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The Sahel (from Arabic ساحل sahil for shore or border) is the boundary zone in Africa between the Sahara to the north and the more fertile region to the south, known as the Sudan (not to be confused with the country of the same name).
The term was first used as a phytogeographical term, referring to the band of land between 75 and 450 isohyets (bands of precipitation). Subsequent researchers have referred to a wide range of isohyets in determining the location of the Sahel. It has also been used to refer to the countries of West-Africa .
The Sahel is primarily savanna and runs from the Atlantic Ocean to the Horn of Africa, changing from semi-arid grasslands to thorn savanna . 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.
A map of the region can be viewed here.
About 12,500 years ago, the Sahel was a part of the Saharan desert, and was covered in sand dunes which have shaped the landscape that we see today. The Sahel receives 150-500 mm (6-20 in) of rainfall a year, primarily in the monsoon season. The rainfall is characterized by year to year and decadal variability. The two largest determinants of land productivity in the Sahel are water and micro-nutrients , mostly nitrogen and phosphate.
There is a strong correlation between rainfall in the Sahel and intense hurricane activity in the Atlantic.
Traditionally, most of the people in the Sahel have been semi-nomads , farming and raising cattle in a system of transhumance, which is probably the most sustainable way of utilizing the Sahel. The difference between the dry north with higher levels of soil-nutrients and the wetter south is utilized so that the herds graze on high quality feed in the North during the wet season, and trek several hundred kilometers down to the south, to graze on more abundant, but less nutritious feed during the dry period.
There was a major drought in the Sahel in 1914, caused by a annual rains far below average, that caused a large-scale famine. The 1960's 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, and as the long drought-period from 1968-1974 kicked in, the grazing quickly became unsustainable, and large-spread 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 catastrophy lead to the founding of the International Fund for Agricultural Development.
External links and references
- Notes on Sahel Africa
- Landsea, C., and Gray, W. The Strong Association between Western Sahel Monsoon Rainfall and Intense Atlantic Hurricanes. Journal Of Climate, Vol. 5, No. 5, May 1992
- Sahel rainfall index, 1898 - 2002
- Desertification - a threat to the Sahel
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