that the prices of cowpea hay and groundnut haulm were consistently higher than those of other feeds throughout the year. The price of cowpea hay ranged from 367 FCFA/kg dry matter (DM (1 USD ≈ 500 FCFA in October, i.e. immediately after harvest, to 667 FCFA/kg DM in August, i.e. in the wet season. Results also showed that there was no relationship between price and quality for all feed types. However, prices and quality of feeds differed significantly across seasons suggesting that the season was a major determinant for the price of livestock feeds in suburban areas of West Africa’s Sahel.

What Four Decades of Earth Observation Tell Us about Land Degradation in the Sahel?

Directory of Open Access Journals (Sweden)

Cheikh Mbow

2015-04-01

Full Text Available The assessment of land degradation and the quantification of its effects on land productivity have been both a scientific and political challenge. After four decades of Earth Observation (EO applications, little agreement has been gained on the magnitude and direction of land degradation in the Sahel. The large number of EO datasets and methods associated with the complex interactions among biophysical and social drivers of ecosystem changes make it difficult to apply aggregated EO indices for these non-linear processes. Hence, while many studies stress that the Sahel is greening, others indicate no trend or browning. The different generations of sensors, the granularity of studies, the study period, the applied indices and the assumptions and/or computational methods impact these trends. Consequently, many uncertainties exist in regression models between rainfall, biomass and various indices that limit the ability of EO science to adequately assess and develop a consistent message on the magnitude of land degradation. We suggest several improvements: (1 harmonize time-series data, (2 promote knowledge networks, (3 improve data-access, (4 fill data gaps, (5 agree on scales and assumptions, (6 set up a denser network of long-term field-surveys and (7 consider local perceptions and social dynamics. To allow multiple perspectives and avoid erroneous interpretations, we underline that EO results should not be interpreted without contextual knowledge.

Farmers´ perceptions of climate change and agricultural adaptation strategies in rural Sahel

DEFF Research Database (Denmark)

Mertz, Ole; Mbow, Cheikh; Reenberg, Anette

2009-01-01

Farmers in the Sahel have always been facing climatic variability at intra- and inter-annual and decadal time scales. While coping and adaptation strategies have traditionally included crop diversification, mobility, livelihood diversification, and migration, singling out climate as a direct driver...... of changes is not so simple. Using focus group interviews and a household survey, this study analyzes the perceptions of climate change and the strategies for coping and adaptation by sedentary farmers in the savanna zone of central Senegal. Households are aware of climate variability and identify wind...

Future supply and demand of net primary production in the Sahel

Directory of Open Access Journals (Sweden)

F. Sallaba

2017-12-01

Full Text Available In the 21st century, climate change in combination with increasing demand, mainly from population growth, will exert greater pressure on the ecosystems of the Sahel to supply food and feed resources. The balance between supply and demand, defined as the annual biomass required for human consumption, serves as a key metric for quantifying basic resource shortfalls over broad regions.Here we apply an exploratory modelling framework to analyse the variations in the timing and geography of different NPP (net primary production supply–demand scenarios, with distinct assumptions determining supply and demand, for the 21st century Sahel. We achieve this by coupling a simple NPP supply model forced with projections from four representative concentration pathways with a global, reduced-complexity demand model driven by socio-economic data and assumptions derived from five shared socio-economic pathways.For the scenario that deviates least from current socio-economic and climate trends, we find that per capita NPP begins to outstrip supply in the 2040s, while by 2050 half the countries in the Sahel experience NPP shortfalls. We also find that despite variations in the timing of the onset of NPP shortfalls, demand cannot consistently be met across the majority of scenarios. Moreover, large between-country variations are shown across the scenarios, in which by the year 2050 some countries consistently experience shortage or surplus, while others shift from surplus to shortage. At the local level (i.e. grid cell, hotspots of total NPP shortfall consistently occur in the same locations across all scenarios but vary in size and magnitude. These hotspots are linked to population density and high demand. For all scenarios, total simulated NPP supply doubles by 2050 but is outpaced by increasing demand due to a combination of population growth and the adoption of diets rich in animal products. Finally, variations in the timing of the onset and end of supply

Integrated pearl millet management in the Sahel : Effects of legume rotation and fallow management on productivity and Striga hermonthica infestation

NARCIS (Netherlands)

Samaké, O.; Stomph, T.J.; Kropff, M.J.; Smaling, E.M.A.

2006-01-01

Increasing population density and food needs in the Sahel are major drivers behind the conversion of land under natural vegetation to arable land. Intensification of agriculture is a necessity for farmers to produce enough food. As manure is scarce and fertilizers expensive, this study looks into

Building resilience to face recurring environmental crisis in African Sahel

Science.gov (United States)

Boyd, Emily; Cornforth, Rosalind J.; Lamb, Peter J.; Tarhule, Aondover; Lélé, M. Issa; Brouder, Alan

2013-07-01

The present food shortages in the Horn of Africa and the West African Sahel are affecting 31 million people. Such continuing and future crises require that people in the region adapt to an increasing and potentially irreversible global sustainability challenge. Given this situation and that short-term weather and seasonal climate forecasting have limited skill for West Africa, the Rainwatch project illustrates the value of near real-time monitoring and improved communication for the unfavourable 2011 West African monsoon, the resulting severe drought-induced humanitarian impacts continuing into 2012, and their exacerbation by flooding in 2012. Rainwatch is now coupled with a boundary organization (Africa Climate Exchange, AfClix) with the aim of integrating the expertise and actions of relevant institutions, agencies and stakeholders to broker ground-based dialogue to promote resilience in the face of recurring crisis.

Analysis for dry and wet years with the WIMISA model of tree-crop competition for wind break systems in the Sahel

NARCIS (Netherlands)

Mayus, M.; Keulen, van H.; Stroosnijder, L.

1999-01-01

A modelling approach was chosen for analyzing the effects of competition between windbreaks and crops for soil water and radiation in the Sahel. The model has a high spatial and temporal resolution to account for the heterogeneity in a windbreak-cropping system. The model was parameterised for

A simple tentative model of the losses caused by the Senegalese grasshopper, Oedaleus senegalensis (Krauss 1877) to millet in the Sahel

DEFF Research Database (Denmark)

Bal, Amadou Bocar; Ouambama, Zakaria; Dieng, Ibnou

2015-01-01

Oedaleus senegalensis is a serious pest of millet in the Sahel, but the correlation to crop loss remains largely unknown. Therefore, the correlation between densities of O. senegalensis, defoliation level and millet yields was investigated in Niger in 2008, and a simple model to foresee the yield...

Colonisation humaine et développement sur une frontière écologique. Le Despoblado, le Sahel du Piura-Pérou Septentrional

Directory of Open Access Journals (Sweden)

1991-01-01

Full Text Available Le despoblado de Piura est une formation végétale mixte arborée et herbacée, un sahel qui, malgré des précipitations très irrégulières, associe plusieurs ressources complémentaires. Elles ont été diversement utilisées au fur et à mesure de l’intervention de nouvelles techniques. - Cueillette des racines et fruits de la pampa d’interfluves. - Arboriculture sur huerta d’inférofluse à l’amont, et cultures saisonnières sur les lits intermittents et petit élevage caprin sur l’algarrobal des interfluves. - Cultures commerciales d’irrigation permanente par dérivation des eaux de la sierra et maintien d’un petit élevage de despoblado. Trois étapes de la colonisation du Piura. Mais la dernière, si elle permet de supporter une forte densité paysanne, ne peut éviter les conséquences des fortes pluies exceptionnelles. COLONIZACIÓN HUMANA Y DESARROLLO SOBRE FRONTERA ECOLÓGICA. EL DESPOBLADO, EL SAHEL DE PIURA, NORTE-PERÚ. El despoblado de Piura es una formación vegetal mixta, arboleda y savana ocasional, un sahel que, a pesar de lluvias muy irregulares, combina varios recursos complementarios. Ésos fueron aprovechados distintamente a medida de la intervención de nuevas técnicas. - Recolección de raíces y frutas en las pampas de las planicies secas - Arboricultura en las huertas de las cabezas de conos torrenciales y cultura estacional sobre los cauces inundables de las quebradas, aguas abajo, y cría de cabras y asnos en el algarrobal de las pampas - Cultivos comerciales de riego permanente por desvío de aguas de los grandes ríos de la sierra, y permanencia de la ganadería de caprinos sobre las pampas del despoblado. Son tres etapas del asentamiento humano. Pero la última, si tiene la ventaja de soportar grandes densidades campesinas, no puede arrastrar el peligro de las lluvias excepcionales. HUMAN SETTLING AND DEVELOPMENT ON AN ECOLOGIC FRONTIERS. THE DESPOBLADO, THE SAHEL OF SEPTENTRIONAL PIURA-PERU. A Piura

Local Vegetation Trends in the Sahel of Mali and Senegal Using Long Time Series FAPAR Satellite Products and Field Measurement (1982–2010

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Martin Brandt

2014-03-01

Full Text Available Local vegetation trends in the Sahel of Mali and Senegal from Geoland Version 1 (GEOV1 (5 km and the third generation Global Inventory Modeling and Mapping Studies (GIMMS3g (8 km Fraction of Absorbed Photosynthetically Active Radiation (FAPAR time series are studied over 29 years. For validation and interpretation of observed greenness trends, two methods are applied: (1 a qualitative approach using in-depth knowledge of the study areas and (2 a quantitative approach by time series of biomass observations and rainfall data. Significant greening trends from 1982 to 2010 are consistently observed in both GEOV1 and GIMMS3g FAPAR datasets. Annual rainfall increased significantly during the observed time period, explaining large parts of FAPAR variations at a regional scale. Locally, GEOV1 data reveals a heterogeneous pattern of vegetation change, which is confirmed by long-term ground data and site visits. The spatial variability in the observed vegetation trends in the Sahel area are mainly caused by varying tree- and land-cover, which are controlled by human impact, soil and drought resilience. A large proportion of the positive trends are caused by the increment in leaf biomass of woody species that has almost doubled since the 1980s due to a tree cover regeneration after a dry-period. This confirms the re-greening of the Sahel, however, degradation is also present and sometimes obscured by greening. GEOV1 as compared to GIMMS3g made it possible to better characterize the spatial pattern of trends and identify the degraded areas in the study region.

Rebuilding Resilience in the Sahel: Regreening in the Maradi and Zinder Regions of Niger

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Jan Sendzimir

2011-09-01

Full Text Available The societies and ecosystems of the Nigerien Sahel appeared increasingly vulnerable to climatic and economic uncertainty in the late twentieth century. Severe episodes of drought and famine drove massive livestock losses and human migration and mortality. Soil erosion and tree loss reduced a woodland to a scrub steppe and fed a myth of the Sahara desert relentlessly advancing southward. Over the past two decades this myth has been shattered by the dramatic reforestation of more than 5 million hectares in the Maradi and Zinder Regions of Niger. No single actor, policy, or practice appears behind this successful regreening of the Sahel. Multiple actors, institutions and processes operated at different levels, times, and scales to initiate and sustain this reforestation trend. We used systems analysis to examine the patterns of interaction as biophysical, livelihood, and governance indicators changed relative to one another during forest decline and rebound. It appears that forest decline was reversed when critical interventions helped to shift the direction of reinforcing feedbacks, e.g., vicious cycles changed to virtuous ones. Reversals toward de-forestation or reforestation were preceded by institutional changes in governance, then livelihoods and eventually in the biophysical environment. Biophysical change sustained change in the other two domains until interventions introduced new ideas and institutions that slowed and then reversed the pattern of feedbacks. However, while society seems better at coping with economic or climatic shock or stress, the resilience of society and nature in the Maradi/Zinder region to global sources of uncertainty remains a pressing question in a society with one of the highest population growth rates on Earth.

The impact of Southern Atlantic moisture source in the precipitation regime of Sahel and Brazilian Nordeste using lagrangian models

Science.gov (United States)

Drumond, A.; Nieto, R.; Gimeno, L.; Ambrizzi, T.; Trigo, R.

2009-04-01

The socio-economical problems related to the severe droughts observed over Brazilian "Nordeste" and Sahel are well known nowadays. Several studies have showed that the precipitation regimes over these regions are influenced by the Inter Tropical Convergence Zone (ITCZ) variability, which can be related with the climatic variations observed in the South and North Tropical Atlantic basins. However, a climatological detailed assessment of the annual cycle of the oceanic moisture contribution to both these regions is still needed in order to get a better understanding of their precipitation regimes and variability. To answer this question, a climatological seasonal analysis of the moisture supply from the South Atlantic to the precipitation in the "Nordeste" and Sahel was performed using a new Lagrangian method of diagnosis which identifies the humidity contributions to the moisture budget over a region. The applied methodology computes budgets of evaporation minus precipitation by calculating changes in the specific humidity along forward-trajectories for the following 10 days. In order to take into account distinct regional contributions we have divided the South Atlantic basin in several latitudinal bands (with a 5° width), and all air-masses residing over each region were tracked forward using the available 5-year dataset (2000-2004). For the Sahel, the preliminary results suggest that the oceanic band northwards 10 degrees south acts as a moisture source for the precipitation along the year and its contribution reaches the maximum during the austral winter, probably related to the ITCZ annual migration over the region. On the other hand, the precipitation over "Nordeste" can be better related to air masses emanating from the oceanic bands between 10 and 20 degrees south. However the response over the region is very heterogeneous spatially and temporally probably due to the high variability of the local climate characteristics. In order to clarify dynamically the

U.S. Army Civil Affairs Forces in the Sahel: Developing an Approach to Building Relevant Partner Capacity in Support of U.S. Africa Command

Science.gov (United States)

2015-06-12

There will likely be similar challenges within military institutions of Sahel nations. Cultural relativism posits that all religious, ethical , aesthetic...issues of cultural relativism and legality. Since independence, African nations have struggled to adopt borders and systems imposed by outsiders...

The Sahel Region of West Africa: Examples of Climate Analyses Motivated By Drought Management Needs

Science.gov (United States)

Ndiaye, O.; Ward, M. N.; Siebert, A. B.

2011-12-01

The Sahel is one of the most drought-prone regions in the world. This paper focuses on climate sources of drought, and some new analyses mostly driven by users needing climate information to help in drought management strategies. The Sahel region of West Africa is a transition zone between equatorial climate and vegetation to the south, and desert to the north. The climatology of the region is dominated by dry conditions for most of the year, with a single peak in rainfall during boreal summer. The seasonal rainfall total contains both interannual variability and substantial decadal to multidecadal variability (MDV). This brings climate analysis and drought management challenges across this range of timescales. The decline in rainfall from the wet decades of the 1950s and 60s to the dry decades of the 1970s and 80s has been well documented. In recent years, a moderate recovery has emerged, with seasonal totals in the period 1994-2010 significantly higher than the average rainfall 1970-1993. These MDV rainfall fluctuations have expression in large-scale sea-surface temperature fluctuations in all ocean basins, placing the changes in drought frequency within broader ocean-atmosphere climate fluctuation. We have evaluated the changing character of low seasonal rainfall total event frequencies in the Sahel region 1950-2010, highlighting the role of changes in the mean, variance and distribution shape of seasonal rainfall totals as the climate has shifted through the three observed phases. We also consider the extent to which updating climate normals in real-time can damp the bias in expected event frequency, an important issue for the feasibility of index insurance as a drought management tool in the presence of a changing climate. On the interannual timescale, a key factor long discussed for agriculture is the character of rainfall onset. An extended dry spell often occurs early in the rainy season before the crop is fully established, and this often leads to crop

Soil Management Practices to Improve Nutrient-use Efficiencies and Reduce Risk in Millet-based Cropping Systems in the Sahel

Directory of Open Access Journals (Sweden)

Koala, S.

2003-01-01

Full Text Available Low soil fertility and moisture deficit are among the main constraints to sustainable crop yields in the Sahel. A study therefore, was conducted at the ICRISAT Sahelian Center, Sadore in Niger to test the hypothesis that integrated soil husbandry practices consisting of manure, fertilizer and crop residues in rotational cropping systems use organic and mineral fertilizes efficiently, thereby resulting in higher yields and reduced risk. Results from an analysis of variance showed that choice of cropping systems explained more than 50% of overall variability in millet and cowpea grain yields. Among the cropping systems, rotation gave higher yields than sole crop and intercropping systems and increased millet yield by 46% without fertilizer. Rainfall-use efficiency and partial factor productivity of fertilizer were similarly higher in rotations than in millet monoculture system. Returns from cowpea grown in cowpea-millet rotation without fertilizer and the medium rates of fertilizers (4 kg P.ha-1 + 15 kg N.ha-1 were found to be most profitable in terms of high returns and low risk, principally because of a higher price of cowpea than millet. The study recommends crop diversification, either in the form of rotations or relay intercropping systems for the Sahel as an insurance against total crop failure.

Applying Customized Climate Advisory Information to Translate Extreme Rainfall Events into Farming Options in the Sudan-Sahel of West Africa

Science.gov (United States)

Salack, S.; Worou, N. O.; Sanfo, S.; Nikiema, M. P.; Boubacar, I.; Paturel, J. E.; Tondoh, E. J.

2017-12-01

In West Africa, the risk of food insecurity linked to the low productivity of small holder farming increases as a result of rainfall extremes. In its recent evolution, the rainy season in the Sudan-Sahel zone presents mixed patterns of extreme climatic events. In addition to intense rain events, the distribution of events is associated with pockets of intra-seasonal long dry spells. The negative consequences of these mixed patterns are obvious on the farm: soil water logging, erosion of arable land, dwartness and dessication of crops, and loss in production. The capacity of local farming communities to respond accordingly to rainfall extreme events is often constrained by lack of access to climate information and advisory on smart crop management practices that can help translate extreme rainfall events into farming options. The objective of this work is to expose the framework and the pre-liminary results of a scheme that customizes climate-advisory information package delivery to subsistence farmers in Bakel (Senegal), Ouahigouya & Dano (Burkina Faso) and Bolgatanga (Ghana) for sustainable family agriculture. The package is based on the provision of timely climate information (48-hours, dekadal & seasonal) embedded with smart crop management practices to explore and exploite the potential advantage of intense rainfall and extreme dry spells in millet, maize, sorghum and cowpea farming communities. It is sent via mobile phones and used on selected farms (i.e agro-climatic farm schools) on which some small on-farm infrastructure were built to alleviate negative impacts of weather. Results provide prominent insight on how co-production of weather/climate information, customized access and guidiance on its use can induce fast learning (capacity building of actors), motivation for adaptation, sustainability, potential changes in cropping system, yields and family income in the face of a rainfall extremes at local scales of Sudan-Sahel of West Africa. Keywords: Climate

The historical spread of Arabian Pastoralists to the eastern African Sahel evidenced by the lactase persistence -13,915*G allele and mitochondrial DNA

Czech Academy of Sciences Publication Activity Database

Priehodová, E.; Austerlitz, F.; Čížková, M.; Mokhtar, M. G.; Poloni, E. S.; Černý, Viktor

2017-01-01

Roč. 29, č. 3 (2017), č. článku e22950. ISSN 1042-0533 R&D Projects: GA ČR GA13-37998S Institutional support: RVO:67985912 Keywords : lactase persistence * Arabs * pastoralism * African Sahel Subject RIV: AC - Archeology, Anthropology, Ethnology OBOR OECD: Archaeology Impact factor: 1.780, year: 2016

Evaluating water controls on vegetation growth in the semi-arid sahel using field and earth observation data

DEFF Research Database (Denmark)

Abdi, Abdulhakim M.; Boke-Olen, Niklas; Tenenbaum, David E.

2017-01-01

Water loss is a crucial factor for vegetation in the semi-arid Sahel region of Africa. Global satellite-driven estimates of plant CO2 uptake (gross primary productivity, GPP) have been found to not accurately account for Sahelian conditions, particularly the impact of canopy water stress. Here, we...... identify the main biophysical limitations that induce canopy water stress in Sahelian vegetation and evaluate the relationships between field data and Earth observation-derived spectral products for up-scaling GPP. We find that plant-available water and vapor pressure deficit together control the GPP...

Climate variability and environmental stress in the Sudan-Sahel zone of West Africa

DEFF Research Database (Denmark)

Mertz, Ole; D'haen, Sarah Ann Lise; Maiga, Abdou

2012-01-01

Environmental change in the Sudan-Sahel region of West Africa (SSWA) has been much debated since the droughts of the 1970s. In this article we assess climate variability and environmental stress in the region. Households in Senegal, Mali, Burkina Faso, Niger, and Nigeria were asked about climatic...... to household perceptions, observed rainfall patterns showed an increasing trend over the past 20 years. However, August rainfall declined, and could therefore potentially explain the contrasting negative household perceptions of rainfall trends. Most households reported degradation of soils, water resources......, vegetation, and fauna, but more so in the 500–900 mm zones. Adaptation measures to counter environmental degradation included use of manure, reforestation, soil and water conservation, and protection of fauna and vegetation. The results raise concerns for future environmental management in the region...

Rôle et place de la chèvre dans les ménages du Sahel burkinabé

OpenAIRE

Gnanda, BI.; Wereme N'Diaye, A.; O. Sanon, H.; Somda, J.; Nianogo, JA.

2016-01-01

Role and Position of the Goat in Households of the Burkinabian Sahel. A formal household survey was carried out in Burkina Faso with 150 Sahelian farms in order to appreciate the role and the position of goat breeding in the life and the functioning of these family units. The results of the investigation show that the Burkinabe Sahelian stockbreeders first start usually by raising a goat, because of its high prolificacy, but with the view to acquire more or less rapidly other species of rumin...

The Role of Meteorology and Surface Condition to Multi-Decadal Variations of Dust Emission in Sahara and Sahel

Science.gov (United States)

Kim, D.; Chin, M.; Diehl, T. L.; Bian, H.; Brown, M. E.; Remer, L. A.; Stockwell, W. R.

2014-12-01

North Africa is the world's largest dust source region influencing regional and global climate, human health, and even the local economy. However North Africa as a dust source is not uniform but it consists of the arid region (Sahara) and the semi-arid region (Sahel) with emission rates depending on meteorological and surface conditions. Several recent studies have shown that dust from North Africa seems to have a decreasing trend in the past three decades. The goal of this study is to better understand the controlling factors that determine the change of dust in North Africa using observational data and model simulations. First we analyze surface bareness conditions determined from a long-term satellite observed Normalized Difference Vegetation Index for 1980-2008. Then we examine the key meteorological variables of precipitation and surface winds. Modeling experiments were conducted using the NASA Goddard Chemistry Aerosol Radiation and Transport (GOCART) model, which has been recently updated with a dynamic dust source function. Using the method we separate the dust originating from the Sahel from that of the Sahara desert. We find that the surface wind speed is the most dominant factor affecting Sahelian dust emission while vegetation has a modulating effect. We will show regional differences in meteorological variables, surface conditions, dust emission, and dust distribution and address the relationships among meteorology, surface conditions, and dust emission/loading in the past three decades (1980-2008).

Woody Vegetation Die off and Regeneration in Response to Rainfall Variability in the West African Sahel

Directory of Open Access Journals (Sweden)

Martin Brandt

2017-01-01

Full Text Available The greening in the Senegalese Sahel has been linked to an increase in net primary productivity, with significant long-term trends being closely related to the woody strata. This study investigates woody plant growth and mortality within greening areas in the pastoral areas of Senegal, and how these dynamics are linked to species diversity, climate, soil and human management. We analyse woody cover dynamics by means of multi-temporal and multi-scale Earth Observation, satellite based rainfall and in situ data sets covering the period 1994 to 2015. We find that favourable conditions (forest reserves, low human population density, sufficient rainfall led to a rapid growth of Combretaceae and Balanites aegyptiaca between 2000 and 2013 with an average increase of 4% woody cover. However, the increasing dominance and low drought resistance of drought prone species bears the risk of substantial woody cover losses following drought years. This was observed in 2014–2015, with a die off of Guiera senegalensis in most places of the study area. We show that woody cover and woody cover trends are closely related to mean annual rainfall, but no clear relationship with rainfall trends was found over the entire study period. The observed spatial and temporal variation contrasts with the simplified labels of “greening” or “degradation”. While in principal a low woody plant diversity negatively impacts regional resilience, the Sahelian system is showing signs of resilience at decadal time scales through widespread increases in woody cover and high regeneration rates after periodic droughts. We have reaffirmed that the woody cover in Sahel responds to its inherent climatic variability and does not follow a linear trend.

Woody vegetation die off and regeneration in response to rainfall variability in the west African Sahel

Science.gov (United States)

Brandt, Martin; Tappan, G. Gray; Aziz Diouf, Abdoul; Beye, Gora; Mbow, Cheikh; Fensholt, Rasmus

2017-01-01

The greening in the Senegalese Sahel has been linked to an increase in net primary productivity, with significant long-term trends being closely related to the woody strata. This study investigates woody plant growth and mortality within greening areas in the pastoral areas of Senegal, and how these dynamics are linked to species diversity, climate, soil and human management. We analyse woody cover dynamics by means of multi-temporal and multi-scale Earth Observation, satellite based rainfall and in situ data sets covering the period 1994 to 2015. We find that favourable conditions (forest reserves, low human population density, sufficient rainfall) led to a rapid growth of Combretaceae and Balanites aegyptiaca between 2000 and 2013 with an average increase of 4% woody cover. However, the increasing dominance and low drought resistance of drought prone species bears the risk of substantial woody cover losses following drought years. This was observed in 2014–2015, with a die off of Guiera senegalensis in most places of the study area. We show that woody cover and woody cover trends are closely related to mean annual rainfall, but no clear relationship with rainfall trends was found over the entire study period. The observed spatial and temporal variation contrasts with the simplified labels of “greening” or “degradation”. While in principal a low woody plant diversity negatively impacts regional resilience, the Sahelian system is showing signs of resilience at decadal time scales through widespread increases in woody cover and high regeneration rates after periodic droughts. We have reaffirmed that the woody cover in Sahel responds to its inherent climatic variability and does not follow a linear trend.

The hydrogeological conditions in Sahel Hasheesh, Eastern Desert, Eg

Directory of Open Access Journals (Sweden)

Mohamed A. Abdalla

2016-06-01

Full Text Available The groundwater development in Egypt in the present time is of a vital importance than in past few years. A comprehensive plan for new land reclamation projects has been recently established. To achieve these plans new sources of water must be available. This has been done by conducting a number of VES’S where interpreted by a comparison with the existing drilled borehole soil samples. The optimum resistivity model is obtained by matching method using “IPI2Win” Moscow State University 2000 software computer programs for resistivity interpretation. The results of the quantitative interpretation of the resistivity curves has been represented as geoelectric sections, showing the thickness and true electric resistivity values of the different geoelectric layers. The results of quantitative interpretation of the vertical electrical soundings show subsurface five geoelectric units and the aquifer system belongs to lower Miocene and the total salinity of 2451.2 ppm. The depth to water surface is 88.05 m and the total dissolved solids are 2451.2 ppm (Mekhemer well. The salt assemblages in Sahel Hasheesh are NaCl, MgCl2, MgSO4, CaSO4, Ca(HCO32. This marine water is of brackish sodium chloride water type (NaCl.

The hydrogeological conditions in Sahel Hasheesh, Eastern Desert, Eg

Science.gov (United States)

Abdalla, Mohamed A.; Mekhemer, Hatem M.; Mabrou, Walid Abdallah

2016-06-01

The groundwater development in Egypt in the present time is of a vital importance than in past few years. A comprehensive plan for new land reclamation projects has been recently established. To achieve these plans new sources of water must be available. This has been done by conducting a number of VES'S where interpreted by a comparison with the existing drilled borehole soil samples. The optimum resistivity model is obtained by matching method using "IPI2Win" Moscow State University 2000 software computer programs for resistivity interpretation. The results of the quantitative interpretation of the resistivity curves has been represented as geoelectric sections, showing the thickness and true electric resistivity values of the different geoelectric layers. The results of quantitative interpretation of the vertical electrical soundings show subsurface five geoelectric units and the aquifer system belongs to lower Miocene and the total salinity of 2451.2 ppm. The depth to water surface is 88.05 m and the total dissolved solids are 2451.2 ppm (Mekhemer well). The salt assemblages in Sahel Hasheesh are NaCl, MgCl2, MgSO4, CaSO4, Ca(HCO3)2. This marine water is of brackish sodium chloride water type (NaCl).

Koranic Education Centres: A viable educational alternative for the disadvantaged learner in Sahel Africa?

Science.gov (United States)

Bah-Lalya, Ibrahima

2015-08-01

Within the international momentum for achieving Education for All (EFA) and the Millennium Development Goals (MDGs), many African countries have made considerable progress during the last decade in terms of access to basic education. However, a significant number of children enrolled in the early grades of primary schools either repeat classes or drop out and never graduate. Moreover, there are currently about 30 million school-age children in sub-Saharan Africa who have never attended any form of schooling. In view of this situation, sub-Saharan African countries have been looking for alternative options to educate those who have not been accounted for in the formal school system. This note considers informal Koranic Education Centres (KECs) which are trying to fill the gap of schooling in the Sahel-Saharan strip. The author looks at the challenges this form of schooling faces and at how to meet them efficiently. He sounds out the possibility of using KECs to cater for those who have been left aside by formal schooling. Based on existing studies, data compiled by educational systems and a study conducted by the Working Group on Non-Formal Education (WGNFE) of the Association for the Development of Education in Africa (ADEA) in four West African countries (Burkina Faso, Mali, Mauritania and Senegal) in 2013, the author of this research note came to the conclusion that a holistic approach, where the two systems (the Koranic and the formal) collaborate and support one another, could effectively contribute to alleviating the dropout predicament and to reducing the number of unschooled children. It could offer a second-chance opportunity to dropout and unschooled children in the Sahel and Saharan zone. However, before this can become a viable alternative, a number of major challenges need to be addressed. Through its WGNFE, ADEA intends to further investigate the holistic approach of combining formal "modern" and informal "Koranic" schooling to come up with tangible

Mapping regional livelihood benefits from local ecosystem services assessments in rural Sahel.

Science.gov (United States)

Malmborg, Katja; Sinare, Hanna; Enfors Kautsky, Elin; Ouedraogo, Issa; Gordon, Line J

2018-01-01

Most current approaches to landscape scale ecosystem service assessments rely on detailed secondary data. This type of data is seldom available in regions with high levels of poverty and strong local dependence on provisioning ecosystem services for livelihoods. We develop a method to extrapolate results from a previously published village scale ecosystem services assessment to a higher administrative level, relevant for land use decision making. The method combines remote sensing (using a hybrid classification method) and interviews with community members. The resulting landscape scale maps show the spatial distribution of five different livelihood benefits (nutritional diversity, income, insurance/saving, material assets and energy, and crops for consumption) that illustrate the strong multifunctionality of the Sahelian landscapes. The maps highlight the importance of a diverse set of sub-units of the landscape in supporting Sahelian livelihoods. We see a large potential in using the resulting type of livelihood benefit maps for guiding future land use decisions in the Sahel.

Mapping regional livelihood benefits from local ecosystem services assessments in rural Sahel

Science.gov (United States)

Sinare, Hanna; Enfors Kautsky, Elin; Ouedraogo, Issa; Gordon, Line J.

2018-01-01

Most current approaches to landscape scale ecosystem service assessments rely on detailed secondary data. This type of data is seldom available in regions with high levels of poverty and strong local dependence on provisioning ecosystem services for livelihoods. We develop a method to extrapolate results from a previously published village scale ecosystem services assessment to a higher administrative level, relevant for land use decision making. The method combines remote sensing (using a hybrid classification method) and interviews with community members. The resulting landscape scale maps show the spatial distribution of five different livelihood benefits (nutritional diversity, income, insurance/saving, material assets and energy, and crops for consumption) that illustrate the strong multifunctionality of the Sahelian landscapes. The maps highlight the importance of a diverse set of sub-units of the landscape in supporting Sahelian livelihoods. We see a large potential in using the resulting type of livelihood benefit maps for guiding future land use decisions in the Sahel. PMID:29389965

Mapping regional livelihood benefits from local ecosystem services assessments in rural Sahel.

Directory of Open Access Journals (Sweden)

Katja Malmborg

Full Text Available Most current approaches to landscape scale ecosystem service assessments rely on detailed secondary data. This type of data is seldom available in regions with high levels of poverty and strong local dependence on provisioning ecosystem services for livelihoods. We develop a method to extrapolate results from a previously published village scale ecosystem services assessment to a higher administrative level, relevant for land use decision making. The method combines remote sensing (using a hybrid classification method and interviews with community members. The resulting landscape scale maps show the spatial distribution of five different livelihood benefits (nutritional diversity, income, insurance/saving, material assets and energy, and crops for consumption that illustrate the strong multifunctionality of the Sahelian landscapes. The maps highlight the importance of a diverse set of sub-units of the landscape in supporting Sahelian livelihoods. We see a large potential in using the resulting type of livelihood benefit maps for guiding future land use decisions in the Sahel.

The effect of a dynamic background albedo scheme on Sahel/Sahara precipitation during the mid-Holocene

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F. S. E. Vamborg

2011-02-01

Full Text Available We have implemented a new albedo scheme that takes the dynamic behaviour of the surface below the canopy into account, into the land-surface scheme of the MPI-ESM. The standard (static scheme calculates the seasonal canopy albedo as a function of leaf area index, whereas the background albedo is a gridbox constant derived from satellite measurements. The new (dynamic scheme additionally models the background albedo as a slowly changing function of organic matter in the ground and of litter and standing dead biomass covering the ground. We use the two schemes to investigate the interactions between vegetation, albedo and precipitation in the Sahel/Sahara for two time-slices: pre-industrial and mid-Holocene. The dynamic scheme represents the seasonal cycle of albedo and the correspondence between annual mean albedo and vegetation cover in a more consistent way than the static scheme. It thus gives a better estimate of albedo change between the two time periods. With the introduction of the dynamic scheme, precipitation is increased by 30 mm yr⁻¹ for the pre-industrial simulation and by about 80 mm yr⁻¹ for the mid-Holocene simulation. The present-day dry bias in the Sahel of standard ECHAM5 is thus reduced and the sensitivity of precipitation to mid-Holocene external forcing is increased by around one third. The locations of mid-Holocene lakes, as estimated from reconstructions, lie south of the modelled desert border in both mid-Holocene simulations. The magnitude of simulated rainfall in this area is too low to fully sustain lakes, however it is captured better with the dynamic scheme. The dynamic scheme leads to increased vegetation variability in the remaining desert region, indicating a higher frequency of green spells, thus reaching a better agreement with the vegetation distribution as derived from pollen records.

Revisiting the coupling between NDVI trends and cropland changes in the Sahel drylands

DEFF Research Database (Denmark)

Tong, Xiaoye; Brandt, Martin Stefan; Hiernaux, Pierre

2017-01-01

The impact of human activities via land use/cover changes on NDVI trends is critical for an improved understanding of satellite-observed changes in vegetation productivity in drylands. The dominance of positive NDVI trends in the Sahel, the so-called re-greening, is sometimes interpreted...... as a combined effect of an increase in rainfall and cropland expansion or agricultural intensification. Yet, the impact of changes in land use has yet to be thoroughly tested and supported by empirical evidence. At present, no studies have considered the importance of the different seasonal NDVI signals...... of cropped and fallowed fields when interpreting NDVI trends, as both field types are commonly merged into a single ‘cropland’ class. We make use of the distinctly different phenology of cropped and fallowed fields and use seasonal NDVI curves to separate these two field types. A fuzzy classifier is applied...

Impact of aerosols on solar energy production - Scenarios from the Sahel Zone

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Neher, Ina; Meilinger, Stefanie; Crewell, Susanne

2017-04-01

Solar energy is one option to serve the rising global energy demand with low environmental impact. Building an energy system with a considerable share of solar power requires long-term investment and a careful investigation of potential sites. Therefore, understanding the impacts from varying regionally and locally determined meteorological conditions on solar energy production will influence energy yield projections. Aerosols reduce global solar radiation due to absorption and scattering and therewith solar energy yields. Depending on aerosol size distribution they reduce the direct component of the solar radiation and modify the direction of the diffuse component compared to standard atmospheric conditions without aerosols. The aerosol size distribution and composition in the atmosphere is highly variable due to meteorological and land surface conditions. A quantitative assessment of aerosol effects on solar power yields and its relation to land use change is of particular interest for developing countries countries when analyzing the potential of local power production. This study aims to identify the effect of atmospheric aerosols in three different land use regimes, namely desert, urban/polluted and maritime on the tilted plane of photovoltaic energy modules. Here we focus on the Sahel zone, i.e. Niamey, Niger (13.5 N;2.1 E), located at the edge of the Sahara where also detailed measurements of the atmospheric state are available over the year 2006. Guided by observations a model chain is used to determine power yields. The atmospheric aerosol composition will be defined by using the Optical Properties of Aerosols and Clouds (OPAC) library. Direct and diffuse radiation (up- and downward component) are then calculated by the radiative transfer model libRadtran which allows to calculate the diffuse component of the radiance from different azimuth and zenith angles. Then the diffuse radiance will be analytically transformed to an east, south and west facing

Dealing with extreme environmental degradation: stress and marginalization of Sahel dwellers.

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Van Haaften, E H; Van de Vijver, F J

1999-07-01

Psychological aspects of environmental degradation are hardly investigated. In the present study these aspects were examined among Sahel dwellers, who live in environments with different states of degradation. The degradation was assessed in terms of vegetation cover, erosion, and loss of organic matter. Subjects came from three cultural groups: Dogon (agriculturalists, n = 225), Mossi (agriculturalists, n = 914), and Fulani (pastoralists, n = 844). Questionnaires addressing marginalization, locus of control, and coping were administered. Environmental degradation was associated with higher levels of stress, marginalization, passive coping (avoidance), a more external locus of control, and lower levels of active coping (problem solving and support seeking). Compared to agriculturalists, pastoralists showed a stronger variation in all psychological variables across all regions, from the least to the most environmentally degraded. Women showed higher scores of stress, (external) locus of control, problem solving, and support seeking than men. The interaction of gender and region was significant for several variables. It was concluded that environmental degradation has various psychological correlates: people are likely to display an active approach to environmental degradation as long as the level of degradation is not beyond their control.

Effect of pregnancy on some biochemical parameters in Sahel goats in semi-arid zones.

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Sandabe, U K; Mustapha, A R; Sambo, E Y

2004-05-01

The effects of pregnancy on some biochemical parameters were studied using 20 sexually mature, cycling goats with weight range 20-25 kg. They were randomly separated into two groups of 10 animals each. In one group, oestrus was detected while going round with a buck in the morning and evening; a single buck on detection of oestrus mated the does and the does were tagged as pregnant after confirmation of non-return of oestrus. The other group was kept cycling and tagged as non-pregnant. The mean serum glucose concentration in pregnant does was 63.35 +/- 7.70 mg/dl, significantly lower than 71.59 +/- 1.14 mg/dl for non-pregnant does (p 0.05), as did the liver enzymes (ALT, AST). Therefore this study showed that low serum glucose and high cholesterol levels are features of mid to late pregnancy in Sahel goats.

Sahara and Sahel vulnerability to climate changes, lessons from the past

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Lezine, Anne-Marie; Hély, Christelle; Grenier, Christophe; Braconnot, Pascale

2010-05-01

Since the Sahelian drought in the 1970s, climate variability in north tropical Africa has been the subject of intensive research focusing on the functioning of the Atlantic monsoon system as well as on past variations in rainfall from historical and natural archives. An "abrupt" climate change has been recorded off the Mauritanian coast at the end of the African Humid Period (AHP) 5500 years ago illustrating the onset of the modern climate regime [deMenocal et al., 2000]. At lake Yoa in NE Chad, [Kroepelin et al., 2008] report a "gradual" environmental change. Was this change abrupt or gradual, and amplified or not through vegetation change and feedbacks to the atmosphere is still the subject of debate. Here, we compile paleohydrological and palynological data between 10 and 28°N in the Sahara and Sahel with the purpose of understanding the response of the hydrological system and the vegetation cover to rainfall fluctuations from the onset of the AHP. Our data set is extracted from published studies. It is composed of 1651 dated samples from about 420 localities in the present day Sahara and Sahel. The occurrence of high and intermediate lake levels, fluvial terraces and wetlands as well as of dune edification are analysed with a 1000 yr period from 16 000 yrs BP to present. Clear trends are observed in the evolution of paleohydrological indicators versus time and latitude showing the progression of the centre of the distribution of humidity from south to north during the humid period and to the south after the AHP. The humidity maximum is observed with some temporal delay as compared to the June solar radiation maximum at 30°N. The reasons are investigated along the line of pure climate based processes and/or hydrological impacts. Further, the overall coherence among these signals is examined. Using climate simulations for different key periods in the Holocene, we investigate the relative impact of the insolation forcing, of the remnant ice sheet in the early

A Tool for Creating Regionally Calibrated High-Resolution Land Cover Data Sets for the West African Sahel: Using Machine Learning to Scale Up Hand-Classified Maps in a Data-Sparse Environment

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Van Gordon, M.; Van Gordon, S.; Min, A.; Sullivan, J.; Weiner, Z.; Tappan, G. G.

2017-12-01

Using support vector machine (SVM) learning and high-accuracy hand-classified maps, we have developed a publicly available land cover classification tool for the West African Sahel. Our classifier produces high-resolution and regionally calibrated land cover maps for the Sahel, representing a significant contribution to the data available for this region. Global land cover products are unreliable for the Sahel, and accurate land cover data for the region are sparse. To address this gap, the U.S. Geological Survey and the Regional Center for Agriculture, Hydrology and Meteorology (AGRHYMET) in Niger produced high-quality land cover maps for the region via hand-classification of Landsat images. This method produces highly accurate maps, but the time and labor required constrain the spatial and temporal resolution of the data products. By using these hand-classified maps alongside SVM techniques, we successfully increase the resolution of the land cover maps by 1-2 orders of magnitude, from 2km-decadal resolution to 30m-annual resolution. These high-resolution regionally calibrated land cover datasets, along with the classifier we developed to produce them, lay the foundation for major advances in studies of land surface processes in the region. These datasets will provide more accurate inputs for food security modeling, hydrologic modeling, analyses of land cover change and climate change adaptation efforts. The land cover classification tool we have developed will be publicly available for use in creating additional West Africa land cover datasets with future remote sensing data and can be adapted for use in other parts of the world.

Seasonal labour migration strategies in the Sahel: coping with poverty or optimising security?

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Hampshire, K; Randall, S

1999-01-01

This study examined the relationship between seasonal labor migration and poverty for various Fulani populations in the Sahel region of northern Burkina Faso, who represent the spectrum of production systems from pure pastoralism to agropastoralism to cultivation. There is a general trend of rising seasonal labor participation with increasing household wealth; limited financial and human resources mean that families belonging to the lower income population are excluded from this option. However, other ethnic and economic differences among the population compound this picture. Agriculturalists are more likely to migrate than pastoralists, and the Fulani subgroup Fulbe Djelgobe is unlikely to migrate at all unless desperate. The impacts of circular labor also differ. For a few agriculturalists and agropastoralists, migration to the cities is rewarding; for most the gains are small but are still essential. Pastoralists are more likely to experience negative outcomes than agriculturalists. Unless sufficient provision is made to fill in labor deficits in the migrants' absence, the cost of domestic production may seriously outweigh any benefits in the long run.

The paradoxical evolution of runoff in the pastoral Sahel: analysis of the hydrological changes over the Agoufou watershed (Mali) using the KINEROS-2 model

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Gal, Laetitia; Grippa, Manuela; Hiernaux, Pierre; Pons, Léa; Kergoat, Laurent

2017-09-01

In recent decades, the Sahel has witnessed a paradoxical increase in surface water despite a general precipitation decline. This phenomenon, commonly referred to as the Sahelian paradox, is not completely understood yet. The role of cropland expansion due to the increasing food demand by a growing population has been often put forward to explain this situation for the cultivated Sahel. However, this hypothesis does not hold in pastoral areas where the same phenomenon is observed. Several other processes, such as the degradation of natural vegetation following the major droughts of the 1970s and the 1980s, the development of crusted topsoils, the intensification of the rainfall regime and the development of the drainage network, have been suggested to account for this situation. In this paper, a modeling approach is proposed to explore, quantify and rank different processes that could be at play in pastoral Sahel. The kinematic runoff and erosion model (KINEROS-2) is applied to the Agoufou watershed (245 km2), in the Gourma region in Mali, which underwent a significant increase of surface runoff during the last 60 years. Two periods are simulated, the past case (1960-1975) preceding the Sahelian drought and the present case (2000-2015). Surface hydrology and land cover characteristics for these two periods are derived by the analysis of aerial photographs, available in 1956, and high-resolution remote sensing images in 2011. The major changes identified are (1) a partial crusting of isolated dunes, (2) an increase of drainage network density, (3) a marked decrease in vegetation with the nonrecovery of tiger bush and vegetation growing on shallow sandy soils, and (4) important changes in soil properties with the apparition of impervious soils instead of shallow sandy soil. The KINEROS-2 model was parameterized to simulate these changes in combination or independently. The results obtained by this model display a significant increase in annual discharge between the

Investigating the Relationship between the Inter-Annual Variability of Satellite-Derived Vegetation Phenology and a Proxy of Biomass Production in the Sahel

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Michele Meroni

2014-06-01

Full Text Available In the Sahel region, moderate to coarse spatial resolution remote sensing time series are used in early warning monitoring systems with the aim of detecting unfavorable crop and pasture conditions and informing stakeholders about impending food security risks. Despite growing evidence that vegetation productivity is directly related to phenology, most approaches to estimate such risks do not explicitly take into account the actual timing of vegetation growth and development. The date of the start of the season (SOS or of the peak canopy density can be assessed by remote sensing techniques in a timely manner during the growing season. However, there is limited knowledge about the relationship between vegetation biomass production and these variables at the regional scale. This study describes the first attempt to increase our understanding of such a relationship through the analysis of phenological variables retrieved from SPOT-VEGETATION time series of the Fraction of Absorbed Photosynthetically Active Radiation (FAPAR. Two key phenological variables (growing season length (GSL; timing of SOS and the maximum value of FAPAR attained during the growing season (Peak are analyzed as potentially related to a proxy of biomass production (CFAPAR, the cumulative value of FAPAR during the growing season. GSL, SOS and Peak all show different spatial patterns of correlation with CFAPAR. In particular, GSL shows a high and positive correlation with CFAPAR over the whole Sahel (mean r = 0.78. The negative correlation between delays in SOS and CFAPAR is stronger (mean r = −0.71 in the southern agricultural band of the Sahel, while the positive correlation between Peak FAPAR and CFAPAR is higher in the northern and more arid grassland region (mean r = 0.75. The consistency of the results and the actual link between remote sensing-derived phenological parameters and biomass production were evaluated using field measurements of aboveground herbaceous biomass

Linking the sub-Saharan and West Eurasian gene pools: maternal and paternal heritage of the Tuareg nomads from the African Sahel.

