Search Results (34)

Across Africa, drought seldom occurs alone. Rainfall deficits often coincide with heat, rapid soil moisture loss and reduced streamflow, producing compound events whose impacts exceed those of any single driver. This review synthesises station observations, satellite and reanalysis products, and climate model simulations to clarify where such events are most common, how they form, how they affect societies and ecosystems, and how risks are changing. A practical tiered definition tailored to African conditions is outlined and applied to identify five recurrent hotspots: the Sahel, the Greater Horn of Africa, southern Africa, the margins of the Congo Basin and the Guinea Coast. The review sets out a physically consistent sequence that links basin-scale sea surface temperature anomalies to shifts in monsoon circulation, and then to land processes that amplify and prolong heat and dryness through reduced evapotranspiration and soil-moisture memory. Documented impacts include lower crop and pasture productivity, pressure on rivers, reservoirs and groundwater, stress on hydropower and wider consequences for food and energy security. Compound drought frequency across these hotspots has risen by 18–55% since 1980, with the probability of the most severe events roughly doubling at 1.5 °C of global warming and tripling at 3 °C. The review highlights near-term priorities, including compound-aware monitoring, sub-seasonal-to-seasonal early warning and conjunctive water management. Full article

Land cover (LC) change is reshaping terrestrial ecosystems and profoundly impacting sustainable development in Africa, yet the long-term, continental-scale spatiotemporal dynamics of these shifts remain obscured. To address the above issue, this study systematically explores the spatiotemporal dynamics of LC across Africa from 1985 to 2022 by leveraging the fine-resolution remote-sensing-derived GLC_FCS30D LC dataset within a stratified Intensity Analysis framework. To decompose landscape changes into interval, category, and transition levels across five climatic sub-regions of Africa, we systematically evaluate the temporal consistency of land systems. This hierarchical approach disentangles systematic transition pathways from random fluctuations, thereby revealing the distinct regional regimes governing continental transformation of LC. Our results ultimately show a strong LC change acceleration in Africa after 2010, mainly in Southern, Eastern, and Western Africa, which together made up 80 to 90% of the continent’s LC dynamics. During the whole study period, shrubland and grassland had the highest gross turnover due to their high bidirectional volatility. Intensity-wise, forest remained inactive even though it was a persistent net loser to crop in East Africa (2010–2020), to shrub in Southern Africa (1990–2022), and to wetland in West Africa during the post-2000 intervals. Wetland had a major change in dynamics from historical growth during 1985–1990 to systematic decline in 2015–2022. Cropland increased by systematically targeting shrubland and grassland, mainly in East Africa. Additionally, the Sahel contributed 40% of continental grassland to bare area transitions, despite some recovery of grassland in the region. These findings show that aggregate net-change metrics obscure the volatility in African LC; therefore, distinct regional regimes such as agricultural expansion and forest degradation necessitate spatially differentiated management strategies. Full article

Rainfall variability strongly governs vegetation dynamics in the Semi-Arid Tropics (SAT) of Sub-Saharan Africa (SSA). Yet the impacts of heavy rainfall are less well quantified than those of drought. This study proposes a modified heavy rainfall index (mR95pT) to enable robust comparison of extreme rainfall signals across seasons and regions. The index mitigates the strong seasonal background signal inherent to constant-threshold approaches and highlights episodic heavy rainfall events more clearly. Using CHIRPS precipitation (1981–2022, to derive long-term climatological means) and MODIS NDVI (2003–2022) aggregated to 0.05° and 16-day intervals, we computed the cumulative precipitation, the original ETCCDI-based index (R95pT), and mR95pT across three subregions (Sahel, Southern Africa, and Eastern Africa) and examined event-scale detectability. mR95pT reduced spurious concentration around climatological wet-season peaks and more clearly captured episodic events (e.g., cyclone-related extremes). The vegetation stress (VS) responses were quantified based on the Vegetation Condition Index (VCI) and a probabilistic framework conditioned on background wetness (SPI-3) and heavy rainfall intensity (mR95pT). Under near-normal wetness (SPI-3 ≈ 0), the baseline VS probability was 18% in Eastern Africa and 13% in the other regions. Conditioning on heavy rainfall increased VS probability (relative to the SPI-3 ≈ 0 baseline) by +0.8 to +38% (Eastern Africa), +0.6 to +24% (Southern Africa), and +11 to +39% (Sahel), with the additional effect diminishing under very wet conditions. Overall, mR95pT and the proposed probabilistic framework provide a scalable pathway to monitor both drought- and heavy-rain-related vegetation risks over data-sparse semi-arid regions. Full article

