阅读下面短文，判断正误。
Not many years ago, some
farmers were worried because hawks ( 鹰)
were taking many of their chicken. The farmers didn't 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 cannot only
chickens but also field mice. They eat more field mice than chickens. But the
farmers didn't 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 plants are food for
the animals. If the animals can't 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 doesn't 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.
To keep the balance of
nature is important for us to remember.
