A 3,000-mile (5,000 km) band of semi-arid country extending across Africa south of the Sahara desert , the Sahel zone ("the shore" in Arabic) passes through Mauritania, Senegal, Mali, Burkina Faso, Niger, Chad, and the Cape Verde Islands. Similar semi-arid conditions prevail in Sudan, Ethiopia, and Somalia. These countries are among the poorest in the world. The low annual rainfall in this region is variable (4-20 in or 10-50 cm) and falls in a short, intense period in July and August. In some years the rains fail to develop, and droughts are a common occurrence. The uncertain rainfall of the Sahel makes it generally unfavorable for agriculture.
For centuries, the indigenous nomadic Tuareg people used the Sahel in a sustainable way, constantly moving herds of camels from one grazing area to the next; they practiced little agriculture. In the nineteenth and twentieth centuries, following European colonization, herds of water-dependent, non-native cattle were introduced, which were poorly suited to the arid conditions of the region. The above average rainfall of the 1950s and 1960s attracted large numbers of farmers and pastoralists into the Sahel, which placed new stresses on this fragile ecosystem . A series of droughts of the 1970s and 1980s in the Sahel resulted in episodes of large-scale starvation.
Studies of long-term climate patterns show that while droughts have been common in the Sahel for at least 2,500 years, the droughts of recent years have increased in frequency and duration. Records also show that the annual rainfall has decreased and that the sands of the Sahara have shifted some 60 miles (100 km) south into the region.
The causes of these changes have been linked to the expanding human settlement of the Sahel, with consequent increased demands on the area to produce more food and more firewood. These demands were met by increases in domestic animal herds and by more intensive agriculture. This in turn led to drastic reductions in vegetation cover. Land was cleared for farming and human settlements, vegetation was overgrazed, and large numbers of trees were cut for firewood. In this way, the natural vegetation of the Sahel (sparse, coarse grasses interspersed with thorn trees and shrubs) was dramatically altered and the ecosystem degraded.
Less vegetation cover meant more soil erosion and less groundwater recharge as heavy seasonal rainstorms hit exposed ground, carrying away valuable topsoil in flash floods. Less vegetation also meant more soil erosion from wind and rain, as there were fewer root systems to bind the soil together. In addition, fewer plants meant that less water was released into the air from their leaves to form rainmaking clouds. The net result of these processes was the trend towards less annual rainfall, more soil erosion, and desertification . Other reasons for famine and desertification in the Sahel include political events (such as prolonged civil wars) and social changes (such as the breakdown of the old sustainable tribal systems of using the land).
[Neil Cumberlidge Ph.D. ]
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