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This paper is a critical synthesis of the causes, effects and challenges of the Sahelian droughts. The results show that the four main causes of the Sahelian droughts are as follows: sea surface temperature changes, vegetation and land degradation, dust feedbacks and human-induced climate change. However, human-induced climate change is seen as the major drought-determining factor because it controls sea surface temperatures, dust feedbacks and vegetation degradation. Increase rainfall and greening have been observed in the Sahel since the 1990s; yet, food yields remain low while tree mortality rates are high. The implication of this is that the rainfall is not available for agriculture since various human-induced climate change processes such as deforestation and the expansions of arable farms do not make the moisture available for agriculture. The increase in tree mortality has also been found to increase atmospheric CO₂ in the study area. However, this study hypothesizes that the increase in CO₂ might be responsible for the increase in greening and rainfall observed. This can be explained by an increased aerial fertilization effect of CO₂ that triggers plant productivity and water management efficiency through reduced transpiration. Also, the increase greening can be attributed to rural–urban migration which reduces the pressure of the population on the land. The remittances from migrant urban workers may make farming more sustainable in the rural areas, thus enhancing greening. The principal challenges in overcoming the effects of the droughts are HIV/AIDS and Malaria, political instability, data availability, proliferation of extensive non-mechanized farms and lack of adequate observations.
