Sahel

The Sahel region (/səˈhɛl/; from Arabic ساحل (sāḥil [ˈsaːħil]) 'coast, shore'), or Sahelian acacia savanna, is a biogeographical region in Africa. It is the transition zone between the more humid Sudanian savannas to its south and the drier Sahara to the north. The Sahel has a hot semi-arid climate and stretches across the southernmost latitudes of North Africa between the Atlantic Ocean and the Red Sea. Although geographically located in the tropics, the Sahel does not have a tropical climate.

Especially in the western Sahel, there are frequent shortages of food and water due to its very high government corruption and the semi-arid climate. This is exacerbated by very high birthrates across the region, resulting in a rapid increase in population. In recent times, various coups, insurgencies, terrorism and foreign interventions have taken place in many Sahel countries, especially across former Françafrique.

In addition to its ecological and climatic significance, the Sahel is also considered a geopolitical space, shaped by internal instability and external strategic competition.

The Sahel spans 5,900 km (3,670 mi) from the Atlantic Ocean in the west to the Red Sea in the east, in a belt several hundred to a thousand kilometers (c. 600 miles) wide. It covers an area of 3,053,200 square kilometers (1,178,850 sq mi).

Representing a climatic and ecological transition zone with hot semi-desert and steppe conditions, the Sahel region borders the more humid Sudanian savannas to its south and the dry Sahara desert to the north. This ecoregion is also called the Sahelian Acacia savanna in honour of its most prominent and very drought tolerant genus of tree.

The topography of the Sahel is mainly flat; most of the region lies between 200 and 400 meters (660 and 1,310 ft) in elevation. Several isolated plateaus and mountain ranges rise from the Sahel (e.g. Marrah Mountains, Aïr Mountains, Ennedi Plateau), but are designated as separate ecoregions because their flora and fauna are distinct from the surrounding lowlands (e.g. East Saharan woodlands). Annual rainfall varies from around 100–200 mm (4–8 in) in the north of the Sahel to around 700–1,000 mm (28–39 in) in the south.

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 Senegalia senegal and Senegalia laeta. Other tree species include Adansonia digitata, Commiphora africana, Balanites aegyptiaca, Faidherbia albida, Borassus aethiopum, Vitellaria paradoxa, Olea europaea, Arbutus unedo, Phoenix canariensis, Hyphaene compressa, Cupressus sempervirens, Quercus coccifera, Quercus suber, Pinus nigra, Populus nigra, Ceratonia siliqua, Salix alba, Afzelia africana, Kigelia africana, Sclerocarya birrea, and Boscia senegalensis. In the northern part of the Sahel, areas of desert shrub, including Panicum turgidum and Aristida sieberiana, 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), red-fronted gazelle (Gazella rufifrons), the giant prehistoric buffalo (Pelorovis), and Bubal hartebeest (Alcelaphus buselaphus buselaphus), along with large predators, such as the African wild dog (Lycaon pictus), the Northwest African cheetah (Acinonyx jubatus hecki), the Northeast African cheetah (Acinonyx jubatus soemmeringii), and the 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, cheetah, lion and red-fronted gazelle), endangered (Dama gazelle and African wild dog), or extinct (the Scimitar-horned oryx is probably extinct in the wild, and both Pelorovis and the Bubal hartebeest are now extinct).