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Pereira, Luísa; Cerný, Viktor; Cerezo, María; Silva, Nuno M; Hájek, Martin; Vasíková, Alzbeta; Kujanová, Martina; Brdicka, Radim; Salas, Antonio

2010-08-01

The Tuareg presently live in the Sahara and the Sahel. Their ancestors are commonly believed to be the Garamantes of the Libyan Fezzan, ever since it was suggested by authors of antiquity. Biological evidence, based on classical genetic markers, however, indicates kinship with the Beja of Eastern Sudan. Our study of mitochondrial DNA (mtDNA) sequences and Y chromosome SNPs of three different southern Tuareg groups from Mali, Burkina Faso and the Republic of Niger reveals a West Eurasian-North African composition of their gene pool. The data show that certain genetic lineages could not have been introduced into this population earlier than approximately 9000 years ago whereas local expansions establish a minimal date at around 3000 years ago. Some of the mtDNA haplogroups observed in the Tuareg population were involved in the post-Last Glacial Maximum human expansion from Iberian refugia towards both Europe and North Africa. Interestingly, no Near Eastern mtDNA lineages connected with the Neolithic expansion have been observed in our population sample. On the other hand, the Y chromosome SNPs data show that the paternal lineages can very probably be traced to the Near Eastern Neolithic demic expansion towards North Africa, a period that is otherwise concordant with the above-mentioned mtDNA expansion. The time frame for the migration of the Tuareg towards the African Sahel belt overlaps that of early Holocene climatic changes across the Sahara (from the optimal greening approximately 10 000 YBP to the extant aridity beginning at approximately 6000 YBP) and the migrations of other African nomadic peoples in the area.

Modelling spatial and temporal dynamics of gross primary production in the Sahel from earth-observation-based photosynthetic capacity and quantum efficiency

DEFF Research Database (Denmark)

Tagesson, Håkan Torbern; Ardoe, Jonas; Cappelaere, Bernard

2017-01-01

based on earth observation (EO) (normalized difference vegetation index (NDVI), renormalized difference vegetation index (RDVI), enhanced vegetation index (EVI) and shortwave infrared water stress index (SIWSI)); and (3) to study the applicability of EO upscaled Fopt and α for GPP modelling purposes...... impacted by anthropogenic land use. Upscaled GPP for the Sahel 2001-2014 was 736 ± 39 gCm-2yr-1. This study indicates the strong applicability of EO as a tool for spatially explicit estimates of GPP, Fopt and α incorporating EO-based Fopt and α in dynamic global vegetation models could improve estimates...

The influence of land surface properties on Sahel climate. Part 1: Desertification

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Xue, Yongkang; Shukla, Jagadish

1993-01-01

This is a general circulation model sensitivity study of the physical mechanisms of the effects of desertification on the Sahel drought. The model vegetation types were changed in the prescribed desertification area, which led to changes in the surface characteristics. The model was integrated for three months (June, July, August) with climatological surface conditions (control) and desertification conditions (anomaly) to examine the summer season response to the changed surface conditions. The control and anomaly experiments consisted of five pairs of integrations with different initial conditions and/or sea surface temperature boundary conditions. In the desertification experiment, the moisture flux convergence and rainfall were reduced in the test area and increased to the immediate south of this area. The simulated anomaly dipole pattern was similar to the observed African drought patterns in which the axis of the maximum rainfall shifts to the south. The circulation changes in the desertification experiment were consistent with those observed during sub-Saharan dry years. The tropical easterly jet was weaker and the African easterly jet was stronger than normal. Further, in agreement with the observations, the easterly wave disturbances were reduced in intensity but not in number. Descending motion dominated the desertification area. The surface energy budget and hydrological cycle were also changed substantially in the anomaly experiment.

Climate variability and environmental stress in the Sudan-Sahel zone of West Africa.

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Mertz, Ole; D'haen, Sarah; Maiga, Abdou; Moussa, Ibrahim Bouzou; Barbier, Bruno; Diouf, Awa; Diallo, Drissa; Da, Evariste Dapola; Dabi, Daniel

2012-06-01

Environmental change in the Sudan-Sahel region of West Africa (SSWA) has been much debated since the droughts of the 1970s. In this article we assess climate variability and environmental stress in the region. Households in Senegal, Mali, Burkina Faso, Niger, and Nigeria were asked about climatic changes and their perceptions were compared across north-south and west-east rainfall gradients. More than 80% of all households found that rainfall had decreased, especially in the wettest areas. Increases in wind speeds and temperature were perceived by an overall 60-80% of households. Contrary to household perceptions, observed rainfall patterns showed an increasing trend over the past 20 years. However, August rainfall declined, and could therefore potentially explain the contrasting negative household perceptions of rainfall trends. Most households reported degradation of soils, water resources, vegetation, and fauna, but more so in the 500-900 mm zones. Adaptation measures to counter environmental degradation included use of manure, reforestation, soil and water conservation, and protection of fauna and vegetation. The results raise concerns for future environmental management in the region, especially in the 500-900 mm zones and the western part of SSWA.

Remote sensing of desert dust aerosols over the Sahel : potential use for health impact studies

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Deroubaix, A. D.; Martiny, N. M.; Chiapello, I. C.; Marticorena, B. M.

2012-04-01

Since the end of the 70's, remote sensing monitors the desert dust aerosols due to their absorption and scattering properties and allows to make long time series which are necessary for air quality or health impact studies. In the Sahel, a huge health problem is the Meningitis Meningococcal (MM) epidemics that occur during the dry season : the dust has been suspected to be crucial to understand their onsets and dynamics. The Aerosol absorption Index (AI) is a semi-quantitative index derived from TOMS and OMI observations in the UV available at a spatial resolution of 1° (1979-2005) and 0.25° (2005-today) respectively. The comparison of the OMI-AI and AERONET Aerosol Optical thickness (AOT) shows a good agreement at a daily time-step (correlation ~0.7). The comparison of the OMI-AI with the Particle Matter (PM) measurement of the Sahelian Dust Transect is lower (~0.4) at a daily time-step but it increases at a weekly time-step (~0.6). The OMI-AI reproduces the dust seasonal cycle over the Sahel and we conclude that the OMI-AI product at a 0.25° spatial resolution is suitable for health impact studies, especially at a weekly epidemiological time-step. Despite the AI is sensitive to the aerosol altitude, it provides a daily spatial information on dust. A preliminary investigation analysis of the link between weekly OMI AI and weekly WHO epidemiological data sets is presented in Mali and Niger, showing a good agreement between the AI and the onset of the MM epidemics with a constant lag (between 1 and 2 week). The next of this study is to analyse a deeper AI time series constituted by TOMS and OMI data sets. Based on the weekly ratios PM/AI at 2 stations of the Sahelian Dust Transect, a spatialized proxy for PM from the AI has been developed. The AI as a proxy for PM and other climate variables such as Temperature (T°), Relative Humidity (RH%) and the wind (intensity and direction) could then be used to analyze the link between those variables and the MM epidemics

[Population resettlement and women's changing roles in the Sahel].

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Ouedraogo, D O

1992-01-01

For many decision makers in the Sahel, relocating populations from poor, over-populated regions to relatively fertile zones regulated by the state seemed the best approach to improving women's conditions, particularly in household affairs. In the original territories, women have their personal fields where they raise vegetables and other products which they sell to secure their own income. During the dry season, they engage in other activities for money (e.g., production and sale of millet beer and sale of pottery). Women have relative economic autonomy. Within the family household and in villages, they isolate themselves in their own spaces (e.g., kitchen and wells) and discuss their specific problems. In government-controlled zones where families resettle, the families are supposed to plant the same varieties of imposed cultivation (e.g., rice) judged to be more productive. They must sow, plow, and harvest using the same techniques. All activities are controlled. Women have no decision power and must submit to the logic of the chief of agricultural production. They no longer have time to dedicate themselves to individual economic activity (especially in irrigated zones, where there are two annual plantings), or to assure a good education for their children. They have little time to dedicate to hygiene and nutrition. These government-controlled agricultural zones have established an exploitation model that contributes to the socioeconomic destabilization of families. The retreat of women's economic power is often accompanied by degradation of family well-being. Agricultural development schemes that involve agricultural migrations have marginalized women even more than they were before resettlement in spite of improvement in family income. It is narrowly linked to short-term development. In conclusion, agricultural resettlement schemes do not improve the status of women.

Accelerating improvements in nutritional and health status of young children in the Sahel region of Sub-Saharan Africa: review of international guidelines on infant and young child feeding and nutrition.

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Wuehler, Sara E; Hess, Sonja Y; Brown, Kenneth H

2011-04-01

The United Nations Convention on the Rights of the Child holds governments responsible to ensure children's right to the highest attainable standard of health by providing breastfeeding support, and access to nutritious foods, appropriate health care, and clean drinking water. International experts have identified key child care practices and programmatic activities that are proven to be effective at reducing infant and young child undernutrition, morbidity, and mortality. Nevertheless, progress towards reducing the prevalence of undernutrition has been sporadic across countries of the Sahel sub-region of Sub-Saharan Africa. In view of this uneven progress, a working group of international agencies was convened to 'Reposition children's right to adequate nutrition in the Sahel.' The first step towards this goal was to organize a situational analysis of the legislative, research, and programmatic activities related to infant and young child nutrition (IYCN) in six countries of the sub-region: Burkina Faso, Chad, Mali, Mauritania, Niger, and Senegal. The purposes of this introductory paper are to review current information concerning the nutritional and health status of infants and young children in the Sahel and to summarize international guidelines on optimal IYCN practices. These guidelines were used in completing the above-mentioned situational analyses and encompass specific recommendations on: (i) breastfeeding (introduction within the first hour after birth, exclusivity to 6 months, continuation to at least 24 months); (ii) complementary feeding (introduction at 6 months, use of nutrient dense foods, adequate frequency and consistency, and responsive feeding); (iii) prevention and/or treatment of micronutrient deficiencies (vitamin A, zinc, iron and anaemia, and iodine); (iv) prevention and/or treatment of acute malnutrition; (v) feeding practices adapted to the maternal situation to reduce mother-to-child transmission of HIV; (vi) activities to ensure food

Sequía, inmigración y políticas locales: el Sahel en la encrucijada del desarrollo

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Sara Nso

2008-10-01

Full Text Available Este artículo trata de delimitar los principales factores socio-económicos y políticos que ponen en relación desertificación y flujos migratorios internacionales, en el área Sahel. A través del estudio -no exhaustivo para todos los países de la muestra, por ausencia de datos disponibles- de dichas realidades en Burkina Faso, Gambia, Guinea-Bissau, Guinea, Malí, Mauritania, Níger y Senegal, el análisis del elemento local será privilegiado, sin despreciar por ello el valor de las dinámicas regionales. Desde una perspectiva "transnacionalista", se aportarán así las claves para la comprensión global de la problemática saheliana, con el objetivo de sacar a esta región de la encrucijada del subdesarrollo.

Statistical relationship between surface PM10 concentration and aerosol optical depth over the Sahel as a function of weather type, using neural network methodology

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Yahi, H.; Marticorena, B.; Thiria, S.; Chatenet, B.; Schmechtig, C.; Rajot, J. L.; Crepon, M.

2013-12-01

work aims at assessing the capability of passive remote-sensed measurements such as aerosol optical depth (AOD) to monitor the surface dust concentration during the dry season in the Sahel region (West Africa). We processed continuous measurements of AODs and surface concentrations for the period (2006-2010) in Banizoumbou (Niger) and Cinzana (Mali). In order to account for the influence of meteorological condition on the relationship between PM10 surface concentration and AOD, we decomposed the mesoscale meteorological fields surrounding the stations into five weather types having similar 3-dimensional atmospheric characteristics. This classification was obtained by a clustering method based on nonlinear artificial neural networks, the so-called self-organizing map. The weather types were identified by processing tridimensional fields of meridional and zonal winds and air temperature obtained from European Centre for Medium-Range Weather Forecasts (ECMWF) model output centered on each measurement station. Five similar weather types have been identified at the two stations. Three of them are associated with the Harmattan flux; the other two correspond to northward inflow of the monsoon flow at the beginning or the end of the dry season. An improved relationship has been found between the surface PM10 concentrations and the AOD by using a dedicated statistical relationship for each weather type. The performances of the statistical inversion computed on the test data sets show satisfactory skills for most of the classes, much better than a linear regression. This should permit the inversion of the mineral dust concentration from AODs derived from satellite observations over the Sahel.

Long-Term Monitoring of Water Dynamics in the Sahel Region Using the Multi-Sar

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Bertram, A.; Wendleder, A.; Schmitt, A.; Huber, M.

2016-06-01

Fresh water is a scarce resource in the West-African Sahel region, seasonally influenced by droughts and floods. Particularly in terms of climate change, the importance of wetlands increases for flora, fauna, human population, agriculture, livestock and fishery. Hence, access to open water is a key factor. Long-term monitoring of water dynamics is of great importance, especially with regard to the spatio-temporal extend of wetlands and drylands. It can predict future trends and facilitate the development of adequate management strategies. Lake Tabalak, a Ramsar wetland of international importance, is one of the most significant ponds in Niger and a refuge for waterbirds. Nevertheless, human population growth increased the pressure on this ecosystem, which is now degrading for all uses. The main objective of the study is a long-term monitoring of the Lake Tabalak's water dynamics to delineate permanent and seasonal water bodies, using weather- and daytime-independent multi-sensor and multi-temporal Synthetic Aperture Radar (SAR) data available for the study area. Data of the following sensors from 1993 until 2016 are used: Sentinel-1A, TerraSARX, ALOS PALSAR-1/2, Envisat ASAR, RADARSAT-1/2, and ERS-1/2. All SAR data are processed with the Multi-SAR-System, unifying the different characteristics of all above mentioned sensors in terms of geometric, radiometric and polarimetric resolution to a consistent format. The polarimetric representation in Kennaugh elements allows fusing single-polarized data acquired by older sensors with multi-polarized data acquired by current sensors. The TANH-normalization guarantees a consistent and therefore comparable description in a closed data range in terms of radiometry. The geometric aspect is solved by projecting all images to an earth-fixed coordinate system correcting the brightness by the help of the incidence angle. The elevation model used in the geocoding step is the novel global model produced by the TanDEM-X satellite

Bilan et perspectives des cultures vivrières dans les pays du Sahel

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Egg Johny

2006-07-01

Full Text Available Twenty-five years after the beggining of the policies of adjustment and liberalization which is the situation of the food crops in the countries of the Sahel? The balance-sheet is approached by contrasting the cereals sub sector, facing to a very strong control by the State, and the onion whose growth is related to the increase in the demand of the great urban centers. The increase in the production of cereals was accompanied by deep changes in the structures. The market became more efficient and better integrated on a regional scale. But, the level and the instability of the prices of cereals increased, making difficult the provisioning of the poor. Clear differences in trajectories appear. Mali, which implemented a policy of reforming cereals market and successful the revival of rice sector, must manage at the same time the improvement of the competitiveness of its cereals and the access to cereals of the low incomes consumers. Niger must face the increase in the vulnerability of a great part of the rural households. The production of onion experienced a spectacular increase in Senegal after the devaluation of franc FCA in response to the urban market. That of Niger intended mainly for the close countries progressed more slowly. But in both cases, the regulation of the European onion imports constitutes a paramount stake.

Diagnosis of vegetation recovery within herbaceous sub-systems in the West African Sahel Region

Science.gov (United States)

Anchang, J.; Hanan, N. P.; Prihodko, L.; Sathyachandran, S. K.; Ji, W.; Ross, C. W.

2017-12-01

The West African Sahel (WAS) region is an extensive water limited environment that features a delicate balance of herbaceous and woody vegetation sub systems. These play an important role in the cycling of carbon while also supporting the dominant agro-pastoral human activities in the region. Quantifying the temporal trends in vegetation with regard to these two systems is therefore very important in assessing resource sustainability and food security. In water limited areas, rainfall is a primary driver of vegetation productivity and past watershed scale studies in the WAS region have shown that increase in the slope of the productivity-to-rainfall relationship is indicative of increasing cover and density of herbaceous plants. Given the importance of grazing resources to the region, we perform a wall-to-wall pixel based analysis of changing short-term vegetation sensitivity to changing annual rainfall (hereafter referred to as dS) to examine temporal trends in herbaceous vegetation health. Results indicate that 43% of the Sahelian region has experienced changes (P Western and Central Mali and South Western Niger. Positive dS is indicative of herbaceous vegetation recovery, in response to changing management and rainfall conditions that promote long-term herbaceous community recovery following degradation during the 1970-1980s droughts.

The supply and demand of net primary production in the Sahel

International Nuclear Information System (INIS)

Abdi, A M; Seaquist, J; Tenenbaum, D E; Eklundh, L; Ardö, J

2014-01-01

Net primary production (NPP) is the principal source of energy for ecosystems and, by extension, human populations that depend on them. The relationship between the supply and demand of NPP is important for the assessment of socio-ecological vulnerability. We present an analysis of the supply and demand of NPP in the Sahel using NPP estimates from the MODIS sensor and agri-environmental data from FAOSTAT. This synergistic approach allows for a spatially explicit estimation of human impact on ecosystems. We estimated the annual amount of NPP required to derive food, fuel and feed between 2000 and 2010 for 22 countries in sub-Saharan Africa. When comparing annual estimates of supply and demand of NPP, we found that demand increased from 0.44 PgC to 1.13 PgC, representing 19% and 41%, respectively, of available supply due to a 31% increase in the human population between 2000 and 2010. The demand for NPP has been increasing at an annual rate of 2.2% but NPP supply was near-constant with an inter-annual variability of approximately 1.7%. Overall, there were statistically significant (p < 0.05) increases in the NPP of cropland (+6.0%), woodland (+6.1%) and grassland/savanna (+9.4%), and a decrease in the NPP of forests (−0.7%). On the demand side, the largest increase was for food (20.4%) followed by feed (16.7%) and fuel (5.5%). The supply-demand balance of NPP is a potentially important tool from the standpoint of sustainable development, and as an indicator of stresses on the environment stemming from increased consumption of biomass. (letter)

LONG-TERM MONITORING OF WATER DYNAMICS IN THE SAHEL REGION USING THE MULTI-SAR-SYSTEM

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A. Bertram

2016-06-01

Full Text Available Fresh water is a scarce resource in the West-African Sahel region, seasonally influenced by droughts and floods. Particularly in terms of climate change, the importance of wetlands increases for flora, fauna, human population, agriculture, livestock and fishery. Hence, access to open water is a key factor. Long-term monitoring of water dynamics is of great importance, especially with regard to the spatio-temporal extend of wetlands and drylands. It can predict future trends and facilitate the development of adequate management strategies. Lake Tabalak, a Ramsar wetland of international importance, is one of the most significant ponds in Niger and a refuge for waterbirds. Nevertheless, human population growth increased the pressure on this ecosystem, which is now degrading for all uses. The main objective of the study is a long-term monitoring of the Lake Tabalak’s water dynamics to delineate permanent and seasonal water bodies, using weather- and daytime-independent multi-sensor and multi-temporal Synthetic Aperture Radar (SAR data available for the study area. Data of the following sensors from 1993 until 2016 are used: Sentinel-1A, TerraSARX, ALOS PALSAR-1/2, Envisat ASAR, RADARSAT-1/2, and ERS-1/2. All SAR data are processed with the Multi-SAR-System, unifying the different characteristics of all above mentioned sensors in terms of geometric, radiometric and polarimetric resolution to a consistent format. The polarimetric representation in Kennaugh elements allows fusing single-polarized data acquired by older sensors with multi-polarized data acquired by current sensors. The TANH-normalization guarantees a consistent and therefore comparable description in a closed data range in terms of radiometry. The geometric aspect is solved by projecting all images to an earth-fixed coordinate system correcting the brightness by the help of the incidence angle. The elevation model used in the geocoding step is the novel global model produced by the

Assessing Land Degradation/Recovery in the African Sahel from Long-Term Earth Observation Based Primary Productivity and Precipitation Relationships

DEFF Research Database (Denmark)

Fensholt, Rasmus; Rasmussen, Kjeld; Kaspersen, Per Skougaard

2013-01-01

degradation. Consequently, RUE may be regarded as means of normalizing ANPP for the impact of annual precipitation, and as an indicator of non-precipitation related land degradation. Large scale and long term identification and monitoring of land degradation in drylands, such as the Sahel, can only......The ‘rain use efficiency’ (RUE) may be defined as the ratio of above-ground net primary productivity (ANPP) to annual precipitation, and it is claimed to be a conservative property of the vegetation cover in drylands, if the vegetation cover is not subject to non-precipitation related land...... useless as a means of normalizing for the impact of annual precipitation on ANPP. By replacing ΣNDVI by a ‘small NDVI integral’, covering only the rainy season and counting only the increase of NDVI relative to some reference level, this problem is solved. Using this approach, RUE is calculated...

Long-term increase in diffuse groundwater recharge following expansion of rainfed cultivation in the Sahel, West Africa

Science.gov (United States)

Ibrahim, Maïmouna; Favreau, Guillaume; Scanlon, Bridget R.; Seidel, Jean Luc; Le Coz, Mathieu; Demarty, Jérôme; Cappelaere, Bernard

2014-09-01

Rapid population growth in sub-Saharan West Africa and related cropland expansion were shown in some places to have increased focused recharge through ponds, raising the water table. To estimate changes in diffuse recharge, the water content and matric potential were monitored during 2009 and 2010, and modeling was performed using the Hydrus-1D code for two field sites in southwest Niger: (1) fallow land and (2) rainfed millet cropland. Monitoring results of the upper 10 m showed increased water content and matric potential to greater depth under rainfed cropland (>2.5 m) than under fallow land (≤1.0 m). Model simulations indicate that conversion from fallow land to rainfed cropland (1) increases vadose-zone water storage and (2) should increase drainage flux (˜25 mm year-1) at 10-m depth after a 30-60 year lag. Therefore, observed regional increases in groundwater storage may increasingly result from diffuse recharge, which could compensate, at least in part, groundwater withdrawal due to observed expansion in irrigated surfaces; and hence, contribute to mitigate food crises in the Sahel.

Management of protected areas in Sahel savannah ecoregion of Nigeria under the threat of desertification

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BOROKINI Temitope Israel

2013-12-01

Full Text Available This study was conducted to assess the challenges facing 8 selected protected areas in the Sahel Savannah ecoregion and proffer solutions to these challenges in order to ensure conservation and sustainability of Nigeria’s biodiversity. Primary data were collected from randomly-selected 120 staffs using questionnaire administration from 8 Forest Reserves within Borno and Yobe states of Nigeria. A high level of encroachment of all the studied protected areas was observed, which ranged from deforestation, overgrazing, poaching to converting protected areas into farmlands. Other notable challenges include poor staffing, inadequate equipment and funding. The respondents further reported that majority of the defaulters were farmers and local people in the area, involved in such practices for their survival in the wake of harsher climate and desert encroachment in the region. This paper calls for a revision of the Government Policy on Forestry in Nigeria to allow the people own and plant forests, implementation of community based forest resources management, provision of environment and user-friendly solar powered cooking stoves and sustainable farming systems such as crop rotation, intercropping, sustainable irrigation, organic farming and agroforestry. In addition, sources of income for the locals need to be diversified, such as honey bee production.

Rôle et place de la chèvre dans les ménages du Sahel burkinabé

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Gnanda, BI.

2016-01-01

Full Text Available Role and Position of the Goat in Households of the Burkinabian Sahel. A formal household survey was carried out in Burkina Faso with 150 Sahelian farms in order to appreciate the role and the position of goat breeding in the life and the functioning of these family units. The results of the investigation show that the Burkinabe Sahelian stockbreeders first start usually by raising a goat, because of its high prolificacy, but with the view to acquire more or less rapidly other species of ruminants, in particular cattle. Although the generation of income of goat rearing remains low compared to other ruminants (bovine, ovine; their non-monetary role in poverty alleviation is highlighted. That is shown through the large proportion of the population (91% of the target-group implied in goat breeding, the first position of goats in the non-commercial (social transaction, and their position in terms of risk prevention against the climatic hazards for livestock farmers. Despite its critical role, the goat remains the least favored ruminant species in regarding health protection and food supplementation.

The paradoxical evolution of runoff in the pastoral Sahel: analysis of the hydrological changes over the Agoufou watershed (Mali using the KINEROS-2 model

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L. Gal

2017-09-01

Full Text Available In recent decades, the Sahel has witnessed a paradoxical increase in surface water despite a general precipitation decline. This phenomenon, commonly referred to as the Sahelian paradox, is not completely understood yet. The role of cropland expansion due to the increasing food demand by a growing population has been often put forward to explain this situation for the cultivated Sahel. However, this hypothesis does not hold in pastoral areas where the same phenomenon is observed. Several other processes, such as the degradation of natural vegetation following the major droughts of the 1970s and the 1980s, the development of crusted topsoils, the intensification of the rainfall regime and the development of the drainage network, have been suggested to account for this situation. In this paper, a modeling approach is proposed to explore, quantify and rank different processes that could be at play in pastoral Sahel. The kinematic runoff and erosion model (KINEROS-2 is applied to the Agoufou watershed (245 km2, in the Gourma region in Mali, which underwent a significant increase of surface runoff during the last 60 years. Two periods are simulated, the past case (1960–1975 preceding the Sahelian drought and the present case (2000–2015. Surface hydrology and land cover characteristics for these two periods are derived by the analysis of aerial photographs, available in 1956, and high-resolution remote sensing images in 2011. The major changes identified are (1 a partial crusting of isolated dunes, (2 an increase of drainage network density, (3 a marked decrease in vegetation with the nonrecovery of tiger bush and vegetation growing on shallow sandy soils, and (4 important changes in soil properties with the apparition of impervious soils instead of shallow sandy soil. The KINEROS-2 model was parameterized to simulate these changes in combination or independently. The results obtained by this model display a significant increase in annual

Selection for earlier flowering crop associated with climatic variations in the Sahel.

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Yves Vigouroux

Full Text Available Climate changes will have an impact on food production and will require costly adaptive responses. Adapting to a changing environment will be particularly challenging in sub-Saharan Africa where climate change is expected to have a major impact. However, one important phenomenon that is often overlooked and is poorly documented is the ability of agro-systems to rapidly adapt to environmental variations. Such an adaptation could proceed by the adoption of new varieties or by the adaptation of varieties to a changing environment. In this study, we analyzed these two processes in one of the driest agro-ecosystems in Africa, the Sahel. We performed a detailed study in Niger where pearl millet is the main crop and covers 65% of the cultivated area. To assess how the agro-system is responding to recent recurrent drought, we analyzed samples of pearl millet landraces collected in the same villages in 1976 and 2003 throughout the entire cultivated area of Niger. We studied phenological and morphological differences in the 1976 and 2003 collections by comparing them over three cropping seasons in a common garden experiment. We found no major changes in the main cultivated varieties or in their genetic diversity. However, we observed a significant shift in adaptive traits. Compared to the 1976 samples, samples collected in 2003 displayed a shorter lifecycle, and a reduction in plant and spike size. We also found that an early flowering allele at the PHYC locus increased in frequency between 1976 and 2003. The increase exceeded the effect of drift and sampling, suggesting a direct effect of selection for earliness on this gene. We conclude that recurrent drought can lead to selection for earlier flowering in a major Sahelian crop. Surprisingly, these results suggest that diffusion of crop varieties is not the main driver of short term adaptation to climatic variation.

A comparison of the physical properties of desert dust retrieved from the sunphotometer observation of major events in the Sahara, Sahel, and Arabian Peninsula

KAUST Repository

Masmoudi, Mohamed

2015-05-01

© 2015 Elsevier B.V. The objective of this work is to assess the variability of the size-distribution, real (n) and imaginary (k) parts of the refractive index, asymmetry parameter (g), and single scattering albedo (SSA) of desert dust events observed in the Sahara, Sahel, and Arabian Peninsula areas. For this we use the level-2 inversions of 14 AERONET sunphotometers representative of the area of study. In the dataset, the dust-dominated events are discriminated on the basis of their large optical depth and low (<. 0.3) Ångström exponent (α) calculated between 440. nm and 870. nm. In all the volume size-distributions a coarse mode (CM) of particles is observed but a fine mode (FM) of particles with radii. <. 0.2. μm is also present. The volume fraction represented by the FM is lower (3%) during the most intense dust storms than during moderate ones (12%). The inter-site variability of the characteristics of the CM-dominated situations is found to be non-significant and at 440, 675, 870, and 1020. nm a common set of values can be adopted for n (1.54 ± 0.03, 1.53 ± 0.02, 1.50 ± 0.02, 1.48 ± 0.02), k (0.0037 ± 0.0007, 0.0012 ± 0.0002, 0.0011 ± 0.0002, 0.0012 ± 0.0002), g (0.77 ± 0.01, 0.74 ± 0.01, 0.73 ± 0.01, 0.74 ± 0.01), and the SSA (0.90 ± 0.02, 0.97 ± 0.01, 0.98 ± 0.01, 0.98 ± 0.01). However; during the less intense dust-events the growing influence of the FM leads to regional differentiation of the dust properties and 2 main areas can be distinguished: 1) the relatively clean central Sahara/Sahel, and 2) the more polluted continuum constituted by the Mediterranean coast and the Arabian Peninsula.

A comparison of the physical properties of desert dust retrieved from the sunphotometer observation of major events in the Sahara, Sahel, and Arabian Peninsula

KAUST Repository

Masmoudi, Mohamed; Alfaro, Sté phane C.; El Metwally, Mossad

2015-01-01

© 2015 Elsevier B.V. The objective of this work is to assess the variability of the size-distribution, real (n) and imaginary (k) parts of the refractive index, asymmetry parameter (g), and single scattering albedo (SSA) of desert dust events observed in the Sahara, Sahel, and Arabian Peninsula areas. For this we use the level-2 inversions of 14 AERONET sunphotometers representative of the area of study. In the dataset, the dust-dominated events are discriminated on the basis of their large optical depth and low (<. 0.3) Ångström exponent (α) calculated between 440. nm and 870. nm. In all the volume size-distributions a coarse mode (CM) of particles is observed but a fine mode (FM) of particles with radii. <. 0.2. μm is also present. The volume fraction represented by the FM is lower (3%) during the most intense dust storms than during moderate ones (12%). The inter-site variability of the characteristics of the CM-dominated situations is found to be non-significant and at 440, 675, 870, and 1020. nm a common set of values can be adopted for n (1.54 ± 0.03, 1.53 ± 0.02, 1.50 ± 0.02, 1.48 ± 0.02), k (0.0037 ± 0.0007, 0.0012 ± 0.0002, 0.0011 ± 0.0002, 0.0012 ± 0.0002), g (0.77 ± 0.01, 0.74 ± 0.01, 0.73 ± 0.01, 0.74 ± 0.01), and the SSA (0.90 ± 0.02, 0.97 ± 0.01, 0.98 ± 0.01, 0.98 ± 0.01). However; during the less intense dust-events the growing influence of the FM leads to regional differentiation of the dust properties and 2 main areas can be distinguished: 1) the relatively clean central Sahara/Sahel, and 2) the more polluted continuum constituted by the Mediterranean coast and the Arabian Peninsula.

Seasonal contrast in the surface energy balance of the Sahel

Science.gov (United States)

Miller, R. L.; Slingo, A.; Barnard, J. C.; Kassianov, E.

2009-07-01

during a dust aerosol outbreak is balanced comparably by net surface longwave and the sensible heat flux during the dry season, with the sensible flux increasing in importance with the onset of the summer monsoon winds. Measurements of surface fluxes by the AMF indicate broader features of the West African monsoon circulation and should be used to evaluate model simulations of the Sahel climate.

The present situation of photo-electric plants in the Sahel zone: Possibilities and limits of a marketing strategy using the example of the Niger. Zur gegenwaertigen Situation photovoltaischer Anlagen in der Sahelzone: Moeglichkeiten und Grenzen einer Vermarktungsstrategie am Beispiel des Niger

Energy Technology Data Exchange (ETDEWEB)

Hempel, C. (GTZ - Sonderenergieprogramm Niger, Niamey (Niger))

1993-01-01

The report is aimed at three targets: First one deals with the meteorological data as the basis for the technical design of photo-electric plants, secondly there is a short survey of the present situation of photo-electrics in Nigeria (referring also to other Sahel countries), and thirdly, the possibilities and limits of a marketing strategy for photo-electric plants are sketched out for this region. (orig.)

Measurements of land surface features using an airborne laser altimeter: the HAPEX-Sahel experiment

International Nuclear Information System (INIS)

Ritchie, J.C.; Menenti, M.; Weltz, M.A.

1997-01-01

An airborne laser profiling altimeter was used to measure surface features and properties of the landscape during the HAPEX-Sahel Experiment in Niger, Africa in September 1992. The laser altimeter makes 4000 measurements per second with a vertical resolution of 5 cm. Airborne laser and detailed field measurements of vegetation heights had similar average heights and frequency distribution. Laser transects were used to estimate land surface topography, gully and channel morphology, and vegetation properties ( height, cover and distribution). Land surface changes related to soil erosion and channel development were measured. For 1 km laser transects over tiger bush communities, the maximum vegetation height was between 4-5 and 6-5 m, with an average height of 21 m. Distances between the centre of rows of tiger bush vegetation averaged 100 m. For two laser transects, ground cover for tiger bush was estimated to be 225 and 301 per cent for vegetation greater than 0-5m tall and 190 and 25-8 per cent for vegetation greater than 10m tall. These values are similar to published values for tiger bush. Vegetation cover for 14 and 18 km transects was estimated to be 4 per cent for vegetation greater than 0-5 m tall. These cover values agree within 1-2 per cent with published data for short transects (⩾ 100 m) for the area. The laser altimeter provided quick and accurate measurements for evaluating changes in land surface features. Such information provides a basis for understanding land degradation and a basis for management plans to rehabilitate the landscape. (author)

Phenotypic variations in osmotic lysis of Sahel goat erythrocytes in non-ionic glucose media.

Science.gov (United States)

Igbokwe, Nanacha Afifi; Igbokwe, Ikechukwu Onyebuchi

2016-03-01

Erythrocyte osmotic lysis in deionised glucose media is regulated by glucose influx, cation efflux, and changes in cell volume after water diffusion. Transmembrane fluxes may be affected by varied expression of glucose transporter protein and susceptibility of membrane proteins to glucose-induced glycosylation and oxidation in various physiologic states. Variations in haemolysis of Sahel goat erythrocytes after incubation in hyposmotic non-ionic glucose media, associated with sex, age, late pregnancy, and lactation, were investigated. The osmotic fragility curve in glucose media was sigmoidal with erythrocytes from goats in late pregnancy (PRE) or lactation (LAC) or from kid (KGT) or middle-aged (MGT) goats. Non-sigmoidal phenotype occurred in yearlings (YGT) and old (OGT) goats. The composite fragility phenotype for males and non-pregnant dry (NPD) females was non-sigmoidal. Erythrocytes with non-sigmoidal curves were more stable than those with sigmoidal curves because of inflectional shift of the curve to the left. Erythrocytes tended to be more fragile with male than female sex, KGT and MGT than YGT and OGT, and LAC and PRE than NPD. Thus, sex, age, pregnancy, and lactation affected the haemolytic pattern of goat erythrocytes in glucose media. The physiologic state of the goat affected the in vitro interaction of glucose with erythrocytes, causing variations in osmotic stability with variants of fragility phenotype. Variations in the effect of high extracellular glucose concentrations on the functions of membrane-associated glucose transporter, aquaporins, and the cation cotransporter were presumed to be relevant in regulating the physical properties of goat erythrocytes under osmotic stress.

“El florecimiento del terrorismo islámico en el Sahel, un reto para la seguridad de Europa Occidental. Estudio de caso: Malí y España (2011- 2013)”

OpenAIRE

Rodríguez Uribe, Mónica Alejandra

2015-01-01

El objetivo central de este Estudio de Caso, consiste en investigar en qué sentido la proximidad geográfica y el hecho de que la región del Sahel constituya una zona de tránsito, influyen a que el crecimiento del terrorismo islámico en Malí comprenda una amenaza tanto para la seguridad nacional, como para la estabilidad de España. Se avanzará posteriormente con la descripción de herramientas específicas, tanto judiciales como de cooperación que el gobierno español ha buscado apoyar a nivel ...

Deriving albedo maps for HAPEX-Sahel from ASAS data using kernel-driven BRDF models

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P. Lewis

1999-01-01

Full Text Available This paper describes the application and testing of a method for deriving spatial estimates of albedo from multi-angle remote sensing data. Linear kernel-driven models of surface bi-directional reflectance have been inverted against high spatial resolution multi-angular, multi- spectral airborne data of the principal cover types within the HAPEX-Sahel study site in Niger, West Africa. The airborne data are obtained from the NASA Airborne Solid-state Imaging Spectrometer (ASAS instrument, flown in Niger in September and October 1992. The maps of model parameters produced are used to estimate integrated reflectance properties related to spectral albedo. Broadband albedo has been estimated from this by weighting the spectral albedo for each pixel within the map as a function of the appropriate spectral solar irradiance and proportion of direct and diffuse illumination. Partial validation of the results was performed by comparing ASAS reflectance and derived directional-hemispherical reflectance with simulations of a millet canopy made with a complex geometric canopy reflectance model, the Botanical Plant Modelling System (BPMS. Both were found to agree well in magnitude. Broadband albedo values derived from the ASAS data were compared with ground-based (point sample albedo measurements and found to agree extremely well. These results indicate that the linear kernel-driven modelling approach, which is to be used operationally to produce global 16 day, 1 km albedo maps from forthcoming NASA Earth Observing System spaceborne data, is both sound and practical for the estimation of angle-integrated spectral reflectance quantities related to albedo. Results for broadband albedo are dependent on spectral sampling and on obtaining the correct spectral weigthings.

Increasing the Effectiveness of the “Great Green Wall” as an Adaptation to the Effects of Climate Change and Desertification in the Sahel

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David O'Connor

2014-10-01

Full Text Available The Great Green Wall (GGW has been advocated as a means of reducing desertification in the Sahel through the planting of a broad continuous band of trees from Senegal to Djibouti. Initially proposed in the 1980s, the plan has received renewed impetus in light of the potential of climate change to accelerate desertification, although the implementation has been lacking in all but two of 11 countries in the region. In this paper, we argue that the GGW needs modifying if it is to be effective, obtain the support of local communities and leverage international support. Specifically, we propose a shift from planting trees in the GGW to utilizing shrubs (e.g., Leptospermum scoparium, Boscia senegalensis, Grewia flava, Euclea undulata or Diospyros lycioides, which would have multiple benefits, including having a faster growth rate and proving the basis for silvo-pastoral livelihoods based on bee-keeping and honey production.

Arthropod diversity and assemblage structure response to deforestation and desertification in the Sahel of western Senegal

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Brandon J. Lingbeek

2017-07-01

Full Text Available Drylands are highly vulnerable to desertification and among the most endangered ecosystems. To understand how biodiversity responds to environmental degradation in these fragile ecosystems, we examined whether arthropod, beetle, spider and ant diversity and assemblage structure differed (1 between seasons, (2 among locations (3 between protected areas of tropical dry forest and adjacent communal lands suffering from desertification, as well as (4 how vegetation impacts assemblage structures. We established 12 plots spaced homogenously throughout each protected area and the adjacent communal land at three locations: Beersheba, Bandia and Ngazobil. Within each plot, we measured canopy closure, vegetation height, percent cover of bare ground, leaf litter, grasses and forbs and collected arthropods using pitfall traps during the 2014 dry (May and rainy (September seasons. We collected 123,705 arthropods representing 733 morphospecies, 10,849 beetles representing 216 morphospecies, 4969 spiders representing 91 morphospecies and 59,183 ants representing 45 morphospecies. Results showed greater arthropod and beetle diversities (P = 0.002–0.040 in the rainy season, no difference in diversity among locations for any taxonomic group and a difference (P ≤ 0.001 in diversity for all taxa between protected areas and communal lands. Assemblage structures of all taxa responded (P = 0.001 to vegetation characteristics, differed (P = 0.015–0.045 between seasons and, with a few exceptions, locations and fragments. Our results illustrate the importance of a multi-taxa approach in understanding biodiversity response to anthropogenic disturbances as well as the value of protected areas in preserving biodiversity of the Sahel.

Land Cover Land Use change and soil organic carbon under climate variability in the semi-arid West African Sahel (1960-2050)

Science.gov (United States)

Dieye, Amadou M.

Land Cover Land Use (LCLU) change affects land surface processes recognized to influence climate change at local, national and global levels. Soil organic carbon is a key component for the functioning of agro-ecosystems and has a direct effect on the physical, chemical and biological characteristics of the soil. The capacity to model and project LCLU change is of considerable interest for mitigation and adaptation measures in response to climate change. A combination of remote sensing analyses, qualitative social survey techniques, and biogeochemical modeling was used to study the relationships between climate change, LCLU change and soil organic carbon in the semi-arid rural zone of Senegal between 1960 and 2050. For this purpose, four research hypotheses were addressed. This research aims to contribute to an understanding of future land cover land use change in the semi-arid West African Sahel with respect to climate variability and human activities. Its findings may provide insights to enable policy makers at local to national levels to formulate environmentally and economically adapted policy decisions. This dissertation research has to date resulted in two published and one submitted paper.

Petite motorisation et exploitations maraîchères de taille limitée du Sahel tunisien Partie 2: Evaluation sur le terrain des performances et des coûts de préparation du sol

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Chehaibi, S.

2003-01-01

Full Text Available Low Power Mechanisation and Small-scale Vegetable Production in the Tunisian Sahel Region. Part 2: On the Field Evaluation of Performances and of Soil Preparation Costs. In this study, it was investigated to what extent low power mechanisation could be introduced in vegetable production in the Tunisian Sahel region by evaluating its performance (labour input and field efficiency by means of field experiments in which different traction equipment was used for carrying out several cultivation operations. Furthermore, costs per unit area for soil preparation in both sandy clay and clayish sand were calculated for four different power classes and for small fields. The results showed that two wheel tractors had a real labour input for scuffling between plant rows ranging from 11.3 h/ha to 18.7 h/ha. These inputs ranged from 5.5 h/ha to 6.7 h/ha for tied crops. For mowing, the two wheel tractor had labour inputs of 17.3 and 14.2 h/ha for the first and the second cut, respectively, while for potato digging, the first and the second passage of secondary tillage these values were 11.5, 14.3 and 10.4 h/ha, respectively. Superficial soil preparation by means of a four wheel tractor gave rise to values between 2.7 and 3.5 h/ha. With respect to the cost estimation for soil preparation, the lowest costs were obtained by means of the low power mechanisation. Similar conclusions were drawn for the field efficiencies for the operations investigated. In general, these efficiencies were above 70%.

Surface fluxes of water vapour, momentum and CO{sub 2} over a savanna in Niger. A contribution to HAPEX-SAHEL

Energy Technology Data Exchange (ETDEWEB)

Verhoef, A; De Bruin, H A.R.; Krikke, R [Dept. of Meteorology. Landbouwuniversiteit, Wageningen (Netherlands)

1995-11-01

For large scale models such as Global Circulation Models (GCM) the lower boundary condition is often provided by a SVAT model (Soil-Vegetation-Atmosphere Transfer). A wide range of SVATs is in use nowadays, varying from models based on the simple big-leaf concept to complicated multiple source models. Obviously, a SVAT intended to provide the lower boundary condition in GCM`s needs to be able to describe a wide range of surface types, varying from completely vegetated to sparsely vegetated or completely bare surfaces. Especially sparse canopy surface types exhibit rather demanding features with respect to the exchange of momentum, water vapour, CO{sub 2} and heat between the surface and the atmosphere. In this paper attention is focused on a sparse canopy. We will compare SVAT model simulations with data collected in 1992 at a Savannah site, in the framework of the HAPEX-SAHEL project (a large-scale study of land atmosphere interactions in the semi-arid tropics). Two existing SVAT models are considered (Choudhury-Monteith and Deardorff). In a separate study these models have been tested. A combined model has been constructed, consisting of the `best` parts of the original SVAT`s. Some preliminary results will be presented. 4 figs., 14 refs., 1 appendix

Radiative transfer in shrub savanna sites in Niger: preliminary results from HAPEX-Sahel. 2. Photosynthetically active radiation interception of the woody layer

International Nuclear Information System (INIS)

Bégué, A.; Hanan, N.P.; Prince, S.D.

