Scientists are trying to make the deserts（沙漠)into good land(土地)again. They want to bring water to the desert, so people can live and grow food. They are learning a lot about the desert. But more and more of the earth is becoming deserts. Scientists think that people make deserts. People are doing bad things for the earth.

Some places on the earth don't get very much rain. But they still don't become deserts. Because some green plants are growing there. Some green plants and grass are very important to dry places. Plants don't let the hot sun make the earth very dry. Plants don't let the wind blow the dirt away. When a little of rain falls，the plants hold the water. Without (没有)plants, the land can become a desert much more easily.