Home › Regions › Physiographic Regions
The Sahel
The semi-arid belt where the Sahara frays into savanna
Rain decides everything here. Along a belt some 5,400 kilometers long, running from the Atlantic shore of Senegal to the Red Sea hills of Sudan, the Sahara does not stop so much as fade: sand gives way to thorn scrub, thorn scrub to grass, grass to the wooded savanna of the tropics. The Sahel is that fade. Its boundary is drawn not by treaties but by rainfall lines, and those lines migrate. A run of wet years pushes the grass north and the herders follow; a run of dry ones pulls it back and the herds die. Roughly 135 million people farm, graze, and trade along this shifting seam, and their fortunes turn on a few centimeters of summer rain.
Geographers usually define the Sahel by isohyets, the lines of equal rainfall between about 150 and 600 millimeters a year, which is why no two maps of it agree. It spans Senegal, Mauritania, Mali, Burkina Faso, Niger, Nigeria, Chad and Sudan, and by some readings Eritrea. The Sahara is its northern wall; the Sahel is the transition below it, and the two should not be confused. The land is mostly flat, ancient, and sand-covered, broken by the volcanic Air massif of Niger, where Mont Idoukal-n-Taghes reaches 2,022 meters. The Niger River swings through in a great inland delta, and Lake Chad, once a small sea, has shrunk drastically since the 1960s.
The Sahel was long a corridor of wealth rather than a periphery. Caravans of salt and gold crossed it, and the empires of Ghana, Mali and Songhai grew rich taxing that traffic, endowing Timbuktu with libraries while Europe was still copying manuscripts by candlelight. Today the region is better known for hardship. The great droughts of the 1970s and 1980s killed livestock and people alike, and jihadist insurgency, coups and mass displacement have since unsettled Mali, Burkina Faso and Niger. Yet the picture is not uniformly bleak. Satellite records show large tracts regreening where farmers protect natural regrowth, and the Great Green Wall initiative aims to restore degraded land across the belt. What happens here shapes migration and food security far beyond Africa.