1994-01-01

Interception by the woody layer of photosynthetically active radiation (PAR) was measured and calculated for two Guiera senegalensis J.F. Gmel, shrub savannas in Ouallam, Western Niger, in 1991 as part of the HAPEX-Sahel experiment. Two different scales were considered. At the plant scale, PAR interception was measured throughout the day with amorphous silicon sensors, together with detailed measurements of the structure of the shrubs (size of the ‘envelope’ of the shrub, area index, and angular distribution of the leaves and the branches). These data permitted us to develop and validate a simple radiative transfer model in which the shrubs are represented by porous cylinders; the total transmissivity (or porosity) of the shrubs estimated by the model was approximately 0.4. It indicates that semi-arid shrubs cannot be considered opaque objects and that the fraction of ground covered with plants is a poor indicator of the PAR interception efficiency of the canopy. The model was also applied at a landscape scale to calculate the daily PAR interception of two shrub savanna sites. This value is needed to model primary production in conjunction with remotely sensed and production data acquired simultaneously on the sites. (author)

Simulation of the Impact of Climate Variability on Malaria Transmission in the Sahel

Science.gov (United States)

Bomblies, A.; Eltahir, E.; Duchemin, J.

2007-12-01

A coupled hydrology and entomology model for simulation of malaria transmission and malaria transmitting mosquito population dynamics is presented. Model development and validation is done using field data and observations collected at Banizoumbou and Zindarou, Niger spanning three wet seasons, from 2005 through 2007. The primary model objective is the accurate determination of climate variability effects on village scale malaria transmission. Malaria transmission dependence on climate variables is highly nonlinear and complex. Temperature and humidity affect mosquito longevity, temperature controls parasite development rates in the mosquito as well as subadult mosquito development rates, and precipitation determines the formation and persistence of adequate breeding pools. Moreover, unsaturated zone hydrology influences overland flow, and climate controlled evapotranspiration rates and root zone uptake therefore also influence breeding pool formation. High resolution distributed hydrologic simulation allows representation of the small-scale ephemeral pools that constitute the primary habitat of Anopheles gambiae mosquitoes, the dominant malaria vectors in the Niger Sahel. Remotely sensed soil type, vegetation type, and microtopography rasters are used to assign the distributed parameter fields for simulation of the land surface hydrologic response to precipitation and runoff generation. Predicted runoff from each cell flows overland and into topographic depressions, with explicit representation of infiltration and evapotranspiration. The model's entomology component interacts with simulated pools. Subadult (aquatic stage) mosquito breeding is simulated in the pools, and water temperature dependent stage advancement rates regulate adult mosquito emergence into the model domain. Once emerged, adult mosquitoes are tracked as independent individual agents that interact with their immediate environment. Attributes relevant to malaria transmission such as gonotrophic

Re-greening the Sahel: farmer-led innovation in Burkina Faso and Niger

Science.gov (United States)

Reij, Chris; Smale, Melinda; Tappan, G. Gray; Spielman, David J.; Pandya-Lorch, Rajul

2009-01-01

did 30 years ago. These findings suggest a human and environmental success story at a scale not seen anywhere else in Africa. The re-greening of the Sahel began when local farmers’ practices were rediscovered and enhanced in simple, low-cost ways by innovative farmers and nongovernmental organizations. An evolving coalition of local, national, and international actors then enabled large-scale diffusion and continued use of these improved practices where they benefited farmers.

Evaluation of CMIP5 models in the context of food security assessments in Sahel and Eastern Africa

Science.gov (United States)

Shukla, S.; Funk, C. C.; Dettinger, M. D.; Robertson, F. R.

2012-12-01

Global climate change will adversely impact agricultural production in many African countries, mainly in the Sahel region and Eastern Africa that are already considered food insecure regions. The impacts of climate change will be particularly severe in these food insecure countries due to their high dependence on domestic agriculture production, rapid population growth, and lack of technological advances. Early planning and the targeted use of resources will therefore be critical to informing and motivating climate change adaptation actions that can save lives and mitigate economic losses. We seek to use Climate Model Intercomparison Project Phase-5 (CMIP5) global climate model projections to assess and attribute food and water security conditions in the above mentioned regions over next two decades or so. As a first order of business, however, we need to understand how the different models represent the tropical ocean response to anthropogenic warming. We pursue this question through an evaluation of the performance of eight different coupled ocean-atmosphere models under the conditions of the 'historical' experiment. The historical experiment forces the simulations with observed 1850-2005 greenhouse gas, aerosol and land cover. While all the models show substantial warming of the tropical oceans, the pattern and atmospheric response to that warming varies substantially. This analysis suggests that the Community Climate System Model (CCSM4) provides the most realistic 1850-2005 changes over the Indo-Pacific. We then present initial downscaling results, based on large scale forcing from the CCSM4, combined with statistical downscaling based on a combination of monthly simulations from Community Atmopsheric Model 4 (CAM4) and observed gridded time series of African rainfall and air temperatures.

How Does Gender Affect Sustainable Intensification of Cereal Production in the West African Sahel? Evidence from Burkina Faso.

Science.gov (United States)

Theriault, Veronique; Smale, Melinda; Haider, Hamza

2017-04-01

Better understanding of gender differences in the adoption of agricultural intensification strategies is crucial for designing effective policies to close the gender gap while sustainably enhancing farm productivity. We examine gender differences in adoption rates, likelihood and determinants of adopting strategy sets that enhance yields, protect crops, and restore soils in the West African Sahel, based on analysis of cereal production in Burkina Faso. Applying a multivariate probit model to a nationally representative household panel, we exploit the individual plot as unit of analysis and control for plot manager characteristics along with other covariates. Reflecting the socio-cultural context of farming combined with the economic attributes of inputs, we find that female managers of individual cereal fields are less likely than their male counterparts to adopt yield-enhancing and soil-restoring strategies, although no differential is apparent for yield-protecting strategies. More broadly, gender-disaggregated regressions demonstrate that adoption determinants differ by gender. Plot manager characteristics, including age, marital status, and access to credit or extension services do influence adoption decisions. Furthermore, household resources influence the probability of adopting intensification strategy sets differently by gender of the plot manager. Variables expressing the availability of household labor strongly influence the adoption of soil-restoring strategies by female plot managers. By contrast, household resources such as extent of livestock owned, value of non-farm income, and area planted to cotton affect the adoption choices of male plot managers. Rectifying the male bias in extension services along with improving access to credit, income, and equipment to female plot managers could contribute to sustainable agricultural intensification.

West African think tank strengthens outreach and partnerships ...

International Development Research Centre (IDRC) Digital Library (Canada)

28 avr. 2016 ... Les femmes du Sahel obtiennent de meilleurs rendements de leurs cultures. Moins d'engrais et rendements plus élevés pour les agricultrices du Sahel. Voir davantageLes femmes du Sahel obtiennent de meilleurs rendements de leurs cultures ...

Bridging gender gaps with dairy goats and root crops | CRDI ...

International Development Research Centre (IDRC) Digital Library (Canada)

5 mai 2016 ... Les femmes du Sahel obtiennent de meilleurs rendements de leurs cultures. Moins d'engrais et rendements plus élevés pour les agricultrices du Sahel. Voir davantageLes femmes du Sahel obtiennent de meilleurs rendements de leurs cultures ...

The project RUSSADE: geoethic education to face environmental problems in the Sahel

Science.gov (United States)

Ferrero, Elena; Semita, Carlo

2016-04-01

The hard environmental and climatic conditions in Sahel countries affect life choices of younger generations, whose number continues to increase especially in large Sahelian cities, with increasing levels of discomfort and lack of adequate education and governance. To improve job opportunities and consequently the quality of life at all levels of the population, it is important to guarantee a better access to basic natural resources, such as soil, water, food. At the same time it is essential to spread awareness and knowledge of the vulnerability and of the risks that threaten natural resources, both for natural processes and for the interaction with human not sustainable activities. For this purpose, a Master course has been achieved in the project RUSSADE (Réseau des Universités Sahéliennes pour la Sécurité Alimentaire et la Durabilité Environnementale - www.russade.eu), funded in the ACP-EU Cooperation Programme in higher education (EDULINK II). The Master course includes teaching modules dedicated to these issues and takes care of their integration with other modules in the technical and application fields of the rural development. For instance, the objectives of the teaching module "Land and natural resources management" provide for the transmission of skills to diagnose types of soil degradation risks, to guide options for protection, conservation and soil restoration and to identify the components of integrated soil fertility management in particular African contexts (Subunit "Land management"); to choose appropriate methods of management and exploitation of water resources (defining the limits in the use of water resources) (Subunit "Water supply"); to propose alternative solutions concerning conventional energy resources, to know and promote the various possibilities of solar and other renewable energies production (Subunit "Using solar and other renewable energies"). Some teaching modules introduce and discuss risks related to inadequate waste

Less rain, more water in ponds: a remote sensing study of the dynamics of surface waters from 1950 to present in pastoral Sahel (Gourma region, Mali

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J. Gardelle

2010-02-01

Full Text Available Changes in the flooded area of ponds in the Gourma region from 1950 to present are studied by remote sensing, in the general context of the current multi-decennial Sahel drought. The seasonal and interannual variations of the areas covered by surface water are assessed using multi-date and multi-sensor satellite images (SPOT, FORMOSAT, LANDSAT-MSS, –TM, and -ETM, CORONA, and MODIS and aerial photographs (IGN. Water body classification is adapted to each type of spectral resolution, with or without a middle-infrared band, and each spatial resolution, using linear unmixing for mixed pixels of MODIS data. The high-frequency MODIS data document the seasonal cycle of flooded areas, with an abrupt rise early in wet season and a progressive decrease in the dry season. They also provide a base to study the inter-annual variability of the flooded areas, with sharp contrasts between dry years such as 2004 (low and early maximal area and wetter years such as 2001 and 2002 (respectively high and late maximal area.The highest flooded area reached annually greatly depends on the volume, intensity and timing of rain events. However, the overall reduction by 20% of annual rains during the last 40 years is concomitant with an apparently paradoxical large increase in the area of surface water, starting from the 1970's and accelerating in the mid 1980's. Spectacular for the two study cases of Agoufou and Ebang Mallam, for which time series covering the 1954 to present period exist, this increase is also diagnosed at the regional scale from LANDSAT data spanning 1972–2007. It reaches 108% between September 1975 and 2002 for 91 ponds identified in central Gourma. Ponds with turbid waters and no aquatic vegetation are mostly responsible for this increase, more pronounced in the centre and north of the study zone. Possible causes of the differential changes in flooded areas are discussed in relation with the specifics in topography, soil texture and vegetation

Rain-Use-Efficiency: What it Tells us about the Conflicting Sahel Greening and Sahelian Paradox

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Cécile Dardel

2014-04-01

Full Text Available Rain Use Efficiency (RUE, defined as Aboveground Net Primary Production (ANPP divided by rainfall, is increasingly used to diagnose land degradation. Yet, the outcome of RUE monitoring has been much debated since opposite results were found about land degradation in the Sahel region. The debate is fueled by methodological issues, especially when using satellite remote sensing data to estimate ANPP, and by differences in the ecological interpretation. An alternative method which solves part of these issues relies on the residuals of ANPP regressed against rainfall (“ANPP residuals”. In this paper, we use long-term field observations of herbaceous vegetation mass collected in the Gourma region in Mali together with remote sensing data (GIMMS-3g Normalized Difference Vegetation Index to estimate ANPP, RUE, and the ANPP residuals, over the period 1984–2010. The residuals as well as RUE do not reveal any trend over time over the Gourma region, implying that vegetation is resilient over that period, when data are aggregated at the Gourma scale. We find no conflict between field-derived and satellite-derived results in terms of trends. The nature (linearity of the ANPP/rainfall relationship is investigated and is found to have no impact on the RUE and residuals interpretation. However, at odds with a stable RUE, an increased run-off coefficient has been observed in the area over the same period, pointing towards land degradation. The divergence of these two indicators of ecosystem resilience (stable RUE and land degradation (increasing run-off coefficient is referred to as the “second Sahelian paradox”. When shallow soils and deep soils are examined separately, high resilience is diagnosed on the deep soil sites. However, some of the shallow soils show signs of degradation, being characterized by decreasing vegetation cover and increasing run-off coefficient. Such results show that contrasted changes may co-exist within a region where a

Specification of parameters for development of a spatial database for drought monitoring and famine early warning in the African Sahel

Science.gov (United States)

Rochon, Gilbert L.

1989-01-01

Parameters were described for spatial database to facilitate drought monitoring and famine early warning in the African Sahel. The proposed system, referred to as the African Drought and Famine Information System (ADFIS) is ultimately recommended for implementation with the NASA/FEMA Spatial Analysis and Modeling System (SAMS), a GIS/Dymanic Modeling software package, currently under development. SAMS is derived from FEMA'S Integration Emergency Management Information System (IEMIS) and the Pacific Northwest Laborotory's/Engineering Topographic Laboratory's Airland Battlefield Environment (ALBE) GIS. SAMS is primarily intended for disaster planning and resource management applications with the developing countries. Sources of data for the system would include the Developing Economics Branch of the U.S. Dept. of Agriculture, the World Bank, Tulane University School of Public Health and Tropical Medicine's Famine Early Warning Systems (FEWS) Project, the USAID's Foreign Disaster Assistance Section, the World Resources Institute, the World Meterological Institute, the USGS, the UNFAO, UNICEF, and the United Nations Disaster Relief Organization (UNDRO). Satellite imagery would include decadal AVHRR imagery and Normalized Difference Vegetation Index (NDVI) values from 1981 to the present for the African continent and selected Landsat scenes for the Sudan pilot study. The system is initially conceived for the MicroVAX 2/GPX, running VMS. To facilitate comparative analysis, a global time-series database (1950 to 1987) is included for a basic set of 125 socio-economic variables per country per year. A more detailed database for the Sahelian countries includes soil type, water resources, agricultural production, agricultural import and export, food aid, and consumption. A pilot dataset for the Sudan with over 2,500 variables from the World Bank's ANDREX system, also includes epidemiological data on incidence of kwashiorkor, marasmus, other nutritional deficiencies, and

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Dynamics of Poverty and Land Degradation in the Sahel (West Africa). Poverty and land degradation are severe and interrelated problems in the Sahel. Burkina Faso, Niger, North Of Sahara, South Of Sahara. PROJECT ...

Les unités pastorales du Sahel sénégalais, outils de gestion de l’elevage et des espaces pastoraux. projet durable ou projet de développement durable ?

Directory of Open Access Journals (Sweden)

Abdrahmane Wane

2006-12-01

Full Text Available Au Ferlo (Sahel sénégalais, la durabilité de l’élevage pastoral repose sur la diversité et la flexibilité des régimes de mobilité. Depuis les années 90, le Projet d’Appui à l’Elevage (PAPEL intervient dans la zone pour organiser la gestion des ressources naturelles à l’échelle des unités pastorales (UP, avec l’objectif affiché d’assurer le contrôle et la durabilité de cette activité. Nous avons tenté d’évaluer la pertinence de la généralisation de ce projet d’envergure à l’aune des caractéristiques propres au pastoralisme, dorénavant reconnu comme la meilleure forme de mise en valeur dans l’environnement incertain du Ferlo. Même si les unités pastorales de gestion des ressources ont prouvé leur intérêt dans plusieurs cas de la première phase du projet en zone pastorale, il semble que dans le contexte sénégalais actuel de politique sectorielle agricole, et d’accaparement privé des ressources foncières, la généralisation systématique du schéma des UP sur tout le territoire risquerait plutôt de menacer la durabilité de la mobilité pastorale.In Ferlo (Senegalese Sahel, the sustainability of the livestock farming depends on the diversity and the flexibility of the regulations of mobility. Since the 90s, the PAPEL (Senegalese Support Project for Livestock has intervened in the area in order to manage the natural resources on the scale of the pastoral units (UP with the declared objective to ensure the control and the sustainability of this activity.  We tried to estimate the relevance of the general implementation of this large-scale project by the yardstick of the characteristics peculiar to Pastoralism, henceforth known as the best valorisation form in the uncertain environment of Ferlo. Even if the pastoral units as tools of the natural resource management have demonstrated their interest in many cases of the first stage of the project in the pastoral area, it seems that, in the

Calorific value of Prosopis africana and Balanites aegyptiaca wood: Relationships with tree growth, wood density and rainfall gradients in the West African Sahel

Energy Technology Data Exchange (ETDEWEB)

Montes, Carmen Sotelo; Weber, John C. [World Agroforestry Centre (ICRAF), Sahel Office, B.P. E 5118 Bamako (Mali); Silva, Dimas Agostinho da; Bolzon de Muniz, Graciela Ines [Universidade Federal do Parana (UFPR), Av. Lothario Meissner, 900, CEP.: 80270-170-Curitiba (Brazil); Garcia, Rosilei A. [Universidade Federal Rural do Rio de Janeiro (UFRRJ), Instituto de Florestas, Departamento de Produtos Florestais, BR 465, km 07, 23890-000, Seropedica, Rio de Janeiro (Brazil)

2011-01-15

Prosopis africana and Balanites aegyptiaca are native tree species in the West African Sahel and provide wood for fuel, construction and other essential products. A provenance/progeny test of each species was established at one relatively dry site in Niger, and evaluated at 13 years. Gross calorific value of the wood was determined for a random sample of trees in each test: gross CV and CVm{sup 3} = gross calorific value in MJ kg{sup -1} and MJ m{sup -3}, respectively. The major objectives were to determine if gross CV was positively correlated with wood density and tree growth, and if gross CV and/or CVm{sup 3} varied with rainfall gradients in the sample region. Provenances were grouped into a drier and more humid zone, and correlations were computed among all trees and separately in each zone. Results indicated that gross CV was not significantly correlated with density in either species. Gross CV was positively correlated with growth of P. africana (but not B. aegyptiaca) only in the drier zone. Gross CVm{sup 3} was positively correlated with growth of both species, and the correlations were stronger in the drier zone. Multiple regressions with provenance latitude, longitude and elevation indicated that provenance means for gross CV increased, in general, from the drier to the more humid zones. Regressions with gross CVm{sup 3} were not significant. Results are compared with earlier research reports from the provenance/progeny tests and with other tropical hardwood species; and practical implications are presented for tree improvement and conservation programs in the region. (author)

Njv Magazine 3 final

African Journals Online (AJOL)

En-Joy

Twenty-five adult Sahel does and two. Sahel bucks ... ovarian mesenterial attachment. Width was ..... TABLE II Variation in the amount of foetal fluid (ml), pH and Specific gravity with C-R length (cm) at. 28, 56 .... culture in Borno State. Nig. Vet.

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2009-03-29

Dynamics of Poverty and Land Degradation in the Sahel (West Africa). Project. Poverty and land degradation are severe and interrelated problems in the Sahel. Start Date: March 29, 2009. End Date: December 3, 2013. Topic: Poverty, SMALLHOLDERS, DESERTIFICATION, SOIL DEGRADATION, SOIL RESOURCES, SOIL ...

Removal and Adsorption of Vanadium and Boron by Some Egyptian Clay Sediments

International Nuclear Information System (INIS)

Mahdy, R.M.

2016-01-01

Due to the increase concerns of the environmental pollution problems, to have safer environment, it seems so important to propose an effective exploration of geological barriers, which are suitable for waste materials disposal. In fact, clay sediments play an essential role as natural adsorbents to immobilize nuclear elements contaminates such as uranium, vanadium and boron. In this study, the clay sediments was collected from either clay exploitation localities or from nearby radioactive mineralization provinces in Egypt. The obtained data clarifies that the adsorption of vanadium and boron by clay sediments were increased by increasing the initial concentration of vanadium and boron The adsorption maxima (B) for vanadium in kaolin samples namely Mossaba Salama, El Teah and EL Eessala reached 71.4, 66.7 and 47.6). On the other hand, the adsorption maxima (B) in bentonite samples namely North Coast – H ( El Sahel el shamaly) (high viscosity) followed by North Coast (El Sahel el shamaly) then North Coast (El Sahel el shamaly) (low viscosity) and finally Kasr El Sagha reached 135.1, 79.4, 61.5 and 47.6 respectively.The adsorption maxima for boron in kaolinite samples namely Mossaba Salama, El Teah and EL Eessala reached 47.5, 30.6 and 27.0 while in the bentonite samples it was arranged from Kaser El Sagha (35.7), North Coast (H) El Sahel el shamaly ( H) (32.3), North Coast (L) (27.9) ( El Sahel el shamaly L) to North Coast (El Sahel el shamaly) (3.5)

Search Results | Page 2 | IDRC - International Development ...

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Dynamics of Poverty and Land Degradation in the Sahel (West Africa). Poverty and land degradation are severe and interrelated problems in the Sahel. Land degradation reduces current agricultural productivity and is a form of "dissaving" natural capital that will affect future production and income. Project.

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Results 71 - 80 of 138 ... Integrated Nutrient and Water Management for Sustainable Food Production in the Sahel (CIFSRF). In the Sahel, agricultural production is strictly limited by drought and low soil fertility. In 2005 and 2010, these two factors led to food scarcity in Niger. Project.

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International Development Research Centre (IDRC) Digital Library (Canada)

2011-03-01

Integrated Nutrient and Water Management for Sustainable Food Production in the Sahel (CIFSRF). Project. In the Sahel, agricultural production is strictly limited by drought and low soil fertility. Start Date: March 1, 2011. End Date: September 1, 2014. Topic: FOOD CROPS, SOIL FERTILITY, FERTILIZERS, FERTILIZING, ...

Comparative influence of land and sea surfaces on the Sahelian drought: a numerical study

Directory of Open Access Journals (Sweden)

Arona Diedhiou

Full Text Available The aim of this work is to compare the relative impact of land and sea surface anomalies on Sahel rainfall and to describe the associated anomalies in the atmospheric general circulation. This sensitivity study was done with the Météo-France climate model: ARPEGE. The sensitivity to land surface conditions consists of changes in the management of water and heat exchanges by vegetation cover and bare soil. The sensitivity to ocean surfaces consists in forcing the lower boundary of the model with worldwide composite sea surface temperature (SST anomalies obtained from the difference between 4 dry Sahel years and 4 wet Sahel years observed since 1970. For each case, the spatiotemporal variability of the simulated rainfall anomaly and changes in the modelled tropical easterly jet (TEJ and African easterly jet (AEJ are discussed. The global changes in land surface evaporation have caused a rainfall deficit over the Sahel and over the Guinea Coast. No significant changes in the simulated TEJ and an enhancement of the AEJ are found; at the surface, the energy budget and the hydrological cycle are substantially modified. On the other hand, SST anomalies induce a negative rainfall anomaly over the Sahel and a positive rainfall anomaly to the south of this area. The rainfall deficit due to those anomalies is consistent with previous diagnostic and sensitivity studies. The TEJ is weaker and the AEJ is stronger than in the reference. The composite impact of SST and land surfaces anomalies is also analyzed: the simulated rainfall anomaly is similar to the observed mean African drought patterns. This work suggests that large-scale variations of surface conditions may have a substantial influence on Sahel rainfall and shows the importance of land surface parameterization in climate change modelling. In addition, it points out the interest in accurately considering the land and sea surfaces conditions in sensitivity studies on Sahel rainfall.

Comparative influence of land and sea surfaces on the Sahelian drought: a numerical study

Directory of Open Access Journals (Sweden)

A. Diedhiou

1996-01-01

Full Text Available The aim of this work is to compare the relative impact of land and sea surface anomalies on Sahel rainfall and to describe the associated anomalies in the atmospheric general circulation. This sensitivity study was done with the Météo-France climate model: ARPEGE. The sensitivity to land surface conditions consists of changes in the management of water and heat exchanges by vegetation cover and bare soil. The sensitivity to ocean surfaces consists in forcing the lower boundary of the model with worldwide composite sea surface temperature (SST anomalies obtained from the difference between 4 dry Sahel years and 4 wet Sahel years observed since 1970. For each case, the spatiotemporal variability of the simulated rainfall anomaly and changes in the modelled tropical easterly jet (TEJ and African easterly jet (AEJ are discussed. The global changes in land surface evaporation have caused a rainfall deficit over the Sahel and over the Guinea Coast. No significant changes in the simulated TEJ and an enhancement of the AEJ are found; at the surface, the energy budget and the hydrological cycle are substantially modified. On the other hand, SST anomalies induce a negative rainfall anomaly over the Sahel and a positive rainfall anomaly to the south of this area. The rainfall deficit due to those anomalies is consistent with previous diagnostic and sensitivity studies. The TEJ is weaker and the AEJ is stronger than in the reference. The composite impact of SST and land surfaces anomalies is also analyzed: the simulated rainfall anomaly is similar to the observed mean African drought patterns. This work suggests that large-scale variations of surface conditions may have a substantial influence on Sahel rainfall and shows the importance of land surface parameterization in climate change modelling. In addition, it points out the interest in accurately considering the land and sea surfaces conditions in sensitivity studies on Sahel rainfall.

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Region: Burkina Faso, Benin, Mali, Niger, North of Sahara, South of Sahara, Canada. Program: Agriculture and Food Security. Total Funding: CA$ 1,675,091.00. Integrated Nutrient and Water Management for Sustainable Food Production in the Sahel (CIFSRF). Project. In the Sahel, agricultural production is strictly limited ...

Integrated Nutrient and Water Management for Sustainable Food ...

International Development Research Centre (IDRC) Digital Library (Canada)

Integrated Nutrient and Water Management for Sustainable Food Production in the Sahel (CIFSRF). In the Sahel, agricultural production is strictly limited by drought and low soil fertility. In 2005 and 2010, these two factors led to food scarcity in Niger. However, innovative technologies such as microdose fertilization ...

CTC Sentinel. Volume 5, Issue 2, February 2012

Science.gov (United States)

2012-02-01

Los Zetas grew independent of the Gulf Cartel, the organization was at a disadvantage because it did not have contacts in Colombia or other...Terrorism in North Africa and the Sahel: Al-Qaida’s Franchise or Freelance,” Middle East Institute, August 201; “Islamist Terrorism in the Sahel

[Contribution of migrations to the process of urbanization].

Science.gov (United States)

Bocquier, P

1997-10-01

An average of 22% of the populations of the Sahel countries resided in urban areas in the mid-1970s, a lower level than in the rest of sub-Saharan Africa. The proportion urban has increased by about 5.5% annually over the past 2 decades. By 1993, four Sahel countries had over 30% of their populations in urban areas, and only Burkina Faso had less than 20% urban. The landlocked Sahel countries of Burkina Faso, Mali, Niger, and Chad have maintained rates of urbanization comparable to those of the coastal countries (Cape Verde, Gambia, Mauritania, and Senegal), which had more significant levels of urbanization in the past. The rate of growth of the urban population of all of sub-Saharan Africa was around 5.0% during the past 20 years. Only Dakar among the Sahel capitals has a population of over 1 million. Cities are small, and the urban environment is usually limited to the capital. In Guinea-Bissau, for example, the capital concentrates nearly 85% of the urban population. The increased rates of urbanization are due mainly to migration. In the landlocked countries covered by surveys of the Migration and Urbanization Networks in Western Africa (Burkina Faso, Mali, and Niger), the rural exodus was directed primarily to other countries. In Senegal and Mauritania, on the other hand, around two-thirds of migrations were internal. Women contribute more than men to urban growth in the Sahel. Returning migrants also show a strong preference for capital cities. Labor markets are international for men but national for women. Urban unemployment rates in the Sahel countries studied were lower for migrants than nonmigrants.

Can Old Regimes Handle New Wars?

DEFF Research Database (Denmark)

Henningsen, Troels

Research on New Wars argues that since the 1980s states and regimes have become more vulnerable to violence from non-state actors. Two developments in the Sahel region support the New Wars thesis: an increase in Islamist radicalization and new access to the global black market, both of which......, the paper finds that regimes in the Sahel region are still able to cope with the rise in non-state threats. The paper first shortly compares the longevity of the present regimes in the Sahel region to all previous ones, second examines in-depth how Chad and Mali fight the insurgents. Findings are that since...

Maxillofacial and mandibular phenotypes in the skulls of red Sokoto ...

African Journals Online (AJOL)

This work examined phenotypic expressions in the anatomy of the mandible and maxillofacial region of the Red Sokoto and Sahel goats in Nigeria. The infraorbital foramen was placed above premolar two (PM2) in Red Sokoto but above premolar one (PM1) in Sahel. The Red Sokoto displayed interdigital septa (ruggae) ...

Studies of 21st-Century Precipitation Trends Over West Africa

Science.gov (United States)

Druyan, Leonard M.

2010-01-01

West Africa includes a semi-arid zone between the Sahara Desert and the humid Gulf of Guinea coast, approximately between 10 N and 20 N, which is irrigated by summer monsoon rains. This article refers to the region as the Sahel. Rain-fed agriculture is the primary sustenance for Sahel populations, and severe droughts (in the 1970s and 1980s), therefore, have devastating negative societal impacts. The future frequency of Sahel droughts and the evolution of its hydrological balance are therefore of great interest. The article reviews 10 recent research studies that attempt to discover how climate changes will affect the hydrology of the Sahel throughout the 21st century. All 10 studies rely on atmosphere ocean global climate model (AOGCM) simulations based on a range of greenhouse gas emissions scenarios. Many of the simulations are contained in the Intergovernmental Panel on Climate Change archives for Assessment Reports #3 and #4. Two of the studies use AOGCM data to drive regional climate models. Seven studies make projections for the first half of the 21st century and eight studies make projections for the second half. Some studies make projections of wetter conditions and some predict more frequent droughts, and each describes the atmospheric processes associated with its prediction. Only one study projects more frequent droughts before 2050, and that is only for continent-wide degradation in vegetation cover. The challenge to correctly simulate Sahel rainfall decadal trends is particularly daunting because multiple physical mechanisms compete to drive the trend upwards or downwards. A variety of model deficiencies, regarding the simulation of one or more of these physical processes, taints models climate change projections. Consequently, no consensus emerges regarding the impact of anticipated greenhouse gas forcing on the hydrology of the Sahel in the second half of the 21st century.

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International Development Research Centre (IDRC) Digital Library (Canada)

South of Sahara. Sud du Sahara. Read more about Droit des femmes à l'eau à usage agricole au Sahel (Mauritanie, Niger, Sénégal). Language French. Read more about Women's Right to Water for Agricultural Use in the Sahel (Mauritanie, Niger, Sénégal). Language English. Read more about Because Gender Matters ...

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International Development Research Centre (IDRC) Digital Library (Canada)

Results 11 - 20 of 58 ... Spatial fields' dispersion as a farmer strategy to reduce agro-climatic risk at the household level in pearl millet-based systems in the Sahel : a modeling perspective. The rainfall pattern in the Sahel is very erratic with a high spatial variability.Wetested the often reported hypothesis that the dispersion of ...

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International Development Research Centre (IDRC) Digital Library (Canada)

South of Sahara. Sud du Sahara. Read more about Étude de la dynamique de la pauvreté et de la dégradation des sols au Sahel, en Afrique de l'Ouest. Language French. Read more about Dynamics of Poverty and Land Degradation in the Sahel (West Africa). Language English. Read more about Passage à grande ...

People and pixels in the Sahel: a study linking coarse-resolution remote sensing observations to land users' perceptions of their changing environment in Senegal

Directory of Open Access Journals (Sweden)

Stefanie M. Herrmann

2014-09-01

Full Text Available Mounting evidence from satellite observations of a re-greening across much of the Sahel and Sudan zones over the past three decades has raised questions about the extent and reversibility of desertification. Historical ground data that could help in interpreting the re-greening are scarce. To fill that void, we tapped into the collective memories of local land users from central and western Senegal in 39 focus groups and assessed the spatial association between their perceptions of vegetation changes over time and remote sensing-derived trends. To provide context to the vegetation changes, we also explored the land users' perspective on the evolution of other environmental and human variables that are potentially related to the greening, using participatory research methods. While increases in vegetation were confirmed by the study participants for certain areas, which spatially corresponded to satellite-observed re-greening, vegetation degradation dominated their perceptions of change. This degradation, although spatially extensive according to land users, flies under the radar of coarse-resolution remote sensing data because it is not necessarily associated with a decrease in biomass but rather with undesired changes in species composition. Few significant differences were found in the perceived trends of population pressure, environmental, and livelihood variables between communities that have greened up according to satellite data and those that have not. Our findings challenge the prevailing chain of assumptions of the satellite-observed greening trend indicating an improvement of environmental conditions in the sense of a rehabilitation of the vegetation cover after the great droughts of the 1970s and 1980s, and the improvement of environmental conditions possibly translating into more stable livelihoods and greater well-being of the populations. For monitoring desertification and rehabilitation, there is a need to develop remote sensing

Potential climate effect of mineral aerosols over West Africa: Part II—contribution of dust and land cover to future climate change

Science.gov (United States)

Ji, Zhenming; Wang, Guiling; Yu, Miao; Pal, Jeremy S.

2018-04-01

Mineral dust aerosols are an essential component of climate over West Africa, however, little work has been performed to investigate their contributions to potential climate change. A set of regional climate model experiments with and without mineral dust processes and land cover changes is performed to evaluate their climatic effects under the Representative Concentration Pathway 8.5 for two global climate models. Results suggest surface warming to be in the range of 4-8 °C by the end of the century (2081-2100) over West Africa with respect to the present day (1981-2000). The presence of mineral dusts dampens the warming by 0.1-1 °C in all seasons. Accounting for changes in land cover enhances the warming over the north of Sahel and dampens it to the south in spring and summer; however, the magnitudes are smaller than those resulting from dusts. Overall dust loadings are projected to increase, with the greatest increase occurring over the Sahara and Sahel in summer. Accounting for land cover changes tends to reduce dust loadings over the southern Sahel. Future precipitation is projected to decrease by 5-40 % in the western Sahara and Sahel and increase by 10-150 % over the eastern Sahel and Guinea Coast in JJA. A dipole pattern of future precipitation changes is attributed to dust effects, with decrease in the north by 5-20 % and increase by 5-20 % in the south. Future changes in land cover result in a noisy non-significant response with a tendency for slight wetting in MAM, JJA, and SON and drying in DJF.

93 une urbanisation linéaire, dynamique demographique et ...

African Journals Online (AJOL)

Mohand

d'Alger, dans l'ensemble Sahel-Mitidja sur un linéaire côtier de 2 km. Rattaché administrativement à la daira de ... connait une dynamique démographique remar- quable, dans sa périphérie orientale - composé de l'ensemble Sahel-. Mitidja ..... «Etude agro-pédologique de la plaine de la Mitidja». Florin B.; Semoud N. 2010.

Sensitivity of Sahelian Precipitation to Desert Dust under ENSO variability: a regional modeling study

Science.gov (United States)

Jordan, A.; Zaitchik, B. F.; Gnanadesikan, A.

2016-12-01

Mineral dust is estimated to comprise over half the total global aerosol burden, with a majority coming from the Sahara and Sahel region. Bounded by the Sahara Desert to the north and the Sahelian Savannah to the south, the Sahel experiences high interannual rainfall variability and a short rainy season during the boreal summer months. Observation-based data for the past three decades indicates a reduced dust emission trend, together with an increase in greening and surface roughness within the Sahel. Climate models used to study regional precipitation changes due to Saharan dust yield varied results, both in sign convention and magnitude. Inconsistency of model estimates drives future climate projections for the region that are highly varied and uncertain. We use the NASA-Unified Weather Research and Forecasting (NU-WRF) model to quantify the interaction and feedback between desert dust aerosol and Sahelian precipitation. Using nested domains at fine spatial resolution we resolve changes to mesoscale atmospheric circulation patterns due to dust, for representative phases of El Niño-Southern Oscillation (ENSO). The NU-WRF regional earth system model offers both advanced land surface data and resolvable detail of the mechanisms of the impact of Saharan dust. Results are compared to our previous work assessed over the Western Sahel using the Geophysical Fluid Dynamics Laboratory (GFDL) CM2Mc global climate model, and to other previous regional climate model studies. This prompts further research to help explain the dust-precipitation relationship and recent North African dust emission trends. This presentation will offer a quantitative analysis of differences in radiation budget, energy and moisture fluxes, and atmospheric dynamics due to desert dust aerosol over the Sahel.

Regionalizing Africa: Patterns of Precipitation Variability in Observations and Global Climate Models

Science.gov (United States)

Badr, Hamada S.; Dezfuli, Amin K.; Zaitchik, Benjamin F.; Peters-Lidard, Christa D.

2016-01-01

Many studies have documented dramatic climatic and environmental changes that have affected Africa over different time scales. These studies often raise questions regarding the spatial extent and regional connectivity of changes inferred from observations and proxies and/or derived from climate models. Objective regionalization offers a tool for addressing these questions. To demonstrate this potential, applications of hierarchical climate regionalizations of Africa using observations and GCM historical simulations and future projections are presented. First, Africa is regionalized based on interannual precipitation variability using Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) data for the period 19812014. A number of data processing techniques and clustering algorithms are tested to ensure a robust definition of climate regions. These regionalization results highlight the seasonal and even month-to-month specificity of regional climate associations across the continent, emphasizing the need to consider time of year as well as research question when defining a coherent region for climate analysis. CHIRPS regions are then compared to those of five GCMs for the historic period, with a focus on boreal summer. Results show that some GCMs capture the climatic coherence of the Sahel and associated teleconnections in a manner that is similar to observations, while other models break the Sahel into uncorrelated subregions or produce a Sahel-like region of variability that is spatially displaced from observations. Finally, shifts in climate regions under projected twenty-first-century climate change for different GCMs and emissions pathways are examined. A projected change is found in the coherence of the Sahel, in which the western and eastern Sahel become distinct regions with different teleconnections. This pattern is most pronounced in high-emissions scenarios.

Evaluation of indigenous tomato hybrids under plastic tunnel

International Nuclear Information System (INIS)

Farooq, M.; Ullah, H.; Nawab, N.N.; Qureshi, K.M.

2013-01-01

Evaluation of indigenous tomato hybrids under plastic tunnel Seventeen locally developed indeterminate tomato hybrids were evaluated along with 'Sahel' as check under plastic tunnel for yield and yield components at National Agricultural Research Centre, Islamabad. Maximum yield of 71.58 tha/sup -1/ was recorded in NTT-12-08 while minimum yield (34.75 tha/sup -1/) was observed in NTT-16-08. Sahel used as check bore maximum number of fruits plant/sup -1/(30.26) and followed by NTT-04-08 and NTT-03-08 bearing 28.68 and 24.16 fruits plant/sup -1/, respectively. The highest mean fruit weight of 170.63 g was recorded in NTT-05-08 while minimum fruit weight (80.90 g) was observed in Sahel (check). Maximum fruit length of 7.89 cm was recorded in Sahel which is oblong in shape while minimum (5.70 cm) in NTT-14-08. Similarly a significant difference was observed among hybrids for fruit diameter. Fruits having more diameter are round to roundish in shape. Fruit diameter ranged from 8.85 to 5.49 cm. Fruit firmness also varied significantly ranging from 3.54 to 1.67 kg m/sup -3/ in Sahel and NTT-07-08, respectively. Maximum pericarp thickness (0.90 cm) was recorded in NTT-10-08 while minimum pericarp thickness of 0.58 cm was observed in NTT-16-08. NTT-01-08 exhibits the highest number of locules (5.22). It was followed by NTT-02-08 having 4.55 locules while minimum (2.0) locules were observed in NTT-09-08. (author)

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International Development Research Centre (IDRC) Digital Library (Canada)

Fin des deux solitudes de l'élevage et de l'agriculture au Sahel (open access). Les femmes de Toukounous, petite localité située à 20 km de Niamey, participent à un moment charnière de l''histoire agricole du Niger et du Sahel. En effet, leur région ne vit que maintenant l''intégration de l''agriculture et de l''élevage, étape ...

Staying with the system

DEFF Research Database (Denmark)

Rasmussen, Laura Vang; Nielsen, Jonas Østergaard

2014-01-01

Scholars have studied the Sahel intensely since major droughts hit the region in the early 1970s. One of the most persistent of these in terms of both volume and time span is Anette Reenberg. In this paper we explore her studies of the Sahel published in peer-reviewed journals and their impact over...... the last three decades. Reenberg has had a remarkably stable theoretical agenda concerned with the importance of understanding the social and biophysical systems as one coupled human-environmental system. This agenda has influenced contemporary as well as subsequent Danish scholars publishing on the Sahel......-environmental system framework in the journal may be attributed to Reenberg’s theoretical agenda as well as a new international stream of research joining the human and environmental sciences in an interdisciplinary effort. Hence, it is also shown how Reenberg’s theoretical agenda have influenced scholars trying...

Security in the Sahel

DEFF Research Database (Denmark)

Hahonou, Eric Komlavi

of volatile security. In this policy brief, Eric Hahonou argues that without complementary activities, the multiplication of border offices could even expand opportunities for corruption. Instead, security policy should focus on creating a culture of effectiveness including systematic and regular staff...

Sensitivity of MENA Tropical Rainbelt to Dust Shortwave Absorption: A High Resolution AGCM Experiment

KAUST Repository

Bangalath, Hamza Kunhu; Stenchikov, Georgiy L.

2016-01-01

Shortwave absorption is one of the most important, but the most uncertain, components of direct radiative effect by mineral dust. It has a broad range of estimates from different observational and modeling studies and there is no consensus on the strength of absorption. To elucidate the sensitivity of the Middle East and North Africa (MENA) tropical summer rainbelt to a plausible range of uncertainty in dust shortwave absorption, AMIP-style global high resolution (25 km) simulations are conducted with and without dust, using the High-Resolution Atmospheric Model (HiRAM). Simulations with dust comprise three different cases by assuming dust as a very efficient, standard and inefficient absorber. Inter-comparison of these simulations shows that the response of the MENA tropical rainbelt is extremely sensitive to the strength of shortwave absorption. Further analyses reveal that the sensitivity of the rainbelt stems from the sensitivity of the multi-scale circulations that define the rainbelt. The maximum response and sensitivity are predicted over the northern edge of the rainbelt, geographically over Sahel. The sensitivity of the responses over the Sahel, especially that of precipitation, is comparable to the mean state. Locally, the response in precipitation reaches up to 50% of the mean, while dust is assumed to be a very efficient absorber. Taking into account that Sahel has a very high climate variability and is extremely vulnerable to changes in precipitation, the present study suggests the importance of reducing uncertainty in dust shortwave absorption for a better simulation and interpretation of the Sahel climate.

Sensitivity of MENA Tropical Rainbelt to Dust Shortwave Absorption: A High Resolution AGCM Experiment

KAUST Repository

Bangalath, Hamza Kunhu

2016-06-13

Shortwave absorption is one of the most important, but the most uncertain, components of direct radiative effect by mineral dust. It has a broad range of estimates from different observational and modeling studies and there is no consensus on the strength of absorption. To elucidate the sensitivity of the Middle East and North Africa (MENA) tropical summer rainbelt to a plausible range of uncertainty in dust shortwave absorption, AMIP-style global high resolution (25 km) simulations are conducted with and without dust, using the High-Resolution Atmospheric Model (HiRAM). Simulations with dust comprise three different cases by assuming dust as a very efficient, standard and inefficient absorber. Inter-comparison of these simulations shows that the response of the MENA tropical rainbelt is extremely sensitive to the strength of shortwave absorption. Further analyses reveal that the sensitivity of the rainbelt stems from the sensitivity of the multi-scale circulations that define the rainbelt. The maximum response and sensitivity are predicted over the northern edge of the rainbelt, geographically over Sahel. The sensitivity of the responses over the Sahel, especially that of precipitation, is comparable to the mean state. Locally, the response in precipitation reaches up to 50% of the mean, while dust is assumed to be a very efficient absorber. Taking into account that Sahel has a very high climate variability and is extremely vulnerable to changes in precipitation, the present study suggests the importance of reducing uncertainty in dust shortwave absorption for a better simulation and interpretation of the Sahel climate.

Variability and Predictability of West African Droughts. A Review in the Role of Sea Surface Temperature Anomalies

Science.gov (United States)

Rodriguez-Fonseca, Belen; Mohino, Elsa; Mechoso, Carlos R.; Caminade, Cyril; Biasutti, Michela; Gaetani, Marco; Garcia-Serrano, J.; Vizy, Edward K.; Cook, Kerry; Xue, Yongkang;

Robust features of future climate change impacts on sorghum yields in West Africa

International Nuclear Information System (INIS)

Sultan, B; Guan, K; Lobell, D B; Kouressy, M; Biasutti, M; Piani, C; Hammer, G L; McLean, G

2014-01-01

West Africa is highly vulnerable to climate hazards and better quantification and understanding of the impact of climate change on crop yields are urgently needed. Here we provide an assessment of near-term climate change impacts on sorghum yields in West Africa and account for uncertainties both in future climate scenarios and in crop models. Towards this goal, we use simulations of nine bias-corrected CMIP5 climate models and two crop models (SARRA-H and APSIM) to evaluate the robustness of projected crop yield impacts in this area. In broad agreement with the full CMIP5 ensemble, our subset of bias-corrected climate models projects a mean warming of +2.8 °C in the decades of 2031–2060 compared to a baseline of 1961–1990 and a robust change in rainfall in West Africa with less rain in the Western part of the Sahel (Senegal, South-West Mali) and more rain in Central Sahel (Burkina Faso, South-West Niger). Projected rainfall deficits are concentrated in early monsoon season in the Western part of the Sahel while positive rainfall changes are found in late monsoon season all over the Sahel, suggesting a shift in the seasonality of the monsoon. In response to such climate change, but without accounting for direct crop responses to CO 2 , mean crop yield decreases by about 16–20% and year-to-year variability increases in the Western part of the Sahel, while the eastern domain sees much milder impacts. Such differences in climate and impacts projections between the Western and Eastern parts of the Sahel are highly consistent across the climate and crop models used in this study. We investigate the robustness of impacts for different choices of cultivars, nutrient treatments, and crop responses to CO 2 . Adverse impacts on mean yield and yield variability are lowest for modern cultivars, as their short and nearly fixed growth cycle appears to be more resilient to the seasonality shift of the monsoon, thus suggesting shorter season varieties could be considered a

Robust features of future climate change impacts on sorghum yields in West Africa

Science.gov (United States)

Sultan, B.; Guan, K.; Kouressy, M.; Biasutti, M.; Piani, C.; Hammer, G. L.; McLean, G.; Lobell, D. B.

