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　　Scientists are trying to make the deserts into a good land again. They want to bring water to the deserts, so people can live and grow plants there. They are learning a lot about the deserts. But more and more of the earth is becoming deserts all the time. Scientists may not be able to change the deserts in time. Why is more and more land becoming deserts? Scientists think that people make deserts. People are doing bad things to the earth. Some places on the earth don't get very much rain. But they still don't let the hot sun make the earth even drier. Plants don't let the wind blow the dirt away(吹跑). When a little bit of rain falls, the plants hold the water. Without plants, the land can become desert much more easily.