Can people create deserts?

Bordering the southern edge of the Sahara is a region called the Sahel. It extends from Mauritania and northern Senegal through Mail, Burkina Faso, Niger and Chad into Sudan. The Sahel has an average annual rainfall of between 100 and 400 mm (4-16in) and, in the past, it was grazing land.

From the 1960s, this zone has suffered droughts, so that over large areas all the plants have died and the Sahara has been advancing southwards by 10km (6 miles) or more a year. Droughts are only partly responsible for this disaster, in which millions of cattle and thousands of people have died of starvation. The people themselves have played a part by overgrazing the land, and removing shrubs and trees for use as firewood.