2014-10-01

West Africa is highly vulnerable to climate hazards and better quantification and understanding of the impact of climate change on crop yields are urgently needed. Here we provide an assessment of near-term climate change impacts on sorghum yields in West Africa and account for uncertainties both in future climate scenarios and in crop models. Towards this goal, we use simulations of nine bias-corrected CMIP5 climate models and two crop models (SARRA-H and APSIM) to evaluate the robustness of projected crop yield impacts in this area. In broad agreement with the full CMIP5 ensemble, our subset of bias-corrected climate models projects a mean warming of +2.8 °C in the decades of 2031-2060 compared to a baseline of 1961-1990 and a robust change in rainfall in West Africa with less rain in the Western part of the Sahel (Senegal, South-West Mali) and more rain in Central Sahel (Burkina Faso, South-West Niger). Projected rainfall deficits are concentrated in early monsoon season in the Western part of the Sahel while positive rainfall changes are found in late monsoon season all over the Sahel, suggesting a shift in the seasonality of the monsoon. In response to such climate change, but without accounting for direct crop responses to CO2, mean crop yield decreases by about 16-20% and year-to-year variability increases in the Western part of the Sahel, while the eastern domain sees much milder impacts. Such differences in climate and impacts projections between the Western and Eastern parts of the Sahel are highly consistent across the climate and crop models used in this study. We investigate the robustness of impacts for different choices of cultivars, nutrient treatments, and crop responses to CO2. Adverse impacts on mean yield and yield variability are lowest for modern cultivars, as their short and nearly fixed growth cycle appears to be more resilient to the seasonality shift of the monsoon, thus suggesting shorter season varieties could be considered a potential

Recent variations in geopotential height associated with West African monsoon variability

Science.gov (United States)

Okoro, Ugochukwu K.; Chen, Wen; Nath, Debashis

2018-02-01

In the present study, the atmospheric circulation patterns associated with the seasonal West Africa (WA) monsoon (WAM) rainfall variability has been investigated. The observational rainfall data from the Climatic Research Unit (CRU) and atmospheric fields from the National Center for Environmental Prediction (NCEP) reanalysis 2, from 1979 to 2014, have been used. The rainfall variability extremes, classified as wet or dry years, are the outcomes of simultaneous 6-month SPI at the three rainfall zones, which shows increasing trends [Guinea Coast (GC = 0.012 year-1), Eastern Sudano Sahel (ESS = 0.045 year-1) and Western Sudano Sahel (WSS = 0.056 year-1) from Sen's slope]; however, it is significant only in the Sahel region (α = 0.05 and α = 0.001 at ESS and WSS, respectively, from Mann-Kendall test). The vertical profile of the geopotential height (GpH) during the wet and dry years reveals that the 700 hPa anomalies show remarkable pattern at about 8°N to 13°N. This shows varying correlation with the zonal averaged vertically integrated moisture flux convergence and rainfall anomalies, respectively, as well as the oceanic pulsations indexes [Ocean Nino Index (ONI) and South Atlantic Ocean dipole index (SAODI), significant from t test], identified as precursors to the Sahel and GC rainfall variability respectively. The role of GpH anomalies at 700 hPa has been identified as the facilitator to the West African Westerly Jet's input to the moisture flux transported over the WA. This is a new perspective of the circulation processes associated with WAM and serves as a basis for modeling investigations.

Couplings between the seasonal cycles of surface thermodynamics and radiative fluxes in the semi-arid Sahel

Science.gov (United States)

Guichard, F.; Kergoat, L.; Mougin, E.; Timouk, F.; Bock, O.; Hiernaux, P.

2009-04-01

A good knowledge of surface fluxes and atmospheric low levels is central to improving our understanding of the West African monsoon. This study provides a quantitative analysis of the peculiar seasonal and diurnal cycles of surface thermodynamics and radiative fluxes encountered in Central Sahel. It is based on a multi-year dataset collected in the Malian Gourma over a sandy soil at 1.5°W-15.3°N (a site referred to as Agoufou) with an automated weather station and a sunphotometer (AERONET), complemented by observations from the AMMA field campaign. The seasonal cycle of this Tropical region is characterized by a broad maximum of temperature in May, following the first minimum of the solar zenith angle by a few weeks, when Agoufou lies within the West African Heat-Low, and a late summer maximum of equivalent potential temperature within the core of the monsoon season, around the second yearly maximum of solar zenith angle, as the temperature reaches its Summer minimum. More broadly, subtle balances between surface air temperature and moisture fields are found on a range of scales. For instance, during the monsoon, apart from August, their opposite daytime fluctuations (warming, drying) lead to an almost flat diurnal cycle of the equivalent potential temperature at the surface. This feature stands out in contrast to other more humid continental regions. Here, the strong dynamics associated with the transition from a drier hot Spring to a brief cooler wet tropical Summer climate involves very large transformations of the diurnal cycles. The Summer increase of surface net radiation, Rnet, is also strong; typically 10-day mean Rnet reaches about 5 times its Winter minimum (~30 W.m-2) in August (~150 W.m-2). A major feature revealed by observations is that this increase is mostly driven by modifications of the surface upwelling fluxes shaped by rainfall events and vegetation phenology (surface cooling and darkening), while the direct impact of atmospheric changes on

Environmental change in the Sahel

DEFF Research Database (Denmark)

Rasmussen, Kjeld; D'haen, Sarah Ann Lise; Fensholt, Rasmus

2016-01-01

and choice of indicators, (2) biases, for example, related to selection of study sites, methodological choices, measurement accuracy, perceptions among interlocutors, and selection of temporal and spatial scales of analysis. The analysis of the root causes for different interpretations suggests...... that differences in findings could often be considered as complementary insights rather than mutually exclusive. This will have implications for the ways in which scientific results can be expected to support regional environmental policies and contribute to knowledge production....

Statistical and dynamical assessment of land-ocean-atmosphere interactions across North Africa

Science.gov (United States)

Yu, Yan

North Africa is highly vulnerable to hydrologic variability and extremes, including impacts of climate change. The current understanding of oceanic versus terrestrial drivers of North African droughts and pluvials is largely model-based, with vast disagreement among models in terms of the simulated oceanic impacts and vegetation feedbacks. Regarding oceanic impacts, the relative importance of the tropical Pacific, tropical Indian, and tropical Atlantic Oceans in regulating the North African rainfall variability, as well as the underlying mechanism, remains debated among different modeling studies. Classic theory of land-atmosphere interactions across the Sahel ecotone, largely based on climate modeling experiments, has promoted positive vegetation-rainfall feedbacks associated with a dominant surface albedo mechanism. However, neither the proposed positive vegetation-rainfall feedback with its underlying albedo mechanism, nor its relative importance compared with oceanic drivers, has been convincingly demonstrated up to now using observational data. Here, the multivariate Generalized Equilibrium Feedback Assessment (GEFA) is applied in order to identify the observed oceanic and terrestrial drivers of North African climate and quantify their impacts. The reliability of the statistical GEFA method is first evaluated against dynamical experiments within the Community Earth System Model (CESM). In order to reduce the sampling error caused by short data records, the traditional GEFA approach is refined through stepwise GEFA, in which unimportant forcings are dropped through stepwise selection. In order to evaluate GEFA's reliability in capturing oceanic impacts, the atmospheric response to a sea-surface temperature (SST) forcing across the tropical Pacific, tropical Indian, and tropical Atlantic Ocean is estimated independently through ensembles of dynamical experiments and compared with GEFA-based assessments. Furthermore, GEFA's performance in capturing terrestrial

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Results 591 - 600 of 1119 ... Journal articles. Food security RAINFED FARMING BURKINA FASO CLIMATE CHANGE ADAPTATION RUNOFF WATER SAHEL ... PROTECTION Environmental economics ENVIRONMENTAL MANAGEMENT ...

Diagnosing GCM errors over West Africa using relaxation experiments. Part II: intraseasonal variability and African easterly waves

Science.gov (United States)

Pohl, Benjamin; Douville, Hervé

2011-10-01

A near-global grid-point nudging of the Arpege-Climat atmospheric General Circulation Model towards ECMWF reanalyses is used to diagnose the regional versus remote origin of the summer model biases and variability over West Africa. First part of this study revealed a limited impact on the monsoon climatology compared to a control experiment without nudging, but a significant improvement of interannual variability, although the amplitude of the seasonal anomalies remained underestimated. Focus is given here on intraseasonal variability of monsoon rainfall and dynamics. The reproducible part of these signals is investigated through 30-member ensemble experiments computed for the 1994 rainy season, a year abnormally wet over the Sahel but representative of the model systematic biases. In the control experiment, Arpege-Climat simulates too few rainy days that are associated with too low rainfall amounts over the central and western Sahel, in line with the seasonal dry biases. Nudging the model outside Africa tends to slightly increase the number of rainy days over the Sahel, but has little effect on associated rainfall amounts. However, results do indicate that a significant part of the monsoon intraseasonal variability simulated by Arpege-Climat is controlled by lateral boundary conditions. Parts of the wet/dry spells over the Sahel occur in phase in the 30 members of the nudging experiment, and are therefore embedded in larger-scale variability patterns. Inter-member spread is however not constant across the selected summer season. It is partly controlled by African Easterly Waves, which show dissimilar amplitude from one member to another, but a coherent phasing in all members. A lowpass filtering of the nudging fields suggests that low frequency variations in the lateral boundary conditions can lead to eastward extensions of the African Easterly Jet, creating a favorable environment for easterly waves, while high frequency perturbations seem to control their

Diagnosing GCM errors over West Africa using relaxation experiments. Part II: intraseasonal variability and African easterly waves

Energy Technology Data Exchange (ETDEWEB)

Pohl, Benjamin [CNRM-GAME, Meteo-France, CNRS, Toulouse (France); Centre de Recherches de Climatologie, CNRS, Universite de Bourgogne, Dijon (France); Douville, Herve [CNRM-GAME, Meteo-France, CNRS, Toulouse (France)

2011-10-15

A near-global grid-point nudging of the Arpege-Climat atmospheric General Circulation Model towards ECMWF reanalyses is used to diagnose the regional versus remote origin of the summer model biases and variability over West Africa. First part of this study revealed a limited impact on the monsoon climatology compared to a control experiment without nudging, but a significant improvement of interannual variability, although the amplitude of the seasonal anomalies remained underestimated. Focus is given here on intraseasonal variability of monsoon rainfall and dynamics. The reproducible part of these signals is investigated through 30-member ensemble experiments computed for the 1994 rainy season, a year abnormally wet over the Sahel but representative of the model systematic biases. In the control experiment, Arpege-Climat simulates too few rainy days that are associated with too low rainfall amounts over the central and western Sahel, in line with the seasonal dry biases. Nudging the model outside Africa tends to slightly increase the number of rainy days over the Sahel, but has little effect on associated rainfall amounts. However, results do indicate that a significant part of the monsoon intraseasonal variability simulated by Arpege-Climat is controlled by lateral boundary conditions. Parts of the wet/dry spells over the Sahel occur in phase in the 30 members of the nudging experiment, and are therefore embedded in larger-scale variability patterns. Inter-member spread is however not constant across the selected summer season. It is partly controlled by African Easterly Waves, which show dissimilar amplitude from one member to another, but a coherent phasing in all members. A lowpass filtering of the nudging fields suggests that low frequency variations in the lateral boundary conditions can lead to eastward extensions of the African Easterly Jet, creating a favorable environment for easterly waves, while high frequency perturbations seem to control their

Large-scale control of the Arabian Sea monsoon inversion in August

Science.gov (United States)

Wu, Chi-Hua; Wang, S.-Y. Simon; Hsu, Huang-Hsiung

2017-12-01

The summer monsoon inversion in the Arabian Sea is characterized by a large amount of low clouds and August as the peak season. Atmospheric stratification associated with the monsoon inversion has been considered a local system influenced by the advancement of the India-Pakistan monsoon. Empirical and numerical evidence from this study suggests that the Arabian Sea monsoon inversion is linked to a broader-scale monsoon evolution across the African Sahel, South Asia, and East Asia-Western North Pacific (WNP), rather than being a mere byproduct of the India-Pakistan monsoon progression. In August, the upper-tropospheric anticyclone in South Asia extends sideways corresponding with the enhanced precipitation in the subtropical WNP, equatorial Indian Ocean, and African Sahel while the middle part of this anticyclone weakens over the Arabian Sea. The increased heating in the adjacent monsoon systems creates a suppression effect on the Arabian Sea, suggesting an apparent competition among the Africa-Asia-WNP monsoon subsystems. The peak Sahel rainfall in August, together with enhanced heating in the equatorial Indian Ocean, produces a critical effect on strengthening the Arabian Sea thermal inversion. By contrast, the WNP monsoon onset which signifies the eastward expansion of the subtropical Asian monsoon heating might play a secondary or opposite role in the Arabian Sea monsoon inversion.

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2009-07-27

Saharan Africa such as the Sahel. Start Date: July 27, 2009. End Date: December 31, 2013. Topic: Climate change, ADAPTATION TO CHANGE, DROUGHT, AGRICULTURAL RESEARCH, AGRICULTURAL INNOVATIONS, AGRICULTURAL ...

Development of a cross-protective synthetic RNA vaccine against ...

International Development Research Centre (IDRC) Digital Library (Canada)

... Biotechnology (Boston, USA), Moredun Research Institute (Edinburgh, UK), ... Natural Resources Management for Sustainable Food Security in the Sahel ... are key strategies in Ethiopia's efforts to fight poverty and improve food security.

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2014-01-01

Results 111 - 120 of 138 ... Review of pasture and fodder production and productivity for small ruminants in the Sahel. Published date. January 1, 2014. Research in Action. Crops Agrifood markets ...

Building Livelihood Resilience to Alleviate Poverty in Semi-arid ...

International Development Research Centre (IDRC) Digital Library (Canada)

Saharan Africa such as the Sahel. The complex nature of vulnerability calls for an integrated systems-based approach combining the adoption of agricultural innovations, resource management, new market opportunities, and ...

Regional Integration and Cooperation in West Africa: A ...

International Development Research Centre (IDRC) Digital Library (Canada)

Regional Integration and Cooperation in West Africa: A Multidimensional Perspective. Book cover Regional ... New initiative will match climate knowledge to developing country needs ... New project to improve water management in the Sahel.

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Results 21 - 30 of 65 ... Impression management pervades kidnapping episodes. ... Farming and livestock production in the Sahel : merging the two solutions ... and Evaluation of Climate Change Adaptive Capacities: Handbook and User Guide.

COMBATING TERRORISM: Actions Needed to Enhance Implementation of Trans-Sahara Counterterrorism Partnership

National Research Council Canada - National Science Library

Johnson, Jr., Charles M; Merritt, Zina D; Alley, Ashley; Barton, Nanette J; Dornisch, David; Lowe, Reid L; Miller, John F

2008-01-01

In 2005 through 2008, the key agencies distributed the majority of the obligated and committed resources to countries in the Sahel region, supporting a range of diplomacy, development assistance, and military activities...

Don't Trust the Big Man

National Research Council Canada - National Science Library

Coerr, Stanton S

2008-01-01

The African region below the Sahel, with its legacy of racist European colonial rule followed in the early 1960s by the emergence of incompetent, kleptocratic, and ruthless African rule, is dominated...

A National Security Strategy of Cooperative Engagement for Sub-Saharan Africa

National Research Council Canada - National Science Library

Gunzinger, Mark A; Thomas, David L

1996-01-01

Extending from the urban centers of South Africa to the lesser-developed regions of the arid Sahel, Sub-Saharan Africa spans the post-Cold War spectrum of political, economic, and military challenges...

Vegetative propagation of twelve fodder tree species indigenous to ...

African Journals Online (AJOL)

Vegetative propagation of twelve fodder tree species indigenous to the Sahel, West Africa. Catherine Ky-Dembele, Jules Bayala, Antoine Kalinganire, Fatoumata Tata Traoré, Bréhima Koné, Alain Olivier ...

All projects related to canada | Page 12 | IDRC - International ...

International Development Research Centre (IDRC) Digital Library (Canada)

2011-11-01

Integrated Nutrient and Water Management for Sustainable Food Production in the Sahel (CIFSRF) ... equality") is an important principle of Canada's international cooperation program. Start Date: November 1, 2011. End Date: March 31, 2015.

Better fertilizer use in the Sahel

International Development Research Centre (IDRC) Digital Library (Canada)

INTERNATIONAL DEVELOPMENT RESEARCH CENTRE. MULTI-FUNDER INITIATIVE. The Canadian International Food Security Research Fund (CIFSRF) is a program of Canada's International Development Research. Centre (IDRC) undertaken with the financial support of the Government of Canada provided through ...

Ghana Journal of Agricultural Science - Vol 20 (1987)

African Journals Online (AJOL)

A preliminary study of pre-harvest insect infestation and storability of four Ghanaian ... Seed germination and growth of Eleucine indica and Euphorbia heterophylla as ... Lambing and neonatal behaviour of Djallonke x Sahel crossbred sheep.

Mobilizing Private Sector Investment in Adaptation to Climate Change

International Development Research Centre (IDRC) Digital Library (Canada)

Climate change and the private sector Private sector investment in climate change adaptation has ... Encouraging investments in adaptation This research will create an evidence base ... New project to improve water management in the Sahel.

Genes in the Field: On-Farm Conservation of Crop Diversity | IDRC ...

International Development Research Centre (IDRC) Digital Library (Canada)

... the UN, the World Bank, the International Plant Genetic Resources Institute, and the International ... He is coauthor (with Doreen Stabinsky) or Valuing Local Knowledge: Indigenous ... New project to improve water management in the Sahel.

Does EO NDVI seasonal metrics capture variations in species composition and biomass due to grazing in semi-arid grassland savannas?

DEFF Research Database (Denmark)

Olsen, J. L.; Miehe, S.; Ceccato, Pietro

2015-01-01

Most regional scale studies of vegetation in the Sahel have been based on Earth observation (EO) imagery due to the limited number of sites providing continuous and long term in situ meteorological and vegetation measurements. From a long time series of coarse resolution normalized difference...... vegetation index (NDVI) data a greening of the Sahel since the 1980s has been identified. However, it is poorly understood how commonly applied remote sensing techniques reflect the influence of extensive grazing (and changes in grazing pressure) on natural rangeland vegetation. This paper analyses the time...... exclosures as compared to grazed areas, substantially exceeding the amount of biomass expected to be ingested by livestock for this area. The seasonal integrated NDVI (NDVI small integral; capturing only the signal inherent to the growing season recurrent vegetation), derived using absolute thresholds...

Watershed: The Role of Fresh Water in the Israeli-Palestinian Conflict

International Development Research Centre (IDRC) Digital Library (Canada)

They offer immediate solutions to water problems in Israel and the Occupied Palestinian Territories. ... problems of water supply and water quality, and regional conflicts over water. ... New project to improve water management in the Sahel.

Children with protein energy malnutrition: management and out ...

African Journals Online (AJOL)

Children with protein energy malnutrition: management and out-come in a ... Sahel Medical Journal ... Demographic data, predisposing factors, clinical types of PEM, outcome of management and time of discharge or death were also extracted ...

Scaling Up Pulse Innovations for Food and Nutrition Security in ...

International Development Research Centre (IDRC) Digital Library (Canada)

Researchers will study the entire value chain for beans and chickpeas - from production to consumers. ... government agencies to integrate the new products into local supply chains. ... New project to improve water management in the Sahel.

All projects related to Burkina Faso | Page 3 | IDRC - International ...

International Development Research Centre (IDRC) Digital Library (Canada)

... with the general rise in food prices has increased food insecurity in the Sahel. ... Consumer Unity &Trust Society (CUTS International) is an international ... between researchers, inventors and innovators and public decision-makers with a ...

Diversity, Globalization, and the Ways of Nature | IDRC ...

International Development Research Centre (IDRC) Digital Library (Canada)

... geographer, received his doctorate in 1973 from the Université Louis Pasteur in Strasbourg, France. ... New project to improve water management in the Sahel ... IDRC congratulates first cohort of Women in Climate Change Science Fellows.

Dějiny sahelu pohledem genetické diverzity jeho obyvatel

Czech Academy of Sciences Publication Activity Database

Černý, Viktor

2016-01-01

Roč. 64, č. 5 (2016), s. 241-243 ISSN 0044-4812 R&D Projects: GA ČR GA13-37998S Institutional support: RVO:67985912 Keywords : genetic diversity * Sahel Subject RIV: AC - Archeology, Anthropology, Ethnology

The Effect of Breed, Age and Fasting Status on Macro-nutrient ...

African Journals Online (AJOL)

acer

Experimental Layout: Carcasses of 32 male ... randomized 2x2x2 factorial design involving two breeds (Sahel, Sokoto ... interactions between the factors were excluded from the final .... SPSS (1999) Statistical Package for the Social. Sciences.

All projects related to | Page 101 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

Financial Services and the Deployment of Agricultural Innovations in the Sahel. Project. Over the past 20 years, numerous innovations to improve food crop yields have ... Areas Network Phase III: Devolution to the American University of Beirut.

Adaptation Stories

International Development Research Centre (IDRC) Digital Library (Canada)

By Reg'

adaptation to climate change from various regions of the Sahel. Their .... This simple system, whose cost and maintenance were financially sustainable, brought ... method that enables him to learn from experience and save time, which he ...

Large Mines and the Community: Socioeconomic and ...

International Development Research Centre (IDRC) Digital Library (Canada)

Felix Remy is a principal mining specialist with the World Bank, where he has managed and ... New Dutch-Canadian funding for the Climate and Development Knowledge Network ... New project to improve water management in the Sahel.

a survey of sorghum downy mildew in sorghum in the sudano

African Journals Online (AJOL)

DR. AMINU

Sahel savanna AEZs respectively) indicated that the disease was present only at the seedling stage ... In the southern guinea ... northern Nigeria, sorghum downy mildew in sorghum .... There was a significant (P>0.05) difference in SDM.

Natural Resources Management for Sustainable Food Security in ...

International Development Research Centre (IDRC) Digital Library (Canada)

Natural Resources Management for Sustainable Food Security in the Sahel ... as well as strategies for managing the resource base with a view to improving food security. ... InnoVet-AMR grants to support development of innovative veterinary ...

Publications | Page 602 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

Results 6011 - 6020 of 6388 ... Costs and benefits of flue gas desulfurization for pollution control at the Mae Moh Power Plant, Thailand (open access) ... Farming and livestock production in the Sahel : merging the two solutions (open access).

Social Impact Investment: Increasing Private Sector Investment to ...

International Development Research Centre (IDRC) Digital Library (Canada)

The social impact investment market is now global in scope and it is rapidly expanding in some ... of social impact investing to address environmental, social, and economic challenges. ... New project to improve water management in the Sahel.

Genetic history of the African Sahelian populations.

Science.gov (United States)

Černý, V; Kulichová, I; Poloni, E S; Nunes, J M; Pereira, L; Mayor, A; Sanchez-Mazas, A

2018-03-01

From a biogeographic perspective, Africa is subdivided into distinct horizontal belts. Human populations living along the Sahel/Savannah belt south of the Sahara desert have often been overshadowed by extensive studies focusing on other African populations such as hunter-gatherers or Bantu in particular. However, the Sahel together with the Savannah bordering it in the south is a challenging region where people had and still have to cope with harsh climatic conditions and show resilient behaviours. Besides exponentially growing urban populations, several local groups leading various lifestyles and speaking languages belonging to three main linguistic families still live in rural localities across that region today. Thanks to several years of consistent population sampling throughout this area, the genetic history of the African Sahelian populations has been largely reconstructed and a deeper knowledge has been acquired regarding their adaptation to peculiar environments and/or subsistence modes. Distinct exposures to pathogens-in particular, malaria-likely contributed to their genetic differentiation for HLA genes. In addition, although food-producing strategies spread within the Sahel/Savannah belt relatively recently, during the last five millennia according to recent archaeological and archaeobotanical studies, remarkable amounts of genetic differences are also observed between sedentary farmers and more mobile pastoralists at multiple neutral and selected loci, reflecting both demographic effects and genetic adaptations to distinct cultural traits, such as dietary habits. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Prehistoric dark soils/sediments of Central Sudan, case study from the Mesolithic landscape at the Sixth Nile Cataract

Czech Academy of Sciences Publication Activity Database

Lisá, Lenka; Bajer, A.; Pacina, J.; McCool, J-P.; Cílek, Václav; Rohovec, Jan; Matoušková, Šárka; Kallistová, Anna; Gottvald, Z.

2017-01-01

Roč. 149, č. 1 (2017), s. 273-282 ISSN 0341-8162 Institutional support: RVO:67985831 Keywords : climate change * micromorphology * sahel * saprolite * soil chemistry Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Geology Impact factor: 3.191, year: 2016

Download this PDF file

African Journals Online (AJOL)

Southern African Journal of Environmental Education, Vol. ... savanna in the Sahel, and then to desert scrub in the southern fringes of the Sahara Desert at ... Guinea savanna .... In Hirji, R., Johnson, P., Maro, P. & Chiuta, T.M. (Eds), Defining.

An appraisal of the of eco-climatic characteristics in Northern Nigeria

African Journals Online (AJOL)

USER

2013-08-01

Aug 1, 2013 ... defined using quantitative definitions for the time series. The point data have .... savanna vegetation types; Guinea, Sudan and Sahel savanna, the .... dominant to extreme north while the best are to the south and the central ...

Browse Title Index

African Journals Online (AJOL)

Items 351 - 400 of 437 ... Vol 7, No 2 (2010), Rumen content characteristics and herbage digestibility of cattle and camel grazing native pasture in a Sahel savanna ecosystem ... Vol 11, No 1 (2014), Structure and functional significance of ...

Seasonal age differences in weight and biometrics of migratory ...

African Journals Online (AJOL)

Calidris alpina) caught in Eilat, Israel, before and after they accomplish the crossing of the combined ecological barrier of the Sinai, Sahara and Sahel deserts. Between 1999–2001, a total of 410 adults and 342 juveniles were banded.

Paraneoplastic syndromes revealing ovarian teratoma in young and ...

African Journals Online (AJOL)

Paraneoplastic syndromes revealing ovarian teratoma in young and menopausal women: report of two cases. Majdouline Boujoual, Ihsan Hakimi, Farid Kassidi, Youssef Akhoudad, Nawal Sahel, Adil Rkiouak, Mohamed Allaoui, Hafsa Chahdi, Mohamed Oukabli, Jaouad Kouach, Driss Rahali Moussaoui, Mohamed ...

Contribution of different livestock species as sources of meat in Bauchi

African Journals Online (AJOL)

, 169, 119 and 7 were White Fulani, Red Bororo, Sokoto Gudali and Kuri breeds ... Of the 28,321 goats slaughtered, the contributions of Sokoto Red, Kano brown, Sahel and West African Dwarf were 20,265; 7,469; 575 and 12 respectively.

Appendicitis: A Study of Negative Appendicectomies | Kpolugbo ...

African Journals Online (AJOL)

Post-operative complications were noted in 3% of the negative appendicectomy group but in the positive appendicectomy group complications were much more common particularly when the appendix was ruptured. (Key Words: Negative appendicectomy, perforated appendix and postoperative complications.) Sahel Med.

Employment and Growth | Page 25 | IDRC - International ...

International Development Research Centre (IDRC) Digital Library (Canada)

Read more about Dynamics of Poverty and Land Degradation in the Sahel (West Africa). Language English. Read more about Shaping Social Protection in Africa : National Transfer Accounts. Language English. Read more about Ageing and Development : National Transfer Accounts (Latin America and the Caribbean).

Conceptualizing the mobility of space through the Malian conflict

DEFF Research Database (Denmark)

Walther, Olivier; Retaillé, Denis

2013-01-01

The ongoing Malian conflict has sparked renewed media and academic interest in the Sahel. This paper shows how the various actors involved in the conflict, including nation-states, Tuareg rebels, and Islamist terrorists have adopted mobile strategies, which are not effectively explained using...

All projects related to | Page 500 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

2007-10-23

Project. Climate change poses a real challenge to communities of the Sahel, that of surviving in a fragile environment undergoing rapid mutation. Start Date: October 23, 2007. End Date: March 21, 2011. Topic: CLIMATE CHANGE, ADAPTATION TO CHANGE, DISASTER PREPAREDNESS, DISASTER MANAGEMENT, ...

Employment and Growth | Page 46 | IDRC - International ...

International Development Research Centre (IDRC) Digital Library (Canada)

Read more about Strengthening Procurement Systems in Latin America and the Caribbean. Language English. Read more about Opportunities in CARICOM Migration : Brain Circulation, Diasporic Tourism, and Investment. Language English. Read more about Dynamics of Poverty and Land Degradation in the Sahel (West ...

All projects related to | Page 362 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

2017-07-26

The agricultural and pastoral production deficit combined with the general rise in food prices has increased food insecurity in the Sahel. End Date: July 26, 2017. Topic: DESERTIFICATION, Natural Resources, ADAPTATION TO CHANGE, Food security, Climate change, RESOURCES MANAGEMENT. Region: Burkina Faso ...

Woody plants in agro-ecosystems of semi-arid regions

NARCIS (Netherlands)

Breman, H.; Kessler, J.J.

1995-01-01

A quantitative analysis of the role of woody plants in semi-arid regions, focusing on the Sahel and Sudan zones in West-Africa, is given for the assessment of their benefits in agro-sylvopastoral land-use systems with productive and sustainability objectives.

Search Results | Page 693 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

Results 6921 - 6930 of 9602 ... ... Science Granting Councils Initiative in Sub-Saharan Africa (1) Apply Science Granting ... Innovative Approaches to Task Shifting in Mental Health ... Natural Resources Management for Sustainable Food Security in the Sahel ... research centre located in Ougadougou, Burkina Faso. Project.

Improved ground hydrology calculations for global climate models (GCMs) - Soil water movement and evapotranspiration

Science.gov (United States)

Abramopoulos, F.; Rosenzweig, C.; Choudhury, B.

1988-01-01

A physically based ground hydrology model is presented that includes the processes of transpiration, evaporation from intercepted precipitation and dew, evaporation from bare soil, infiltration, soil water flow, and runoff. Data from the Goddard Institute for Space Studies GCM were used as inputs for off-line tests of the model in four 8 x 10 deg regions, including Brazil, Sahel, Sahara, and India. Soil and vegetation input parameters were caculated as area-weighted means over the 8 x 10 deg gridbox; the resulting hydrological quantities were compared to ground hydrology model calculations performed on the 1 x 1 deg cells which comprise the 8 x 10 deg gridbox. Results show that the compositing procedure worked well except in the Sahel, where low soil water levels and a heterogeneous land surface produce high variability in hydrological quantities; for that region, a resolution better than 8 x 10 deg is needed.

Atmospheric feedbacks in North Africa from an irrigated, afforested Sahara

Science.gov (United States)

Kemena, Tronje Peer; Matthes, Katja; Martin, Thomas; Wahl, Sebastian; Oschlies, Andreas

2018-06-01

Afforestation of the Sahara has been proposed as a climate engineering method to sequester a substantial amount of carbon dioxide, potentially effective to mitigate climate change. Earlier studies predicted changes in the atmospheric circulation system. These atmospheric feedbacks raise questions about the self-sustainability of such an intervention, but have not been investigated in detail. Here, we investigate changes in precipitation and circulation in response to Saharan large-scale afforestation and irrigation with NCAR's CESM-WACCM Earth system model. Our model results show a Saharan temperature reduction by 6 K and weak precipitation enhancement by 267 mm/year over the Sahara. Only 26% of the evapotranspirated water re-precipitates over the Saharan Desert, considerably large amounts are advected southward to the Sahel zone and enhance the West African monsoon (WAM). Different processes cause circulation and precipitation changes over North Africa. The increase in atmospheric moisture leads to radiative cooling above the Sahara and increased high-level cloud coverage as well as atmospheric warming above the Sahel zone. Both lead to a circulation anomaly with descending air over the Sahara and ascending air over the Sahel zone. Together with changes in the meridional temperature gradient, this results in a southward shift of the inner-tropical front. The strengthening of the Tropical easterly jet and the northward displacement of the African easterly jet is associated with a northward displacement and strengthening of the WAM precipitation. Our results suggest complex atmospheric circulation feedbacks, which reduce the precipitation potential over an afforested Sahara and enhance WAM precipitation.

Internal diversification of non-Sub-Saharan haplogroups in Sahelian populations and the spread of pastoralism beyond the Sahara.

Science.gov (United States)

Kulichová, Iva; Fernandes, Verónica; Deme, Alioune; Nováčková, Jana; Stenzl, Vlastimil; Novelletto, Andrea; Pereira, Luísa; Černý, Viktor

2017-10-01

Today, African pastoralists are found mainly in the Sahel/Savannah belt spanning 6,000 km from west to east, flanked by the Sahara to the north and tropical rainforests to the south. The most significant group among them are the Fulani who not only keep cattle breeds of possible West Eurasian ancestry, but form themselves a gene pool containing some paternally and maternally-transmitted West Eurasian haplogroups. We generated complete sequences for 33 mitogenomes belonging to haplogroups H1 and U5 (23 and 10, respectively), and genotyped 16 STRs in 65 Y chromosomes belonging to haplogroup R1b-V88. We show that age estimates of the maternal lineage H1cb1, occurring almost exclusively in the Fulani, point to the time when the first cattle herders settled the Sahel/Savannah belt. Similar age estimates were obtained for paternal lineage R1b-V88, which occurs today in the Fulani but also in other, mostly pastoral populations. Maternal clade U5b1b1b, reported earlier in the Berbers, shows a shallower age, suggesting another possibly independent input into the Sahelian pastoralist gene pool. Despite the fact that animal domestication originated in the Near East ∼ 10 ka, and that it was from there that animals such as sheep, goats as well as cattle were introduced into Northeast Africa soon thereafter, contemporary cattle keepers in the Sahel/Savannah belt show uniparental genetic affinities that suggest the possibility of an ancient contact with an additional ancestral population of western Mediterranean ancestry. © 2017 Wiley Periodicals, Inc.

Impact of climate change on mid-twenty-first century growing seasons in Africa

Energy Technology Data Exchange (ETDEWEB)

Cook, Kerry H.; Vizy, Edward K. [The University of Texas at Austin, Department of Geological Sciences, Jackson School of Geosciences, Austin, TX (United States)

2012-12-15

Changes in growing seasons for 2041-2060 across Africa are projected using a regional climate model at 90-km resolution, and confidence in the predictions is evaluated. The response is highly regional over West Africa, with decreases in growing season days up to 20% in the western Guinean coast and some regions to the east experiencing 5-10% increases. A longer growing season up to 30% in the central and eastern Sahel is predicted, with shorter seasons in parts of the western Sahel. In East Africa, the short rains (boreal fall) growing season is extended as the Indian Ocean warms, but anomalous mid-tropospheric moisture divergence and a northward shift of Sahel rainfall severely curtails the long rains (boreal spring) season. Enhanced rainfall in January and February increases the growing season in the Congo basin by 5-15% in association with enhanced southwesterly moisture transport from the tropical Atlantic. In Angola and the southern Congo basin, 40-80% reductions in austral spring growing season days are associated with reduced precipitation and increased evapotranspiration. Large simulated reductions in growing season over southeastern Africa are judged to be inaccurate because they occur due to a reduction in rainfall in winter which is over-produced in the model. Only small decreases in the actual growing season are simulated when evapotranspiration increases in the warmer climate. The continent-wide changes in growing season are primarily the result of increased evapotranspiration over the warmed land, changes in the intensity and seasonal cycle of the thermal low, and warming of the Indian Ocean. (orig.)

Economic benefits of combining soil and water conservation measures with nutrient management in semiarid Burkina Faso

NARCIS (Netherlands)

Zougmoré, R.; Mando, A.; Stroosnijder, L.; Ouédraogo, E.

2004-01-01

Nutrient limitation is the main cause of per capita decline in crop production in the Sahel, where water shortage also limits an efficient use of available nutrients. Combining soil and water conservation measures with locally available nutrient inputs may optimize crop production and economic

Assessment of the Teleconnection Between El Nino Southern ...

African Journals Online (AJOL)

Cluster analysis grouped the rainfall data into three clusters namely Coastal South, Middle belt and Sahel North, while Southern Oscillation Index (SOI) data from 1988 to 2013 was retrieved from National Ocean Atmospheric Administration (NOAA) as updated by the National Centre for Environmental Prediction (NCEP).

Sahelian pathways : climate and society in Central and South Mali

NARCIS (Netherlands)

Bruijn, de M.E.; Kaag, A M.M.; Til, van A.; Dijk, van J.W.M.

2005-01-01

Climate change is a global problem with local consequences. However, the direction and magnitude of these consequences in extremely vulnerable regions - such as the Sahel - cannot yet be predicted with any certainty. The studies in this volume focus on people for whom climate variability, mainly

Early lambing – kidding, prolificacy and twinning in the Nigerian ...

African Journals Online (AJOL)

%) was the most prolific, followed by WAD (4.64%) and Red Sokoto goat (3.86%). ... With the breeds of goat, WAD goat (3.31%) had more occurrence of twinning followed by Red Sokoto (2.88%), while Sahel goat had the lowest occurrence of ...

Mesenteric Cysts Presenting with Acute Intestinal Obstruction: A ...

African Journals Online (AJOL)

The 3 children needed bowel resection with primary anastomosis. All made uneventful recovery. A high index of suspicion is important when managing children with acute intestinal obstruction as mesenteric cyst may be an uncommon cause. (Key words: Mesenteric Cyst: Intestinal Obstruction). Sahel Medical Journal ...

Sud du Sahara | Page 239 | CRDI - Centre de recherches pour le ...

International Development Research Centre (IDRC) Digital Library (Canada)

Ouganda - phase IV. Langue French. Read more about Uganda Health Information Network (UHIN) - Phase IV. Langue English. Read more about Étude de la dynamique de la pauvreté et de la dégradation des sols au Sahel, en Afrique de l'Ouest.

Search Results | Page 14 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

Results 131 - 140 of 1119 ... Integrated nutrient and water management for sustainable food production in the Sahel : final technical report (March 2011 - August 2014). Harsh climate, characterized by low and erratic precipitation patterns, droughts, and poor soil fertility decrease cereal production in Sub-saharan Africa.

Le djihadisme au Sahel : enjeux et perspectives

African Journals Online (AJOL)

religieux, mais aussi dans la vie politique économique et, bien sûr, culturelle ..... vont se charger de propager les idées et de recruter des combattants ou des ..... africaines ont véritablement manqué de stratégie à ce niveau, trop prisonnières.

Exploring land use change in the Sahel

DEFF Research Database (Denmark)

Rasmussen, Laura Vang

perceptions of land use changes became apparent, however, already in the beginning of 2000, when researchers within the Land Change Science community raised their concerns about general narratives of field expansions that were assumed to progress linearly and be solely driven by population growth. Calls...... for more research on Sahelian land use changes have thus multiplied as the complexity and sometimes intricate processes of land change became apparent, and especially, the need for novel approaches that combine different perspectives has continuously been highlighted. As part of the interdisciplinary...... research program LASYRE (LAnd SYstem REsilience), this thesis responds to thes calls by applying a portfolio of different perspectives to the study of Sahelian land use changes and the causal mechanisms behind them. It examines the land use changes that have taken place in Northern Burkina Faso over...

Electricity privatizations in Sahel: A U-turn?

International Nuclear Information System (INIS)

Gualberti, Giorgio; Alves, Luis; Micangeli, Andrea; Graca Carvalho, Maria da

2009-01-01

This paper examines the process of privatization of electrical utilities for the country members of CILLS (Burkina Faso, Cape Verde, The Gambia, Guinea-Bissau, Mali, Mauritania, Niger, Chad and Senegal). These Sahelian countries, the majority of whom rank at the bottom positions of the HDI and present extremely low access rates to modern energy services, together started a process of energy sector reform and energy utility privatization in the 1990s. The reforms, endorsed by the International Financial Institutions, focused on the privatization of the electrical utilities, and encountered many difficulties. The objective of this article is to analyze what happened in each of these nine countries and to understand the reasons that led to a general halt or reversal of the process. The analysis is first introduced by a brief examination of regional energy situations and of the international context in which the reforms took place; this includes the policy guidelines introduced by the IFIs and the investment decisions of energy corporations. We analyze management processes and ownership changes for each country. Finally, the article identifies the problems encountered as a result of reform design and the interaction of behaviors between the governments, the International Corporations and the IFIs; lastly, we draw conclusions.

Gumbel Weibull distribution function for Sahel precipitation ...

African Journals Online (AJOL)

user

insecurity, migration, social conflicts, etc.). An efficient management of under and over ground water is a ... affects their incomes (Udual and Ini, 2012). Researches on modeling, prediction and forecasting ... Douentza in Mopti region, situated on the national road 15 highway linking Mopti to Gao and Kidal regions. This small ...

Sahel Journal of Veterinary Sciences: Advanced Search

African Journals Online (AJOL)

Search tips: Search terms are case-insensitive; Common words are ignored; By default only articles containing all terms in the query are returned (i.e., AND is implied); Combine multiple words with OR to find articles containing either term; e.g., education OR research; Use parentheses to create more complex queries; e.g., ...

Examining disadoption of gum arabic production in Sudan

NARCIS (Netherlands)

Rahim, A.; Ruben, R.; Ierland, van E.C.

2008-01-01

Gum arabic production in Sudan has developed over the years in a well-established traditional bush-fallow system in which the gum tree (Acacia senegal) is rotated with annual crops. Following the Sahel drought, the gum area has suffered from deforestation and gum production has declined. Several

Prospects for agroforestry in REDD+ landscapes in Africa

DEFF Research Database (Denmark)

Minang, Peter A.; Duguma, Lalisa A.; Bernard, Florence

2014-01-01

Vegetation dynamics of the West African Sahel has attracted great scientific interest over the last 40 years because of the dramatic inter-decadal variability observed in the resource base of the region directly impacting on the livelihoods of the West African population. From farmers to pastoral...

Sokoto Journal of Veterinary Sciences - Vol 10, No 2 (2012)

African Journals Online (AJOL)

Identification and analysis of dog use, management practices and implications for rabies control in Ilorin, Nigeria · EMAIL FREE FULL TEXT EMAIL FREE FULL ... Induction of estrus in Sahel goats using Fluorogestone Acetate (FGA) sponges and Equine Chorionic Gonadotrophin (ECG) · EMAIL FREE FULL TEXT EMAIL ...

Wind erosion modelling in a Sahelian environment

NARCIS (Netherlands)

Faye-Visser, S.M.; Sterk, G.; Karssenberg, D.

2005-01-01

In the Sahel field observations of wind-blown mass transport often show considerable spatial variation related to the spatial variation of the wind erosion controlling parameters, e.g. soil crust and vegetation cover. A model, used to predict spatial variation in wind erosion and deposition is a

Effects of compost amendment and the biocontrol agent Clonostachys rosea on the development of charcoal rot (Macrophomina phaseolina) on cowpea

NARCIS (Netherlands)

Ndiaye, M.; Termorshuizen, A.J.; Bruggen, van A.H.C.

2010-01-01

Macrophomina phaseolina is a destructive pathogen causing charcoal rot of cowpea and other crops in the semi- arid areas of the Sahel (north-west Africa). Chemical management is not feasible in conditions of subsistence farming, and the plurivorous nature of the fungus limits the effectiveness of

Influence of grazing regimes on cattle nutrition and performance and vegetation dynamics in Sahelian rangelands

NARCIS (Netherlands)

Ayantunde, A.A.

1998-01-01

In the West African Sahel, common herd management practices such as night grazing and corralling influence time available for grazing. When animals are used to deposit manure in the cropping fields, conflicts often arise between the need for animals to graze long enough for adequate feed

Allelochemicals Effect of Aqueous Leachate from Oudneya Africana R

African Journals Online (AJOL)

nesrine

2014-03-05

Mar 5, 2014 ... This present study was conducted to investigate the possible allelopathic effect of Oudneya africana. (donor species) on Bromus tectorum (weed species) and Triticum aestivum (cv. Sahel1; crop species) through germination bioassay experiment. B. tectorum is a winter annual grass that grows in winter.

PERCEPTIONS DE LA vARIABILITÉ CLIMATIqUE ET STRATÉGIES ...

African Journals Online (AJOL)

pas suivie d'une restauration écologique (Waziri,. 2014). Depuis cette décennie, le Sahel connaît de profonds changements liés à l'environnement climatique et .... l'érosion éolienne. .... la vente du bois énergie et de la vulgarisation des.

Linking research to urban planning at the ICLEI World Congress 2018

International Development Research Centre (IDRC) Digital Library (Canada)

2018-06-06

Jun 6, 2018 ... One of the polluted water stream flows within Banglore city. ... actions that promote fair and socially equitable access to resources and economic possibilities? ... and leverage goal areas and to operationalize an integrated implementation approach. ... New project to improve water management in the Sahel.

Haematological responses of three Nigerian goat breeds to field ...

African Journals Online (AJOL)

Similarly, correlation coefficient between Haemonchus worm count (HWC) and FEC showed positive correlation value which was significantly (p<0.01) higher among ... In addition, Sahel White and Red Sokoto breeds had microcytic, hypochromic anaemia with a significantly (p<0.05) lower haematocrit values than the West ...

