Sahel (other)

The Sahel region (; ) 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''.

Geography

The Sahel spans 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 .

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 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 in the north of the Sahel to around in the south.

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 ''Senegalia senegal'' and ''Senegalia 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 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).

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

Climate

The Sahel has a tropical semi-arid climate ( Köppen climate classification ''BSh''). The climate is typically hot, sunny, dry and somewhat windy all year long. The Sahel's climate is similar to, but less extreme than, the climate of the Sahara desert located just to the north.

The Sahel mainly receives a low to very low amount of precipitation annually. The steppe has a very long, prevailing dry season and a short rainy season. The precipitation is also extremely irregular, and varies considerably from season to season. Most of the rain usually falls during four to six months in the middle of the year, while the other months may remain absolutely dry. The interior of the Sahel region generally receives between 200 mm and 700 mm of rain yearly. A system of subdivisions often adopted for the Sahelian climate based on annual rainfall is as follows: the Saharan-Sahelian climate, with mean annual precipitation between around 100 and 200 mm (such as Khartoum, Sudan), the strict Sahelian climate, with mean annual precipitation between around 200 and 700 mm (such as Niamey, Niger) and the Sahelian-Sudanese climate, with mean annual precipitation between around 700 and 900 mm (such as Ouagadougou, Burkina Faso). The relative humidity in the steppe is low to very low, often between 10% and 25% during the dry season and between 25% and 75% during the rainy season. The least humid places have a relative humidity under 35%.

The Sahel is characterized by constant, intense heat, with an unvarying temperature. The Sahel rarely experiences cold temperatures. During the hottest period, the average high temperatures are generally between (and even more in the hottest regions), often for more than three months, while the average low temperatures are around . During the "coldest period", the average high temperatures are between and the average low temperatures are between . Everywhere in the Sahel, the average mean temperature is over .

The Sahel has a high to very high sunshine duration year-round, between 2,400 hours (about 55% of the daylight hours) and 3,600 hours (more than 80% of the daylight hours). The sunshine duration in the Sahel approaches desert levels, and is comparable to that in the Arabian Desert, for example, even though the Sahel is only a steppe and not a desert. The cloud cover is low to very low. For example, Niamey, Niger has 3,082 hours of bright sunshine; Gao, Mali has near 3,385 hours of sunshine; Timbuktu, Mali has 3,409 sunny hours, and N'Djamena, Chad has 3,205 hours of sunlight.

Culture

Traditionally, most of the people in the Sahel have been semi- nomads, farming and raising livestock in a system of transhumance. The difference between the dry North with higher levels of soil nutrients and the wetter South with more vegetation, is utilized by having the herds graze on high-quality feed in the North during the wet season, and trek several hundred kilometers to the South to graze on more abundant, but less nutritious feed during the dry period.

In Western Sahel, polygamy and child marriage are common. Female genital mutilation is also practiced across the Sahel.

Etymology

The term "Sahel" is borrowed from the Arabic name for the region, '. ' literally means "coast, shore", which has been explained as a figurative reference to the southern edge of the vast Sahara. However, such use is unattested in Classical Arabic, and it has been suggested that the word may originally have been derived from the Arabic word ' "plain" instead.

History

Early agriculture

Around 4000 BC, the climate of the Sahara and the Sahel started to become drier at an exceedingly fast pace. This climate change caused lakes and rivers to shrink significantly and caused increasing desertification. This, in turn, decreased the amount of land conducive to settlements and caused migrations of farming communities to the more humid climate of West Africa.

Sahelian kingdoms

The Sahelian kingdoms were a series of monarchies centered in the Sahel between the 9th and 18th centuries. The wealth of the states, like the legendary Mali Empire at the time of Mansa Musa, came from controlling the trans-Saharan trade routes across the desert, especially with the Maghreb. Their power came from having large pack animals like camels and horses that were fast enough to keep a large empire under central control and were also useful in battle. All of these empires were quite decentralized with member cities having a great deal of autonomy.

The larger Sahelian kingdoms emerged from 750 AD and erected several large cities in the Niger valley

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