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(单词翻译:双击或拖选)
旱灾的成因与影响
Its signs are subtle and slow: the earth dries; water levels fall; the rains do not come; and the land is gripped by drought. At its most basic, a drought occurs when more water is used than isreplenished. It is a balance between supply and demand, with both natural and human factors in play.
The weather is constantly in flux1. A low pressure system allows moist air to rise, cool and form rain clouds. A high pressure system traps the air beneath it, and banishes2 the clouds. Droughts form when changing wind patterns cause high pressure systems to last for months, or even years.
Aggravating3 the problem is society's demand for water. Farms are heavily dependent on water to irrigate4 crops and provide pasture for livestock5. Urban areas also place huge demands on available water supplies. If the demand can't be reduced, then the drought begins to take itstoll. Crops eventually wither6 and die. Soil erodes7 away into clouds of dust. Forest fires spread rapidly.
The damage to the environment has large-scale consequences for us human population. Short-term droughts cause stress on both the environment and people. Long-term droughts can lead to war, famine, disease or mass migrations8.
In the 1930s, a severe drought in the Great Plains caused massive crop failures. In some places, the drought lasted 8 years. So much soil blew away became known as the Dust Bowl. Over 50 million acres of land were affected9, forcing many farmers to abandon their own property.
But by historical standards, the Dust Bowl was mild and short-lived. Some droughts have lasted for decades. The famines they create have killed over 40 million people in the 20th century alone.
Like other forms of weather, droughts are one of the earth's natural processes. There is very little we can do to stop them. The best we can do is prepare for when droughts do come before everything blows away.
1 flux | |
n.流动;不断的改变 | |
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2 banishes | |
v.放逐,驱逐( banish的第三人称单数 ) | |
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3 aggravating | |
adj.恼人的,讨厌的 | |
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4 irrigate | |
vt.灌溉,修水利,冲洗伤口,使潮湿 | |
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5 livestock | |
n.家畜,牲畜 | |
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6 wither | |
vt.使凋谢,使衰退,(用眼神气势等)使畏缩;vi.枯萎,衰退,消亡 | |
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7 erodes | |
侵蚀,腐蚀( erode的第三人称单数 ); 逐渐毁坏,削弱,损害 | |
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8 migrations | |
n.迁移,移居( migration的名词复数 ) | |
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9 affected | |
adj.不自然的,假装的 | |
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