Identification of potentially competing Afrotropical and Palaearctic ...

African Journals Online (AJOL)

Identification of potentially competing Afrotropical and Palaearctic bird species in the Sahel. Jared M Wilson, Will RL Cresswell. Abstract. Areas experiencing a seasonal influx of migrants may be expected to have a high potential for competition between resident and migrant populations. Described differences in foraging ...

Search Results | Page 14 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

Results 131 - 138 of 138 ... ... TEACHING AIDS 10 Apply TEACHING AIDS filter · RESEARCH CAPACITY 9 Apply ... Helping young migrant job seekers ... Integrated nutrient and water management for sustainable food production in the Sahel ... without assessing the risks posed by the flood of equipment into African countries?

Weeding method and pre-sowing tillage effects on weed growth and pearl millet yield in a sandy soil of the West African Sahelian zone.

NARCIS (Netherlands)

Klaij, M.C.; Hoogmoed, W.B.

1996-01-01

Weed control for the West African Sahel rainfed crops is done mainly manually, resulting in high labor requirements. Because of the seasonality of rainfed farming, weed control is often late and incomplete, resulting in considerable losses in crop yield. We examined the case of weed control in

Search Results | Page 6 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

Results 51 - 58 of 58 ... Integrated nutrient and water management for sustainable food production in the Sahel : final technical report (March 2011 - August 2014). Harsh climate, characterized by low and erratic precipitation patterns, droughts, and poor soil fertility decrease cereal production in Sub-saharan Africa. Published ...

Expanding the Canadian Queen Elizabeth II Diamond Jubilee ...

International Development Research Centre (IDRC) Digital Library (Canada)

Barriers to education in many low- and middle-income countries (LMICs) limit the ... exposure to experience from developing and emerging economies remains limited and in turn this limits ... fellows and early career scientists in universities and leading businesses. ... New project to improve water management in the Sahel.

World market or regional integration and food security in West Africa

NARCIS (Netherlands)

L.J. de Haan (Leo); A. Klaasse Bos (Andries); C. Lutz (Clemens)

1994-01-01

textabstractThe problem of food security in West Africa was put on the international agenda in 1974 at the international food conference in Rome following the Great Sahelian Drought of 1968-1973. In those years preoccupation with food security was limited mainly to the Sahel countries and

Farmers' perceptions of erosion by wind and water in northern Burkina Faso

NARCIS (Netherlands)

Visser, S.M.; Leenders, J.K.; Leeuwis, M.

2003-01-01

Wind and water erosion are widespread phenomena throughout the Sahel, especially in the early rainy season, when high-intensity rainstorms are often preceded by severe windstorms. This paper describes the results of a survey on the farmers' perceptions of wind and water erosion processes and control

Search Results | Page 21 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

Results 201 - 210 of 1119 ... ... 174 Apply Reports filter · Journal articles 112 Apply Journal articles filter .... Financial Services and the Deployment of Agricultural Innovations in the Sahel. Over the past 20 years, numerous innovations to improve food crop ... Climate change, environmental degradation, emerging infectious ...

Research for Development in the Dry Arab Region: The Cactus Flower

International Development Research Centre (IDRC) Digital Library (Canada)

2006-01-01

Jan 1, 2006 ... ... research project and their common journey to embrace sustainable resource use. ... East and North Africa region and proposes some innovative new directions, ... New project to improve water management in the Sahel ... Congratulations to the first cohort of Women in Climate Change Science Fellows!

Estimation of rainfall inputs and direct recharge to the deep unsaturated zone of southern Niger using the chloride profile method.

NARCIS (Netherlands)

Bromley, J.; Edmunds, W.M.; Fellman, E.; Brouwer, J.; Gaze, S.R.; Sudlow, J.; Taupin, J.D.

1997-01-01

An estimate of direct groundwater recharge below a region of natural woodland (tiger bush) has been made in south-west Niger using the solute profile technique. Data has been collected from a 77 m deep well dug within the study area covered by HAPEX-Sahel (Hydrological and Atmospheric Pilot

Allelotoxicity of Oudneya africana R. Br. aqueous leachate on ...

African Journals Online (AJOL)

This present study was conducted to investigate the possible allelopathic effect of Oudneya africana (donor species) on Bromus tectorum (weed species) and Triticum aestivum (cv. Sahel1; crop species) through germination bioassay experiment. B. tectorum is a winter annual grass that grows in winter wheat and other ...

Quantitative analyses of shrinkage characteristics of neem ...

African Journals Online (AJOL)

Quantitative analyses of shrinkage characteristics of neem (Azadirachta indica A. Juss.) wood were carried out. Forty five wood specimens were prepared from the three ecological zones of north eastern Nigeria, viz: sahel savanna, sudan savanna and guinea savanna for the research. The results indicated that the wood ...

Effect on stone lines on soil chemical characteristics under continuous sorghum cropping in semiarid Burkina Faso

NARCIS (Netherlands)

Zougmore, R.; Gnankambary, Z.; Guillobez, L.S.; Stroosnijder, L.

2002-01-01

In the semiarid Sahel, farmers commonly lay stone lines in fields to disperse runoff. This study was conducted in northern Burkina Faso to assess the chemical fertility of soil under a permanent, non-fertilised sorghum crop, which is the main production system in this area, 5 years after laying

Decline of woody vegetation in a saline landscape in the Groundnut Basin, Senegal

DEFF Research Database (Denmark)

Sambou, Antoine; Theilade, Ida; Fensholt, Rasmus

2016-01-01

Several studies have documented that vegetation in the Sahel is highly dynamic and is affected by the prevailing climatic conditions, as well as by human use of the areas. However, little is known about vegetation dynamics in the large saline areas bordering the rivers of West Africa. Combining s...

Soil nutrient and sediment loss as affected by erosion barriers and nutrient source in semi-arid Burkina Faso

NARCIS (Netherlands)

Zougmore, R.; Mando, A.; Stroosnijder, L.

2009-01-01

In semi-arid Sahel, soil erosion by water is one major factor accounting for negative nutrient balances in agricultural systems. A field experiment was conducted on a Ferric Lixisol in Burkina Faso to assess the effects of soil and water conservation barriers (stone rows or grass strips of

Animal Research International - Vol 6, No 1 (2009)

African Journals Online (AJOL)

Survey Of Ketosis And Hypoproteinaemia In Slaughtered Cattle In The Sahel Region Of Nigeria · EMAIL FULL TEXT EMAIL FULL TEXT DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. IC Igbokwe, SN Okonkwo, HG Hamza, NA Igbokwe. http://dx.doi.org/10.4314/ari.v6i1.48099 ...

Effect of rotation of cowpea (Vigna unguiculata) with fonio (Digitaria exilis) and millet (Pennisetum glaucum) on Macrophomina phaseolina densities and cowpea yield

NARCIS (Netherlands)

Ndiaye, M.; Termorshuizen, A.J.; Bruggen, van A.H.C.

2008-01-01

Macrophomina phaseolina, the causal agent of charcoal rot, causes great damage to cowpea in the Sahel. One of the few options to manage the disease is by cropping nonhosts that may reduce the soil inoculum below a damage threshold level. To test this, fonio (Digitaria exilis) and millet (Pennisetum

2640-IJBCS-Article-Ouango Maurice Savadogo

African Journals Online (AJOL)

hp

abundance and diversity in different land use types (cropland, shallow land, degraded land and forest). Four sites were ... might be at the beginning stage in the Sahel, especially in croplands, and clear change of soil biological quality ... soil conditions, cultural practices, crop type ..... provision of ecosystem services that can.

An empirical analysis of the simultaneous effects of nitrogen, phosphorus and potassium in millet

NARCIS (Netherlands)

Voortman, R.L.; Brouwer, J.

2003-01-01

Low soil fertility is a major constraint for increasing millet production on the acid sandy soils of the West African Sahel. On these soils, all three macronutrients: nitrogen (N), phosphate ( P) and potassium ( K), may be expected to limit crop yields. The important question is therefore: which of

The responses of three nigerian indigenous goat breeds to primary ...

African Journals Online (AJOL)

Responses of three Nigerian breeds of goat; Red Sokoto (RS), West African Dwarf (WAD) and Sahel White (SW) were investigated following primary and secondary experimental infections ... On day 42 post infection, (n=12) goats, (4 per breed) of the infected animals were humanely euthanized and worm count determined.

African Climate Change Fellowship | CRDI - Centre de recherches ...

International Development Research Centre (IDRC) Digital Library (Canada)

Extrants. Articles de revue. Spatial fields' dispersion as a farmer strategy to reduce agro-climatic risk at the household level in pearl millet-based systems in the Sahel : a modeling ... L'Initiative des conseils subventionnaires de la recherche scientifique en Afrique subsaharienne remporte le prix de la diplomatie scientifique.

Fertilizer micro-dosing: a profitable innovation for Sahelian women ...

International Development Research Centre (IDRC) Digital Library (Canada)

2016-06-06

Jun 6, 2016 ... The localized application of small quantities of fertilizer (micro-dosing), combined with improved planting pits for rainwater harvesting, has generated greater profits and food security for women farmers in the Sahel. Women have taken to the new methods developed by West African and Canadian ...

Fertilizer micro-dosing

International Development Research Centre (IDRC) Digital Library (Canada)

Localized application of small quantities of fertilizer (micro-dosing), combined with improved planting pits for rainwater harvesting, has generated greater profits and food security for women farmers in the Sahel. • Women are 25% more likely to use combined applications, and have expanded areas of food crops (cowpea,.

Energy and Water Resources of Burkina Faso as Catalyst for ...

African Journals Online (AJOL)

PROF. OLIVER OSUAGWA

2014-06-01

Jun 1, 2014 ... were to study the energy situation, search for sources of water for the ... engineering and hydrological surveys on selected construction sites to ... western regions. ... assistance from France and the Development .... directly to the national network of Burkina ..... lants in the Sahel: Case study of Burkina Faso.

Development Cooperation in a Fractured Global Order: An Arduous ...

International Development Research Centre (IDRC) Digital Library (Canada)

The turbulence the world is experiencing approaching the 21st century is not just because ... Chief of Strategic Planning and senior advisor at the World Bank; visiting professor at ... New Dutch-Canadian funding for the Climate and Development Knowledge Network ... New project to improve water management in the Sahel.

Micro-element contents of roselle ( Hibiscus sabdariffa L.) at different ...

African Journals Online (AJOL)

In the western Sahel, leaves of Roselle (Hibiscus sabdariffa) have considerable economic importance because of their nutritional and medical uses. These plant organs are used to supplement nutrients provided by cereals such as millet and sorghum. However, there is a lack of information on the nutrient composition of ...

Sud du Sahara | Page 137 | CRDI - Centre de recherches pour le ...

International Development Research Centre (IDRC) Digital Library (Canada)

Through participation in IDRC's Resource Mobilization for Research (RMR) project, IDID staff undertook an ambitious set of organizational changes. They: ... In 2005, it took over, and continues to build on, the Sahel program created in 1993 by the International Institute for Environment and Development. Read more about ...

South of Sahara | Page 153 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

Through participation in IDRC's Resource Mobilization for Research (RMR) project, IDID staff undertook an ambitious set of organizational changes. They: ... In 2005, it took over, and continues to build on, the Sahel program created in 1993 by the International Institute for Environment and Development. Read more about ...

The Sahelian crisis and the poor : the role of Islam in social security among Fulbe pastoralists, Central Mali

NARCIS (Netherlands)

Bruijn, de M.E.

1994-01-01

This paper examines how poor members of Fulbe society, a group of agropastoralists in the Sahel, central Mali, are surviving after two decades of environmental disaster. The focus is on the Jalloube of the Hayre in central Mali. Social security relations and institutions based on Islam seem to be

Balanites aegyptiaca (L. Delile: geographical distribution and ethnobotanical knowledge by local populations in the Ferlo (north Senegal

Directory of Open Access Journals (Sweden)

Sagna, MB.

2014-01-01

Full Text Available Balanites aegyptiaca (L. Delile is a species of tropical flora for which the variety aegyptiaca is adapted to Sahelian climate. The species is among those chosen for the restoration of Sahelian ecosystems in the context of the pan-African reforestation project, the Great Green Wall for the Sahara and Sahel Initiative (GGW. This study redefines the distribution range and its ecology and studies its uses in the Ferlo region in the north of Senegal using surveys carried out among the local population. The eco-geographical study shows that the species occupies several Sahel-Saharan regions of Africa and the Middle East. With broad ecological amplitude, it is very resistant to drought and relatively indifferent to the type of soil. Results of the ethno-botanical survey show that local people in the Ferlo region have a wealth of knowledge and expertise on B. aegyptiaca. These surveys also revealed the extent to which local populations rely on the tree for food, fodder, construction and medicine. The fruit and wood are the most highly prized parts of the tree, with the greatest use of the fruit in people's diets. In medicinal terms, B. aegyptiaca is used to treat several affections. Marketing the fruits could be of socio-economic interest for local people, and in particular, for women. This study is particularly opportune since B. aegyptiaca var. aegyptiaca is currently being planted in large numbers within the Great Green Wall for the Sahara and the Sahel Initiative (GGW. It also provides information that could help in better management of this natural resource, adapted both to the hostile Sahelian climate and of great use to Mankind.

Prevalence and Biotyping of Pasteurella Haemolytica Isolates from ...

African Journals Online (AJOL)

P. haemolytica isolated from Sahel sheep and goat in Maiduguri was characterized phenotypically. A total of 92 P. haemolytica isolates were obtained from the nasopharyngeal swabs while a total of 15 isolates came from pneumonic lung samples. The results showed that 37(20.22%) P. haemolytica isolates were obtained ...

Effect of rain drop washes on soil fertility in cotton production zone of ...

African Journals Online (AJOL)

Crop production in the Sahel is limited by nutrients availability. The study aimed to estimate the contribution of avifauna, crop rotation and trees to soil fertility and crop production improvement. Pot experiment was carried out with soils sampled in Faidherbia albida parklands in cotton production zone of West Burkina Faso.

adoption of improved aquaculture practices by shrimp farmers in ...

African Journals Online (AJOL)

Dr.Adesope

ABSTRACT. Crop production in the Sahel is limited by nutrients availability. The study aimed to estimate the contribution of avifauna, crop rotation and trees to soil fertility and crop production improvement. Pot experiment was carried out with soils sampled in Faidherbia albida parklands in cotton production zone of West ...

Influence of shift work on the physical work capacity of Tunisian ...

African Journals Online (AJOL)

Methods: It is a cross-sectional design using a standardized questionnaire and many physical capacity tests on a representative sample of 1181 nurses and nursing assistants from two university hospital centers of the school of Medicine of Monastir located in the Tunisian Sahel. 293 participants have been recruited by ...

Multiple shoot regeneration of cotton (Gossypium hirsutum L.) via ...

African Journals Online (AJOL)

user

2011-03-14

Mar 14, 2011 ... Induction of multiple shoots of cotton (Gossypium hirsutum L.) plant in two commercial varieties (Sahel and Varamin) using shoot apex was done. Explants were isolated from 3 - 4 days old seedlings, then they were cultured on a shoot induction media, modified MS nutrient agar with combinations: 1- ...

The influence of sex on the haematological values of apparently ...

African Journals Online (AJOL)

Blood samples were collected from fifty apparently healthy adult Sahel goats, twenty five each of male and female in Maiduguri to assess the influence of sex on their haematology. The red blood cell (RBC) counts, white blood cell (WBC) counts, haemoglobin (Hb) concentration, packed cell volume (PCV), platelet counts, ...

Densities of Palearctic warblers and Afrotropical species within the ...

African Journals Online (AJOL)

Densities of Palearctic warblers and Afrotropical species within the same guild in Sahelian West Africa. Jared M Wilson, Will Cresswell. Abstract. Declines in populations of Palearctic migrants wintering in the Sahel of Africa have been linked to the impacts of climate change and habitat degradation in the region. Despite this ...

Seasonal Differences Of The Nutrient Content Of The Milk Of The ...

African Journals Online (AJOL)

The Fulani are semi-nomadic pastoralist who inhabited western Sahel from Mauritania and Senegal across Mali, Burkina Faso, the Republic of Niger and Northern Nigeria to Chad. Their culture is centred around cattle and dairy products contribute substantially to the diets of Fulani children and adults. Having found in ...

: tous les projets | Page 355 | CRDI - Centre de recherches pour le ...

International Development Research Centre (IDRC) Digital Library (Canada)

Sujet: REFUGEES, MIGRANTS, REMITTANCES, PEACE RESEARCH, CONFLICT RESOLUTION. Région: Egypt, North of Sahara, South of Sahara. Programme: Gouvernance et justice. Financement total : CA$ 235,200.00. Étude de la dynamique de la pauvreté et de la dégradation des sols au Sahel, en Afrique de l'Ouest.

climatology of air mass trajectories and aerosol optical thickness ...

African Journals Online (AJOL)

George

We present in this paper a climatological study of back trajectories of air masses ... obtained by inversion of photometric measurements of AERONET network. ... the arid Sahel region adjacent in the north to the Sahara ... the city a strategic position in the study of the .... atmospheric emergencies, diagnostic case studies and.

Meer dan zandkastelen : Architektonisch reisverhaal

NARCIS (Netherlands)

Van der Eerden, J.

1993-01-01

This book is the account of a journey through the Sahara, from the Maghreb to the countries of the Sahel. The writer describes the history of the area and the technology, styles and backgrounds of its architecture. This is alternated with an account of the writer's experiences during the trip

Search Results | Page 18 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

Results 171 - 180 of 1119 ... UN-Habitat State of the World's Cities Report 2010/2011 : Hunger in Cities ... improve global awareness of urban issues by presenting state-of-the-art data ... Regulation of Food and Beverage Advertising and Marketing in India ... general rise in food prices has increased food insecurity in the Sahel.

Search Results | Page 67 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

... Apply ADAPTIVE CAPACITY filter · INDIA 43 Apply INDIA filter · Natural Resources 41 Apply Natural ... Showing 661 - 670 of 1762 results : "water adaptation" ... the need to go beyond technical responses to rising sea-levels and inland flooding. ... Climate change poses a real challenge to communities of the Sahel, that of ...

Publications | Page 614 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

Results 6131 - 6140 of 6371 ... Waterpipe tobacco smoking : building the evidence base; part 1: the smoke chemistry (open access) · Farming and livestock production in the Sahel : merging the two solutions (open access). The women of Toukounous, a small town 20 km from Niamey, are participating in a new departure from ...

Effect of nocturnal grazing and supplementation on diet selection, eating time, forage intake and weight changes of cattle

NARCIS (Netherlands)

Ayantunde, A.A.; Fernandez-Rivera, S.; Hiernaux, P.H.Y.; Keulen, van H.; Udo, H.M.J.; Chanono, M.

2000-01-01

Sixty-four Azawak male calves were used to study the effect of nocturnal grazing (NG) and supplementation (S) in the dry season on forage and water intake, faecal output, eating time and weight changes of cattle in the Sahel. Treatments were factorial combinations of four levels of NG (0, 2, 4 and 6

Genetic diversity of Tamarindus indica populations: Any clues on the ...

African Journals Online (AJOL)

Tamarindus indica is a domesticated species of high economic value for the Sahel region. Despite this importance, very few data is available on its diversity as well as its structure leading to controversial discussions on its origin. Thus it is questionable whether the knowledge of its genetic diversity and organisation may ...

Spatial variability and farmer resource allocation in millet production in Niger

NARCIS (Netherlands)

Gandah, M.

1999-01-01

The Sahel of West Africa is the agro-ecological zone located between 12 ^oand 16 ^oN, with an annual rainfall of between 300 and 1000 mm. Crops are grown in a subsistence type of agriculture during the 75 to 125 days growing period between May and

Overview of restoration and management practices in the degraded ...

African Journals Online (AJOL)

The highest deforestation and forest degradation rates in Africa occur in the dry forests and woodlands where pressure for land is increasing, poverty is rampant, livelihood options are few and climate change effects are severe. This paper examines factors that cause land and forest degradation in the Sahel and dry forests ...

Improving crop yields for Sahelian Women | IDRC - International ...

International Development Research Centre (IDRC) Digital Library (Canada)

2016-06-07

Jun 7, 2016 ... Less is more: Improving yields for Sahelian women with tiny dozes of fertilizer Farmers living in the semi-arid Sahel belt of West Africa are increasing the yields and income earned from their crops, thanks to a simple technique that combines small quantities of fertilizers (microdosing) with improved ...

International Journal of Biological and Chemical Sciences - Vol 11 ...

African Journals Online (AJOL)

Dynamique de la résorption utérine chez la chèvre du Sahel: effet de la parité · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. Boureima Traore, Moussa Zongo, Were Pitala, Moise Haro, Drissa Sanou, Laya Sawadogo, 2926-2657 ...

Sr-Nd-Hf isotopic fingerprinting of transatlantic dust derived from North Africa

Science.gov (United States)

Zhao, Wancang; Balsam, William; Williams, Earle; Long, Xiaoyong; Ji, Junfeng

2018-03-01

Long-range transport of African dust plays an important role in understanding dust-climate relationships including dust source areas, dust pathways and associated atmospheric and/or oceanic processes. Clay-sized Sr-Nd-Hf isotopic compositions can be used as geochemical fingerprints to constrain dust provenance and the pathways of long-range transported mineral dust. We investigated the clay-sized Sr-Nd-Hf isotopic composition of surface samples along four transects bordering the Sahara Desert. The transects are from Mali, Niger/Benin/Togo, Egypt and Morocco. Our results show that the Mali transect on the West African Craton (WAC) produces lower εNd (εNd-mean = -16.38) and εHf (εHf-mean = -9.59) values than the other three transects. The Egyptian transect exhibits the lowest 87Sr/86Sr ratios (87Sr/86Srmean = 0.709842), the highest εHf (εHf-mean = -0.34) and εNd values of the four transects. Comparison of the clay-sized Sr-Nd-Hf isotopic values from our North African samples to transatlantic African dust collected in Barbados demonstrates that the dust's provenance is primarily the western Sahel and Sahara as well as the central Sahel. Summer emission dust is derived mainly from the western Sahel and Sahara regions. The source of transatlantic dust in spring and autumn is more varied than in the summer and includes dust not only from western areas, but also south central areas. Comparison of the Sr-Nd-Hf isotopic fingerprints between the source and sink of transatlantic dust also suggests that a northwestward shift in dust source occurs from the winter, through the spring and into the summer. The isotopic data we develop here provide another tool for discriminating changes in dust archives resulting from paleoenvironmental evolution of source regions.

Climate dynamics: a network-based approach for the analysis of global precipitation.

Science.gov (United States)

Scarsoglio, Stefania; Laio, Francesco; Ridolfi, Luca

2013-01-01

Precipitation is one of the most important meteorological variables for defining the climate dynamics, but the spatial patterns of precipitation have not been fully investigated yet. The complex network theory, which provides a robust tool to investigate the statistical interdependence of many interacting elements, is used here to analyze the spatial dynamics of annual precipitation over seventy years (1941-2010). The precipitation network is built associating a node to a geographical region, which has a temporal distribution of precipitation, and identifying possible links among nodes through the correlation function. The precipitation network reveals significant spatial variability with barely connected regions, as Eastern China and Japan, and highly connected regions, such as the African Sahel, Eastern Australia and, to a lesser extent, Northern Europe. Sahel and Eastern Australia are remarkably dry regions, where low amounts of rainfall are uniformly distributed on continental scales and small-scale extreme events are rare. As a consequence, the precipitation gradient is low, making these regions well connected on a large spatial scale. On the contrary, the Asiatic South-East is often reached by extreme events such as monsoons, tropical cyclones and heat waves, which can all contribute to reduce the correlation to the short-range scale only. Some patterns emerging between mid-latitude and tropical regions suggest a possible impact of the propagation of planetary waves on precipitation at a global scale. Other links can be qualitatively associated to the atmospheric and oceanic circulation. To analyze the sensitivity of the network to the physical closeness of the nodes, short-term connections are broken. The African Sahel, Eastern Australia and Northern Europe regions again appear as the supernodes of the network, confirming furthermore their long-range connection structure. Almost all North-American and Asian nodes vanish, revealing that extreme events can

Climate dynamics: a network-based approach for the analysis of global precipitation.

Directory of Open Access Journals (Sweden)

Stefania Scarsoglio

Full Text Available Precipitation is one of the most important meteorological variables for defining the climate dynamics, but the spatial patterns of precipitation have not been fully investigated yet. The complex network theory, which provides a robust tool to investigate the statistical interdependence of many interacting elements, is used here to analyze the spatial dynamics of annual precipitation over seventy years (1941-2010. The precipitation network is built associating a node to a geographical region, which has a temporal distribution of precipitation, and identifying possible links among nodes through the correlation function. The precipitation network reveals significant spatial variability with barely connected regions, as Eastern China and Japan, and highly connected regions, such as the African Sahel, Eastern Australia and, to a lesser extent, Northern Europe. Sahel and Eastern Australia are remarkably dry regions, where low amounts of rainfall are uniformly distributed on continental scales and small-scale extreme events are rare. As a consequence, the precipitation gradient is low, making these regions well connected on a large spatial scale. On the contrary, the Asiatic South-East is often reached by extreme events such as monsoons, tropical cyclones and heat waves, which can all contribute to reduce the correlation to the short-range scale only. Some patterns emerging between mid-latitude and tropical regions suggest a possible impact of the propagation of planetary waves on precipitation at a global scale. Other links can be qualitatively associated to the atmospheric and oceanic circulation. To analyze the sensitivity of the network to the physical closeness of the nodes, short-term connections are broken. The African Sahel, Eastern Australia and Northern Europe regions again appear as the supernodes of the network, confirming furthermore their long-range connection structure. Almost all North-American and Asian nodes vanish, revealing that

Interactions of atmospheric gases and aerosols with the monsoon dynamics over the Sudano-Guinean region during AMMA

Directory of Open Access Journals (Sweden)

A. Deroubaix

2018-01-01

Full Text Available Carbon monoxide, CO, and fine atmospheric particulate matter, PM2.5, are analyzed over the Guinean Gulf coastal region using the WRF-CHIMERE modeling system and observations during the beginning of the monsoon 2006 (from May to July, corresponding to the Africa Multidisciplinary Monsoon Analysis (AMMA campaign period. Along the Guinean Gulf coast, the contribution of long-range pollution transport to CO or PM2.5 concentrations is important. The contribution of desert dust PM2.5 concentration decreases from  ∼ 38 % in May to  ∼ 5 % in July. The contribution of biomass burning PM2.5 concentration from Central Africa increases from  ∼ 10 % in May to  ∼ 52 % in July. The anthropogenic contribution is  ∼ 30 % for CO and  ∼ 10 % for PM2.5 during the whole period. When focusing only on anthropogenic pollution, frequent northward transport events from the coast to the Sahel are associated with periods of low wind and no precipitation. In June, anthropogenic PM2.5 and CO concentrations are higher than in May or July over the Guinean coastal region. Air mass dynamics concentrate pollutants emitted in the Sahel due to a meridional atmospheric cell. Moreover, a part of the pollution emitted remotely at the coast is transported and accumulated over the Sahel. Focusing the analysis on the period 8–15 June, anthropogenic pollutants emitted along the coastline are exported toward the north especially at the beginning of the night (18:00 to 00:00 UTC with the establishment of the nocturnal low level jet. Plumes originating from different cities are mixed for some hours at the coast, leading to high pollution concentration, because of specific disturbed meteorological conditions.

Browse Title Index

African Journals Online (AJOL)

Items 401 - 450 of 763 ... ... for Sahel precipitation modeling and predicting: Case of Mali, Abstract PDF ... Vol 9, No 3 (2015), Heavy metal content in fish and water from River ... Vol 7, No 9 (2013), Heavy metal levels in soil samples from highly ... Vol 10, No 12 (2016), Hydrogeochemical and isotopic characterization of the ...

Effect of polyethylene glycol (PEG) 6000 on germination and ...

African Journals Online (AJOL)

Millet crop is an important cereal for food security and the fight against poverty and malnutrition in the arid Sahel. It is a staple grain for millions of people in West Africa and India. It has the advantage of tolerating drought-prone environments and low fertility soils. Recent climate change exacerbates the phenomenon of ...

GLOBAL JOURNAL OF AGRICULTURAL SCIENCES ISSN 1596-2903

African Journals Online (AJOL)

Ada Global

mean rainfall for locations in the West African Sahel will reduce yields substantially and in many cases could lead to total crop failure. The study ... roughness, and the amount of dust generation are seen as possible triggers to a .... Table 1: Coefficient of determintion (R2) for the multiple regression models. Model 1. Location.

Sexospécificités | Page 19 | CRDI - Centre de recherches pour le ...

International Development Research Centre (IDRC) Digital Library (Canada)

This collective work looks at the origins, examples, and consequences of the gender divide with regards to the access, use, and control of water in the Sahel. The book draws on the IDRC-funded research project, "Effectiveness of women's economic rights: the case of access to water for agricultural use in Mauritania, Niger, ...

: tous les projets | Page 253 | CRDI - Centre de recherches pour le ...

International Development Research Centre (IDRC) Digital Library (Canada)

Au Sahel, la sécheresse et la piètre fertilité des sols limitent grandement le rendement des cultures. Date de début : 1 mars 2011. End Date: 1 septembre 2014. Sujet: FOOD CROPS, SOIL FERTILITY, FERTILIZERS, FERTILIZING, RAIN FED FARMING, WATER MANAGEMENT, CROP YIELD, Food security. Région: Burkina ...

Irrigation and climate information in Burkina Faso (AARC) | Page 5 ...

International Development Research Centre (IDRC) Digital Library (Canada)

Since the 1970s, the Sahel has experienced a marked decline in rainfall and a high variability in the timing of the rainy season (Intergovernmental Panel on Climate Change, 2007). As a result, farmers have struggled to plan their crops and manage irrigation for food production. In Burkina Faso, many farmers have resorting ...

Timing of mounding for bambara groundnut affects crop development and yield in a rainfed tropical environment

DEFF Research Database (Denmark)

Ouedrago, Mahama; M'bi, Bertin Zagre; Liu, Fulai

2013-01-01

-ecological zone of Burkina Faso were conducted. Yield data confirm the findings from a drier part of Burkina Faso; i.e., mounding of bambara groundnut should not be carried out around the time of flowering. In a semi-arid area, such as Sudan–Sahel agro-ecological zone and with germplasm maturing within 90 days...

Variation in macro-elements and protein contents of roselle ...

African Journals Online (AJOL)

Roselle is an important part of the human diet in many countries, particularly in the Sahel zone of West Africa. The leaves of Roselle are consumed as a green vegetable and in sauce. Nevertheless, little attention has been paid to their nutrient composition at different stages of plant growth. Therefore, the experiment was ...

German unity, conventional disarmament, confidence-building defense, and a new European order of peace and security

International Nuclear Information System (INIS)

Brauch, H.G.

1992-01-01

This paper discusses a solar development initiative, or a demilitarized SDI, sponsored jointly by the CSCE countries as a conversion project which could contributed to conflict avoidance. If hydrogen can be obtained in solar energy plants in a cost-effective way, if desalination can be achieved on a massive scale, the social vision of a demilitarized SDI may be more realistic: to use solar energy for desalination of water and their transport to regions, e.g., in the Sahel where there is a shortage. The gas pipeline deal between the USSR and several West European countries could be a model for such a cooperative high technology conversion project that serves a basic human need; to supply water cheaply to permit farming and to offer survival for the people in the Sahel and in other parts of the world where there is a surplus of sun but a shortage of water. This vision will contribute to a dismantling of cold war institutions that impede the realization of a new European peace order

The Malian Crisis and the Challenge of Regional Cooperation

Directory of Open Access Journals (Sweden)

Wolfram Lacher

2013-06-01

Full Text Available The weakness of regional security cooperation has been a key factor in the gradual destabilization of the Sahel-Sahara region over the past decade. While organized crime, extremist activity, and cross-border movements of arms and fighters have strengthened linkages among non-state actors in the region, state policies have failed to keep up. With the escalation of the crisis in Mali, West African states have adopted an approach diverging strongly from that of Mali’s North African neighbours. Western governments’ tendency to understand insecurity in the region through the notion of the Sahel has compounded the problem. Insecurity in the region, including criminal and extremist networks, is more Saharan than Sahelian in scope. North African states are part of the problem, and need to be part of the solution. A new framework for regional cooperation is needed – and while this can only be established on the initiative of regional states themselves, external actors need to adapt their policies to help such a framework emerge.

Heavy metal pollutants in surficial sediments from different coastal sites in Aden Governorate, Yemen

International Nuclear Information System (INIS)

Ali, Anis Ahmed; Baharoon Aqil Abdulrahman

2004-01-01

Concentrations of Gd, Pb, Zn, Cu, Ni, Co, Cr, Mn and Fe in surficial sediments (<63μm) from the shores in Aden Governorate were determined by atomic absorption spectrophotometry method. The obtained concentration data show significant regional variations concerning both the total and leachable metals in sediments. Total metal concentrations of Cd and Pb were greatest in sediments from labor Island; Cu, Cr, and Fe occurred in the highest levels in Bandar Fuqum sediments, while maximum levels of Mn, Co, and Ni were observed in sediments from Sahel Abyan and Fuqum. Labile, easily extractable species of metals such as Cd and Pb, are similar to their total concentrations, and additionally Cu, Zn, Cr, and Fe were found in the highest concentrations in sediments from labor Island. Sediments from Sahel Abyan and Khawr Bir Ahmed were characterized by a maximum accumulation of bioavailable species of Co and Mn, respectively. The linear regression slopes for metals correlated were <1, this explains the slow enrichment of these metals in the sediments, and attributes their geological nature. (author)

Quantifying Livestock Heat Stress Impacts in the Sahel

Science.gov (United States)

Broman, D.; Rajagopalan, B.; Hopson, T. M.

2014-12-01

Livestock heat stress, especially in regions of the developing world with limited adaptive capacity, has a largely unquantified impact on food supply. Though dominated by ambient air temperature, relative humidity, wind speed, and solar radiation all affect heat stress, which can decrease livestock growth, milk production, reproduction rates, and mortality. Indices like the thermal-humidity index (THI) are used to quantify the heat stress experienced from climate variables. Livestock experience differing impacts at different index critical thresholds that are empirically determined and specific to species and breed. This lack of understanding has been highlighted in several studies with a limited knowledge of the critical thresholds of heat stress in native livestock breeds, as well as the current and future impact of heat stress,. As adaptation and mitigation strategies to climate change depend on a solid quantitative foundation, this knowledge gap has limited such efforts. To address the lack of study, we have investigated heat stress impacts in the pastoral system of Sub-Saharan West Africa. We used a stochastic weather generator to quantify both the historic and future variability of heat stress. This approach models temperature, relative humidity, and precipitation, the climate variables controlling heat stress. Incorporating large-scale climate as covariates into this framework provides a better historical fit and allows us to include future CMIP5 GCM projections to examine the climate change impacts on heat stress. Health and production data allow us to examine the influence of this variability on livestock directly, and are considered in conjunction with the confounding impacts of fodder and water access. This understanding provides useful information to decision makers looking to mitigate the impacts of climate change and can provide useful seasonal forecasts of heat stress risk. A comparison of the current and future heat stress conditions based on climate variables for West Africa will be presented, An assessment of current and future risk was obtained by linking climatic heat stress to cattle health and production. Seasonal forecasts of heat stress are also provided by modeling the heat stress climate variables using persistent large-scale climate features.

Pattern of Blood Pressure in Adolescents | Mijinyawa | Sahel ...

African Journals Online (AJOL)

Multiple linear regression analysis identified body mass index, height and socioeconomic status as independent predictors of rise in SBP. These variables, as well as age similarly predicted rise in diastolic blood pressure. Going by the definition of hypertension of equal greater than the 95th percentile for the individual's sex ...

Evaluating U.S. and EU Trans Sahel Policies

Science.gov (United States)

2013-03-01

elected leaders as well as young Africans who are leaders in civil society and entrepreneurship . Protecting Human Rights, Civil Society, and...GSPC: Newest Franchise in al-Qa‘ida‘s Global Jihad,‖ The Combating Terrorism Center, United States Military Academy, West Point, April 2007, 2. 40

The influence of seasonal rainfall upon Sahel vegetation

DEFF Research Database (Denmark)

Proud, Simon Richard; Rasmussen, Laura Vang

2011-01-01

Throughout the Sahelian region of Africa, vegetation growth displays substantial inter-annual variation, causing widespread concern in the region as rain-fed agriculture and pastoralism are a means of sustenance for the predominantly rural population. Previously proposed factors behind variations...... yields, carbon storage and landscape changes without the need to resort to rainfall estimates that are sometimes of low accuracy. In addition, it may be possible to apply the results to other dry land regions worldwide....

JIHADIST GROUPS IN THE SAHEL. AN ETYMOLOGICAL ANALYSIS

Directory of Open Access Journals (Sweden)

Francesco Saverio Angió

2018-01-01

Full Text Available The names of the insurgent groups include historical, cultural, ethnic, territorial and doctrinal references that appear too specific to be considered accidental and thus could be indicative of their strategy. The examples of terrorist attacks carried out by these groups support this argument, as they adopted or changed their name beforehand, shortly before a spinoff group, a new alliance or an offshoot emerged, or when an attack occurred in a non-traditional geographic area of action. Unfortunately, too often mass media and government officials utilise incorrect and/or superficial translations of these names, thus contributing to a lack of detailed information on the jihadists. The etymological analysis of the Arabic names of the Sahelian jihadist insurgents intends to and contributes to increase the knowledge on the nature and actions of these groups

Variability of aerosol vertical distribution in the Sahel

Directory of Open Access Journals (Sweden)

O. Cavalieri

2010-12-01

Full Text Available In this work, we have studied the seasonal and inter-annual variability of the aerosol vertical distribution over Sahelian Africa for the years 2006, 2007 and 2008, characterizing the different kind of aerosols present in the atmosphere in terms of their optical properties observed by ground-based and satellite instruments, and their sources searched for by using trajectory analysis. This study combines data acquired by three ground-based micro lidar systems located in Banizoumbou (Niger, Cinzana (Mali and M'Bour (Senegal in the framework of the African Monsoon Multidisciplinary Analysis (AMMA, by the AEROsol RObotic NETwork (AERONET sun-photometers and by the space-based Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP onboard the CALIPSO satellite (Cloud-Aerosol Lidar and Infrared Pathfinder Observations.

During winter, the lower levels air masses arriving in the Sahelian region come mainly from North, North-West and from the Atlantic area, while in the upper troposphere air flow generally originates from West Africa, crossing a region characterized by the presence of large biomass burning sources. The sites of Cinzana, Banizoumbou and M'Bour, along a transect of aerosol transport from East to West, are in fact under the influence of tropical biomass burning aerosol emission during the dry season, as revealed by the seasonal pattern of the aerosol optical properties, and by back-trajectory studies.

Aerosol produced by biomass burning are observed mainly during the dry season and are confined in the upper layers of the atmosphere. This is particularly evident for 2006, which was characterized by a large presence of biomass burning aerosols in all the three sites.

Biomass burning aerosol is also observed during spring when air masses originating from North and East Africa pass over sparse biomass burning sources, and during summer when biomass burning aerosol is transported from the southern part of the continent by the monsoon flow.

During summer months, the entire Sahelian region is under the influence of Saharan dust aerosols: the air masses in low levels arrive from West Africa crossing the Sahara desert or from the Southern Hemisphere crossing the Guinea Gulf while in the upper layers air masses still originate from North, North-East. The maximum of the desert dust activity is observed in this period which is characterized by large AOD (above 0.2 and backscattering values. It also corresponds to a maximum in the extension of the aerosol vertical distribution (up to 6 km of altitude. In correspondence, a progressive cleaning up of the lowermost layers of the atmosphere is occurring, especially evident in the Banizoumbou and Cinzana sites.

Summer is in fact characterized by extensive and fast convective phenomena.

Lidar profiles show at times large dust events loading the atmosphere with aerosol from the ground up to 6 km of altitude. These events are characterized by large total attenuated backscattering values, and alternate with very clear profiles, sometimes separated by only a few hours, indicative of fast removal processes occurring, likely due to intense convective and rain activity.

The inter-annual variability in the three year monitoring period is not very significant. An analysis of the aerosol transport pathways, aiming at detecting the main source regions, revealed that air originated from the Saharan desert is present all year long and it is observed in the lower levels of the atmosphere at the beginning and at the end of the year. In the central part of the year it extends upward and the lower levels are less affected by air masses from Saharan desert when the monsoon flow carries air from the Guinea Gulf and the Southern Hemisphere inland.

Aspiration Pneumonia in Acute Stroke | SALAMI | Sahel Medical ...

African Journals Online (AJOL)

Abstract. This was a prospective study that was conducted between July 2000 and September 2001. It was designed to determine the incidence and the risk factor(s) of aspiration pneumonia in patients with acute cerebrovascular accident. Aspiration pneumonia was recorded in 23.5% of the 68 patients that were recruited.

Sahel Medical Journal - Vol 5, No 4 (2002)

African Journals Online (AJOL)

Prevalence of Yersinia enterocolitica Among Diarrhoeal Patients Attending University of Benin Teaching Hospital Benin City, Nigeria · EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. AI Omoigberale, PO Abiodun, 182-185. http://dx.doi.org/10.4314/smj2.v5i4.12825 ...

Agroforesterie et alimentation des moutons au Mali | CRDI - Centre ...

International Development Research Centre (IDRC) Digital Library (Canada)

Review of pasture and fodder production and productivity for small ruminants in the Sahel. 53216. Rapports. Accroître la sécurité alimentaire en associant étroitement élevage, arbres et cultures par la pratique de l'agroforesterie au Mali : rapport technique final (1er mars 2011 - 1er septembre 2014). Téléchargez le PDF.

Social Memory of Short-term and Long-term Variability in the Sahelian Climate

Science.gov (United States)

Roderick J. McIntosh

2006-01-01

The 170,000 km2 interior floodplain of the Middle Niger (Mali) is a tight mosaic of alluvial and desert microenvironments. The interannual to intermillennial climate change profiles of this fluvial anomaly thrust deep into the Sahel and southern Sahara are masterpieces of abrupt phase shifts and unpredictability. Response has been of two kinds. The Office du Niger was...

Publications | Page 233 | CRDI - Centre de recherches pour le ...

International Development Research Centre (IDRC) Digital Library (Canada)

Compostage artisanale d'ordure ménagère à Pouytenga : risques de contamination et stratégie de leur réduction (restricted access) · Sahel agroforesterie, no. 6, avril - juin 2006 (open access) · Numérisation et mise sur Internet des ressources documentaires de l'IFAN Cheikh Anta Diop : rapport technique final; 2002-2006 ...

A Review Of Preterm Admissions Into Special Care Baby Unit, In ...

African Journals Online (AJOL)

There is little or no report of preterm (babies born less than 37 completed weeks of gestation) admission from this part of Sahel Savannah of Nigeria. This study of four-year period is presented to identify areas that require improvement, such as in the Labour ward and neonatal care. The case files of the 428 preterm ...

proprietes hydriques des sols dans deux zones a ecosystemes

African Journals Online (AJOL)

Hoogmoed W. B. and Stroosnijder L. 1984. Crust formation on sandy soils in the sahel. I: rainfall and infiltration. Soil & Tilage. Research 4 : 5 - 23. Le Houérou H. N. 1996. Drought-tolerant and water- efficient trees and shrubs for rehabilitation of tropical and subtropical arid lands of Africa and Asia. Land-Husbandry 1 : 43 ...

champ ecole paysan, une approche participative pour l'amelioration

African Journals Online (AJOL)

Stroosnijder.1995. Choix et modalités d'exécution des mesures de conservation de l'eau et des sols au Sahel. Department of Agronomy, Wageningen Agricultural Uni- versity (WAU), PO Box 341, 6700 AH Wa- geningen, The Netherlands, 94 p. Khosa T.B., Van Averbek W., Böhringer R. et E. Albertse. 2002. Enriching the ...

ETUDE DE LA DISTRIBUTION DES CATIONS ECHANGEABLES

African Journals Online (AJOL)

SEI Joseph

d'Observatoires de Surveillance Écologique à Long Terme (ROSELT) mise en place par l'Observatoire du Sahel ... d'une image satellite en ayant recours aux cartes des ressources en sols et pédologiques existantes. Il en ressort une carte pédologique couvrant toute la zone de Menzel Habib répartis en huit classes.

The Sign Language Situation in Mali

Science.gov (United States)

Nyst, Victoria

2015-01-01

This article gives a first overview of the sign language situation in Mali and its capital, Bamako, located in the West African Sahel. Mali is a highly multilingual country with a significant incidence of deafness, for which meningitis appears to be the main cause, coupled with limited access to adequate health care. In comparison to neighboring…

Valuation of Conditions of Mechanized Milking of Cows and of the ...

African Journals Online (AJOL)

The aim of this study is to evaluate mainly the conditions the milking and the mammary health status of cows in the central East Sousse (Tunisian Sahel). The study was conducted on a sample of 20 small and means dairy cattle herds aboveground divided into two study areas. This study examined the general conditions of ...

C:\\Users\\AISA\\Desktop\\PDF 26(2)\\SOGODOGO.xps

African Journals Online (AJOL)

AISA

intervention du projet «Gestion intégrée de l'eau et des éléments nutritifs pour une production agricole durable dans le sahel» ACDI/CRDI au Mali. Ses objectifs étaient d'éviter que le paysan brade sa production immédiatement après les récoltes.

Vegetative propagation by root and stem cuttings of Leptadenia ...

