The history of life on earth has been a history of interaction between living things and their surroundings.To a large extent, the physical form and the habits of the earth's vegetation and its animal life have been molded by the environment.Considering the whole span of earthly time, the opposite effect, in which life actually modifies its surroundings,has been relatively slight.Only in the present century has one species--man acquired significant power to alter the nature of his world.

　　地球上生命的历史一直就是一部生物与其环境相互作用的历史。在很大程度上，地球上动植物的形态以及习性都是由外部环境所塑造的。考虑到地球上生命存在的整个时间，相反作用——即生命对其周围环境的实际改变作用一却相对很小。只有在当前这个世纪才有一个物种——人类，获得了强大的力量，改变了其所生存的世界的自然状态。