Agriculture serves as a critical foundation for livelihoods, food security, and sustainable development across the Sahara–Sahelian region. However, this vital sector faces mounting pressures from recurrent armed conflicts that systematically undermine its resilience and long-term sustainability. This study provides a comprehensive analysis of agricultural technical efficiency across 23 African countries in the Sahara–Sahelian region from 2009 to 2021, employing a robust bias-corrected bootstrap Data Envelopment Analysis approach. The findings reveal a concerning regional deterioration, with technical efficiency declining at an average annual rate of 1.7% throughout the study period. Conflict-affected countries demonstrated distinctive vulnerability patterns, exhibiting both higher average efficiency levels (0.875) and greater volatility, with annual declines of 1.8%. Sub-regional analysis highlights the Sahel’s particular fragility, where efficiency decreased by 2.2% yearly, nearly double the decline rate observed in North Africa. The most severe efficiency losses were recorded in countries experiencing intense and protracted conflict, notably Burkina Faso (4.0%) and Mali (3.5%), underscoring the severe association between conflict exposure and the erosion of agricultural productive capacity. These findings underscore the importance of developing integrated strategies that simultaneously address security challenges, climate adaptation, and institutional reform for effective resilience-building. Policy recommendations highlight the importance of enhanced regional connectivity, knowledge transfer, and targeted investments in agricultural capacity building—all aligned with both Sustainable Development Goals and the African Union’s Agenda 2063 objectives for achieving sustainable agricultural transformation in conflict-affected regions. Full article

In sub-Saharan Africa, land degradation and climate change continue to undermine agricultural productivity by reducing soil productivity and water availability. This review identifies soil and water conservation technologies successfully applied in climatically analogous regions of sub-Saharan Africa with the aim of informing effective technology transfer to Senegal, particularly Sédhiou and Tambacounda. Using K-means clustering on WorldClim bioclimatic variables, 35 comparable countries were identified, of which 17 met inclusion criteria based on data availability and ≥60% climatic similarity. Eighty-five technologies were documented and assessed for their compatibility across rainfall patterns, land gradients, and uses, with 12 emerging as consistently effective. Quantitative evidence shows that zai/tassa pits, stone bunds, and half-moons increase crop yields by 50–200%, while stone bunds and mulching reduce runoff by up to 80% and improve soil moisture retention. Terracing and tied-ridging were also linked to higher water-use efficiency, with tied-ridging increasing soil moisture by 13%. Burkina Faso, Kenya, and Malawi lead in adoption and diversity, whereas Senegal lags due to institutional gaps, limited funding, and weak extension systems. These technologies offer a readily available, evidence-based toolkit for building agricultural resilience in Senegal. However, their successful adoption requires stronger policy integration, stakeholder empowerment, cross-border learning, and private-sector engagement. Full article