African Journals Online (AJOL)

The aim of this study was to investigate the possibilities of the propagation of Leptadenia hastata cuttings during the 3 seasons of the year in Sahel. The cuttings of 20 cm of length, collected from the basal, apical and root parts of the plants, were used. Study investigations consisted in observing the buds and leaves ...

Regional Planning, Local Visions : Participatory Futuring in West Africa

OpenAIRE

Peter Easton

2000-01-01

The note examines regional planning, and future participatory methods for economic development in West Africa, based on the work carried out by the Club du Sahel - a branch of the Organization for Economic Cooperation and Development (OECD) - responsible for coordinating northern donor agencies, in support of food security, and natural resource management in the desert-edge portions of Wes...

Composition nutritionnelle de 10 fruits sauvages consommés dans ...

African Journals Online (AJOL)

In the Sahel, wild fruits are still under collection by rural people in order to sell them, for their economic purpose, and integrate them in their diet. Chemical methods were used for the determination of the nutritional value of these fruits. It appears that dried fruits had the highest carbohydrate (the fruits of Hyphaene thebaica ...

Search Results | Page 799 | IDRC - International Development ...

International Development Research Centre (IDRC) Digital Library (Canada)

Results 7981 - 7990 of 9602 ... South of Sahara (1981) Apply South of Sahara filter · North of Sahara (1690) Apply .... Bridging gender gaps with dairy goats and root crops. Introducing dairy goats in semi-arid regions of Tanzania has led to farmers earning ... to famines from the Sahel to the Horn of Africa, conflicts and natural ...

Actual evapotranspiration in drylands from in-situ and satellite data

DEFF Research Database (Denmark)

Garcia Garcia, Monica; Sandholt, Inge; Ceccato, Pietro

2013-01-01

satisfactory results for ¿¿ at the Sahelian savanna, comparable to parameterizations using field-measured Soil Water Content (SWC) with r2 greater than 0.80. In the Mediterranean grasslands however, with much lower daily ¿E values, model results were not as good as in the Sahel (r2 = 0.57–0.31) but still...

Variation in NAT2 acetylation phenotypes is associated with differences in food-producing subsistence modes and ecoregions in Africa

Czech Academy of Sciences Publication Activity Database

Podgorná, Eliška; Diallo, I.; Vangenot, Ch.; Sanchez-Mazas, A.; Sabbagh, A.; Černý, Viktor; Poloni, E. S.

2015-01-01

Roč. 15, č. 263 (2015) ISSN 1471-2148 R&D Projects: GA ČR GA13-37998S Institutional support: RVO:67985912 Keywords : NAT2 * acetylation polymorphism * African Sahel * pastoral nomads * subsistence mode * ecoregion * natural selection Subject RIV: AC - Archeology, Anthropology, Ethnology Impact factor: 3.406, year: 2015 http://www.biomedcentral.com/1471-2148/15/263

Lateral extrusion of Tunisia : Contribution of Jeffara Fault (southern branch) and Petroleum Implications

Science.gov (United States)

Ghedhoui, R.; Deffontaines, B.; Rabia, M. C.

2012-04-01

Contrasting to the northward African plate motion toward Eurasia and due to its geographic position in the North African margin, since early cretaceous, Tunisia seems to be submitted to an eastward migration. The aim of this work is to study the southern branch of this inferred tectonic splay that may guide the Tunisian extrusion characterised to the east by the Mediterranean sea as a free eastern boundary. The Jeffara Fault zone (southern Tunisia), represent a case example of such deformation faced by Tunisia. Helped by the results of previous researchers (Bouaziz, 1995 ; Rabiaa, 1998 ; Touati et Rodgers, 1998 ; Sokoutis D. et al., 2000 ; Bouaziz et al., 2002 ; Jallouli et al., 2005 ; Deffontaines et al., 2008…), and new evidences developed in this study, we propose a geodynamic Tunisian east extrusion model, due to such the northern African plate migration to the Eurasian one. In this subject, structural geomorphology is undertaken herein based on both geomorphometric drainage network analysis (Deffontaines et al., 1990), the Digital Terrain Model photo-interpretation (SRTM) combined with photo-interpretation of detailed optical images (Landsat ETM+), and confirmed by field work and numerous seismic profiles at depth. All these informations were then integrated within a GIS (Geodatabase) (Deffontaines 1990 ; Deffontaines et al. 1994 ; Deffontaines, 2000 ; Slama, 2008 ; Deffontaines, 2008) and are coherent with the eastern extrusion of the Sahel block. We infer that the NW-SE Gafsa-Tozeur, which continue to the Jeffara major fault zone acting as a transtensive right lateral motion since early cretaceous is the southern branch of the Sahel block extrusion. Our structural analyses prove the presence of NW-SE right lateral en-echelon tension gashes, NW-SE aligned salt diapirs, numerous folds offsets, en-echelon folds, and so on that parallel this major NW-SE transtensive extrusion fault zone.These evidences confirm the fact that the NW-SE Jeffara faults correspond

Soil quality and rice productivity problems in Sahelian irrigation schemes

NARCIS (Netherlands)

Asten, van P.J.A.

2003-01-01

In irrigation schemes in theSahel, rice yields and cropping

caractérisation de la tolérance de nerica à la sécheresse de mi ...

African Journals Online (AJOL)

Administrator

1Université de Cocody, UFR des Sciences de la Terre et des Ressources Minières, laboratoire de Pédologie. Appliquée, 22 BP 582 Abidjan 22, Abidjan, ..... Caractéristiques climatiques et pédologiques du site. La Figure 1 montre les distributions ..... sandy soils of the Sahel: a case study from. Niger, West Africa. Agriculture ...

Scaling Up Post-Harvest Management Innovations for Grain ...

International Development Research Centre (IDRC) Digital Library (Canada)

Services financiers et déploiement d'innovations agricoles au Sahel. Au cours des vingt dernières années, plusieurs innovations visant à améliorer les rendements des cultures vivrières ont été développées dans les centres de recherche agronomique d'Afrique de l... Voir davantageServices financiers et déploiement ...

Reduction of tree cover in West African woodlands and promotion in semi-arid farmlands

Science.gov (United States)

Brandt, Martin; Rasmussen, Kjeld; Hiernaux, Pierre; Herrmann, Stefanie; Tucker, Compton J.; Tong, Xiaoye; Tian, Feng; Mertz, Ole; Kergoat, Laurent; Mbow, Cheikh; David, John L.; Melocik, Katherine A.; Dendoncker, Morgane; Vincke, Caroline; Fensholt, Rasmus

2018-05-01

Woody vegetation in farmland acts as a carbon sink and provides ecosystem services for local people, but no macroscale assessments of the impact of management and climate on woody cover exist for drylands. Here we make use of very high spatial resolution satellite imagery to derive wall-to-wall woody cover patterns in tropical West African drylands. Our study reveals that mean woody cover in farmlands along all semi-arid and sub-humid rainfall zones is 16%, on average only 6% lower than in savannahs. In semi-arid Sahel, farmland management promotes woody cover around villages (11%), while neighbouring savannahs had on average less woody cover. However, farmlands in sub-humid zones have a greatly reduced woody cover (21%) as compared with savannahs (33%). In the region as a whole, rainfall, terrain and soil are the most important (80%) determinants of woody cover, while management factors play a smaller (20%) role. We conclude that agricultural expansion causes a considerable reduction of trees in woodlands, but observations in Sahel indicate that villagers safeguard trees on nearby farmlands which contradicts simplistic ideas of a high negative correlation between population density and woody cover.

On the data-driven inference of modulatory networks in climate science: an application to West African rainfall

Science.gov (United States)

González, D. L., II; Angus, M. P.; Tetteh, I. K.; Bello, G. A.; Padmanabhan, K.; Pendse, S. V.; Srinivas, S.; Yu, J.; Semazzi, F.; Kumar, V.; Samatova, N. F.

2015-01-01

Decades of hypothesis-driven and/or first-principles research have been applied towards the discovery and explanation of the mechanisms that drive climate phenomena, such as western African Sahel summer rainfall~variability. Although connections between various climate factors have been theorized, not all of the key relationships are fully understood. We propose a data-driven approach to identify candidate players in this climate system, which can help explain underlying mechanisms and/or even suggest new relationships, to facilitate building a more comprehensive and predictive model of the modulatory relationships influencing a climate phenomenon of interest. We applied coupled heterogeneous association rule mining (CHARM), Lasso multivariate regression, and dynamic Bayesian networks to find relationships within a complex system, and explored means with which to obtain a consensus result from the application of such varied methodologies. Using this fusion of approaches, we identified relationships among climate factors that modulate Sahel rainfall. These relationships fall into two categories: well-known associations from prior climate knowledge, such as the relationship with the El Niño-Southern Oscillation (ENSO) and putative links, such as North Atlantic Oscillation, that invite further research.

WÉGOUBRI, the sahelian bocage: an integrate approach for environment preservation and social development in sahelian agriculture (Burkina Faso

Directory of Open Access Journals (Sweden)

H. Girard

2009-01-01

Full Text Available The NGO Terre Verte pursues the realisation of bocage perimeters (wégoubri in the mooré language in Burkina Faso. They are an innovative concept of rural development that has been established in the 1990s in the experimental farm of Guiè and is now adopted in other experimental farms in Burkina Faso. The deterioration of the rural landscape in the Sahel region has worsened in the last decades, endangering local populations. The creation of bocage perimeters in this rural landscape is a way to remediate problems linked to overly extensive agriculture. Through a holistic approach to the problem, the experimental farm of Guiè has been able to integrate environmental preservation into the Sahel agriculture thanks to three axes of intervention: applied research, education and direct help to the peasants. An experimental farm relies on five technical teams, each supervised by a coordinator.The concept is based on the creation of bocage perimeters in a mixed propriety regime, comprising individually owned plots and common grounds, managed by an association of beneficiaries. The result is a restored environment, in which agriculture is no longer tantamount to erosion and livestock farming to overgrazing, where trees and bushes are harmoniously integrated into the environment.The increase in agricultural yields observed after a few years of soil restoration leads to the conclusion that those projects will be economically viable. A system of credits for farmers could allow the implementation of such a system, which represents the only solution for the millions of hectares of degraded soil in the Sahel region.L’ONG Terre Verte réalise au Burkina Faso des périmètres bocagers (wégoubri en langue mooré. Il s’agit d’un concept novateur de développement rural mis au point dans la ferme pilote de Guiè dans les années 1990, adopté depuis par d’autres fermes pilotes du pays. La dégradation du paysage rural du Sahel s’est aggravée au

Why Failing Terrorist Groups Persist: The Case of Al-Qaeda in the Islamic Maghreb

Science.gov (United States)

2012-06-01

and Nigeria in the South). As an AQ franchise organization their goals now include attacking western interests within the Sahel.10 Lastly, AQIM...concerning NEA. 317 Official, interview concerning NEA. 318 Official, interview concerning NEA 76 open society and encouraged entrepreneurship as...focused on criminal entrepreneurship than the AQIM Islamist ideology.359 The Joint Staff does not see an end to AQIM without a significant change in

Résultats de recherche | Page 55 | CRDI - Centre de recherches ...

International Development Research Centre (IDRC) Digital Library (Canada)

Conception d'un modèle technique pour le pilotage de l'irrigation de complément à partir des bassins de collecte des eaux de ruissellement. La présente étude est menée dans la partie sahélienne du Burkina Faso, zone particulièrement sensible comme l''ensemble du Sahel africain confronté depuis plusieurs décennies à ...

Burkina Faso : tous les projets | Page 3 | CRDI - Centre de ...

International Development Research Centre (IDRC) Digital Library (Canada)

Au Sahel, le déficit de la production agricole et pastorale, combiné à la hausse générale des prix des denrées, ont augmenté l'insécurité alimentaire. End Date: 26 juillet 2017. Sujet: DESERTIFICATION. Région: Burkina Faso, Mali. Programme: Agriculture et sécurité alimentaire. Financement total : CA$ 1,142,600.00.

Gestion des ressources naturelles pour une sécurité alimentaire ...

International Development Research Centre (IDRC) Digital Library (Canada)

Au Sahel, le déficit de la production agricole et pastorale, combiné à la hausse générale des prix des denrées, ont augmenté l'insécurité alimentaire. Pour garantir leur sécurité alimentaire, les populations rurales utilisent des techniques de production agricole visant à maximiser leur production sans nécessairement se ...

Gestion intégrée de l'eau et des nutriments pour la production ...

International Development Research Centre (IDRC) Digital Library (Canada)

Au Sahel, la sécheresse et la piètre fertilité des sols limitent grandement le rendement des cultures. En 2005 et 2010, ces deux facteurs ont conduit à des pénuries alimentaires au Niger. Pourtant, des technologies novatrices comme le microdosage des engrais associé à la récupération des eaux de pluie peuvent accroître ...

Long-Term Trend and Seasonal Variability of Horizontal Visibility in Nigerian Troposphere

Directory of Open Access Journals (Sweden)

Mukhtar Balarabe

2015-10-01

Full Text Available A study of the long-term variability; trend and characteristics of visibility in four zones of Nigeria was carried out. Visibility and other meteorological data from NOAA-NCDC and aerosol index data over Nigeria during 1984–2013 are analyzed using time series and  simple regression model. There are significant decreasing trends for every region and season during the 30-years period; the fluctuations exhibited nearly similar pattern. The 30-year mean visibilities for the four zones (Sahel; North Central; Southern; and Coastal were 13.8 ± 3.9; 14.3 ± 4.2; 13.6 ± 3.5 and 12.8 ± 3.1 km with decreasing trends at the rates of 0.08; 0.06; 0.02 and 0.02 km/year. In all the zones; visibilities were better in summer while worse in Harmattan (dry season. During summer visibility was best in Sahel and North-central; however; in Harmattan visibility was best in southern and coastal zones. It was best between May and June (17.6; 18.9; 16.6 and 15.1 km with a second peak in September. The 30-year seasonal averages were 16.2 ± 2.1; 16.8 ± 2.4; 15.4 ± 1.8 and 14.0 ± 2.2 km in summer; and 10.2 ± 2.5; 10.9 ± 2.9; 11.0 ± 3.3 and 11.4 ± 3.0 km in Harmattan for the respective zones. Sahel and North Central had the worse visibility reduction during Harmattan compared with Southern and coastal areas. An analysis based on simple regression equation reveals a strong and negative relationship between visibility on one hand; AI; and AOD on the other hand. The analysis also discusses the variability regarding the frequency of occurrence of a dust storm; dust haze; and good visibility over the period of study.

Attributing Climate Conditions for Stable Malaria Transmission to Human Activity in sub-Saharan Africa

Science.gov (United States)

Sheldrake, L.; Mitchell, D.; Allen, M. R.

2015-12-01

Temperature and precipitation limit areas of stable malaria transmission, but the effects of climate change on the disease remain controversial. Previously, studies have not separated the influence of anthropogenic climate change and natural variability, despite being an essential step in the attribution of climate change impacts. Ensembles of 2900 simulations of regional climate in sub-Saharan Africa for the year 2013, one representing realistic conditions and the other how climate might have been in the absence of human influence, were used to force a P.falciparium climate suitability model developed by the Mapping Malaria Risk in Africa project. Strongest signals were detected in areas of unstable transmission, indicating their heightened sensitivity to climatic factors. Evidently, impacts of human-induced climate change were unevenly distributed: the probability of conditions being suitable for stable malaria transmission were substantially reduced (increased) in the Sahel (Greater Horn of Africa (GHOA), particularly in the Ethiopian and Kenyan highlands). The length of the transmission season was correspondingly shortened in the Sahel and extended in the GHOA, by 1 to 2 months, including in Kericho (Kenya), where the role of climate change in driving recent malaria occurrence is hotly contested. Human-induced warming was primarily responsible for positive anomalies in the GHOA, while reduced rainfall caused negative anomalies in the Sahel. The latter was associated with anthropogenic impacts on the West African Monsoon, but uncertainty in the RCM's ability to reproduce precipitation trends in the region weakens confidence in the result. That said, outputs correspond well with broad-scale changes in observed endemicity, implying a potentially important contribution of anthropogenic climate change to the malaria burden during the past century. Results support the health-framing of climate risk and help indicate hotspots of climate vulnerability, providing

Assessment of moisture budget over West Africa using MERRA-2's aerological model and satellite data

Science.gov (United States)

Igbawua, Tertsea; Zhang, Jiahua; Yao, Fengmei; Zhang, Da

2018-02-01

The study assessed the performance of NASA's Modern-Era Retrospective Analysis for Research and Applications (MERRA) and MERRA-2 aerological (P-E*) model in reproducing the salient features of West Africa water balance including its components from 1980 to 2013. In this study we have shown that recent reanalysis efforts have generated imbalances between regional integrated precipitation (P) and surface evaporation (E), and the effect is more in the newly released MERRA-2. The atmospheric water balance of MERRA and MERRA-2 were inter-compared and thereafter compared with model forecast output of European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-I) and Japanese 55-year Reanalysis (JRA-55). Results indicated that a bias of 12-20 (5-13) mm/month in MERRA-2 (ERA-I) leads to the classification of the Sahel (14°N-20°N) as a moisture source during the West African Summer Monsoon. Comparisons between MERRA/MERRA-2 and prognostic fields from two ERA-I and JRA-55 indicated that the average P-E* in MERRA is 18.94 (52.24) mm/month which is less than ERA-I (JRA-55) over Guinea domain and 25.03 (4.53) mm/month greater than ERA-I (JRA-55) over the Sahel. In MERRA-2, average P-E* indicated 25.76 (59.06) mm/month which is less than ERA-I (JRA-55) over Guinea and 73.72 (94.22) mm/month less than ERA-I (JRA-55) over the Sahel respectively. These imbalances are due to adjustments in data assimilation methods, satellite calibration and observational data base. The change in convective P parameterization and increased re-evaporation of P in MERRA-2 is suggestive of the cause of positive biases in P and E. The little disagreements between MERRA/MERRA-2 and CRU precipitation highlights one of the major challenges associated with climate research in West Africa and major improvements in observation data and surface fluxes from reanalysis remain vital.

Rainfall over the African continent from the 19th through the 21st century

Science.gov (United States)

Nicholson, Sharon E.; Funk, Chris; Fink, Andreas H.

2018-06-01

Most of the African continent is semi-arid and hence prone to extreme variations in rainfall from year to year. The extreme droughts that have plagued the Sahel and eastern Africa are particularly well known. This article uses a markedly expanded and updated rainfall data set to examine rainfall variability in 13 sectors that cover most of the continent. Annual rainfall is presented for each sector; the March-to-May and October-November seasons are also examined for equatorial sectors. In each case, the article includes the longest and most comprehensive precipitation gauge series ever published. All time series cover at least a century and most cover roughly one and one-half centuries or more. Although towards the end of the 20th century there was a widespread trend towards more arid conditions, few significant trends are evident over the entire period of record. The largest were downward trends in the Sahel and western sectors of North Africa. In those regions, an abrupt reduction in rainfall occurred around 1968, but a synchronous change occurred many other parts of Africa. A recovery did occur in the Sahel, but to varying degrees across the east-west expanse of the region. Noteworthy is that the west-to-east rainfall gradient across the region appears to have weakened in recent decades. For the continent as a whole, another change began in the 1980s decade, with more arid conditions persisting at the continental scale until early in the twenty-first century. No other such period of dry conditions occurred within the roughly one and one-half centuries evaluated here. A notable change also occurred at the seasonal level. During the period 1980 to 1998 rainfall during March-to-May was well below the long-term mean throughout most of the area from 20° N to 35° S. At the same time rainfall was above the long-term mean in most of eastern sectors within this latitude span, indicating a change in the seasonality of rainfall of a large part of Africa.

Assessing Woody Vegetation Trends in Sahelian Drylands Using MODIS Based Seasonal Metrics

Science.gov (United States)

Brandt, Martin; Hiernaux, Pierre; Rasmussen, Kjeld; Mbow, Cheikh; Kergoat, Laurent; Tagesson, Torbern; Ibrahim, Yahaya Z.; Wele, Abdoulaye; Tucker, Compton J.; Fensholt, Rasmus

2016-01-01

Woody plants play a major role for the resilience of drylands and in peoples' livelihoods. However, due to their scattered distribution, quantifying and monitoring woody cover over space and time is challenging. We develop a phenology driven model and train/validate MODIS (MCD43A4, 500m) derived metrics with 178 ground observations from Niger, Senegal and Mali to estimate woody cover trends from 2000 to 2014 over the entire Sahel. The annual woody cover estimation at 500 m scale is fairly accurate with an RMSE of 4.3 (woody cover %) and r(exp 2) = 0.74. Over the 15 year period we observed an average increase of 1.7 (+/- 5.0) woody cover (%) with large spatial differences: No clear change can be observed in densely populated areas (0.2 +/- 4.2), whereas a positive change is seen in sparsely populated areas (2.1 +/- 5.2). Woody cover is generally stable in cropland areas (0.9 +/- 4.6), reflecting the protective management of parkland trees by the farmers. Positive changes are observed in savannas (2.5 +/- 5.4) and woodland areas (3.9 +/- 7.3). The major pattern of woody cover change reveals strong increases in the sparsely populated Sahel zones of eastern Senegal, western Mali and central Chad, but a decreasing trend is observed in the densely populated western parts of Senegal, northern Nigeria, Sudan and southwestern Niger. This decrease is often local and limited to woodlands, being an indication of ongoing expansion of cultivated areas and selective logging.We show that an overall positive trend is found in areas of low anthropogenic pressure demonstrating the potential of these ecosystems to provide services such as carbon storage, if not over-utilized. Taken together, our results provide an unprecedented synthesis of woody cover dynamics in theSahel, and point to land use and human population density as important drivers, however only partially and locally offsetting a general post-drought increase.

Direct Radiative Effect of Mineral Dust on the Middle East and North Africa Climate

KAUST Repository

Bangalath, Hamza Kunhu

2016-11-01

strength of shortwave absorption. Further analyses reveal that the sensitivity of the rainbelt stems from the sensitivity of the multi-scale circulations that define the rainbelt. Importantly, the summer precipitation over the semi-arid strip south of Sahara, including Sahel, increases in response to dust radiative effect. The maximum response and sensitivity are predicted over this region. The sensitivity of the responses over Sahel, especially that of precipitation, is comparable to the mean state. Locally, the precipitation increase reaches up to 50% of the mean, while dust is assumed to be a very efficient absorber. As the region is characterized by the "Sahel drought", the predicted precipitation sensitivity to the dust loading over this region has a wide-range of socioeconomic implications. The present study, therefore, suggests the importance of reducing uncertainty in dust shortwave absorption for a better simulation and interpretation of the MENA climate in general, and of Sahel in particular.

Desempenho de cultivares de tomateiro em sistema orgânico sob cultivo protegido Performance of organically grown tomato cultivars under greenhouse conditions

Directory of Open Access Journals (Sweden)

Paulo César T de Melo

2009-12-01

Full Text Available A agricultura orgânica no Brasil cresce a taxas superiores a 30% ao ano, devido principalmente à maior conscientização dos consumidores que buscam alimentos saudáveis, livres de resíduos químicos e biológicos. Dentre as hortaliças cultivadas em sistema orgânico, o tomate constitui grande desafio para os produtores devido à inexistência de recomendações de manejo cultural e de cultivares desenvolvidas específicas para esse sistema de cultivo. Diante disso, o presente trabalho teve como objetivo avaliar o desempenho de cultivares de tomate sob sistema orgânico, em ambiente protegido. O experimento foi conduzido de maio a outubro de 2004 em campo, no município de Araraquara-SP. O delineamento experimental adotado foi blocos ao acaso, com quatro repetições e oito tratamentos (cultivares Avalon, Colibri, HTX-5415, HTX-8027, Sahel, San Marzano, San Vito e Jane. As plantas foram conduzidas em fileiras duplas, com duas hastes por planta no espaçamento de 0,8 m entre linhas e 0,6 m entre plantas (cerca de 20.000 plantas ha-1, sem poda apical. O híbrido Sahel destacou-se com o melhor desempenho para rendimento comercial. A traça-do-tomateiro se revelou como fator limitante à produção de tomate em sistema orgânico, sendo responsável, em média, por 17% de danos nos frutos colhidos das oito cultivares que foram avaliadas.Organic agriculture in Brazil has been increasing about 30% per year over the last few years, since consumers are seeking for healthier foods, i.e. nutritious and free of pesticide residues. Among organically grown vegetable crops, tomato is an attractive economic opportunity for growers. However, the lack of information about management practices and adapted cultivars to organic production systems under protected cultivation are pointed out as important constraints that prevents this activity to expand. This work aimed at evaluating the performance of indeterminate tomato cultivars in organic management systems

A Climatology of dust emission in northern Africa using surface observations from 1984-2012

Science.gov (United States)

Cowie, Sophie; Knippertz, Peter; Marsham, John

2014-05-01

The huge quantity of mineral dust emitted annually from northern Africa makes this area crucial to the global dust cycle. Once in the atmosphere, dust aerosols have a significant impact on the global radiation budget, clouds, the carbon cycle and can even act as a fertilizer to rain forests in South America. Current model estimates of dust production from northern Africa are uncertain. At the heart of this problem is insufficient understanding of key dust emitting processes such as haboobs (cold pools generated through evaporation of convective precipitation), low-level jets (LLJs) and dry convection (dust devils and dust plumes). Scarce observations in this region, in particular in the Sahara, make model evaluation difficult. This work uses long-term surface observations from 70 stations situated in the Sahara and Sahel to explore the diurnal, seasonal and geographical variations in dust emission events and thresholds. Quality flags are applied to each station to indicate a day-time bias or gaps in the time period 1984-2012. The frequency of dust emission (FDE) is calculated using the present weather codes (WW) of SYNOP reports, where WW = 07,08,09,30-35 and 98. Thresholds are investigated by estimating the wind speeds for which there is a 25%, 50% and 75% probability of dust emission. The 50% threshold is used to calculate strong wind frequency (SWF) and the diagnostic parameter dust uplift potential (DUP); a thresholded cubic function of wind-speed which quantifies the dust generating power of winds. Stations are grouped into 6 areas (North Algeria, Central Sahara, Egypt, West Sahel, Central Sahel and Sudan) for more in-depth analysis of these parameters. Spatially, thresholds are highest in northern Algeria and lowest in the Sahel around the latitude band 16N-21N. Annual mean FDE is anti-correlated with the threshold, showing the importance of spatial variations in thresholds for mean dust emission. The annual cycles of FDE and SWF for the 6 grouped areas are

Alcoholism and bone growth: A literary appraisal | Adebisi | Sahel ...

African Journals Online (AJOL)

Alcoholic preparations is one of the ingredients present in beverages, drugs or chemicals in common use even at pregnancy; and this is well acclaimed to be toxic to the conceptuses, particularly, the developing skeletal tissues. A thorough literature search at MEDLINE and consultation with local scientific publications, and ...

Review Paper Les plantations d'Eucalyptus au Sahel : distribution ...

African Journals Online (AJOL)

SOUMARE

la Francophonie pour avoir soutenu cette étude à travers une bourse de formation. RESUME ..... 1968-2000. Climat saharien. Climat sahélien. Climat soudano-sahélien. Frontières des .... universalis: Global cultivated Eucalyptus forests Map ...

Desertification in the Sahel: a reinterpretation of a reinterpretation

CSIR Research Space (South Africa)

Prince, SD

2007-07-01

Full Text Available In semiarid regions the ratio of annual net primary production to precipitation, rain-use efficiency (RUE), has been used as an index of desertification. In a recent publication (Hein & de Ridder, 2006) it was proposed that an incorrect...

Day and night grazing by cattle in the Sahel

NARCIS (Netherlands)

Ayantunde, A.A.; Fernandez-Rivera, S.; Hiernaux, P.H.; Keulen, van H.; Udo, H.M.J.

2002-01-01

The influence of night grazing on feeding behavior, nutrition and performance of cattle was studied. Twenty-four steers weighing 367 kg (SD = 76) grazed either from 0900 to 1900 (day grazers), 2100 to 0700 (night grazers) or 0900 to 1900 and 2400 to 0400 (day-and-night grazers) during 13 weeks. Four

Glycaemic Index Of Boiled Cocoyam And Stew | Alegbejo | Sahel ...

African Journals Online (AJOL)

Cocoyam can be processed in several ways. It contains digestible starch, protein and other valuable nutrients. Consumption of cocoyam is very high all over Nigeria. This study was undertaken to determine the glycaemic response of diabetic and healthy subjects to equal amounts of carbohydrate in the form of boiled ...

Prolonged hospital stay in measles patients | Ashir | Sahel Medical ...

African Journals Online (AJOL)

Background: Measles is still a major cause of childhood morbidity and mortality in Nigeria despite the availability of safe and effective vaccines. The burden of measles using length of hospital stay as a result of complications in hospitalised children with measles is reported. Methods: We carried out a two year retrospective ...

Klimaændring, ørkendannelse og konflikt i Sahel

DEFF Research Database (Denmark)

Rasmussen, Kjeld; Wæver, Ole

2013-01-01

Årsagssammenhænge ved nuværende begrænsede temperaturstigninger er svære at efterspore, og der er ikke grundlag for at fremmane et billede af et stadig stigende konfliktniveau og krige i regionen af klimagrunde....

Traumatic rupture of the diaphragm | Jamabo | Sahel Medical Journal

African Journals Online (AJOL)

Those treated for traumatic rupture of the diaphragm were selected and analyzed for age, gender, cause of injury, associated injuries sustained and mode of treatment. They were all treated at the University of Port Harcourt Teaching Hospital and a private clinic in Port Harcourt. Results: 12 patients had traumatic rupture of ...

( Camelus dromedarius ) of North east sahel region of Nigeria

African Journals Online (AJOL)

The values for red blood cell count, haemoglobin concentration, packed cell volume and erythrocyte indices were similar to those obtained from camels in Sokoto (North West Region) Nigeria; and also in accord with values published in the literature for Indian camels. Total leucocyte counts were relatively higher but within ...

Developing isotope techniques for water exploration in the Sahel

International Nuclear Information System (INIS)

Aranyossy, J.F.; Louvat, D.; Maksoudi, M.

1991-01-01

The IAEA in the early 1980s started its first activities on hydrogeology in Mali, Niger, and Senegal through its technical co-operation programme. These activities included, first of all, local aquifer studies with environmental isotopes. The studies were found to be particularly useful for obtaining specific information on, for example, relationships between aquifers and between surface water and groundwater, and the existence or absence of recent recharge. Moreover, the IAEA established the basic infrastructures needed for the application of artificial tracer techniques and the use of nuclear instrumentation in hydrology and hydrosedimentology. Several factors underscored the need for co-ordinating the scientific activities already being carried out under existing bilateral projects. Firstly, the ''horizontal'' flow of information was very poor in spite of the similarity between the hydrological and hydrogeological problems encountered in the three countries. Secondly, political frontiers do not generally follow the boundaries of the hydrological basins, so that the same aquifer can be shared between several countries. Thirdly, the costly infrastructure established by the IAEA in certain countries deserved to be utilized at the regional level. To meet these concerns, an African regional project was launched 4 years ago on the development of isotope and nuclear techniques in hydrology in the Sahelian countries. Its main objectives were to further broaden ongoing studies in the participating countries; to strengthen training; to promote exchange of information on various previous studies; to foster co-operation between the different institutes involved in these studies; and to reinforce the infrastructures established by the IAEA and their utilization in the region

2180-IJBCS-Article-epolyste Adjeffa

African Journals Online (AJOL)

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pédologique, une analyse des indicateurs physico-chimiques et une instrumentation piézométrique du périmètre ... Sondage pédologique et analyse de sols. Pour réaliser le sondage pédologique du périmètre irrigué de ..... terres dans les pays du sahel. Diagnostic et conseil aux paysans. Collection « le point sur », 397p.

Indicators of young women’s modern contraceptive use in Burkina Faso and Mali from Demographic and Health Survey data

OpenAIRE

O’Regan, Amy; Thompson, Gretchen

2017-01-01

Background High total fertility rates in Burkina Faso and Mali are leading to population growth beyond the agricultural and fiscal means of its citizens. Providing access to affordable family planning methods is a key step in driving the demographic transition where fertility and mortality rates decline. Furthermore, both nations face significant challenges as climate change is projected to disproportionately impact the western Sahel region undermining environmental, social and economic stabi...

Feasibility, safety and effectiveness of combining home based malaria management and seasonal malaria chemoprevention in children less than 10 years in Senegal

DEFF Research Database (Denmark)

Tine, Roger C K; Ndour, Cheikh T; Faye, Babacar

2014-01-01

Home-based management of malaria (HMM) may improve access to diagnostic testing and treatment with artemisinin combination therapy (ACT). In the Sahel region, seasonal malaria chemoprevention (SMC) is now recommended for the prevention of malaria in children. It is likely that combinations...... of antimalarial interventions can reduce the malaria burden. This study assessed the feasibility, effectiveness and safety of combining SMC and HMM delivered by community health workers (CHWs)....

2354-IJBCS-Article-Obulbiga M Ferdinand

African Journals Online (AJOL)

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niébé pour prévenir le ruissellement et l'érosion dans le sahel au Burkina Faso, 5 p. Zoungrana I. 1991. Recherches sur les aires pâturées du Burkina Faso. Thèse d'Etat,. Université de Bordeaux III, 290 p. Zampaligré N. 2012. The role of ligneous vegetation for livestock nutrition in the sub Sahelian and Sudanian zones of ...

Mapping gains and losses in woody vegetation across global tropical drylands

DEFF Research Database (Denmark)

Tian, Feng; Brandt, Martin Stefan; Liu, Yi Y

2017-01-01

MODerate resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) data to remove the interannual fluctuations of the woody leaf component. We revealed significant trends (P ... trend in the leaf component (VODleaf modeled from NDVI), indicating pronounced gradual growth/decline in woody vegetation not captured by traditional assessments. The method is validated using a unique record of ground measurements from the semiarid Sahel and shows a strong agreement between changes...

Testing Social-driven Forces on the Evolution of Sahelian Rural Systems: A Combined Agent-based Modeling and Anthropological Approach

OpenAIRE

Saqalli , Mehdi; Gérard , B.; Bielders , C.; Defourny , Pierre

2010-01-01

International audience; This article presents the results of a methodology combining an extensive fieldwork, a formalization of field-based individual rules and norms into an agent-based model and the implementation of scenarios analyzing the effects of social and agro-ecological constraints on rural farmers through the study of three different sites in Nigerien Sahel. Two family transition processes are here tested, following field observations and literature-based hypotheses: family organiz...

Factors Influencing the Sahelian Paradox at the Local Watershed Scale: Causal Inference Insights

Science.gov (United States)

Van Gordon, M.; Groenke, A.; Larsen, L.

2017-12-01

While the existence of paradoxical rainfall-runoff and rainfall-groundwater correlations are well established in the West African Sahel, the hydrologic mechanisms involved are poorly understood. In pursuit of mechanistic explanations, we perform a causal inference analysis on hydrologic variables in three watersheds in Benin and Niger. Using an ensemble of techniques, we compute the strength of relationships between observational soil moisture, runoff, precipitation, and temperature data at seasonal and event timescales. Performing analysis over a range of time lags allows dominant time scales to emerge from the relationships between variables. By determining the time scales of hydrologic connectivity over vertical and lateral space, we show differences in the importance of overland and subsurface flow over the course of the rainy season and between watersheds. While previous work on the paradoxical hydrologic behavior in the Sahel focuses on surface processes and infiltration, our results point toward the importance of subsurface flow to rainfall-runoff relationships in these watersheds. The hypotheses generated from our ensemble approach suggest that subsequent explorations of mechanistic hydrologic processes in the region include subsurface flow. Further, this work highlights how an ensemble approach to causal analysis can reveal nuanced relationships between variables even in poorly understood hydrologic systems.

Long-distance autumn migration across the Sahara by painted lady butterflies: exploiting resource pulses in the tropical savannah.

Science.gov (United States)

Stefanescu, Constantí; Soto, David X; Talavera, Gerard; Vila, Roger; Hobson, Keith A

2016-10-01

The painted lady, Vanessa cardui, is a migratory butterfly that performs an annual multi-generational migration between Europe and North Africa. Its seasonal appearance south of the Sahara in autumn is well known and has led to the suggestion that it results from extremely long migratory flights by European butterflies to seasonally exploit the Sahel and the tropical savannah. However, this possibility has remained unproven. Here, we analyse the isotopic composition of butterflies from seven European and seven African countries to provide new support for this hypothesis. Each individual was assigned a geographical natal origin, based on its wing stable hydrogen isotope (δ 2 H w ) value and a predicted δ 2 H w basemap for Europe and northern Africa. Natal assignments of autumn migrants collected south of the Sahara confirmed long-distance movements (of 4000 km or more) starting in Europe. Samples from Maghreb revealed a mixed origin of migrants, with most individuals with a European origin, but others having originated in the Sahel. Therefore, autumn movements are not only directed to northwestern Africa, but also include southward and northward flights across the Sahara. Through this remarkable behaviour, the productive but highly seasonal region south of the Sahara is incorporated into the migratory circuit of V. cardui. © 2016 The Author(s).

Food and population.

Science.gov (United States)

1985-04-06

Agricultural producttivity is currently characterized by the paradox of an abundace of food in the developed world and hunger in much of the developing world. In China, India, and many other countries of Asia, the general food supply has kept pace with population growth and should continue to if family planning programs gain momentum. In Africa, on the other hand, the food supply has been falling behind the growth of the population in the majority of countries for the past decade. The situation is especially serious in the Sahel, where the production wf crops for export has been prioritized over local needs. The Food and Agriculture Organization's global information and early warning system is a promising development and can provide alerts when weather or other conditions threaten a harvest. Donor countries can then send in cereals and other foods before there is an actual famine. About 20 disasters in the Sahel are etimated to have been averted by this system, in operation since 1975. In developed countries, the farming industry needs to be restructured in relation to changes in markets and technologies. Solution of the food-population problem depends upon agricultural policies that balance the economic interests of farmers and consumers and also takes into account the need to preserve the countryside.

2473-IJBCS-Article-Minda Mahamat Saleh

African Journals Online (AJOL)

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faire face à cette situation, les pays du Sahel ont initié un grand projet dénommé Grande. Muraille Verte (GMV), une stratégie pour lutter contre la désertification ... différentes unités pédologiques rencontrées. Le Lac, situé à l'Ouest du tracé, est caractérisé par les sols sableux et par Acacia raddiana et Balanites aegyptiaca ...

2149-IJBCS-Article-Marcel Badji

African Journals Online (AJOL)

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végétales et pédologiques (Badji et al., 2014). C'est dans ce contexte que ce travail a été initié. Il vise à déterminer l'impact de la RNA sur le reverdissement du ..... une opportunité pour reverdir le Sahel et réduire la vulnérabilité des populations rurales. Le Projet majeur africain de la. Grande Muraille Verte, Concepts et ...

Maritime Security in the Gulf of Guinea Subregion: Threats, Challenges and Solutions

Science.gov (United States)

2011-03-16

North America and Western Europe. The region also benefits from the absence of narrow shipping maritime lanes, known as chokepoints, which makes...generating a gross domestic product of $112 billion, exports of about $4.5 billion and imports of about $13.63 billion.15 The ecosystem of the... cocoa needs, while further north, the Savannah and Sahel regions are a major source of cotton, peanuts and shea butter.18 The GoG region has large

AGRHYMET: A drought monitoring and capacity building center in the West Africa Region

OpenAIRE

Seydou B. Traore; Abdou Ali; Seydou H. Tinni; Mamadou Samake; Issa Garba; Issoufou Maigari; Agali Alhassane; Abdallah Samba; Maty Ba Diao; Sanoussi Atta; Pape Oumar Dieye; Hassan B. Nacro; Kouamé G.M. Bouafou

2014-01-01

The AGRHYMET Regional Center, a specialized institution of the Permanent Interstates Committee for Drought Control in the Sahel (CILSS), was created in 1974 at the aftermaths of the severe droughts that affected this region in the early 1970s. The mission assigned to the Center was to train personnel, provide adequate equipment for the meteorological and hydrological stations networks, and set up regional and national multidisciplinary working groups to monitor the meteorological, hydrologica...

Parameters: The US Army War College Quarterly. Volume 43, Number 4, Winter 2013-14

Science.gov (United States)

2014-01-01

example can be found when examining the recent history of the Tuareg, a traditionally nomadic people who live in the Sahara and northern Sahel of Mali...the United States. These actors have new digital tools at their disposal to elude the reach of anti-money-laundering and counterterrorist financing...efforts. For example, bitcoin (BTC) is a digital currency transferred through peer-to-peer networks on the Internet. The software, an early imple

Climate Research and Seasonal Forecasting for West Africans: Perceptions, Dissemination, and Use?.

Science.gov (United States)

Tarhule, Aondover; Lamb, Peter J.

2003-12-01

Beginning in response to the disastrous drought of 1968 73, considerable research and monitoring have focused on the characteristics, causes, predictability, and impacts of West African Soudano Sahel (10° 18°N) rainfall variability and drought. While these efforts have generated substantial information on a range of these topics, very little is known of the extent to which communities, activities at risk, and policy makers are aware of, have access to, or use such information. This situation has prevailed despite Glantz&;s provocative BAMS paper on the use and value of seasonal forecasts for the Sahel more than a quarter century ago. We now provide a systematic reevaluation of these issues based on questionnaire responses of 566 participants (in 13 communities) and 26 organizations in Burkina Faso, Mali, Niger, and Nigeria. The results reveal that rural inhabitants have limited access to climate information, with nongovernmental organizations (NGOs) being the most important source. Moreover, the pathways for information flow are generally weakly connected and informal. As a result, utilization of the results of climate research is very low to nonexistent, even by organizations responsible for managing the effects of climate variability. Similarly, few people have access to seasonal climate forecasts, although the vast majority expressed a willingness to use such information when it becomes available. Those respondents with access expressed great enthusiasm and satisfaction with seasonal forecasts. The results suggest that inhabitants of the Soudano Sahel savanna are keen for changes that improve their ability to cope with climate variability, but the lack of information on alternative courses of action is a major constraint. Our study, thus, essentially leaves unchanged both Glantz&;s negative “tentative conclusion” and more positive “preliminary assessment” of 25 years ago. Specifically, while many of the infrastructural deficiencies and socioeconomic

Provenance Study of Archaeological Ceramics from Syria Using XRF Multivariate Statistical Analysis and Thermoluminescence Dating

OpenAIRE

Bakraji, Elias Hanna; Abboud, Rana; Issa, Haissm

2014-01-01

Thermoluminescence (TL) dating and multivariate statistical methods based on radioisotope X-ray fluorescence analysis have been utilized to date and classify Syrian archaeological ceramics fragment from Tel Jamous site. 54 samples were analyzed by radioisotope X-ray fluorescence; 51 of them come from Tel Jamous archaeological site in Sahel Akkar region, Syria, which fairly represent ceramics belonging to the Middle Bronze Age (2150 to 1600 B.C.) and the remaining three samples come from Mar-T...

CTC Sentinel. Volume 4, Issue 9, September 2011

Science.gov (United States)

2011-09-01

Sahel: Al-Qa’ida’s Franchise or Freelance?” Middle East Institute, August 2011. 11 Djaffar Tamani, “Retour de la Peur en Kabylie,” El- Watan, April 19...blasts at one restaurant , as many as 10 Uighur men shot and stabbed people indiscriminately, including the firefighters who came to the rescue...encountered online to attempt a suicide attack in an Exeter chain restaurant ; diners were only saved by the fact that the bomb blew up in his face

Effet de la fréquence de traite sur la production laitière de la vache ...

African Journals Online (AJOL)

L'amélioration de la productivité laitière par le métissage a eu des résultats limités dans les pays à faible rendement car les métisses résistent peu aux dures conditions climatiques. Des alternatives ont été envisagées sur la vache Zébu la mieux adaptée aux conditions du Sahel. L'objectif de cette étude était de tester.

The Acridian plagues, a new Holocene and Pleistocene palaeoclimatic indicator

Science.gov (United States)

Meco, Joaquín; Petit-Maire, Nicole; Ballester, Javier; Betancort, Juan F.; Ramos, Antonio J. G.

2010-07-01

Five palaeosols, intercalated within the Quaternary dune beds of Fuerteventura and Lanzarote (Canary Islands), off the Moroccan coast, mark wetter climatic episodes. In all of them, billions of calcified insect ootheca testify to past occurrences of Acridian plagues, such as those reaching the western Sahara following heavy rainfall events over the Sahel. The most massive infestation is in the Holocene, and should coincide with the climax of Saharo-Sahelian humidity at the peak of the present interglacial.

Improving Shaping Efforts in Africa’s Maghreb and Sahel

Science.gov (United States)

2011-03-21

threat in North Africa to U.S. interests? Al Qaeda in the Islamic Maghreb (AQIM) is a relatively new franchise of Al Qaeda. Upon declaring allegiance...trafficking to finance their operations. Should a West African franchise of Al Qaeda, or any other terrorist organization with local grievances and/or global...solve issues like desertification, poverty, unemployment , social inequalities, and so on. By adapting to this new environment and by reallocating

Vegetation Change, Tree Diversity and Food Security in the Sahel

DEFF Research Database (Denmark)

Sambou, Antoine

reduce number of trees and palms, which can adversely affect the dietary status of rural communities. To test the hypothesis that trees and palms play an important role in the nutrition of rural communities and represent an important source of macro and micro-nutrients, four rounds of 24 hour food...... recalls using a questionnaire were carried out. Results show that food obtained from tree and palm foods were important sources of vitamin B6, vitamin C, vitamin A and iron (Fe) intake in the three villages. However, the total nutrient balance was much below the recommended values for a range of nutrients...... is likely to have an impact on the nutrition of local people, as they receive an important input of vitamins and minerals from food products from trees and palms....

