英语听力教程第三版(张民伦主编)Unit 1 The Earth at Risk听力原文
B:That's right. We went to America, both North and South and then
we went over to Africa and Southeast Asia.
I: And what did you find in each of these continents?
B:Starting with Africa, our film shows the impact of the population on the environment. Generally speaking, this has caused the Sahara Desert to expand. It's a bit of a vicious circle we find. People cut down trees for firewood and their domestic animals eat all the available plants — and so consequently they have to move south as the Sahara Desert expands further south. I mean, soon the whole of Mali will become a desert. And in East Africa: here the grasslands are supporting too many animals and the result is, of course, there's no grass — nothing for the animals to eat.
I: I see. And the next film deals with North America?
B:That's right. In the USA, as you know, intensive agriculture requires a plentiful supply of rain for these crops to grow, I mean if there isn't enough rain the crops don't grow. And growing crops stabilize soil, without them the top soil just blows away. This is also true for any region that is intensely farmed — most of Europe, for example.