Through the changes'in the ways Of making a living in a family over several gen，erations， man has been warned against waste of natural resources and emphasizing the urgent need to preserve these resources。
Ever since man appeared on the earth， man's survival has been heavily relied on nature。 Almost everything we use in our everyday life comes fromm'notate， ranging from the food we eat， the water we drink， to the wood which is tm'ned into furniture。With the development of technology and population growth， the amount and range of materials used has increased at an alarming rate。
However， natural resources are not inexhaustible。 Some reserves are already on the brink of exhaustion and there is no hope of replacing them。 The widespread water shortage is an example in point。
If man continued to squander natural resources with no thought for the future， the later generations would be in danger。 It is up to us to take effective measures before the situation gets out of hand。