Pearl millet is primarily grown under rainfed conditions in Sub-Saharan Africa. Early droughts are prevalent in the Sahel region, where pearl millet is widely cultivated, and they severely impact pearl millet growth and productivity by affecting plant stand and reducing plant density in the field. Consequently, genetic improvement for early drought tolerance is a promising strategy to enhance productivity in these regions. This study aims to identify pearl millet lines that are tolerant to water stress at the seedling stage by assessing various water-stress-tolerance traits. Two hundred pearl millet inbred lines were screened for drought tolerance by inducing water stress with polyethylene glycol 6000 (PEG 6000) in the laboratory. The experiment was repeated in the greenhouse using pot screening. The experimental design was an alpha lattice with 10 entries × 20 blocks in two replications. Four treatments (0 g/L, 115 g/L, 235 g/L, 289 g/L) were applied in the laboratory: one control and three concentrations of PEG 6000. Control and stress were applied in the greenhouse. Data were collected on germination rate and growth parameters, including root and seedling length, leaf length and width, and chlorophyll content. Results revealed significant differences among the pearl millet inbred lines under both drought and well-watered conditions. The inbred lines IP-16403 and IP-18062 were the most tolerant in both the greenhouse and laboratory. Water stress significantly reduced plant growth, although an increase in root length was observed in some lines. The number of days to 50% emergence was positively and strongly correlated with survival time (+0.45), while leaf width was negatively correlated with survival time (−0.29) and water stress tolerance (−0.37). The drought-tolerant and drought-susceptible pearl millet inbred lines identified in this study provide valuable genetic resources for enhancing pearl millet productivity in arid and semi-arid environments, especially in the face of unpredictable climate variability. Full article

The Sahel Transboundary Taoudéni Basin, covering about 20% of Burkina Faso, hosts vital aquifers critical for water security and development. Effective groundwater monitoring is essential for sustainable resource management. In the Kou sub-basin, groundwater quality assessment is increasingly important. This study integrates hydrochemistry, water stable isotopes (δ¹⁸O, δ²H), GIS, and multivariate statistics to understand subsurface geochemical processes. A total of 48 samples—43 groundwater and 5 surface water—were analyzed for 19 hydrochemical parameters and isotopes. In surface water, δ¹⁸O ranged from −5.96‰ to −5.09‰, and δ²H from −37.65‰ to −29.15‰. In groundwater, δ¹⁸O ranged from −5.93‰ to −4.39‰, and δ²H from −34.62‰ to −25.05‰. The spatial distribution of δ¹⁸O and δ²H was mapped using inverse distance weighted (IDW) interpolation in ArcGIS 10.8. A δ²H vs. δ¹⁸O plot showed groundwater values clustered near the Global Meteoric Water Line, indicating minimal evaporation during recharge. Groundwater chemistry was dominated by Ca²⁺ > Na⁺ > Mg²⁺ > K⁺ and HCO₃⁻ > NO₃⁻ > Cl⁻ > SO₄²⁻. Key hydrogeochemical processes include water–rock interaction (leaching, weathering, ion exchange) and anthropogenic pollution. Isotopic signatures reveal heterogeneous recharge sources and aquifer connectivity. These findings enhance the understanding of water sources and geochemical processes in the Kou basin, supporting informed groundwater resource management. Full article

Accurate sub-seasonal-to-seasonal (S2S) forecasts are critical for mitigating extreme weather impacts and supporting development in West Africa. This study evaluates real-time ECMWF S2S rainfall forecasts during the 2020–2021 West African monsoon (March–October) and uses corresponding hindcasts for comparison. We verify forecasts at 1–4 dekads lead against two satellite-based rainfall datasets (TAMSAT and GPM-IMERG) to cover observational uncertainty. The analysis focuses on spatio-temporal monsoon patterns over the Gulf of Guinea (GoG) and Sahel (SAH). The results show that ECMWF-S2S captures key monsoon features. The forecast skill is generally higher over the Sahel than the GoG, and peaks during the main monsoon period (July–August). Notably, forecasts achieve approximately 80% synchronization with observed rainfall-anomaly timing, indicating that roughly 4 out of 5 dekads have correctly predicted wet/dry phases. Probabilistic evaluation shows strong reliability. The debiased ranked probability skill score (RPSS) is high across thresholds, whereas the average ROC AUC (~0.68) indicates moderate discrimination. However, forecasts tend to under-predict very low rains in the GoG and very high rains in the Sahel. Using multiple datasets and robust metrics helps mitigate observational uncertainty. These results, for the first real-time S2S pilot over West Africa, demonstrate that ECMWF rainfall forecasts are skillful and actionable (especially up to 2–3 dekads ahead), providing confidence for early-warning and planning systems in the region. Full article

