晨读英语美文60篇(含lrc字幕) The Dry Lands
 音频下载[点击右键另存为]同步字幕下载[点击右键另存为][00:00.00]The Dry Lands [00:04.41]In most people’s minds the term desert conjures up [00:07.71]an image of undulating sand dunes beneath the hot sun. [00:11.42]There are, however, [00:13.29]many other kinds of desert. [00:15.46]Antarctica, Greenland and the polar ice packs are cold deserts [00:20.05]where the water is locked up in ice. [00:22.47]As for the Earth’s arid regions, [00:25.02]they exist both in areas such as Arabia where the climate is permanently hot, [00:30.61]and in others such as the steppes of central Asia [00:34.68]where the winters are cold. [00:36.22]The common denominator between them [00:38.72]is that on average more water evaporates than falls as rain. [00:43.21]Where there is practically no rain, [00:45.73]as in the Sahara and the Gobi, [00:48.90]there is virtually no life. [00:49.99]Regions in which enough water falls to allow grazing [00:53.71]and perhaps some dry farming are described as semi-arid. [00:58.35]There are many of these in Africa, [01:01.30] India, Argentina and Australia. [01:04.15]Arid and semi-arid regions make up more than a third of the world’s land surface, [01:11.36]whereas cultivated land accounts only for one-tenth. [01:15.31]They are concentrated in two zones straddling the Tropics of Cancer and Capricorn, [01:21.42]on each side of the Equator. [01:23.95]The main cause of aridity is to be found in the circulation of the atmosphere [01:30.41]above our revolving globe. [01:32.36]The almost permanent ridges of high pressure [01:35.88]that predominate around the 30olatitude mark stop rain from forming. [01:41.74]Great distance from the oceans or the presence of mountain barriers are other factors [01:47.09]that contribute to the aridity of regions like central [01:50.58]Asia or the American Midwest. [01:53.22]So deserts have not been created by humankind, [01:57.26]as is something claimed, though people do contribute to decertification. [02:02.73]In our time increased population pressure and over-intensive agriculture [02:07.87]and grazing are accelerating soil degradation [02:11.80]and worsening the effects of drought in semi-arid regions [02:15.95]such as the African Sahel and northeastern Brazil. [02:20.00]There is another way in which human activity [02:23.19]may affect the evolution of arid regions. [02:26.24]It is thought that the accumulation [02:28.77]in the atmosphere of carbon dioxide from automobile engines, [02:32.37]heating or industry and other gases of industrial [02:36.18]and agricultural origin can lead to global warming through the ‘greenhouse effect’. [02:41.65]It is not yet possible to predict the consequences [02:46.14]of such global warming for different regions, [02:48.34]but it may well be that in a few decades some arid regions [02:52.93]will be direr still while others will be less so. [02:56.87]In that case, people will have brought about a significant climatic change, [03:02.11]comparable to those that have taken place in the course of geological history. |