New project to improve water management in the Sahel | IDRC ...

International Development Research Centre (IDRC) Digital Library (Canada)

2018-06-06

Jun 6, 2018 ... A new IDRC-supported project will help improve water conservation and use ... and tested water retention tanks to supplement irrigation from water runoff to ... where capacity will be built among agricultural stakeholders and ...

Outbreak of Peste Des Petits Ruminant in an Unvaccinated Sahel ...

African Journals Online (AJOL)

Rev Olaleye

Animal Virus Research Laboratory, Department of Veterinary Microbiology and Parasitology,. University of ... are characterized by fever, erosive stomatitis, nasal and ocular ..... vaccine has proven to be efficacious and safe (Awa et al., 2002).

Vegetation improvement and soil biological quality in the Sahel of ...

African Journals Online (AJOL)

The method of Tropical Soil Biology and Fertility (TSBF) was used to assess macro-fauna abundance and diversity in different land use types (cropland, shallow land, degraded land and forest). Four sites were selected, in the Sahelian zone of Burkina Faso, with contrasted Normalized Difference Vegetation Index (NDVI).

Les femmes du Sahel obtiennent de meilleurs rendements de leurs ...

International Development Research Centre (IDRC) Digital Library (Canada)

7 juin 2016 ... L'indice de la faim dans le monde 2013 met en évidence la fragilité de la ... une meilleure méthode de collecte des eaux de pluie, les agriculteurs ont observé ... acheter des engrais et des semences de bonne qualité à crédit.

Energy in the strategy to Sahel Development : Situation - Perspectives - Recommendations

International Nuclear Information System (INIS)

1995-01-01

Burkina Faso does not have fossil energy source. The problem of energy thus arises with acuity for the rural and urban populations. The energy sources used are primarily the hydrocarbons, electrical energy, the woody fuels as new and renewable energies which are the biomass, the solar energy and the wind energy. The hydrocarbons are 100% imported, which makes the country very depend on over sea with respect to its conventional energy supply. These imports represent, for the years 1987 to 1992, 12 to 29% of the export earnings of the country. In addition to this dependence, there is a great weakness of the electrical communication and the too high cost of energy which led to the development of a strategic planning of the scientific research centered on the energy sector. In this field, research made it possible to undertake a study of the Burkina Faso energy system, to evaluate and exploit solar energy and wind mill, to develop the use of new methods allowing the energy saving in the households and the safeguard of the environment. In addition research shows that an economy is possible in the administrative buildings. Work is undertaken on air-conditioning by evaporation, the technology of the cold and the valorization of nonfood plant oils. There is also a work done on the de-pollution of industrial waste water, the energy valorization of the biomass as well as the improvement of the technology of the dolo, local beer containing sorghum. All these scientific research activities aim at the definition of a development policy on the energetic sector which takes into account the reduction of the cost of energy, the access of the populations to this resource, the reduction in the invoice of oil products imports as well as the promotion of environmental protection, the industrial development and that of the new methods of local technology as regards energy in Burkina Faso [fr

Rural flour mills. farmer promotion tool m the Sahel area

Directory of Open Access Journals (Sweden)

Audroing, M.

1993-01-01

Full Text Available The Grameen Bank is a specialized financial institution in Bangladesh that was established to provide credit to the rural poor for the purpose of improving their economic conditions with the hypothesis that if the poor are supplied with working capital they can generate productive self-employment without external assistance. Loans from the Grameen Bank are used primarily for undertaking noncrop activities. The loan repayment performance is excellent. Only 0.5 percent of loans to 975 borrowers surveyed were overdue beyond one year, and overdue weekly installments (before the expiration of the one-year repayment period were only 3.3 percent of the total amount borrowed. The Grameen Bank concept of credit without collateral should work in other countries with widespread poverty and underemployment. But elements like taking the bank to the people and intensive interaction of bank staff with borrowers may be inappropriate and highly expensive for sparsely settled areas with underdeveloped transport systems. For such environments, an appropriate delivery mechanism has to be worked out.

Sahel Journal of Veterinary Sciences - Vol 6, No 1 (2007)

African Journals Online (AJOL)

Prevalence of pneumonia among slaughtered cattle, goats and sheep in Maiduguri abattoir, Maiduguri, Nigeria · EMAIL FULL TEXT EMAIL FULL TEXT DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. JY Adamu, JA Ameh, 5-8 ...

Space-Derived Phenology, Retrieval and Use for Drought and Food Security Monitoring

Science.gov (United States)

Meroni, M.; Kayitakire, F.; Rembold, F.; Urbano, F.; Schucknecht, A.; LEO, O.

2014-12-01

Monitoring vegetation conditions is a critical activity for assessing food security in Africa. Rural populations relying on rain-fed agriculture and livestock grazing are highly exposed to large seasonal and inter-annual fluctuations in water availability. Monitoring the state, evolution, and productivity of vegetation, crops and pastures in particular, is important to conduct food emergency responses and plan for a long-term, resilient, development strategy in this area. The timing of onset, the duration, and the intensity of vegetation growth can be retrieved from space observations and used for food security monitoring to assess seasonal vegetation development and forecast the likely seasonal outcome when the season is ongoing. In this contribution we present a set of phenology-based remote sensing studies in support to food security analysis. Key phenological indicators are retrieved using a model-fit approach applied to SOPT-VEGETATION FAPAR time series. Remote-sensing phenology is first used to estimate i) the impact of the drought in the Horn of Africa, ii) crop yield in Tunisia and, iii) rangeland biomass production in Niger. Then the impact of the start and length of vegetation growing period on the total biomass production is assessed over the Sahel. Finally, a probabilistic approach using phenological information to forecast the occurrence of an end-of-season biomass production deficit is applied over the Sahel to map hot-spots of drought-related risk.

An Assessment of Surface Water Detection Algorithms for the Tahoua Region, Niger

Science.gov (United States)

Herndon, K. E.; Muench, R.; Cherrington, E. A.; Griffin, R.

2017-12-01

The recent release of several global surface water datasets derived from remotely sensed data has allowed for unprecedented analysis of the earth's hydrologic processes at a global scale. However, some of these datasets fail to identify important sources of surface water, especially small ponds, in the Sahel, an arid region of Africa that forms a border zone between the Sahara Desert to the north, and the savannah to the south. These ponds may seem insignificant in the context of wider, global-scale hydrologic processes, but smaller sources of water are important for local and regional assessments. Particularly, these smaller water bodies are significant sources of hydration and irrigation for nomadic pastoralists and smallholder farmers throughout the Sahel. For this study, several methods of identifying surface water from Landsat 8 OLI and Sentinel 1 SAR data were compared to determine the most effective means of delineating these features in the Tahoua Region of Niger. The Modified Normalized Difference Water Index (MNDWI) had the best performance when validated against very high resolution World View 3 imagery, with an overall accuracy of 99.48%. This study reiterates the importance of region-specific algorithms and suggests that the MNDWI method may be the best for delineating surface water in the Sahelian ecozone, likely due to the nature of the exposed geology and lack of dense green vegetation.

Vulnerability and the Role of Education in Environmentally Induced Migration in Mali and Senegal

Directory of Open Access Journals (Sweden)

Victoria van der Land

2013-12-01

Full Text Available In the West African Sahel, the majority of the population depends on subsistence farming and livestock breeding and is thus particularly vulnerable to climatic changes. One possible response to natural hazards is migration. Recent research suggests that environmentally induced mobility is closely linked to the social vulnerability and adaptive capacity of individuals and groups. However, only little attention has been paid thus far to the role of formal education in this context. Our objective was to fill this gap by examining the role of formal education in environmentally induced migration as one characteristic of social vulnerability to environmental change. Our analysis focuses on two regions in the West African Sahel, Bandiagara in Mali and Linguère in Senegal, that are presumed to be particularly affected by climate change and environmental degradation. Our results reveal that formal education plays an important role in reducing vulnerability to environmental stress because people with a higher level of education are usually less dependent on environmentally sensitive economic activities such as farming. Moreover, an agricultural economic activity can be an obstacle to a high level of formal education. We found no significant effect of people's education on the migration experience as such. However, motives for migration differ considerably depending on the amount of education received, suggesting that migration constitutes a livelihood strategy, particularly for the lower educated.

Millet response to water and soil fertility management in the Sahelian Niger : experiments and modeling

OpenAIRE

Akponikpe, Pierre

2008-01-01

In the 400-600 mm annual rainfall zone of the Sahel, soil fertility is the main determinant of yield in rainfed millet cropping systems in all but the driest years. Numerous on-farm and on-station experiments have addressed the issue of improving soil fertility. Yet the widespread use of the experimental results is restricted by the highly site specific millet response to fertility management practices due to high spatially variable soil properties as well as high intra- and inter-annual rain...

Integrated NDVI images for Niger 1986-1987. [Normalized Difference Vegetation Index

Science.gov (United States)

Harrington, John A., Jr.; Wylie, Bruce K.; Tucker, Compton J.

1988-01-01

Two NOAA AVHRR images are presented which provide a comparison of the geographic distribution of an integration of the normalized difference vegetation index (NDVI) for the Sahel zone in Niger for the growing seasons of 1986 and 1987. The production of the images and the application of the images for resource management are discussed. Daily large area coverage with a spatial resolution of 1.1 km at nadir were transformed to the NDVI and geographically registered to produce the images.

Strange bedfellows

DEFF Research Database (Denmark)

Walther, Olivier; Tisseron, Antonin

2015-01-01

Unravelling the Malian puzzle requires looking at the way in which relations between antagonists explain the political violence in Mali. Building on previous work in which we applied social network analysis to West Africa’s conflicts [i], in this research article we will map the alliances and con...... and conflicts between groups involved in the Malian conflict. This map will allow us to formulate some principles to explain the apparent unpredictability of many of the contemporary conflicts in the Sahel-Sahara....

INTRODUCTION OF EXOTIC BREEDS IN EXTENSIVE LIVESTOCK FARMING SYSTEM OF BURKINA FASO: ASSESSMENT AND PROSPECTS.

OpenAIRE

Albert Soudre; Moustapha Grema; Stephane A. R. Tapsoba; Moumouni Sanou; Amadou Traore; Hamidou Hamadou Tamboura.

2018-01-01

A study on the situation of exotic cattle breeds introduced in Burkina Faso was conducted in the province of Soum (Djibo) located in the north of the country, a Sahel area of West Africa. The aim of the study was to i) assess the adaptation of exotic breeds with high productive potential in a difficult climatic context and ii) evaluate their productivity in comparison with the native breeds. A participatory survey associated with field visits were conducted to assess the survival and adaptati...

Sultens tilskuere

OpenAIRE

Wichmann, Søren Sofus

2012-01-01

This project examines the ethical demands that a cosmopolitan approach to ethics lays down on the media in the Western world in covering distant suffering. By examining a number of newspaper articles from danish media regarding a humanitarian crisis in the African Sahel area using theories about distant suffering, and discussing the findings by applying a number of different normative ethical theories, it delivers a view on what such ethical demands might be. It concludes that a politics of p...

Interdisciplinary Water and Sanitation Project in Burkina Faso

OpenAIRE

船水, 尚行

2017-01-01

Interdisciplinary project on water and sanitation was performed in Burkina Faso from 2010 to 2015. The title of the project was “Development of sustainable water and sanitation systems in the African Sahel region”, and the project was supported by SATREPS (JST and JICA) and collaborated with International Institute of Water and Sanitation (2iE). The main purpose of the project was to develop and demonstrate the new system of water and sanitation based on the concept of “do not mix” and “do no...

Interannual Tropical Rainfall Variability in General Circulation Model Simulations Associated with the Atmospheric Model Intercomparison Project.

Science.gov (United States)

Sperber, K. R.; Palmer, T. N.

1996-11-01

The interannual variability of rainfall over the Indian subcontinent, the African Sahel, and the Nordeste region of Brazil have been evaluated in 32 models for the period 1979-88 as part of the Atmospheric Model Intercomparison Project (AMIP). The interannual variations of Nordeste rainfall are the most readily captured, owing to the intimate link with Pacific and Atlantic sea surface temperatures. The precipitation variations over India and the Sahel are less well simulated. Additionally, an Indian monsoon wind shear index was calculated for each model. Evaluation of the interannual variability of a wind shear index over the summer monsoon region indicates that the models exhibit greater fidelity in capturing the large-scale dynamic fluctuations than the regional-scale rainfall variations. A rainfall/SST teleconnection quality control was used to objectively stratify model performance. Skill scores improved for those models that qualitatively simulated the observed rainfall/El Niño- Southern Oscillation SST correlation pattern. This subset of models also had a rainfall climatology that was in better agreement with observations, indicating a link between systematic model error and the ability to simulate interannual variations.A suite of six European Centre for Medium-Range Weather Forecasts (ECMWF) AMIP runs (differing only in their initial conditions) have also been examined. As observed, all-India rainfall was enhanced in 1988 relative to 1987 in each of these realizations. All-India rainfall variability during other years showed little or no predictability, possibly due to internal chaotic dynamics associated with intraseasonal monsoon fluctuations and/or unpredictable land surface process interactions. The interannual variations of Nordeste rainfall were best represented. The State University of New York at Albany/National Center for Atmospheric Research Genesis model was run in five initial condition realizations. In this model, the Nordeste rainfall

Improving agricultural drought monitoring in West Africa using root zone soil moisture estimates derived from NDVI

Science.gov (United States)

McNally, A.; Funk, C. C.; Yatheendradas, S.; Michaelsen, J.; Cappelarere, B.; Peters-Lidard, C. D.; Verdin, J. P.

2012-12-01

The Famine Early Warning Systems Network (FEWS NET) relies heavily on remotely sensed rainfall and vegetation data to monitor agricultural drought in Sub-Saharan Africa and other places around the world. Analysts use satellite rainfall to calculate rainy season statistics and force crop water accounting models that show how the magnitude and timing of rainfall might lead to above or below average harvest. The Normalized Difference Vegetation Index (NDVI) is also an important indicator of growing season progress and is given more weight over regions where, for example, lack of rain gauges increases error in satellite rainfall estimates. Currently, however, near-real time NDVI is not integrated into a modeling framework that informs growing season predictions. To meet this need for our drought monitoring system a land surface model (LSM) is a critical component. We are currently enhancing the FEWS NET monitoring activities by configuring a custom instance of NASA's Land Information System (LIS) called the FEWS NET Land Data Assimilation System. Using the LIS Noah LSM, in-situ measurements, and remotely sensed data, we focus on the following questions: What is the relationship between NDVI and in-situ soil moisture measurements over the West Africa Sahel? How can we use this relationship to improve modeled water and energy fluxes over the West Africa Sahel? We investigate soil moisture and NDVI cross-correlation in the time and frequency domain to develop a transfer function model to predict soil moisture from NDVI. This work compares sites in southwest Niger, Benin, Burkina Faso, and Mali to test the generality of the transfer function. For several sites with fallow and millet vegetation in the Wankama catchment in southwest Niger we developed a non-parametric frequency response model, using NDVI inputs and soil moisture outputs, that accurately estimates root zone soil moisture (40-70cm). We extend this analysis by developing a low order parametric transfer function

Multi-satellite sensor study on precipitation-induced emission pulses of NOx from soils in semi-arid ecosystems

Directory of Open Access Journals (Sweden)

J. Zörner

2016-07-01

Full Text Available We present a top-down approach to infer and quantify rain-induced emission pulses of NOx ( ≡  NO + NO2, stemming from biotic emissions of NO from soils, from satellite-borne measurements of NO2. This is achieved by synchronizing time series at single grid pixels according to the first day of rain after a dry spell of prescribed duration. The full track of the temporal evolution several weeks before and after a rain pulse is retained with daily resolution. These are needed for a sophisticated background correction, which accounts for seasonal variations in the time series and allows for improved quantification of rain-induced soil emissions. The method is applied globally and provides constraints on pulsed soil emissions of NOx in regions where the NOx budget is seasonally dominated by soil emissions. We find strong peaks of enhanced NO2 vertical column densities (VCDs induced by the first intense precipitation after prolonged droughts in many semi-arid regions of the world, in particular in the Sahel. Detailed investigations show that the rain-induced NO2 pulse detected by the OMI (Ozone Monitoring Instrument, GOME-2 and SCIAMACHY satellite instruments could not be explained by other sources, such as biomass burning or lightning, or by retrieval artefacts (e.g. due to clouds. For the Sahel region, absolute enhancements of the NO2 VCDs on the first day of rain based on OMI measurements 2007–2010 are on average 4 × 1014  molec cm−2 and exceed 1 × 1015  molec cm−2 for individual grid cells. Assuming a NOx lifetime of 4 h, this corresponds to soil NOx emissions in the range of 6 up to 65 ng N m−2 s−1, which is in good agreement with literature values. Apart from the clear first-day peak, NO2 VCDs are moderately enhanced (2 × 1014  molec cm−2 compared to the background over the following 2 weeks, suggesting potential further emissions during that period of about 3.3 ng N m−2�

Evaluation of rainfall simulations over West Africa in dynamically downscaled CMIP5 global circulation models

Science.gov (United States)

Akinsanola, A. A.; Ajayi, V. O.; Adejare, A. T.; Adeyeri, O. E.; Gbode, I. E.; Ogunjobi, K. O.; Nikulin, G.; Abolude, A. T.

2018-04-01

This study presents evaluation of the ability of Rossby Centre Regional Climate Model (RCA4) driven by nine global circulation models (GCMs), to skilfully reproduce the key features of rainfall climatology over West Africa for the period of 1980-2005. The seasonal climatology and annual cycle of the RCA4 simulations were assessed over three homogenous subregions of West Africa (Guinea coast, Savannah, and Sahel) and evaluated using observed precipitation data from the Global Precipitation Climatology Project (GPCP). Furthermore, the model output was evaluated using a wide range of statistical measures. The interseasonal and interannual variability of the RCA4 were further assessed over the subregions and the whole of the West Africa domain. Results indicate that the RCA4 captures the spatial and interseasonal rainfall pattern adequately but exhibits a weak performance over the Guinea coast. Findings from the interannual rainfall variability indicate that the model performance is better over the larger West Africa domain than the subregions. The largest difference across the RCA4 simulated annual rainfall was found in the Sahel. Result from the Mann-Kendall test showed no significant trend for the 1980-2005 period in annual rainfall either in GPCP observation data or in the model simulations over West Africa. In many aspects, the RCA4 simulation driven by the HadGEM2-ES perform best over the region. The use of the multimodel ensemble mean has resulted to the improved representation of rainfall characteristics over the study domain.

Projected effects of vegetation feedbacks on drought characteristics with SPEI over West Africa using the RegCM-CLM-CN-DV

Science.gov (United States)

Jaehyeong, L.; Kim, Y.; Erfanian, A.; Wang, G.; Um, M. J.

2017-12-01

This study utilizes the Standardized Precipitation-Evapotranspiration Index (SPEI) to investigate the projected effect of vegetation feedbacks on drought in West Africa using the Regional Climate Model coupled to the NCAR Community Land Model with both the Carbon and Nitrogen module (CN) and Dynamic Vegetation module (DV) activated (RegCM-CLM-CN-DV). The role of vegetation feedbacks is examined based on simulations with and without dynamic vegetation. The four different future climate scenarios from CCSM, GFDL, MIROC and MPI are used as the boundary conditions of RegCM for two historical and future periods, i.e., for 1981 to 2000 and for 2081 to 2100, respectively. Using SPEI, the duration, frequency, severity and spatial extents are quantified over West Africa and analyzed for two regions of the Sahel and the Gulf of Guinea. In this study, we find that the estimated annual SPEIs clearly indicate that the projected future droughts over the Sahel are enhanced and prolonged when DV is activated. The opposite is shown over the Gulf of Guinea in general. AcknowledgementsThis work was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (2015R1C1A2A01054800), by the Korea Meteorological Administration R&D Program under Grant KMIPA 2015-6180 and by the Yonsei University Future-leading Research Initiative of 2015(2016-22-0061).

Are revised models better models? A skill score assessment of regional interannual variability

Science.gov (United States)

Sperber, Kenneth R.; Participating AMIP Modelling Groups

1999-05-01

Various skill scores are used to assess the performance of revised models relative to their original configurations. The interannual variability of all-India, Sahel and Nordeste rainfall and summer monsoon windshear is examined in integrations performed under the experimental design of the Atmospheric Model Intercomparison Project. For the indices considered, the revised models exhibit greater fidelity at simulating the observed interannual variability. Interannual variability of all-India rainfall is better simulated by models that have a more realistic rainfall climatology in the vicinity of India, indicating the beneficial effect of reducing systematic model error.

Ecosystem properties of semi-arid savanna grassland in West Africa and its relationship to environmental variability

DEFF Research Database (Denmark)

Tagesson, Torbern; Fensholt, Rasmus; Guiro, Idrissa

2015-01-01

he Dahra field site in Senegal, West Africa, was established in 2002 to monitor ecosystem properties of semiarid savanna grassland and their responses to climatic and environmental change. This article describes the environment and the ecosystem properties of the site using a unique set of in situ......), biomass, vegetation water content, and land-atmosphere exchanges of carbon (NEE) and energy. The Dahra field site experiences a typical Sahelian climate and is covered by coexisting trees (~3% canopy cover) and grass species, characterizing large parts of the Sahel. This makes the site suitable...

Testicular sperm reserve of Sokoto red and Sahel bucks from Mubi ...

African Journals Online (AJOL)

Age group variability significantly (p3 years recorded highest sperm reserves. Correlation matrix showed significant (p<0.001) positive correlation (r=0.58, 0.75, 0.69, 0.77, 0.76, 0.67, 0.77, and 0.78,) between live weight, BCS, SC, WLTLG,WLTVL, WLTWT, ...

Biometry of the ovary in Balami, Yankassa sheep and Sahel goat ...

African Journals Online (AJOL)

A Aliyu, I.D. Peter, M Zakariah, V.A. Maina, K.D. Malgwi, A.A. Bitrus. Abstract. No Abstract. Keywords: biometry, goat, sheep, reproduction, ovary, follicles. Full Text: EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT · AJOL African Journals Online. HOW TO USE AJOL.

Dynamics of Poverty and Land Degradation in the Sahel (West Africa)

International Development Research Centre (IDRC) Digital Library (Canada)

This project will attempt to breach this knowledge gap. ... will endeavor to understand the dynamics of poverty and land degradation, identify promising ... Studies. Rôle de la migration dans les stratégies de survie des populations rurales : cas ...

Les TIC au secours des éleveurs du Sahel | IDRC - International ...

International Development Research Centre (IDRC) Digital Library (Canada)

7 févr. 2011 ... À quelques pas de la grand-place de Kouthiaba, bourgade située à quelque 600 km de Dakar, des dizaines d'éleveurs essaient d'attirer l'attention des passants sur leur bétail en ce dimanche de « louma », grand marché hebdomadaire des zones rurales du Sénégal.

Indigenizing Civic Education in Africa: Experience in Madagascar and the Sahel

Science.gov (United States)

Antal, Carrie; Easton, Peter

2009-01-01

In Africa, as in many countries of the South, democratization is sometimes perceived as a process modeled upon outside--and specifically Northern--experience. Formal civic education programs in those countries arguably reflect the same bias and have not always been notably successful. Yet there are rich patterns of civic involvement and democratic…

Les théories des mouvements sociaux et la dialectique des niveaux : un cadre d’analyse pour l’étude des évolutions d’Al-Qaïda au Maghreb islamique

Directory of Open Access Journals (Sweden)

Adib Bencherif

2013-10-01

Full Text Available Les théories des mouvements sociaux sont de plus en plus utilisées pour étudier les groupes terroristes. Elles comportent différents niveaux d’analyse: les niveaux macro-analytique, méso-analytique et micro-analytique. Le présent article tente d’adapter ce corpus théorique à l’étude du groupe jihadiste Al-Qaïda au Maghreb islamique (AQMI. En effet, au cours des dernières années, AQMI ne s’est pas développé au Maghreb alors que ses activités ont augmenté exponentiellement dans la région sahélienne, au point d’y développer un sanctuaire pour le groupe au nord du Mali. Le développement d’AQMI au Sahel est-il alors le résultat de choix stratégiques ou celui de dynamiques internes ? Pour expliquer le développement d’AQMI dans la région sahélo-saharienne, l’auteur propose une grille de lecture basée sur les niveaux macro et méso-analytiques et sur leur mise en dialectique. Le niveau macro-analytique met en lumière la structure des opportunités politiques induisant les choix stratégiques d’AQMI et le niveau méso-analytique les dynamiques internes du groupe. La littérature existante sur AQMI étant principalement constituée de monographies et de notes de recherches, l’ambition de cet article est alors de concilier théorie et recherche empirique. Ainsi le cadre d’analyse proposé est inspiré des approches de l’action collective et de la mobilisation des ressources et cherche à améliorer la compréhension des évolutions du groupe. L’étude menée est une analyse qualitative centrée sur les États algérien et malien.The theories of social movements are increasingly used to study terrorist groups and they are characterized by three different levels of analysis: macro, meso, and micro. This article attempts to adapt this theoretical framework to the study of the jihadist group al-Qaeda in the Islamic Maghreb (AQIM. Indeed, in recent years, AQIM failed to develop in North Africa while its

Role of dust direct radiative effect on the tropical rainbelt over Middle East and North Africa: A high resolution AGCM study

KAUST Repository

Bangalath, Hamza Kunhu

2015-04-25

To investigate the influence of direct radiative effect of dust on the tropical summer rainbelt across the Middle East and North Africa (MENA), the present study utilizes the high resolution capability of an Atmospheric General Circulation Model (AGCM),the High Resolution Atmospheric Model (HiRAM). Ensembles of Atmospheric Model Inter-comparison Project (AMIP)-style simulations have been conducted with and without dust radiative impacts, to differentiate the influence of dust on the tropical rainbelt. The analysis focuses on summer season. The results highlight the role of dust induced responses in global and regional scale circulations in determining the strength and the latitudinal extent of the tropical rainbelt. A significant response in the strength and position of the local Hadley circulation is predicted in response to meridionally asymmetric distribution of dust and the corresponding radiative effects. Significant responses are also found in regional circulation features such as African Easterly Jet (AEJ) and West African Monsoon (WAM) circulation. Consistent with these dynamic responses at various scales, the tropical rainbelt across MENA strengthens and shifts northward. Importantly, the summer precipitation over the semi-arid strip south of Sahara, including Sahel, increases up to 20%. As this region is characterized by the “Sahel drought" , the predicted precipitation sensitivity to the dust loading over this region has a wide-range of socioeconomic implications. Overall, the study demonstrates the extreme importance of incorporating dust radiative effects and the corresponding circulation responses at various scales, in the simulations and future projections of this region\\'s climate.

Application of Spectral Analysis Techniques in the Intercomparison of Aerosol Data: Part III. Using Combined PCA to Compare Spatiotemporal Variability of MODIS, MISR and OMI Aerosol Optical Depth

Science.gov (United States)

Li, Jing; Carlson, Barbara E.; Lacis, Andrew A.

2014-01-01

Satellite measurements of global aerosol properties are very useful in constraining aerosol parameterization in climate models. The reliability of different data sets in representing global and regional aerosol variability becomes an essential question. In this study, we present the results of a comparison using combined principal component analysis (CPCA), applied to monthly mean, mapped (Level 3) aerosol optical depth (AOD) product from Moderate Resolution Imaging Spectroradiometer (MODIS), Multiangle Imaging Spectroradiometer (MISR), and Ozone Monitoring Instrument (OMI). This technique effectively finds the common space-time variability in the multiple data sets by decomposing the combined AOD field. The results suggest that all of the sensors capture the globally important aerosol regimes, including dust, biomass burning, pollution, and mixed aerosol types. Nonetheless, differences are also noted. Specifically, compared with MISR and OMI, MODIS variability is significantly higher over South America, India, and the Sahel. MODIS deep blue AOD has a lower seasonal variability in North Africa, accompanied by a decreasing trend that is not found in either MISR or OMI AOD data. The narrow swath of MISR results in an underestimation of dust variability over the Taklamakan Desert. The MISR AOD data also exhibit overall lower variability in South America and the Sahel. OMI does not capture the Russian wild fire in 2010 nor the phase shift in biomass burning over East South America compared to Central South America, likely due to cloud contamination and the OMI row anomaly. OMI also indicates a much stronger (boreal) winter peak in South Africa compared with MODIS and MISR.

Land-Surface Characteristics and Climate in West Africa: Models’ Biases and Impacts of Historical Anthropogenically-Induced Deforestation

Directory of Open Access Journals (Sweden)

Souleymane Sy

2017-10-01

Full Text Available Land Use Land-Cover Change (LULCC, such as deforestation, affects the climate system and land-atmosphere interactions. Using simulations carried out within the LUCID (Land Use and Climate, IDentification of robust Impacts project framework, we first quantify the role of historical land-cover change induced by human activities on surface climate in West Africa. Focusing on two contrasted African regions, we find that climate responses of land-use changes are small but they are still statistically significant. In Western Sahel, a statistically significant near-surface atmospheric cooling and a decrease in water recycling are simulated in summer in response to LULCC. Over the Guinean zone, models simulate a significant decrease in precipitation and water recycling in autumn in response to LULCC. This signal is comparable in magnitude with the effect induced by the increase in greenhouse gases. Simulated climate changes due to historical LULCC could however be underestimated because: (i the prescribed LULCC can be underestimated in those regions; (ii the climate models underestimate the coupling strength between West African surface climate and leaf area index (LAI and (iii the lack of interactive LAI in some models. Finally, our study reveals indirect atmospheric processes triggered by LULCC. Over the Western Sahel, models reveal that a significant decrease in solar reflection tend to cool down the surface and thus counteract the atmospheric feedback. Conversely, over the Guinea zone, models reveal that the indirect atmospheric processes and turbulent heat fluxes dominate the climatic responses over the direct effects of LULCC.

The use of unsaturated zone solutes and deuterium profiles in the study of groundwater recharge in the semi-arid zone of Nigeria

International Nuclear Information System (INIS)

Goni, I.B.; Edmunds, W.M.

2001-01-01

Two unsaturated zone profiles (MF and MG) in NE Nigeria have been sampled for inert tracers (Cl, Br, NO 3 and δ 2 H to investigate recharge rates and processes. The upper MF and MG profiles have sandy lithology, lower moisture content ( 2 H around -30 per mille. All these indicate that present day recharge is taking place. The lower section of the MF profile shows a distinct contrast with high moisture content (up to 27%), very high chloride (average 2892 mg/L) and relatively enriched deuterium (-12 per mille), indicating the effect of evaporative enrichment. This lower section corresponds to low permeability lacustrine deposits probably representing the former bed of Lake Chad where little or no infiltration has been occurring since the mid-Holocene when the lake extended over this area. The sand-covered areas of the Sahel of the NE Nigeria provide an important phreatic aquifer. An estimation of the amount of recharge using the unsaturated zone chloride mass balance gives significant rates of 14 mm/a and 22 mm/a for the upper MF and MG profiles respectively. These rates mainly span the period of the recent Sahel drought and even higher recharge rates may occur during wetter periods. These rates fall within the 14 mm/a to 53 mm/a range estimated for the Manga Grasslands area in the NE Nigeria obtained in an earlier study. From the water resource point of view, the region has potential for perennially-recharged groundwater resources that can sustain the present abstraction level which is mainly via dug wells. (author)

Impacts of Climate Change on Malaria Transmission in Africa

Science.gov (United States)

Eltahir, E. A. B.; Endo, N.; Yamana, T. K.

2017-12-01

Malaria is a major vector-borne parasitic disease transmitted to humans by Anopheles spp mosquitoes. Africa is the hotspot for malaria transmission where more than 90% of malaria deaths occur every year. Malaria transmission is an intricate function of climatic factors, which non-linearly affect the development of vectors and parasites. We project that the risk of malaria will increase towards the end of the 21st century in east Africa, but decrease in west Africa. We combine a novel malaria transmission simulator, HYDREMATS, that has been developed based on comprehensive multi-year field surveys both in East Africa and West Africa, and the most reliable climate projections through regional dynamical downscaling and rigorous selection of GCMs from among CMIP5 models. We define a bell-shaped relation between malaria intensity and temperature, centered around a temperature of 30°C. Future risks of malaria are projected for two highly populated regions in Africa: the highlands in East Africa and the fringes of the desert in West Africa. In the highlands of East Africa, temperature is substantially colder than this optimal temperature; warmer future climate exacerbate malaria conditions. In the Sahel fringes in West Africa, temperature is around this optimal temperature; warming is not likely to exacerbate and might even reduce malaria burden. Unlike the highlands of East Africa, which receive significant amounts of annual rainfall, dry conditions also limit malaria transmission in the Sahel fringes in West Africa. This disproportionate risk of malaria due to climate change should guide strategies for climate adaptation over Africa.

Satellite rainfall monitoring over Africa for food security, using multi-channel MSG data

Science.gov (United States)

Chadwick, R.; Grimes, D.; Saunders, R.; Blackmore, T.; Francis, P.

2009-04-01

Near real-time rainfall estimates are crucial in sub-Saharan Africa for a variety of humanitarian and agricultural purposes. However, for economic and infrastructural reasons, regularly reporting rain-gauges are sparse and precipitation radar networks extremely rare. Satellite rainfall estimates, particularly from geostationary satellites such as Meteosat Second Generation (MSG), present one method of filling this information gap, as they produce data at high temporal and spatial resolution. An algorithm has been developed to produce rainfall estimates for Africa from multi-channel MSG data. The algorithm is calibrated using precipitation radar data collected in Niamey, Niger as part of the African Monsoon Multidisciplinary Analyses (AMMA) project in 2006, and is based on an algorithm used operationally over Europe by the UK Met Office. Contingency tables are used to establish a statistical relationship between multi-channel MSG data and probability of rainfall at several different rain-rate magnitudes as sensed by the radar. Rain-rate estimates can then be produced at a variety of spatial and temporal scales, with MSG scan length (15 minutes) and pixel size (3-4km) as the lower limit. Results will be presented of a validation of this algorithm over the Sahel region of Africa. Rainfall estimates from this algorithm, processed for 2004, will be validated against gridded rain-gauge data at a 0.5 degree and 10 day timescale suitable for drought monitoring purposes. A comparison will also be made against rainfall estimates from the TAMSAT algorithm, which uses single channel IR data from MSG, and has been shown to perform well in the Sahel region.

Drought Duration Biases in Current Global Climate Models

Science.gov (United States)

Moon, Heewon; Gudmundsson, Lukas; Seneviratne, Sonia

2016-04-01

Several droughts in the recent past are characterized by their increased duration and intensity. In particular, substantially prolonged droughts have brought major societal and economic losses in certain regions, yet climate change projections of such droughts in terms of duration is subject to large uncertainties. This study analyzes the biases of drought duration in state-of-the-art global climate model (GCM) simulations from the 5th phase of Coupled Model Intercomparison Project (CMIP5). Drought durations are defined as negative precipitation anomalies and evaluated with three observation-based datasets in the period of 1901-2010. Large spread in biases of GCMs is commonly found in all regions, with particular strong biases in North East Brazil, Africa, Northern Australia, Central America, Central and Northern Europe, Sahel and Asia. Also in most regions, the interquartile range of bias lies below 0, meaning that the GCMs tend to underestimate drought durations. Meanwhile in some regions such as Western South America, the Amazon, Sahel, West and South Africa, and Asia, considerable inconsistency among the three observation-based datasets were found. These results indicate substantial uncertainties and errors in current GCMs for simulating drought durations as well as a large spread in observation-based datasets, both of which are found to be particularly strong in those regions that are often considered to be hot spots of projected future drying. The underlying sources of these uncertainties need to be identified in further study and will be applied to constrain GCM-based drought projections under climate change.

Un projet de développement forestier au Niger : problèmes d'adaptation des objectifs initiaux aux contraintes de réalisation

OpenAIRE

Clément, Jean

1986-01-01

Comme tous les pays du Sahel, le Niger est affronté à de graves problèmes de désertification et de déboisement dont les causes sont diverses : sécheresses successives,intensification du paturage provoquée par l'accroissement des troupeaux, consommation accrue de bois de feu... Sur la base d'une population totale de 6 OOO OOO habitants, la consommation de bois de feu peut être estimée à environ 4 OOO OOO m3 qu'il faut comparer aux 3 OOO OOO m3 d'accroissement en volume annuel des peuplements n...

Les savanes d'Afrique centrale entre enclavement et intégration aux marchés

OpenAIRE

Magrin , Géraud; Jamin , Jean-Yves; Faure , Guy; Duteurtre , Guillaume

2003-01-01

International audience; Les savanes d'Afrique centrale qui s'étendent à travers le nord du Cameroun, le sud du Tchad et la République centrafricaine présentent une certaine homogénéité. Milieux de transition entre Sahel et Afrique forestière, ce sont des espaces enclavés, encore peu urbanisés, au peuplement contrasté, où la culture cotonnière marque fortement les systèmes agraires. Des changements rapides sont néanmoins en cours. La croissance démographique encourage l'intensification des cul...

Encapsulating knowledge from local documents

DEFF Research Database (Denmark)

Reenberg, Anette; Moussa, Ibarhim Bouzou; Some, Bernadette

in a complex web of driving forces, which it is crucial to keep in mind in order to appreciate the role of different factors of change. The article seeks to identify the wide range of influential events that have modified land use decisions in Burkina Faso and Niger for the period from before Independence...... environmental and land use related processes in the Sahel are embedded in many constantly changing influential conditions. On this background, the article cautions against translating insights gained from past experience into generic traits of human-environment dynamics, which can be immediately used to predict...

Biomass burning in West African savannas

International Nuclear Information System (INIS)

Menaut, J.C.; Abbadie, L.; Lavenu, F.; Loudjani, P.; Podaire, A.

1991-01-01

This chapter approaches the influence of West African savanna ecosystems on the regional climate by giving, as precisely as possible, the amount of volatilized elements (e.g., carbon, nitrogen, and sulfur) annually released by bush fires into the atmosphere. In spite of the relative functional similarity of West African savannas, fire behavior and effects vary with the different bioclimatic and phytogeographic zones of the region: Guinea or humid zone; Sudan or mesic zone; and, Sahel or arid zone. In order to reach an acceptable accuracy, results are given for each of the zones described and summarized for West Africa

Bioengineered yogurt: ‘open source’ medicine

Directory of Open Access Journals (Sweden)

Shireesh Apte

2012-12-01

Full Text Available The ease with which commensal bacteria in yogurt can be bioengineered to express an array of biotherapeutics, coupled with altruistic distribution systems that can easily include those, most likely to benefit (think expression of antiplasmodial peptides in the Bifidobacterium genus so that a herder in the Sahel can inoculate this yogurt culture into goat milk thus making ‘antimalarial yogurt’ for free for his entire village. This could potentially go on as long as the plasmid is stable and could lead to a revolution in the way medicines could become ‘open sourced’.

Les TIC au secours des éleveurs du Sahel | CRDI - Centre de ...

International Development Research Centre (IDRC) Digital Library (Canada)

7 févr. 2011 ... ... grand marché hebdomadaire des zones rurales du Sénégal. ... Comment, alors, aider les communautés rurales à pratiquer un mode d'élevage plus ... du Centre de recherches pour le développement international (CRDI). ... Enfin, certains éleveurs ont aussi été initiés à l'informatique pour accéder à ...

Millet growth in windbreak-shielded fields in the Sahel : experiment and model

NARCIS (Netherlands)

Mayus, M.

1998-01-01

In the Sahelian zone, future food supply is insecure due to increasing land degradation. Wind erosion contributes significantly to impoverishment of the sandy soils, which are often loose and sparsely covered by vegetation for most of the year. At the onset of the growing season (May -

Soil variability and effectiveness of soil and water conservation in the Sahel.

NARCIS (Netherlands)

Hien, F.G.; Rietkerk, M.; Stroosnijder, L.

1997-01-01

Sahelian sylvopastoral lands often degrade into bare and crusted areas where regeneration of soil and vegetation is impossible in the short term unless soil and water conservation measures are implemented. Five combinations of tillage with and without mulch on three crust type/soil type combinations

La représentation de l'espace chez des Touaregs du Sahel

Directory of Open Access Journals (Sweden)

Edmond BERNUS

1988-09-01

Full Text Available Une cartographie éphémère, par des cartographes d'occasion qui dessinent habituellement sur le sable. Des Touaregs reportent sur le papier une représentation graphique originale de leurs itinéraires, dans des régions où les repères sont rares et où le réseau hydrographique sert de trame aux aires de nomadisation.

Improved Ground Hydrology Calculations for Global Climate Models (GCMs): Soil Water Movement and Evapotranspiration.

Science.gov (United States)

Abramopoulos, F.; Rosenzweig, C.; Choudhury, B.

1988-09-01

A physically based ground hydrology model is developed to improve the land-surface sensible and latent heat calculations in global climate models (GCMs). The processes of transpiration, evaporation from intercepted precipitation and dew, evaporation from bare soil, infiltration, soil water flow, and runoff are explicitly included in the model. The amount of detail in the hydrologic calculations is restricted to a level appropriate for use in a GCM, but each of the aforementioned processes is modeled on the basis of the underlying physical principles. Data from the Goddard Institute for Space Studies (GISS) GCM are used as inputs for off-line tests of the ground hydrology model in four 8° × 10° regions (Brazil, Sahel, Sahara, and India). Soil and vegetation input parameters are calculated as area-weighted means over the 8° × 10° gridhox. This compositing procedure is tested by comparing resulting hydrological quantities to ground hydrology model calculations performed on the 1° × 1° cells which comprise the 8° × 10° gridbox. Results show that the compositing procedure works well except in the Sahel where lower soil water levels and a heterogeneous land surface produce more variability in hydrological quantities, indicating that a resolution better than 8° × 10° is needed for that region. Modeled annual and diurnal hydrological cycles compare well with observations for Brazil, where real world data are available. The sensitivity of the ground hydrology model to several of its input parameters was tested; it was found to be most sensitive to the fraction of land covered by vegetation and least sensitive to the soil hydraulic conductivity and matric potential.

Climate change and human health: Spatial modeling of water availability, malnutrition, and livelihoods in Mali, Africa

Science.gov (United States)

Jankowska, Marta M.; Lopez-Carr, David; Funk, Chris; Husak, Gregory J.; Chafe, Z.A.

2012-01-01

This study develops a novel approach for projecting climate trends in the Sahel in relation to shifting livelihood zones and health outcomes. Focusing on Mali, we explore baseline relationships between temperature, precipitation, livelihood, and malnutrition in 407 Demographic and Health Survey (DHS) clusters with a total of 14,238 children, resulting in a thorough spatial analysis of coupled climate-health dynamics. Results suggest links between livelihoods and each measure of malnutrition, as well as a link between climate and stunting. A ‘front-line’ of vulnerability, related to the transition between agricultural and pastoral livelihoods, is identified as an area where mitigation efforts might be usefully targeted. Additionally, climate is projected to 2025 for the Sahel, and demographic trends are introduced to explore how the intersection of climate and demographics may shift the vulnerability ‘front-line’, potentially exposing an additional 6 million people in Mali, up to a million of them children, to heightened risk of malnutrition from climate and livelihood changes. Results indicate that, holding constant morbidity levels, approximately one quarter of a million children will suffer stunting, nearly two hundred thousand will be malnourished, and over one hundred thousand will become anemic in this expanding arid zone by 2025. Climate and health research conducted at finer spatial scales and within shorter projected time lines can identify vulnerability hot spots that are of the highest priority for adaptation interventions; such an analysis can also identify areas with similar characteristics that may be at heightened risk. Such meso-scale coupled human-environment research may facilitate appropriate policy interventions strategically located beyond today’s vulnerability front-line.

Population crisis and desertification in the Sudano-Sahelian region.

Science.gov (United States)

Milas, S

1984-01-01

People living in the area just south of the Sahara Desert in Africa face their 3rd major drought since 1900. This drought brings about famine. Drought and famine are only manifestations of more profound problems: soil erosion and degradation. They diminish land productivity which aggravates the population's poverty. Yet soil erosion and degradation occur due to an expanding population. Continued pressures on the land and soil degradation results in desertification. The UN Environment Programme's Assessment of the Status and Trend of Desertification shows that between 1978-84 desertification spread. Expanding deserts now endanger 35% of the world's land and 20% of the population. In the thorn bush savanna zone, most people are subsistence farmers or herdsmen and rely on the soils, forests, and rangelands. Even though the mean population density in the Sahel is low, it is overpopulated since people concentrate in areas where water is available. These areas tend to be cities where near or total deforestation has already occurred. Between 1959-84, the population in the Sahel doubled so farmers have extended cultivation into marginal areas which are vulnerable to desertification. The livestock populations have also grown tremendously resulting in overgrazing and deforestation. People must cook their food which involves cutting down trees for fuelwood. Mismanagement of the land is the key cause for desertification, but the growing poor populations have no choice but to eke out an existence on increasingly marginal lands. Long fallow periods would allow the land to regain its fertility, but with the ever-increasing population this is almost impossible. Humans caused desertification. We can improve land use and farming methods to stop it.

Creation and evaluation of best cotton mutant lines

International Nuclear Information System (INIS)

Rastegari, S. J.; Hosseini, Z.

