The Sahel and Its Environmental Pressures

The Sahel is a semi-arid transitional belt roughly 1,000 kilometers wide and nearly 6,000 kilometers long, stretching from the Atlantic coast of Senegal and Mauritania eastward through Mali, Burkina Faso, Niger, northern Nigeria, and Chad to Sudan and Eritrea on the Red Sea, marking the ecological gradient between the hyper-arid Sahara to the north and the wetter Sudanian savanna to the south. Its name derives from the Arabic sahil, meaning "shore" or "coast," an apt metaphor for a zone whose vegetation and rainfall shift dramatically from year to year at the desert's edge. Annual rainfall in the Sahel typically ranges from about 150 to 600 millimeters, concentrated in a short summer wet season driven by the seasonal northward shift of the Intertropical Convergence Zone, which makes agriculture and pastoralism in the region acutely sensitive to even modest shifts in the timing or volume of the rains.