There are other possible causes including increased population of nomads and cultivating unsuitable crops for export. The whole area is suffering an ecological disaster.
In most of these countries the nomadic herders of cattle, camels, sheep and goats - the Fulani and Tuareg - have had to leave their traditional way of life. In Mauritania many of them are camped outside the towns, destitute. Many of the nomads have moved to Nigeria and other countries south of the area of drought.
Traditionally this was the country of the horsemen who ruled the ancient empires of Ghana, Mali and Songhai and the Hausa-Fulani states of northern Nigeria, Niger and Chad. Timbuktu, the center of Islamic learning, was found in this area (in modern Mali). Mansa Musa the king of Mali caused astonishment at his wealth when he visited Cairo on his way to the Makkah pilgrimage in 1324. Thus its modern condition of poverty is a great decline from a glorious past. There was trade in gold from the area of modern Ghana (not the same as ancient Ghana) and also salt. The gold reached Europe in Medieval times and was probably the main source of gold in Europe before the colonial expansion to the Americas. That expansion doomed the trade and caused the decline of these important cultures.
Islam spread along the trade routes which the camel caravans followed from the Red Sea to the Atlantic and north to the Mediterranean.
The long term future of this area is uncertain. If the world climatic change now believed to be underway results in the further drying out of the area, with even less rainfall, most of the population may have to move. But it is possible that rainfall may increase as rain belts from the south expand, in which case the area might be able to carry a larger agricultural population. So far, climate models show either change is possible. One model shows the more important influence to be a northerly push of the Monsoon type rainfall pattern, caused by increased temperatures in the Sahara. This would bring rain further north and more reliably. If this happens the area could support more people. However, in the past when rain moved north there was a greater difference between the temperatures of the north Atlantic and the equatorial waters. At present the north Atlantic is warming. So, a second model suggests that rain will not push north and the Sahel could actually become drier.
A speculative future for the area might be as a site for large scale solar energy if the necessary devices are produced cheaply enough. It is also possible that the current drought is part of a natural cycle and the rainfall will return.
Another theory is that the 1980s drought was caused by increased sulphur oxides in the higher atmosphere - something that has eased as a result of pollution controls in the western industrialised countries.
In 2002 the Journal of Climate published an astonishing proposition: that the great droughts which had devastated the Sahel region of Africa had been caused in part by sulphate pollution in Europe and North America. Our smoke, the paper suggested, was partly responsible for the famines that killed hundreds of thousands of people in the 1970s and 1980s. Sulphate emissions have declined since their peak, as coal and oil have been scrubbed of sulphur. From GuardianThere are signs (in Burkina Faso) that appropriate policy - building simple rain capture dams and tree planting - could restore at least part of the area.
July 2005 showed a serious drought throughout the area, especially in Niger. However, September 2007 has seen serious floods over the whole region. Could this be an example of the Monsoon extending further north as the Sahara borders move north?