2001-01-01

During (1997-1999) a study was carried out to recognize the best mutant lines, which were already obtained from a mutation breeding project. A Triple Rectangular Latis Design (8 7) in form of randomized complete blocks (RCB) with fifty- six treatments and three replications, were used in Estahban, Kordkouy and Varamin, under different ecological conditions, rainfall (Kordkouy) desert (Varamin) hot and dry (Estahban). During growing season some important morphological characteristics were recorded. Some lines had specific characters, for example: line 3191 (Chirpan 150 gray) had a low leaf number per plant, line 3169 (Bakhtegan 200 gray) plants were clustered. The results of the data in Varamin station showed that Bakhtegan irradiated with 150 gray line 3485 and Tashkand with 300 gray line 3451 compared to check (Varamin with 4373 kg/ha) had highest yield with 4942 kg/ha, and 4871 kg/ha respectively. In view of boll weight line 3405 of Sahel irradiated with 200 gray had highest boll weight (6.5 g/boll). In Kordkouy station the best mutant line was Chirpan irradiated with 250 gray, line 3208, with 20% yield increase compared to Sahel and 30% yield increase compared to original Chirpan. In respect to irradiation effect on lint percentage and fiber quality, the results showed; there was a positive effect on lint percentage of all varieties, especially in Tashkant, Bakhtegan and Chirpan which are inherently weak in lint percentage. As a whole gamma radiation did not have any negative effect on fiber quality. Even in Estahban 1.6 to 2.4 mm fiber increase were observed in some Chirpan irradiated material (C150-3516) and (C200-3523)

Stress transfer among en echelon and opposing thrusts and tear faults: Triggering caused by the 2003 Mw = 6.9 Zemmouri, Algeria, earthquake

Science.gov (United States)

Lin, J.; Stein, R.S.; Meghraoui, M.; Toda, S.; Ayadi, A.; Dorbath, C.; Belabbes, S.

2011-01-01

The essential features of stress interaction among earthquakes on en echelon thrusts and tear faults were investigated, first through idealized examples and then by study of thrust faulting in Algeria. We calculated coseismic stress changes caused by the 2003 Mw = 6.9 Zemmouri earthquake, finding that a large majority of the Zemmouri afterslip sites were brought several bars closer to Coulomb failure by the coseismic stresses, while the majority of aftershock nodal planes were brought closer to failure by an average of ~2 bars. Further, we calculated that the shallow portions of the adjacent Thenia tear fault, which sustained ~0.25 m slip, were brought >2 bars closer to failure. We calculated that the Coulomb stress increased by 1.5 bars on the deeper portions of the adjacent Boumerdes thrust, which lies just 10–20 km from the city of Algiers; both the Boumerdes and Thenia faults were illuminated by aftershocks. Over the next 6 years, the entire south dipping thrust system extending 80 km to the southwest experienced an increased rate of seismicity. The stress also increased by 0.4 bar on the east Sahel thrust fault west of the Zemmouri rupture. Algiers suffered large damaging earthquakes in A.D. 1365 and 1716 and is today home to 3 million people. If these shocks occurred on the east Sahel fault and if it has a ~2 mm/yr tectonic loading rate, then enough loading has accumulated to produce a Mw = 6.6–6.9 shock today. Thus, these potentially lethal faults need better understanding of their slip rate and earthquake history.

Phytochemical study of prickly pear from southern Morocco

Directory of Open Access Journals (Sweden)

Z. Bouzoubaâ

2016-06-01

Full Text Available This work concerns the phytochemical study of the prickly pear pulp’s fruits of two opuntia cultivars; Achefri and Amouslem widely present in two regions of southern Morocco; Arbaa Sahel and Asgherkis that are different in their altitude and annual rainfall. The results of the phytochemical study show that the levels of antioxidants have a non-significant difference between the fruits of the two sites (comparing Amouslem and Achefri in the same site, on the one hand, for the differences due to the variety or cultivar, on the other hand between Amouslem and Achefri from the two sites to show the site effect.

Asha Ismail Hussein, a survivor

Directory of Open Access Journals (Sweden)

Fernando Alvarez Uría

2017-12-01

Full Text Available Fortunately, clitoral ablation is now a receding practice, but it is still practiced in around 30 countries in the Sahel strip, from Somalia to Senegal. This kind of violence affects 3 million girls every year in Africa and the Middle East, having affected 125 million women. Western European ethnocentrism too often makes invisible the women suffering this violence, which is both physical and symbolic. Once again, critical sociology tries to respond to the social demand of making visible what is invisible—on this occasion resourcing to life stories, such as the one of Asha Ismail Hussein—and hence contribute to banish the intolerable situations from society.

Petroleum and geopolitics

International Nuclear Information System (INIS)

Chaigneau, P.

2004-01-01

Todays, petroleum companies consider that despite the constant increase of petroleum consumption, petroleum will remain the main energy source for at least 40 years. However, after the Iraq conflict, new regional situations are changing. China, for instance, with its growing up demand, will change the physiognomy of the oil market. In parallel, from Indonesia to Africa, petroleum and religion interfere and explain the new conflict areas. As for the US strategy, which is not limited to the energy paradigm, it largely integrates energy in the main lines of its diplomacy, from the 'Wide Middle East' to the 'Sahel initiative', and in its position with respect to Venezuela

Study of Syrian art objects using non-destructive nuclear analytical techniques

International Nuclear Information System (INIS)

Bakraji, E. H.; Rukiah, M.

2009-05-01

Radioisotope X-ray fluorescence (XRF) analysis has been utilized to determine the elemental composition of 38 archaeological pottery samples by the determination of 14 chemical elements. 35 of them come from Tell Jamous archaeological site in Sahel akkar region, Syria and the remained three samples come from an archaeological site in China. The XRF results have been processed using one multivariate statistical method, cluster analysis, in order to determine similarities and correlation between the selected samples based on their elemental composition. The various mineralogical phases of the pottery were identified using X-ray diffraction (XRD) method. Methodology successfully separates the samples where differences among the samples were established. (author)

Petroleum and geopolitics; Petrole et geopolitique

Energy Technology Data Exchange (ETDEWEB)

Chaigneau, P. [Centre d' etudes diplomatiques et strategiques de Paris, 75 (France)

2004-04-01

Todays, petroleum companies consider that despite the constant increase of petroleum consumption, petroleum will remain the main energy source for at least 40 years. However, after the Iraq conflict, new regional situations are changing. China, for instance, with its growing up demand, will change the physiognomy of the oil market. In parallel, from Indonesia to Africa, petroleum and religion interfere and explain the new conflict areas. As for the US strategy, which is not limited to the energy paradigm, it largely integrates energy in the main lines of its diplomacy, from the 'Wide Middle East' to the 'Sahel initiative', and in its position with respect to Venezuela.

Proper Role of Special Operations Forces in the Pan Sahel Region of Africa

National Research Council Canada - National Science Library

Baker, Anthony P

2006-01-01

.... As the designated lead on synchronizing the GWOT efforts for DOD, US SOF remain focused on the Middle East, while continuing to operate in other regions where terrorists may seek sanctuary. The main U.S...

Ecology and management of charcoal rot (Macrophomina phaseolina) on cowpea in the Sahel

NARCIS (Netherlands)

Ndiaye, M.

2007-01-01

Keywords: Senegal/Niger/rotation/millet/isolate characterization/fonio/compost amendment / bioagent/ Clonostachysrosea /solarizationCowpea ( Vignaunguiculata Walp.) is the most important pulse crop in

Performance of PICS bags under extreme conditions in the sahel zone of Niger.

Science.gov (United States)

Baoua, Ibrahim B; Bakoye, Ousmane; Amadou, Laouali; Murdock, Larry L; Baributsa, Dieudonne

2018-03-01

Experiments in Niger assessed whether extreme environmental conditions including sunlight exposure affect the performance of triple-layer PICS bags in protecting cowpea grain against bruchids. Sets of PICS bags and woven polypropylene bags as controls containing 50 kg of naturally infested cowpea grain were held in the laboratory or outside with sun exposure for four and one-half months. PICS bags held either inside or outside exhibited no significant increase in insect damage and no loss in weight after 4.5 months of storage compared to the initial values. By contrast, woven bags stored inside or outside side by side with PICS bags showed several-fold increases in insects present in or on the grain and significant losses in grain weight. Grain stored inside in PICS bags showed no reduction in germination versus the initial value but there was a small but significant drop in germination of grain in PICS bags held outside (7.6%). Germination rates dropped substantially more in grain stored in woven bags inside (16.1%) and still more in woven bags stored outside (60%). PICS bags held inside and outside retained their ability to maintain internal reduced levels of oxygen and elevated levels of carbon dioxide. Exposure to extreme environmental conditions degraded the external polypropylene outer layer of the PICS triple-layer bag. Even so, the internal layers of polyethylene were more slowly degraded. The effects of exposure to sunlight, temperature and humidity variation within the sealed bags are described.

Integrated and sustainable management of the shared aquifer systems in the Sahel region

International Nuclear Information System (INIS)

Edwerd, Mickel

2012-01-01

It highlights the project Justification, the long term objective, the specific objectives and the project implementation strategy. The countries which participate to this project are the following: Algeria, Benin, Burkina Faso, Cameroon, central African Republic, Chad, Gambia, Guinea-Bissau, Mali, Mauritania, Niger, Nigeria and Senegal. Regarding Aquifer System we have: Chad Basin, Liptako-Gourma Aquifer, Iullemeden Aquifer, Senegalo-Mauritanian Aquifer and Taoudeni/Tanezrouft Basin.

Seismicity, seismic input and site effects in the Sahel-Algiers region (north Algeria)

International Nuclear Information System (INIS)

Harbi, A.; Maouche, S.; Oussadou, F.; Vaccari, F.; Aoudia, A.; Panza, G.F.; Benouar, D.

2005-07-01

Algiers city is located in a seismogenic zone. To reduce the impact of seismic risk in this capital city, a realistic modelling of the seismic ground motion using the hybrid method that combines the finite-differences method and the modal summation, is conducted. For this purpose, a complete database in terms of geological, geophysical and earthquake data is constructed. A critical re-appraisal of the seismicity of the zone (2.25 deg. E-3.50 deg. E, 36.50 deg. N-37.00 deg. N) is performed and an earthquake list, for the period 1359-2002, is compiled. The analysis of existing and newly retrieved macroseismic information allowed the definition of earthquake parameters of macroseismic events for which a degree of reliability is assigned. Geological cross-sections have been built up to model the seismic ground motion in the city, caused by the 1989 Mont-Chenoua and the 1924 Douera earthquakes; a set of synthetic seismograms and response spectral ratio is produced for Algiers. The numerical results show that the soft sediments in Algiers centre are responsible of the noticed amplification of the seismic ground motion. (author)

Overlooked mountain rock pools in deserts are critical local hotspots of biodiversity.

Science.gov (United States)

Vale, Cândida Gomes; Pimm, Stuart L; Brito, José Carlos

2015-01-01

The world is undergoing exceptional biodiversity loss. Most conservation efforts target biodiversity hotspots at large scales. Such approach overlooks small-sized local hotspots, which may be rich in endemic and highly threatened species. We explore the importance of mountain rock pools (gueltas) as local biodiversity hotspots in the Sahara-Sahel. Specifically, we considered how many vertebrates (total and endemics) use gueltas, what factors predict species richness, and which gueltas are of most priority for conservation. We expected to provide management recommendations, improve local biodiversity conservation, and simultaneously contribute with a framework for future enhancement of local communities' economy. The identification of local hotspots of biodiversity is important for revaluating global conservation priorities. We quantified the number of vertebrate species from each taxonomic group and endemics present in 69 gueltas in Mauritania, then compared these with species present in a surrounding area and recorded in the country. We evaluated the predictors of species number's present in each guelta through a multiple regression model. We ranked gueltas by their priority for conservation taking into account the percentage of endemics and threats to each guelta. Within a mere aggregate extent of 43 ha, gueltas hold about 32% and 78% of the total taxa analysed and endemics of Mauritania, respectively. The number of species present in each guelta increased with the primary productivity and area of gueltas and occurrence of permanent water. Droughts and human activities threaten gueltas, while 64% of them are currently unprotected. Gueltas are crucial for local biodiversity conservation and human activities. They require urgent management plans in Mauritania's mountains. They could provide refugia under climate change being important for long-term conservation of Sahara-Sahel biodiversity. Given their disproportional importance in relation to their size, they are

Identification of single nucleotide polymorphisms in the agouti signaling protein (ASIP) gene in some goat breeds in tropical and temperate climates.

Science.gov (United States)

Adefenwa, Mufliat A; Peters, Sunday O; Agaviezor, Brilliant O; Wheto, Matthew; Adekoya, Khalid O; Okpeku, Moses; Oboh, Bola; Williams, Gabriel O; Adebambo, Olufunmilayo A; Singh, Mahipal; Thomas, Bolaji; De Donato, Marcos; Imumorin, Ikhide G

2013-07-01

The agouti-signaling protein (ASIP) plays a major role in mammalian pigmentation as an antagonist to melanocortin-1 receptor gene to stimulate pheomelanin synthesis, a major pigment conferring mammalian coat color. We sequenced a 352 bp fragment of ASIP gene spanning part of exon 2 and part of intron 2 in 215 animals representing six goat breeds from Nigeria and the United States: West African Dwarf, predominantly black; Red Sokoto, mostly red; and Sahel, mostly white from Nigeria; black and white Alpine, brown and white Spanish and white Saanen from the US. Twenty haplotypes from nine mutations representing three intronic, one silent and five missense (p.S19R, p.N35K, p.L36V, p.M42L and p.L45W) mutations were identified in Nigerian goats. Approximately 89 % of Nigerian goats carry haplotype 1 (TGCCATCCG) which seems to be the wild type configuration of mutations in this region of the gene. Although we found no association between these polymorphisms in the ASIP gene and coat color in Nigerian goats, in-silico functional analysis predicts putative deleterious functional impact of the p.L45W mutation on the basic amino-terminal domain of ASIP. In the American goats, two intronic mutations, g.293G>A and g.327C>A, were identified in the Alpine breed, although the g.293G>A mutation is common to American and Nigerian goat populations. All Sannen and Sahel goats in this study belong to haplotypes 1 of both populations which seem to be the wild-type composite ASIP haplotype. Overall, there was no clear association of this portion of the ASIP gene interrogated in this study with coat color variation. Therefore, additional genomic analyses of promoter sequence, the entire coding and non-coding regions of the ASIP gene will be required to obtain a definite conclusion.

[The paradox of motherhood].

Science.gov (United States)

Ouaidou, N G

1990-08-01

All Sahelian countries are working to define their population policies. A population policy document avoids dispersion and duplication. It opens the path to efficiency. It makes it easier to achieve governmental socioeconomic objectives. Various recent population-related meetings have at least two points in common: they aim to overstep and improve a given situation and are at the same time some examples of implementing the Ndjamena action program, adopted in January 1989. All these population-centered actions return to the problem of adolescent fertility--a poignant problem. Adolescent pregnancy is a major source of family and social break-ups. This paradox of motherhood makes a violent storm burst in the skies ordinarily serene with joy and hope. It is an enemy perverse to economic development and social progress. Adolescent motherhood is a phenomenon which complicates and aggravates population problems and is taboo to the point it is still imperceptible, unknown. It is a problem of premier importance in the Sahel. Pregnancy strikes a woman so very unprepared for motherhood and its demands. It risks the life of a being which is preparing itself to enter the world. Adolescent pregnancy has equally tragic health effects: poorly performed underground abortions and maternal and infant deaths. Adolescent fertility is a burning problem regardless of the perspective (demographic, economic, social, or health). In Sahelian countries, one is beginning to be interested in and to speak about it. It will be necessary to search for solutions. Schools must be a top target for all activities aiming to check adolescent fertility. The emphasis must be on information, education, and responsibility of girls, boys, teachers, and parents. Education and training are of capital importance for socioeconomic development of the Sahel. All activities implemented in the education sector should include a large place for family life education in pregnancy prevention.

Sub-Saharan Northern African climate at the end of the twenty-first century: forcing factors and climate change processes

Energy Technology Data Exchange (ETDEWEB)

Patricola, C.M. [Cornell University, Department of Earth and Atmospheric Sciences, Ithaca, NY (United States); Texas A and M University, Department of Atmospheric Sciences, College Station, TX (United States); Cook, K.H. [The University of Texas at Austin, Department of Geological Sciences, Jackson School of Geosciences, Austin, TX (United States)

2011-09-15

A regional climate model, the Weather Research and Forecasting (WRF) Model, is forced with increased atmospheric CO{sub 2} and anomalous SSTs and lateral boundary conditions derived from nine coupled atmosphere-ocean general circulation models to produce an ensemble set of nine future climate simulations for northern Africa at the end of the twenty-first century. A well validated control simulation, agreement among ensemble members, and a physical understanding of the future climate change enhance confidence in the predictions. The regional model ensembles produce consistent precipitation projections over much of northern tropical Africa. A moisture budget analysis is used to identify the circulation changes that support future precipitation anomalies. The projected midsummer drought over the Guinean Coast region is related partly to weakened monsoon flow. Since the rainfall maximum demonstrates a southward bias in the control simulation in July-August, this may be indicative of future summer drying over the Sahel. Wetter conditions in late summer over the Sahel are associated with enhanced moisture transport by the West African westerly jet, a strengthening of the jet itself, and moisture transport from the Mediterranean. Severe drought in East Africa during August and September is accompanied by a weakened Indian monsoon and Somali jet. Simulations with projected and idealized SST forcing suggest that overall SST warming in part supports this regional model ensemble agreement, although changes in SST gradients are important over West Africa in spring and fall. Simulations which isolate the role of individual climate forcings suggest that the spatial distribution of the rainfall predictions is controlled by the anomalous SST and lateral boundary conditions, while CO{sub 2} forcing within the regional model domain plays an important secondary role and generally produces wetter conditions. (orig.)

Safety of Seasonal Malaria Chemoprevention (SMC with Sulfadoxine-Pyrimethamine plus Amodiaquine when Delivered to Children under 10 Years of Age by District Health Services in Senegal: Results from a Stepped-Wedge Cluster Randomized Trial.

Directory of Open Access Journals (Sweden)

J L NDiaye

Full Text Available It is recommended that children aged 3 months to five years of age living in areas of seasonal transmission in the sub-Sahel should receive Seasonal Malaria Chemoprevention (SMC with sulfadoxine-pyrimethamine plus amodiaquine (SPAQ during the malaria transmission season. The purpose of this study was to evaluate the safety of SMC with SPAQ in children when delivered by community health workers in three districts in Senegal where SMC was introduced over three years, in children from 3 months of age to five years of age in the first year, then in children up to 10 years of age.A surveillance system was established to record all deaths and all malaria cases diagnosed at health facilities and a pharmacovigilance system was established to detect adverse drug reactions. Health posts were randomized to introduce SMC in a stepped wedge design. SMC with SPAQ was administered once per month from September to November, by nine health-posts in 2008, by 27 in 2009 and by 45 in 2010.After three years, 780,000 documented courses of SMC had been administered. High coverage was achieved. No serious adverse events attributable to the intervention were detected, despite a high level of surveillance.SMC is being implemented in countries of the sub-Sahel for children under 5 years of age, but in some areas the age distribution of cases of malaria may justify extending this age limit, as has been done in Senegal. Our results show that SMC is well tolerated in children under five and in older children. However, pharmacovigilance should be maintained where SMC is implemented and provision for strengthening national pharmacovigilance systems should be included in plans for SMC implementation.ClinicalTrials.gov NCT 00712374.

Large-Scale Control of the Arabian Sea Summer Monsoon Inversion and Low Clouds: A New Perspective

Science.gov (United States)

Wu, C. H.; Wang, S. Y.; Hsu, H. H.; Hsu, P. C.

2016-12-01

The Arabian Sea undergoes a so-called summer monsoon inversion that reaches the maximum intensity in August associated with a large amount of low-level clouds. The formation of inversion and low clouds was generally thought to be a local system influenced by the India-Pakistan monsoon advancement. New empirical and numerical evidence suggests that, rather than being a mere byproduct of the nearby monsoon, the Arabian Sea monsoon inversion is coupled with a broad-scale monsoon evolution connected across the Africa Sahel, South Asia, and the East Asia-western North Pacific (WNP). Several subseasonal variations occur in tandem: The eastward expansion of the Asian-Pacific monsoonal heating likely suppresses the India-Pakistan monsoon while enhancing low-level thermal inversion of Arabian Sea; the upper-tropospheric anticyclone in South Asia weakens in August smoothing zonal contrast in geopotential heights (10°N-30°N); the subtropical WNP monsoon trough in the lower troposphere that signals the revival of East Asian summer monsoon matures in August; the Sahel rainfall peaks in August accompanied by an intensified tropical easterly jet. The occurrence of the latter two processes enhances upper-level anticyclones over Africa and WNP and this, in turn, induces subsidence in between over the Arabian Sea. Numerical experiments demonstrate the combined effect of the African and WNP monsoonal heating on the enhancement of the Arabian Sea monsoon inversion. Connection is further found in the interannual and decadal variations between the East Asian-WNP monsoon and the Arabian Sea monsoon inversion. In years with reduced low clouds of Arabian Sea, the East Asian midlatitude jet stream remains strong in August while the WNP monsoon trough appears to be weakened. The Arabian Sea inversion (ridge) and WNP trough pattern which forms a dipole structure, is also found to have intensified since the 21st century.

HABSEED: a Simple Spatially Explicit Meta-Populations Model Using Remote Sensing Derived Habitat Quality Data

Science.gov (United States)

Heumann, B. W.; Guichard, F.; Seaquist, J. W.

2005-05-01

The HABSEED model uses remote sensing derived NPP as a surrogate for habitat quality as the driving mechanism for population growth and local seed dispersal. The model has been applied to the Sahel region of Africa. Results show that the functional response of plants to habitat quality alters population distribution. Plants more tolerant of medium quality habitat have greater distributions to the North while plants requiring only the best habitat are limited to the South. For all functional response types, increased seed production results in diminishing returns. Functional response types have been related to life history tradeoffs and r-K strategies based on the results. Results are compared to remote sensing derived vegetation land cover.

Identification of aerosol particle sources in semi-rural area of Kwabenya, near Accra, Ghana, by EDXRF techniques

DEFF Research Database (Denmark)

Aboh, Innocent Joy Kwame; Henriksson, Dag; Laursen, Jens

2009-01-01

is frequently exposed to Harmattan dust from the Sahara-Sahel region. In total 171 filters each of PM2.5 and PM(2.5-10) were collected during 1 year. Levels of elements, black carbon (BC) and mass, were determined for both particle sizes. Principal component analysis (PCA) was performed on the datasets from...... Harmattan and non-Harmattan periods. The daily average of PM10 was very high, 179 μgm-3 and the BC contents were 4 μgm-3. The presence of crustal elements was large in PM(2.5-10) as well as in PM2.5, and had amore than tenfold increase in PM(2.5-10) during the Harmattan period. Major characteristic elements...

Water resources for Africa

International Nuclear Information System (INIS)

2003-01-01

Water scarcity is a matter of urgent, national, regional and international concern. For those people, usually women, who are responsible for the daily task of obtaining sufficient water for household use, water shortages are a perpetual worry. It is a situation which affects many individual families and communities throughout the arid and semi-arid regions of Africa. The isotope studies conducted thus far have proved that the majority of regional groundwater systems in northern Africa and the Sahel zone are paleowaters, replenished thousands of years ago, without the possibility of significant replenishment under present climatic conditions. Therefore, removal from such underground reservoirs will eventually deplete the resource. Mapping these paleowaters, and estimating their reservoir sizes, is a priority. (IAEA)

Using remote-sensing and the Simple Biosphere model (SiB4) to analyze the seasonality and productivity of the terrestrial biosphere.

Science.gov (United States)

Cheeseman, M.; Denning, S.; Baker, I. T.

2017-12-01

Understanding the variability and seasonality of carbon fluxes from the terrestrial biosphere is integral to understanding the mechanisms and drivers of the global carbon cycle. However, there are many regions across the globe where in situ observations are sparse, such as the Amazon rainforest and the African Sahel. The latest version of the Simple-Biosphere model (SiB4) predicts a suite of biophysical variables such as terrestrial carbon flux (GPP), solar induced fluorescence (SIF), fraction of photosynthetically active radiation (FPAR), and leaf area index (LAI). By comparing modeled values to a suite of satellite and in situ observations we produce a robust analysis of the seasonality and productivity of the terrestrial biosphere in a variety of biome types across the globe.

Research on Climate Change and Its Impacts Needs Freedom of Research

Directory of Open Access Journals (Sweden)

Nicole Mölders

2013-12-01

Full Text Available Climate change captured my interest as a teenager when, at the dining table, my dad talked about potential anthropogenic climate changes. He brought up subjects such as “climate could change if the Siberian Rivers were to be deviated to the South for irrigation of the (semi arid areas of the former Soviet Union”. Other subjects were afforestation in the Sahel to enhance precipitation recycling, deforestation in the Tropics that could have worldwide impacts on climate, the local climate impacts of the Merowe High Dam in its vicinity and downstream, Atlantropa, a new ice age, and the increase in days with sunshine after the introduction of the high-chimney policy in the Rhein-Ruhr area, just to mention a few.

What four decades of earth observation tell us about land degradation in the Sahel?

DEFF Research Database (Denmark)

Mbow, Cheikh; Brandt, Martin Stefan; Ouedraogo, Issa

2015-01-01

The assessment of land degradation and the quantification of its effects on land productivity have been both a scientific and political challenge. After four decades of Earth Observation (EO) applications, little agreement has been gained on the magnitude and direction of land degradation in the ...

Dust and epidemic meningitis in the Sahel: A public health and operational research perspective

Science.gov (United States)

Thomson, M. C.; Jeanne, I.; Djingarey, M.

2009-03-01

Now that the health communities attention is increasingly focused on climate-health interactions, it has become essential for health decision makers to better understand the role that climate plays in driving disease burdens and health outcomes (both now and in the future) and the opportunity for integrating climate knowledge and information into health decision-making processes to mitigate the negative and strengthen the positive of climate-health interactions. Here we explore the potential climatic indicators and the climate information needs of relevance to the meningitis prevention and control community engaged in the African 'meningitis belt'.

Dust and epidemic meningitis in the Sahel: A public health and operational research perspective

Energy Technology Data Exchange (ETDEWEB)

Thomson, M C [International Research Institute for Climate and Society, Palisades, NY (United States); Jeanne, I [CERMES/Reseau International des Instituts Pasteur, BP 10 887 Niamey (Niger); Djingarey, M [WHO-Multi-Disease Surveillance Centre, Ougadougou (Burkina Faso)], E-mail: mthomson@iri.columbia.edu

2009-03-01

Now that the health communities attention is increasingly focused on climate-health interactions, it has become essential for health decision makers to better understand the role that climate plays in driving disease burdens and health outcomes (both now and in the future) and the opportunity for integrating climate knowledge and information into health decision-making processes to mitigate the negative and strengthen the positive of climate-health interactions. Here we explore the potential climatic indicators and the climate information needs of relevance to the meningitis prevention and control community engaged in the African 'meningitis belt'.

Dust and epidemic meningitis in the Sahel: A public health and operational research perspective

International Nuclear Information System (INIS)

Thomson, M C; Jeanne, I; Djingarey, M

2009-01-01

Now that the health communities attention is increasingly focused on climate-health interactions, it has become essential for health decision makers to better understand the role that climate plays in driving disease burdens and health outcomes (both now and in the future) and the opportunity for integrating climate knowledge and information into health decision-making processes to mitigate the negative and strengthen the positive of climate-health interactions. Here we explore the potential climatic indicators and the climate information needs of relevance to the meningitis prevention and control community engaged in the African 'meningitis belt'.

Sorghum-cowpea intercropping : an effective technique against runoff and soil erosion in the Sahel

NARCIS (Netherlands)

Zougmore, R.; Kambou, F.N.; Ouattara, K.; Guillobez, S.

2000-01-01

In the Central Plateau of Burkina Faso, runoff on bare soil amounts to 40␘f annual rainfall and soil losses reach 4 to 8 Mg ha-? a-?, despite slopes of under 3ÐSeveral studies have shown that mulching the soil surface can reduce runoff by over 60ÐHowever, the scarcity of straw and the

Simulation of Tropical Rainfall Variability

Science.gov (United States)

Bader, J.; Latif, M.

2002-12-01

The impact of sea surface temperature (SST) - especially the role of the tropical Atlantic meridional SST gradient and the El Nino-Southern Oscillation - on precipitation is investigated with the atmospheric general circulation model ECHAM4/T42. Ensemble experiments - driven with observed SST - show that Atlantic SST has a significant influence on precipitation over West Africa and northeast Brazil. SST sensitivity experiments were performed in which the climatological SST was enhanced or decreased by one Kelvin in certain ocean areas. Changing SST in the eastern tropical Atlantic caused only significant changes along the Guinea Coast, with a positive anomaly (SSTA) increasing rainfall and a negative SSTA reducing it. The response was nearly linear. Changing SST in other ocean areas caused significant changes over West Africa, especially in the Sahel area. The response is found to be non linear, with only negative SSTA leading to significant reduction in Sahel rainfall. Also, the impact of the SSTAs from the different ocean regions was not additive with respect to the rainfall. The influence of SST on precipitation over northeast Brazil (Nordeste) was also investigated. Three experiments were performed in which the climatological SST was enhanced/decreased or decreased/enhanced by one Kelvin in the North/South Atlantic and increased by two Kelvin in the Nino3 ocean area. All experiments caused significant changes over Nordeste, with an enhanced/reduced SST gradient in the Atlantic increasing/reducing rainfall. The response was nearly linear. The main effect of the Atlantic SST gradient was a shift of the ITCZ, caused by trade wind changes. The ''El Nino'' event generates a significant reduction in Nordeste rainfall. A significant positive SLP anomaly occurs in northeast Brazil which may be associated with the descending branch of the Walker circulation. Also a significant positive SLP over the Atlantic from 30S to 10N north occurs. This results in a reduced SLP

Large-scale delivery of seasonal malaria chemoprevention to children under 10 in Senegal: an economic analysis

Science.gov (United States)

Pitt, Catherine; Ndiaye, Mouhamed; Conteh, Lesong; Sy, Ousmane; Hadj Ba, El; Cissé, Badara; Gomis, Jules F; Gaye, Oumar; Ndiaye, Jean-Louis

2017-01-01

Abstract Seasonal Malaria Chemoprevention (SMC) is recommended for children under 5 in the Sahel and sub-Sahel. The burden in older children may justify extending the age range, as has been done effectively in Senegal. We examine costs of door-to-door SMC delivery to children up to 10 years by community health workers (CHWs). We analysed incremental financial and economic costs at district level and below from a health service perspective. We examined project accounts and prospectively collected data from 405 CHWs, 46 health posts, and 4 district headquarters by introducing questionnaires in advance and completing them after each monthly implementation round. Affordability was explored by comparing financial costs of SMC to relevant existing health expenditure levels. Costs were disaggregated by administration month and by health service level. We used linear regression models to identify factors associated with cost variation between health posts. The financial cost to administer SMC to 180 000 children over one malaria season, reaching ∼93% of children with all three intended courses of SMC was $234 549 (constant 2010 USD) or $0.50 per monthly course administered. Excluding research–participation incentives, the financial cost was $0.32 per resident (all ages) in the catchment area, which is 1.2% of Senegal’s general government expenditure on health per capita. Economic costs were 18.7% higher than financial costs at $278 922 or $0.59 per course administered and varied widely between health posts, from $0.38 to $2.74 per course administered. Substantial economies of scale across health posts were found, with the smallest health posts incurring highest average costs per monthly course administered. SMC for children up to 10 is likely to be affordable, particularly where it averts substantial curative care costs. Estimates of likely costs and cost-effectiveness of SMC in other contexts must account for variation in average costs across delivery months

Biogenic nitrogen oxide emissions from soils ─ impact on NOx and ozone over West Africa during AMMA (African Monsoon Multidisciplinary Experiment: modelling study

Directory of Open Access Journals (Sweden)

J.-P. Chaboureau

2008-05-01

Full Text Available Nitrogen oxide biogenic emissions from soils are driven by soil and environmental parameters. The relationship between these parameters and NO fluxes is highly non linear. A new algorithm, based on a neural network calculation, is used to reproduce the NO biogenic emissions linked to precipitations in the Sahel on the 6 August 2006 during the AMMA campaign. This algorithm has been coupled in the surface scheme of a coupled chemistry dynamics model (MesoNH Chemistry to estimate the impact of the NO emissions on NOx and O3 formation in the lower troposphere for this particular episode. Four different simulations on the same domain and at the same period are compared: one with anthropogenic emissions only, one with soil NO emissions from a static inventory, at low time and space resolution, one with NO emissions from neural network, and one with NO from neural network plus lightning NOx. The influence of NOx from lightning is limited to the upper troposphere. The NO emission from soils calculated with neural network responds to changes in soil moisture giving enhanced emissions over the wetted soil, as observed by aircraft measurements after the passing of a convective system. The subsequent enhancement of NOx and ozone is limited to the lowest layers of the atmosphere in modelling, whereas measurements show higher concentrations above 1000 m. The neural network algorithm, applied in the Sahel region for one particular day of the wet season, allows an immediate response of fluxes to environmental parameters, unlike static emission inventories. Stewart et al (2008 is a companion paper to this one which looks at NOx and ozone concentrations in the boundary layer as measured on a research aircraft, examines how they vary with respect to the soil moisture, as indicated by surface temperature anomalies, and deduces NOx fluxes. In this current paper the model-derived results are compared to the observations and calculated fluxes presented by Stewart et

Commented distributional list of the Reptiles of Mauritania (West Africa

Directory of Open Access Journals (Sweden)

Padial, J. M.

2006-12-01

Full Text Available This is the first comprehensive review of the reptiles of Mauritania. It includes distributional information and comments. Mauritania harbors 86 species of reptiles belonging to 21 families. Among these families, Colubridae and Lacertidae are the most diverse, with 14 and 13 species respectively. Other families, such as Agamidae, Gekkonidae, Scincidae or Viperidae are also well represented. Among the 80 continental species, 47.5% are Saharan, 33.8% Afrotropical, 16.2% Sahelian and 2.5% Mediterranean. The marine turtles form another important group, with six species. Eight species are excluded from the country list because of old identification errors, there is not enough evidence of their presence or due to changes in political borders. Among the species expected to occur in Mauritania, at least nine may occur in Saharan environments, 13 in the Sahel savannah and two may have been introduced.

Esta es la primera lista de reptiles comentada con datos de distribución para la República Islámica de Mauritania. La fauna de reptiles de Mauritania se compone de 86 especies pertenecientes a 21 familias. Entres ellas, Colubridae y Lacertidae son las más diversas, con 14 y 13 especies respectivamente. Otras familias como Agamidae, Gekkonidae, Scincidae y Viperidae también son representativas. Entre las 80 especies continentales el 47.5% son de distribución sahariana, el 33.8% afrotropical, el 16.2% sahelianas y el 2.5% mediterráneas. Las tortugas marinas, con seis especies, es otro grupo importante. Ocho especies no han sido incluidas en la lista debido a que se trataba de viejos errores de identificación, por carecer de suficiente evidencia o debido a la redistribución de las viejas fronteras políticas. Entre las especies potencialmente presentes, al menos nueve de ellas se esperan para las zonas saharianas, trece para las sabanas del Sahel, y dos podrían haber sido introducidas.

Increasing Megadrought Risk at the Intersection of Decadal to Centennial Variability and Climate Change

Science.gov (United States)

Overpeck, J. T.; Parsons, L. A.; Loope, G. R.; Ault, T.; Cole, J. E.; Otto-Bliesner, B. L.; Buckle, N.; Stevenson, S.; Fasullo, J.

2016-12-01

Even more than the 1930's U.S. Dust Bowl Drought, the 20th century Sahel drought stands out as the most unprecedented drought of the instrumental era, in part because it extended over multiple decades. Paleoclimatic evidence makes it clear that this Sahel drought was nonetheless not really unprecedented - droughts many decades long have occurred in sub-Saharan Africa regularly over the last several thousand years, and these constitute what is now increasingly referred to as "megadrought." Paleoclimatic evidence also makes it clear that all drought-prone semi-arid and arid regions of the globe, including southwestern North America, southeastern Australia, and the Mediterranean/Middle Eastern region likely experienced multiple such multidecadal megadroughts in recent pre-Anthropocene Earth history. In other regions of the globe, including parts of South Asia and Amazonia, short but devastating droughts of the last 50-150 years, were also eclipsed in recent Earth history by much more serious megadrought, although these megadroughts were shorter than the multidecadal droughts of Africa or SW North America. In the past, megadroughts have occurred for reasons that are increasingly well understood in terms of ocean-atmosphere dynamics that led to unusually persistent precipitation deficits. Many of these same dynamics are well simulated in state-of-the-art Earth System Models, and yet comparisons between simulated and observed paleohydroclimatic variability suggests the models generally underestimate the risk of megadrought. Paleohydroclimatic records in some cases overestimate drought persistence, but there appear to be other issues at play that need to be better understood and simulated: positive land-atmosphere feedbacks, overly energetic interannual (i.e., ENSO) modes of variability, and insufficient internal multidecadal to centennial coupled climate system variability. Taking these issues and the impact of anthropogenic climate change into account means that the

Intercomparison and analyses of the climatology of the West African monsoon in the West African monsoon modeling and evaluation project (WAMME) first model intercomparison experiment

Energy Technology Data Exchange (ETDEWEB)

Xue, Yongkang; Sales, Fernando De [University of California, Los Angeles, CA (United States); Lau, W.K.M.; Schubert, Siegfried D.; Wu, Man-Li C. [NASA, Goddard Space Flight Center, Greenbelt, MD (United States); Boone, Aaron [Centre National de Recherches Meteorologiques, Meteo-France Toulouse, Toulouse (France); Feng, Jinming [University of California, Los Angeles, CA (United States); Chinese Academy of Sciences, Institute of Atmospheric Physics, Beijing (China); Dirmeyer, Paul; Guo, Zhichang [Center for Ocean-Land-Atmosphere Interactions, Calverton, MD (United States); Kim, Kyu-Myong [University of Maryland Baltimore County, Baltimore, MD (United States); Kitoh, Akio [Meteorological Research Institute, Tsukuba (Japan); Kumar, Vadlamani [National Center for Environmental Prediction, Camp Springs, MD (United States); Wyle Information Systems, Gaithersburg, MD (United States); Poccard-Leclercq, Isabelle [Universite de Bourgogne, Centre de Recherches de Climatologie UMR5210 CNRS, Dijon (France); Mahowald, Natalie [Cornell University, Ithaca, NY (United States); Moufouma-Okia, Wilfran; Rowell, David P. [Met Office Hadley Centre, Exeter (United Kingdom); Pegion, Phillip [NASA, Goddard Space Flight Center, Greenbelt, MD (United States); National Center for Environmental Prediction, Camp Springs, MD (United States); Schemm, Jae; Thiaw, Wassila M. [National Center for Environmental Prediction, Camp Springs, MD (United States); Sealy, Andrea [The Caribbean Institute for Meteorology and Hydrology, St. James (Barbados); Vintzileos, Augustin [National Center for Environmental Prediction, Camp Springs, MD (United States); Science Applications International Corporation, Camp Springs, MD (United States); Williams, Steven F. [National Center for Atmospheric Research, Boulder, CO (United States)

2010-07-15

This paper briefly presents the West African monsoon (WAM) modeling and evaluation project (WAMME) and evaluates WAMME general circulation models' (GCM) performances in simulating variability of WAM precipitation, surface temperature, and major circulation features at seasonal and intraseasonal scales in the first WAMME experiment. The analyses indicate that models with specified sea surface temperature generally have reasonable simulations of the pattern of spatial distribution of WAM seasonal mean precipitation and surface temperature as well as the averaged zonal wind in latitude-height cross-section and low level circulation. But there are large differences among models in simulating spatial correlation, intensity, and variance of precipitation compared with observations. Furthermore, the majority of models fail to produce proper intensities of the African Easterly Jet (AEJ) and the tropical easterly jet. AMMA Land Surface Model Intercomparison Project (ALMIP) data are used to analyze the association between simulated surface processes and the WAM and to investigate the WAM mechanism. It has been identified that the spatial distributions of surface sensible heat flux, surface temperature, and moisture convergence are closely associated with the simulated spatial distribution of precipitation; while surface latent heat flux is closely associated with the AEJ and contributes to divergence in AEJ simulation. Common empirical orthogonal functions (CEOF) analysis is applied to characterize the WAM precipitation evolution and has identified a major WAM precipitation mode and two temperature modes (Sahara mode and Sahel mode). Results indicate that the WAMME models produce reasonable temporal evolutions of major CEOF modes but have deficiencies/uncertainties in producing variances explained by major modes. Furthermore, the CEOF analysis shows that WAM precipitation evolution is closely related to the enhanced Sahara mode and the weakened Sahel mode, supporting

L’élevage pastoral au Sénégal entre pression spatiale et mutation commerciale

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Géraud Magrin

2011-12-01

Full Text Available L'élevage pastoral est menacé au Sénégal car les dynamiques écologiques, les défrichements et les politiques publiques compromettent l'accès aux ressources sur lequel repose sa mobilité essentielle. Loin des clichés qui le présentent comme une activité homogène et archaïque, l'élevage connaît pourtant des mutations importantes. Sous des formes variées, il se diversifie et se connecte aux marchés urbains nationaux du lait et de la viande, valorisant des marchés de niche. Les dynamiques observées dans le plus urbanisé des États du Sahel préfigurent ainsi celles qui s'amorcent ailleurs.

Biological alterations and self-reported symptoms among insecticides-exposed workers in Burkina Faso.

Science.gov (United States)

Toe, Adama M; Ilboudo, Sylvain; Ouedraogo, Moustapha; Guissou, Pierre I

2012-03-01

Occupationally exposed workers, farm workers and plant protection agents in the Sahel region of Burkina Faso were interviewed to assess adverse health effects of insecticides. The subjects were also examined for changes in both hematological and biochemical parameters. The prevalence of liver and kidney dysfunction was found to be quite high among insecticide applicators, especially among plant protection agents. The prevalence of biochemical alterations seems to be correlated to the frequency of insecticide use. However, no significant differences were found between the hematological parameters among farm workers and plant protection agents. The hematological parameters of all the insecticide applicators were normal. The great majority of insecticide applicators (85%) reported symptoms related to insecticide exposure. The use of insecticides in the agriculture of Burkina Faso is threatening to human health.

A new brachypterous scarab species, Orphnus longicornis (Coleoptera: Scarabaeidae: Orphninae), from the East African Rift.

Science.gov (United States)

Frolov, Andrey; Akhmetova, Lilia

2015-11-05

The Afrotropical Region is the center of the diversity of the scarab beetle genus Orphnus MacLeay, 1819 (Coleoptera: Scarabaeidae: Orphninae), with 94 species occurring from Sahel in the north to Little Karoo in the south (Paulian, 1948; Petrovitz, 1971; Frolov, 2008). The East African Rift is one of the richest regions of the Afrotropics housing more than 20 species of Orphnus (Paulian, 1948; Frolov, 2013), most of which are endemic to this region. Yet the scarab beetle fauna of the East African Rift, and especially the Eastern Arc Mountains, is still inadequately studied. Examination of the material housed in the Museum of Natural History of Humboldt-Universität, Berlin, Germany (ZMHUB), revealed a series of brachypterous Orphnus beetles belonging to an undescribed species. The new species is described and illustrated below.

Revalidation of Acanthinozodium Denis, 1966 with description of three new species and discovery of a remarkable male palpal character (Araneae, Zodariidae

Directory of Open Access Journals (Sweden)

Rudy Jocqué

2015-03-01

Full Text Available The genus name Acanthinozodium Denis, 1966 is considered available and valid, with A. spinulosum Denis, 1966 as its type species. The genus is characterized by the presence of ventral rows of long setae on the femora, large anterior median eyes and a large, dorsal, crater-like pit on the cymbium. Zodariellum Andreeva & Tyschenko, 1968 is removed from its synonymy and now only contains its type species Z. surprisum Andreeva & Tyschenko, 1968. Three new Acanthinozodium species are described: A. crateriferum sp. nov. (♂♀ from Ethiopia, A. sahelense sp. nov. (♂♀ from a wide range in the Sahel region and A. quercicola sp. nov. (♂ from Morocco. The genus appears to have a large distribution in and around the Sahara. The possible function of the cymbial pit is discussed.

Sequestration of carbon in soil organic matter in Senegal: an overview

Science.gov (United States)

Tieszen, Larry L.; Tappan, G. Gray; Toure, A.

2004-01-01

Sequestration of Carbon in Soil Organic Matter (SOCSOM) in Senegal is a multi-disciplinary development project planned and refined through two international workshops. The project was implemented by integrating a core of international experts in remote sensing, biogeochemical modeling, community socio-economic assessments, and carbon measurements in a fully collaborative manner with Senegal organizations, national scientists, and local knowledge and expertise. The study addresses the potential role developing countries in semi-arid areas can play in climate mitigation activities. Multiple benefits to smallholders could accrue as a result of management practices to re-establish soil carbon content lost because of land use changes or management practices that are not sustainable. The specific importance for the Sahel is because of the high vulnerability to climate change in already impoverished rural societies.

Hydrological land surface modelling

DEFF Research Database (Denmark)

Ridler, Marc-Etienne Francois

Recent advances in integrated hydrological and soil-vegetation-atmosphere transfer (SVAT) modelling have led to improved water resource management practices, greater crop production, and better flood forecasting systems. However, uncertainty is inherent in all numerical models ultimately leading...... temperature are explored in a multi-objective calibration experiment to optimize the parameters in a SVAT model in the Sahel. The two satellite derived variables were effective at constraining most land-surface and soil parameters. A data assimilation framework is developed and implemented with an integrated...... and disaster management. The objective of this study is to develop and investigate methods to reduce hydrological model uncertainty by using supplementary data sources. The data is used either for model calibration or for model updating using data assimilation. Satellite estimates of soil moisture and surface...