The top soil in the Sahel was ruined by _____ .

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions .

From Farmland to Desert

It doesn't take long lo turn farmland into desert. American farmers found this out in the 1930s. They planted wheat in large areas of grassland in the south central United States. For a few years there was plenty of rain and lots of wheat. Then the rains stopped, as they often do in this dry region. The wheat dried up and the top soil tumed to dust. Before long, it had all blown away in great dust storms. The area became known as the "Dust Bowl".

What happened in the Dust Bowl is a perfect example of erosion caused by modern farming methods. Top soil blows away more easily when it is no longer protected by grasses or trees. In ten years or less, several feet of good soil can disappear. And once it is gone, there is no way to get it back quickly. It may takefrom one hundred to a thousand years for new top soil to form.

Unfortunately, it seems that farmers have not learned from the example of the Dust Bowl. In the United States alone, five billion tons of top soil are lost every year. Farmers continue to use the same destructive methods. They plant the same crops and use tons of chemical fertilizers.

The situation in other parts of the world is even more serious. The total loss of top soil worldwide is 24 billion tons a year. Areas of the earth with a dry dimate (about one third of the planet) are hit worst. In these areas, about 12 million hectares of land are lost to agriculture per year because of erosion.

In developing countries, this often leads to hunger and death. The recent history of one part of Africa, the Sahel, is a good example. In the 1960s and 1970s much good farmland was taken over for export crops, such as sugar and cotton. Many people moved into the drier interior areas to grovv their food.During that period, there was more rain than usual. Food and cattle production increased and so did the population.

Before long, there were too many people in these areas. The land began to suffer the effects. It was no longer protected by trees, which had been cut down for fírewood. The grass and bushes were gone, eaten by the eattle, sheep, and other animals. Animal manure was used for burning instead of for fertilizing the soil.

Then came a long period of no rain. The ruined top soil quickly blew away. The Sahara Desert advanced in some areas as much as 100 kilometers. In other areas, the semi-desert land became completely unproductive. Now millions of people have no way to make a living. Many have died of hunger, while others have moved to the already crowded cities.

The events in the Sahel were an important lesson for government officials and farmers around the world. But again, the lesson has been ignored. More and more people are hungry on our planet, but farmland continues to be ruined.

Câu 13872: The top soil in the Sahel was ruined by _____ .

A. the plantins of export crops.

B. the effects of too many people and animals.

C. too much manure from cattle and sheep.

D. too much rain for too many years.

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Câu hỏi : 13872

Đáp án : B
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