晨讀英語(yǔ)美文60篇59 Man Is Altering the Balance of Nature

[00:00.00]Man Is Altering the Balance of Nature [00:05.68]The balance of nature is a very elaborate [00:09.66]and very delicate system of checks and counterchecks. [00:13.60]It is continually being altered as climates change, [00:16.66]as new organisms evolve, [00:18.74]as animals or plants permeate to new area. [00:22.68]But the alternations have in the past, [00:25.95]for the most part, [00:27.49]been slow, whereas with the arrival of civilized man, [00:31.09]their speed has been multiplied many fold: [00:33.83]From the evolutionary time scale where change [00:37.66]is measured by periods of ten or a hundred thousand years, [00:41.58]they have been transferred to the human time scale [00:44.67]in which centuries and even decades count. [00:47.38]Everywhere man is altering the balance of nature. [00:51.65]He is facilitating the spread of plants and animals into new regions, [00:56.79]sometimes deliberately, [00:58.44]sometimes unconsciously. [01:00.31]He is covering huge areas with new kinds of plants, [01:04.24]or with houses, factories, [01:06.75]slagheaps and other products of the civilization. [01:10.26]He exterminates some species on a large scale, [01:13.97]but favours the multiplication of others. [01:16.91]In brief, he has done more in five thousand years [01:20.65]to alter the biological aspect of the planet [01:23.38]than has nature in five million. [01:25.79]Many of these changes [01:27.64]which he has brought about have had unforeseen consequences. [01:31.79]Who would have thought that [01:34.09]the throwing away of a piece of Canadian waterweed [01:36.81]would have caused half the waterways of Britain to be blocked for a decade? [01:40.88]Or that the provision of pot cacti for lonely settlers’ wives [01:45.36]would have led to Eastern Australia [01:47.53]being overrun with forest of Prickly Pear? [01:50.29]Who would have prophesied that the cutting down of forests [01:54.11]on the Adriatic coasts, [01:55.98]or in the parts of Central Africa, [01:58.04]could have reached the land to semi desert, [02:01.11]with the very soil washed away from the bare rock? [02:04.50]Who would have thought that improved communications [02:08.10]would have changed history [02:09.86]by the spreading of disease— [02:11.62]sleeping sickness into East Africa, [02:14.01]measles into Oceania, [02:16.13]very possibly malaria into ancient Greece? [02:19.73]These are spectacular examples; [02:22.34]but examples on a smaller scale are everywhere to be found. [02:26.30]We make a nature sanctuary for rare birds, [02:29.68]prescribing absolute security for all species; [02:33.18]and we may find that some common [02:35.48]and hardy kind of bird multiplies beyond measure [02:39.31]and ousts the rare kinds in which we are particularly interested. [02:43.13]We see, owing to some little change brought about by civilization, [02:47.72]the startling spread over the English countryside in hordes. [02:52.22]We improve the yielding capacities of our cattle; [02:55.50]and find that now they exhaust the pastures [02:58.88]which sufficed for less exigent stock. [03:01.63]We gaily set about killing the carnivores that molest our domestic animals, [03:06.44]the hawks that eat our fowls and game-birds; [03:09.49]and find that in so doing we are also removing the brake [03:13.75]that restrains the multiplication of mice [03:16.28]and other little rodents that gnaw away the farmer’s profits.

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