Sahel

For other uses, see Sahel (disambiguation).

The Sahel region: a belt up to 1,000 km (620 miles) wide that spans Africa from the Atlantic Ocean to the Red Sea.

The Sahel^[p] is the ecoclimatic and biogeographic zone of transition between the Sahara desert in the North and the Sudanian Savannas in the south, having a semi-arid climate. It stretches across the north of the African continent between the Atlantic Ocean and the Red Sea. The Arabic word sāḥil (ساحل) literally means "shore, coast" as describing the appearance of the vegetation of the Sahel as a coastline which delimits the sand of the Sahara.

The Sahel covers parts of (from west to east) Senegal, southern Mauritania, central Mali, southern Algeria and Niger, central Chad, southern Sudan, northern South Sudan and Eritrea.

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), red-fronted gazelle (Gazella rufifrons), the giant prehistoric buffalo (Pelorovis) 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 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 Sahelian climate is a tropical semi-arid climate with the dry season mainly (but not exclusively) during the "cold" season (the coldest six months of the year) :

- tropical because the mean monthly temperature of the "coldest" month is equal or superior to 18°C.

- semi-arid because of low annual precipitation, inferior to about 600 mm in a tropical climate (and superior to about 100-150 mm), characterised by irregular and unpredictable short rainy seasons through the years. The dry season generally lasts from about 8 to 11 months a year.

Though erratic the rainy season in a Sahelian climate zone usually occurs during the warm season but not during the very hottest months.

For instance the mean annual precipitation in Khartoum, 156.8 mm, is distributed as follows: 151.3 mm during the "warm" season (warmest six months of the year, April to September), and only 5.5 mm during the "cold" season (the coldest six months, October to March). Therefore 96.5 % of the precipitation drop during the "warm" season. In the latter the hottest months are May and June with however only 0.9 and 1.2 mm respectively of precipitation : the rainy season occurs later in the warm season, from July to September with August being the single truly wet month (according to F. Bagouls and Henri Gaussen definition which considers that a month is wet when P (mean monthly precipitation in mm) > 2 T (mean monthly temperature in °C)).

A subdivision often adopted for the Sahelian climate is as follows :

- The Saharan-Sahelian climate, with a mean annual precipitation between around 100 and 200 mm (Khartoum)

- The strict Sahelian climate, with a mean annual precipitation between around 200 and 400 mm (Kiffa)

- The sahelian-sudanese climate, with a mean annual precipitation between around 400 and 600 mm (Niamey)

The Sahelian climate, with variations, in a) the north-central Australia and more precisely in the north of the Great Sandy Desert in (the Pilbara region : Marble Bar, Port Hedland, and in the north of the Tanami Desert to Tennant Creek), b) the southern Sindh around Karachi, and c) in a small region where the states of Pernambuco, Ceará, Piauí, and Bahia meet in the continental northeast of Brazil.

Since the thresholds values of semi-aridity here (100-200 to 600 mm) are clearly lower than in the Köppen climate classification (390 to 780 mm for stations with mean annual temperature of 25°C and dry season centered in "winter", and even 440 to 880 mm at 30°C), the tropical semi-arid Sahelian climate, incidentally the hottest climate on Earth, is on the borderline of Köppen's hot semi-arid climates (BSh) and Köppen's hot arid climates (BWh).

History

Early agriculture

The first instances of domestication of plants for agricultural purposes in Africa occurred in the Sahel region circa 5000 BC, when sorghum and African rice began to be cultivated^{[citation needed]}. Around this time, and in the same region, the small Guineafowl were domesticated.

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 rather significantly and caused increasing desertification. This, in turn, decreased the amount of land conducive to settlements and helped to cause migrations of farming communities to the more humid climate of West Africa.

Sahelian kingdoms

Main article: Sahelian kingdom

The Sahelian kingdoms were a series of monarchies centered in the Sahel, between the 9th and 18th centuries. Their wealth of the states came from controlling the Trans-Saharan trade routes across the desert, especially the slave trade with the Islamic world. 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 also quite decentralized with member cities having a great deal of autonomy. The first large Sahelian kingdoms emerged after AD 750, and supported several large trading cities in the Niger Bend region, including Timbuktu, Gao, and Djenné.

The Sahel states were limited from expanding south into the forest zone of the Ashanti and Yoruba as mounted warriors were all but useless in the forests and the horses and camels could not survive the heat and diseases of the region.

Colonial period

The western Sahel fell to France in the late 19th century, as part of French West Africa. Chad was added in 1900 as part of French Equatorial Africa. The French territories were decolonialized in 1960.

The eastern Sahel (the part in what is now Sudan) did not fall to the European powers but was annexed by Muhammad Ali of Egypt in 1820. It came under British administration as part of the Sultanate of Egypt in 1914. The Sudanese Sahel became part of independent Sudan in 1956 and entered a lasting period of political instability and warfare, still ongoing in the War in Darfur.

