The balance of nature is a very elaborate and very delicate system of checks and counterchecks. It is continually being altered

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问题 The balance of nature is a very elaborate and very delicate system of checks and counterchecks. It is continually being altered as climates change, as new organisms evolve, as animals or plants permeate to new areas. But the alterations have in the past, for the most part, been slow, whereas with the arrival of civilized man, their speed has been multiplied manifold: from the evolutionary time-scale, where change is measured by periods of ten or a hundred thousand years, they have been transferred to the human time-scale in which centuries and even decades count.
Everywhere man is altering the balance of nature. He is facilitating the spread of plants and animals into new regions, sometimes deliberately, sometimes unconsciously. He is covering huge areas with new kinds of plants, or with houses, factories, slag-heaps and other products of his civilization. He exterminates some species on a large scale, but favours the multiplication of others. In brief, he has done more in five thousand years to alter the biological aspect of the planet than has nature in five million.
Many of these changes which he has brought about have had unforeseen consequences. Who would have thought that the throwing away of a piece of Canadian waterweed would have caused half the waterways of Britain to be blocked for a decade, or that the provision of pot cacti for lonely settlers’ wives would have led to Eastern Australia being overrun with forests of Prickly Pear? Who would have prophesied that the cutting down of forests on the Adriatic coasts, or in parts of Central Africa, could have reduced the land to a semi desert, with the very soil washed away from the bare rock? Who would have thought that improved communications would have changed history by the spreading of disease-sleeping sickness into East Africa, measles into Oceania, very possibly malaria into ancient Greece?

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答案 自然界的平衡是一个非常微妙又异常脆弱的破坏与反破坏的体系。这种平衡随着气候变化,新生物的进化,以及动植物向新领域的蔓延而不停地变化着。但这种变化在以前,或者说很久以前是缓慢的,随着人类文明的到来,变化的速度就急速地提高了:进化速度由以前的以万年甚至十万年为计算单位提高到现在的以百年甚至几十年为单位。 人类正在不断地改变着大自然的平衡。人们有意或无意地使动植物向其他领域扩展变得更加容易。大片的土地被覆盖上了各种各样的新植物,楼房,工厂,一堆堆的矿渣和其他人类文明的产物。人类使一些物种大规模的灭绝,而又倾向于使另一些物种大量地繁衍。总之,人类在五千年内使地球的生物圈发生的变化远远大于大自然自身五百万年里所发生的变化。 人类给自然带来的这些变化当中,许多后果无法预计。有谁会想到随手丢的一根水草会使不列颠一半的水路十年中无法通行,送给那些孤独的当地居民的妻子的一盆仙人掌会使澳大利亚东部遍布“刺儿梨”森林?有谁会预见到在亚得里亚海海岸,或中非的一些地区砍倒一片森林会使整片土地变为半个荒漠,泥土被冲刷走后只剩下裸露的岩石?又有谁会想到交流的增加会使疾病进行传播,使历史改变——瞌睡病传人了东非,麻疹传人了大洋洲,疟疾也可能进入古希腊?

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