Seasonal malaria chemoprevention (SMC) is a strategy recommended by the World Health Organization for children aged 3–59 months in the Sahel and sub-Sahel regions where malaria transmission is seasonal. In Côte d’Ivoire, malaria remains a high priority and accounts for the majority of consultations and deaths in children under five. The recent revision of the criteria for the introduction of seasonal malaria chemoprevention has made the north of Côte d’Ivoire, where malaria transmission is seasonal, eligible for the SMC. We conducted a pilot study in this part of the country to assess the acceptability and feasibility of five cycles of SMC in 1701 children. Seasonal malaria chemoprevention with sulfadoxine–pyrimethamine + amodiaquine (SP + AQ) was administered monthly to eligible children over five months. A qualitative approach and quantitative surveys were used to assess the strategy acceptability and feasibility in the study area. Overall, there was a positive perception, attitude, and adherence towards the seasonal malaria chemoprevention in this study area. Full article

This study evaluates the impact of sub-daily bias correction of gridded rainfall products (RPs) on the estimation rainfall erosivity in Burkina Faso (West African Sahel). Selected RPs, offering half-hourly to hourly rainfall, are assessed against 10 synoptic stations over the period 2001–2020 to appraise their accuracy. The optimal product (the integrated multi-satellite retrievals for GPM, IMERG) is further used as a reference for bias correction, to adjust the rainfall distribution in the remaining RPs. RPs-derived rainfall erosivity is compared to the global rainfall erosivity database (GloREDa) estimates. The findings indicate that bias correction improves the rainfall accuracy estimation for all RPs, in terms of quantitative, categorial metrics and spatial patterns. It also improved the distributions of rainfall event intensities and duration across all products, which further significantly improved the annual rainfall erosivity estimates at various timescales along with spatial patterns across the country, as compared to raw RPs. The study also highlights that bias correction is effective at aligning annual trends in rainfall with those in rainfall erosivity derived from RPs. The study therefore underscores the added value of bias correction as a practice for improving the rainfall representation in high-resolution RPs before long-term rainfall erosivity assessment, particularly in data-scarce regions vulnerable to land degradation. Full article

This study implemented and assessed, over a period of four weeks, a full-scale constructed wetland designed to collect and treat the greywater for a rural household located in an arid environment typical of Africa’s Sahel region. The system was constructed from local materials and consisted of a shower room, a receiving basin, a pre-treatment filter, and a subsurface horizontal flow wetland planted with Chrysopogon zizanioides. Results showed the overall removal of organic matter was greater than 90%, and orthophosphate and ammonium were reduced by 73% and 60%, respectively, allowing for the treated water to retain some embedded nutrients. The removal efficiency of fecal bacteria varied from 3.41 (enterococci) to 4.19 (fecal coliforms) log10 units which meets World Health Organization Guidelines for restricted irrigation. Our assessment of the full-scale household constructed wetland technology adds to the relatively low number of constructed wetland studies conducted outside a laboratory setting. Furthermore, it supports efforts to promote safe reuse of an underutilized resource at the rural household level in Sub-Saharan Africa and other arid regions in the developing world, supporting prospects for using treated greywater for agricultural reuse in regions that experience water scarcity, climate variability, and land degradation. Full article

Sub-Saharan African farmers have long been portrayed with very negative representations, at least since the beginning of coordinated European colonialism in the late 19th century. In the Sahel-Sudan area, agrosystems have been described as overgrazed, forests as endangered, and soils as overexploited, with local and traditional “archaic” practices. Against this background, the objective of this article is to focus on these agrosystems’ resilience, for which several criteria have been monitored. The approach used in this research was to synthesize observations from a large amount of material gathered over multiple years by the authors, drawing on our long-term commitment to, and inter-disciplinary study of, the evolution of surface hydrology, ecosystems, and agrosystems of West Africa. The positive trends in rainfall and streamflows, reinforced by farmer’s practices, confirm the overall regreening and reforestation of the Sahel-Sudan strip, especially in areas with high population densities, including the mangrove areas. The intensification of agricultural systems and the recovery of the water-holding capacity of soils and catchments explain the recorded general increase in terms of food self-sufficiency in the Sahel, as well as in crops yields and food production. Finally, we compare the neo-Malthusian discourse to the actual resilience of these agrosystems. The article concludes with a recommendation calling for the empowerment of smallholder farmers to take greater advantage of the current wet period. Overall, the speed of change in knowledge and know-how transfer and implementation, and the farmers’ ability to adapt to ecological and economic crises, must be highlighted. Far from being resistant to change, West African agriculturalists innovate, experiment, borrow, transform, and choose according to their situation, projects, and social issues. Full article

