语篇提能
阅读理解
A
It is only during the last few years that man has generally realized that in the world of nature a balance exists between all forms of life. No living thing can exist by itself: it is a part of a system in which all forms of life are joined together. If we change one part of the nature order, this will in its turn almost certainly bring about changes in some other part.
The cutting down of forests reduces the supply of oxygen.The killing of weeds and insects by chemicals leads to the widespread poisoning animals and birds.The throwing of the waste products into the ocean does harm to life in the sea, while waste gases change the chemical balance of the atmosphere.
And so we could go on, adding more examples, until in despair we might feel like giving up the struggle to control and keep within limits these harmful human activities. Man is very clever at changing the world around him to satisfy his immediate needs, but not so clever at looking far ahead, or at thinking about what the future results of his action might be.
1．The first paragraph mainly tells us that______.
