The Sahara covers the northern portion of the African continent, a vast area of sand dunes, rock and desolate gravel plain. For some time, the world’s largest desert has been growing. In North Africa, the average rate of advance is 5 kilometer per year. On the southern edge, drifting sand has encroached into the wetter Sahel region, which runs across Africa from the Atlantic to the Red Sea. Since 1900, the Sahara has grown by a total of about one million square kilometer.
The expansion of the Sahara is not unique. In many of the earth’s arid regions, once- fertile land is gradually being turned into desert. Scientists do not agree on the exact causes of this progressive desertification, but what is certain is that it affects many thousands of people each year. Some experts argue that desertification is caused by the over exploitation of natural resources by humans for example, by clearing natural vegetation for use as fuel or by allowing livestock to consume scarce vegetation.
As population growth continues in many poorer countries, such practices are likely to go on, and even to accelerate. How ever, there are other researchers, who argue that the expansion of the Sahara and other desert is a natural process, and is caused by climatic variations of the kind that have occurred frequently in the history of the earth.
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