The atmosphere of southern West Africa (SWA) is one of the world’s most aerosol-laden regions. This study investigated the seasonal variability of aerosol optical thickness using photometric and CALIPSO/CALIOP observations. The mean daily aerosol optical thickness (AOD) at 550 nm over the 11 AERONET stations in SWA ranged from 0.35 in the Sahel area to 0.49 in the Guinea coast area and a maximum of 0.53 observed in the Savanna area. The AERONET and CALIOP observations reveal a seasonal variability of AOD that is comparable across all sub-regions studied. The seasonal variation of the AOD spectral dependency was related to the change in the occurrence of the CALIOP-derived aerosol types, and in particular to the contribution of dust to the AOD. We also observed a north–south gradient of 2 km in the mean extinction height of the dust layer, being at 4 km and 6 km high in the Sahel and Guinea areas, respectively. This gradient is attributed to the northward migration of the monsoon flow. Full article

The Anomaly hotSpots of Agricultural Production (ASAP) Decision Support System was launched operationally in 2017 for providing timely early warning information on agricultural production based on Earth Observation and agro-climatic data in an open and easy to use online platform. Over the last three years, the system has seen several methodological improvements related to the input indicators and to system functionalities. These include: an improved dataset of rainfall estimates for Africa; a new satellite indicator of biomass optimised for near-real-time monitoring; an indicator of crop and rangeland water stress derived from a water balance accounting scheme; the inclusion of seasonal precipitation forecasts; national and sub-national crop calendars adapted to ASAP phenology; and a new interface for the visualisation and analysis of high spatial resolution Sentinel and Landsat data. In parallel to these technical improvements, stakeholders and users uptake was consolidated through the set up of regionally adapted versions of the ASAP system for Eastern Africa in partnership with the Intergovernmental Authority on Development (IGAD) Climate Prediction and Applications Centre (ICPAC), for North Africa with the Observatoire du Sahara et du Sahel (OSS), and through the collaboration with the Angolan National Institute of Meteorology and Geophysics (INAMET), that used the ASAP system to inform about agricultural drought. Finally, ASAP indicators have been used as inputs for quantitative crop yield forecasting with machine learning at the province level for Algeria’s 2021 and 2022 winter crop seasons that were affected by drought. Full article

A growing body of evidence suggests that the COVID-19 pandemic affected not only the functioning of food supply chains but also the performance and outcomes of agri-food systems. In this context, this paper analyses the scholarly literature dealing with the impacts of the pandemic on West African agriculture and food systems. A search carried out on the Web of Science in March 2023 returned 176 records and 87 eligible documents were included in the systematic review. The bibliometric analysis suggests a decreasing interest in the research field. Moreover, a large share of the eligible articles are authored by researchers based outside West Africa. There is a research gap, especially in Cabo Verde, Ivory Coast, Gambia, Guinea, Guinea-Bissau, Mauritania, Niger and Togo. Studies focus on the crop production subsector and consumption stage. The pandemic affected all four dimensions/pillars of food security (viz. availability, access, utilisation/use, and stability). However, most of the analysed documents focus on food access (economic accessibility and physical accessibility). Moreover, COVID-19 affected all the dimensions of agri-food systems (viz. environmental, economic, social, and political) but the analysed articles focus on the pandemic’s socio-economic impacts, especially those relating to food security and health. The promotion of research on the impacts of the pandemic on agri-food systems in West Africa is paramount to designing the evidence-based policies needed to improve the preparedness of the region for current and future crises and shocks. Full article