The extreme east of the Sahel came under Italian control as Italian Eritrea in 1890. Eritrea was annexed by Haile Selassie of Ethiopia in 1962, and became independent in 1993, after the long Eritrean War of Independence.

Recent droughts

Further information: Sahel drought

For hundreds of years, the Sahel region has experienced regular droughts and megadroughts. One megadrought, from 1450 to 1700, lasted 250 years. There was a major drought in the Sahel in 1914, caused by annual rains far below average, that caused a large-scale famine. From 1951 to 2004, the Sahel experienced some of the most consistent and severe droughts in Africa. The 1960s saw a large increase in rainfall in the region, making the northern drier region more accessible. There was a push, supported by governments, for people to move northwards. As the long drought-period from 1968 through 1974 began, the grazing quickly became unsustainable, and large-scale denuding of the terrain followed. Like the drought in 1914, this led to a large-scale famine, but this time it was somewhat tempered by international visibility and an outpouring of aid. This catastrophe led to the founding of the International Fund for Agricultural Development.

Main article: 2010 Sahel drought

In June to August, 2010, famine struck the Sahel. Niger's crops failed to mature in the heat, and famine occurred. 350,000 faced starvation, and 1,200,000 were at risk of famine. In Chad, the temperature reached 47.6 °C (117.7 °F) on June 22 in Faya-Largeau, breaking a record set in 1961 at the same location. Niger tied its highest temperature record set in 1998, also on June 22, at 47.1°C in Bilma. That record was broken the next day, when Bilma hit 48.2 °C (118.8 °F). The hottest temperature recorded in Sudan was reached on June 25, at 49.6 °C (121.3 °F) in Dongola, breaking a record set in 1987. Niger reported on July 14 that diarrhea, starvation, gastroenteritis, malnutrition, and respiratory diseases had sickened or killed many children. The new military junta appealed for international food aid and took serious steps to call on overseas help. On July 26, the heat reached near-record levels over Chad and Niger, and about 20 had reportedly died in northern Niger of dehydration by July 27.

Desertification and soil loss

Over-farming, over-grazing, and over-population of marginal lands and natural soil erosion have caused serious desertification of the region.

Major dust storms are a frequent occurrence, as well. During November 2004, a number of major dust storms hit the Chad, originating in the Bodélé Depression. This is a common area for dust storms (occurring, on average, 100 days every year).

On 25 August 2008, heavy dust storms passed over the eastern plains of Somalia and the northeast of a still drought-hit Kenya. On March 23, 2010, a major sandstorm hit Mauritania, Senegal, the Gambia, Guinea Bissau, Guinea, and inland Sierra Leone. Another struck in southern Algeria, inland Mauritania, Mali, and northern Côte d’Ivoire at the same time.

See also

Community of Sahel-Saharan States Epidemiology Green Sahara Maghreb region of North-Western Africa 2010 Sahel famine 2012 Sahel drought Sahel drought

Sudan (region) Sudanian Savanna Pan Sahel Initiative Sahara Conservation Fund Semi-arid climate Trans-Sahelian Highway

References

[p] ^ The word "Sahel" is pronounced as "suh-Hail" or "suh-Heel".

• Azam (ed.), Conflict and Growth in Africa: The Sahel, Organisation for Economic Co-operation and Development (1999), ISBN 92-64-17101-0.
• (French) Lagha CHEGROUCHE, "L'arc géopolitique de l'énergie : le croissant énergétique, in Le Soir d'Algérie, 19/12/2010 hi

Further reading

• Dai, A.; Lamb, P.J.; Trenberth, K.E.; Hulme, M.; Jones, P.D.; Xie, P. (2004). "The recent Sahel drought is real". International Journal of Climatology 24 (11): 1323–1331. doi:10.1002/joc.1083 .
• Moseley, W.G. 2008. “Strengthening Livelihoods in Sahelian West Africa: The Geography of Development and Underdevelopment in a Peripheral Region.” Geographische Rundschau International Edition, 4(4): 44-50. http://works.bepress.com/cgi/viewcontent.cgi?article=1069&context=william_moseley
• Simon, L., A. Mattelaer and A. Hadfield (2012) "A Coherent EU Strategy for the Sahel". Brussels: European Parliament (DG for External Policies).

External links

• "Sahelian Acacia savanna". Terrestrial Ecoregions. World Wildlife Fund. 
• World Wildlife Fund (2001). "Sahelian Acacia savanna". WildWorld Ecoregion Profile. National Geographic Society. Archived from the original on 2010-03-08. 
• rain4sahara.org: Rain for the Sahel and Sahara