Sahel

See also Sahel, Tunisia, a region of eastern Tunisia, and Sahel (Eritrea), a former province of Eritrea.

The Sahel highlighted in brown. This is roughly the African land area between the lines of 200mm (north) and 600mm (south) mean 20th century annual rainfall. This is limited to land areas directly to the south of the Sahara desert and including the islands of Cape Verde, but not including other areas in Africa with the same rainfall statistics. This is one, but not the only, definition of the Sahel region.

The Sahelian Acacia savanna highlighted in orange. This is the Sahel defined not simply by rainfall, but by Ecoregion: a characteristic, geographically distinct assemblage of natural communities and species. In this case, the Sahel is defined by Acacia tree punctuated grasslands.

The Sahel or Sahel Belt (from Arabic ساحل, sāḥil, shore, border or coast of the Sahara) is a semi-arid tropical savanna and steppe ecoregion in Africa, which forms the transition between the Sahara to the north and the slightly less arid savanna belt to the south, known as the Sudan (not to be confused with the country of the same name).

Vegetation in the Sahel follows seasonal rainfall. In March, during the dry season, rainfall and lush vegetation don’t extend north of the Gulf of Guinea. September brings rain and vegetation into the Sahel as far north as the northern edge of Lake Chad.

Photographs from Senegal show the difference in vegetation between the dry (left) and wet (right) seasons.

Geography

Camels trample the soil in the semiarid Sahel as they move to water holes such as this one in Chad.

The lush green of the rainy season Sahelian forest, along the Bamako-Kayes Road in Mali. Trees in foreground are Acacia, note the large Baobab tree

The Sahel runs 2,400 miles (3862 km) from the Atlantic Ocean in the west to the Red Sea in the east, in a belt that varies from several hundred to a thousand kilometers (620 miles) in width, covering an area of 3,053,200 square kilometers (1,178,800 square miles). It is a transitional ecoregion of semi-arid grasslands, savannas, steppes, and thorn shrublands lying between the wooded Sudanian savanna to the south and the Sahara to the north. The countries of the Sahel today include Senegal, Mauritania, Mali, Burkina Faso, Niger, Nigeria, Chad, Sudan, and Eritrea.

The topography of the Sahel is mainly flat, and the region mostly lies between 200 and 400 meters elevation. Several isolated plateaus and mountain ranges rise from the Sahel, but are designated as separate ecoregions because their flora and fauna are distinct from the surrounding lowlands.

Over the history of Africa the region has been home to some of the most advanced kingdoms benefiting from trade across the desert. Collectively these states are known as the Sahelian kingdoms.

Flora and fauna

The Sahel is mostly covered in grassland and savanna, with areas of woodland and shrubland. Grass cover is fairly continuous across the region, dominated by annual grass species such as Cenchrus biflorus, Schoenefeldia gracilis, and Aristida stipoides. Species of Acacia are the dominant trees, with Acacia tortilis the most common, along with Acacia senegal and Acacia laeta. Other tree species include Commiphora africana, Balanites aegyptiaca, Faidherbia albida, and Boscia senegalensis. In the northern part of the Sahel, areas of desert shrub, including Panicum turgidum and Aristida sieberana, alternate with areas of grassland and savanna. During the long dry season, many trees lose their leaves, and the predominantly annual grasses die.

The Sahel was formerly home to large populations of grazing mammals, including the Scimitar-horned Oryx (Oryx dammah), Dama Gazelle (Gazella dama), Dorcas Gazelle (Gazella dorcas) and Red-fronted Gazelle (Gazella rufifrons), and Bubal Hartebeest (Alcelaphus busephalus buselaphus), along with large predators like the African Wild Dog (Lycaon pictus), Cheetah (Acinonyx jubatus), and Lion (Panthera leo). The larger species have been greatly reduced in number by over-hunting and competition with livestock, and several species are vulnerable (Dorcas Gazelle and Red-fronted Gazelle), endangered (Dama Gazelle, African Wild Dog, cheetah, lion), or extinct (the Scimitar-horned Oryx is probably extinct in the wild, and the Bubal Hartebeest is extinct).

The seasonal wetlands of the Sahel are important for migratory birds moving within Africa and on the African-Eurasian flyways.