王志刚
許多年前,农民为保护他们的鸡而猎杀了很多老鹰。 然而新问题来了,田里的田鼠猖獗了起来,结果农民的庄稼大多给吃光了。这是怎么回事呢?看看下文你就知道了。
Not many years ago, some farmers were worried because hawks were taking many of their chicken. The farmers didnt know what to do. Finally they went to the country officials and asked for help.
“Kill the hawks,” the officials said,“ we will even pay for them. ” So the farmers began to think of ways to kill the hawks.
The farmers killed many hawks. They no longer had to worry about their chickens. But they now had a new worry. Field mice were eating up a lot of the farmers grain.
How did this happen?
Hawks ate not only chickens but also field mice. They ate more field mice than chickens. But the farmers didnt know this. When they killed a lot of hawks, they changed the balance.
When people move into a new place, they often destroy many wild plants. Often these plant are food for the animals. If the animals cant find enough plants to eat, they will starve or have to leave the place.
In one part of the USA, for example the deer there like to eat a certain kind of wild roses. The mountain lions there eat the deer. The number of deer, mountain lions and wild roses doesnt change much if people leave things as they are.
But people killed many mountain lions in order to protect the deer. Soon there were so many deer that they ate up all the wild roses. Then the deer began to eat the green leaves of young trees. These trees were important to the farmers. So the farmers thought of ways to protect their trees. Now the deer had nothing to eat, and many of them died. This was another lesson from nature.