The second cause is misuse or over-use of the land. 　3　Ploughing(耕)large fields and removing bushes and trees mean that the wind will blow away the soil. Once the soil is lost, it is hard to replace, and if there is rain, it has nowhere to go, and brings no benefit.

　　　4　Every spring, the skies over some of eastern cities, thousands of kilometers away from the deserts, can be darkened by sandstorms. Dust from deserts can have a great effect on weather systems. While desertification is perhaps being partly caused by global warming, these sandstorms can make global warming worse by adding to what is known as the greenhouse effect.

　　What can be done to slow down or stop the process of desertification? A great deal of work is already under way. Obviously the first step is to find new water sources. 　5　Some types of grass also hold the soil together, and stop the wind taking it. Without these efforts, it will be harder and harder to stop the world’s deserts in their tracks, and more and more farmers will give up and head for cities. The lesson to be learnt lies beneath the sand.

　　A. It generally arises from two related causes.

　　B. It is not only the farmers and villagers who suffer.

　　C. They have been completely buried by the sand now.

　　D. Scientists are doing the research on the cause of desertification.

　　E. They destroy the land, as the soil dries out and is then blown away.

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