earth-地球_600字

China, deep in the heart of the Gebi Desert, was once a great city.　

　　Cattle are one cause of the problem. In good years, famers increase the numbers of their cattle. Then one year, the rains fail to come. The farmers do not want to kill any of their　

cattle, so the cattle eat all the grass and anything that grows rains fail to come. The farmers do not want to kill any of their cattle, so the cattle eat all the grass and anything that grows on poorer land. If this continues for several years, the grass never grows again and the land becomes a desert. One suggested answer is for farmers to limit the numbers of their cattle.　

　　Another problem is that good soil is gradually lost. When trees are cut down, there is nothing to hold the soil in place on the hillside. So when if rains, the soil is washed down the hills and into the rivers. Strong winds can also blow away the valuable soil that lies on the top of the fields.　

　

　　世界上沙漠的面積每年都在擴大，許多地區曾經人口眾多，五穀豐登，而今卻成了沙漠。中國的敦煌曾經是一個大城市，而現在卻深深陷入戈壁灘的腹地。　

　　造成戈壁灘的原因之一是牲畜問題。年景好時，農民就增加牲畜飼養的頭數。後來有一年天沒有下雨，農民又不想把牲畜殺掉。因此，牲畜就把草和更加貧瘠的土地上所長的任何東西全都吃光。這種情況如果繼續幾年，那麼，草就再也長不出來了，土地也就變成了沙漠。有人提出的解決辦法是讓農民限制飼養牲畜的數量。　

　　另外一個問題就是沃土逐漸流失。樹木被砍伐了，山坡上就沒有什麼東西能夠把土壤保持住了。因此，下雨的時候，土壤從山上被沖刷下來，流到河裡去了。大風也可能把田地表面的肥沃土壤颳走。