酸雨现象不但导致湖泊酸性提高，使许多鱼类繁殖能力下降；而且随着土壤里酸性物质的增加，树木的生长速度开始放慢，对疾病的抵抗力下降。
The result is increased acidity in lakes, which has curtailed the ability of many fish to reproduce, and in the soil, which has slowed the growth of trees and increased their vulnerability to disease.
近几十年以来，人们对奶牛的选育一直偏重于提高奶牛的产奶量，伴随而来的是奶牛的繁殖能力、使用寿命等性能的恶化，从而导致一定程度上奶牛业经济效益的下降。
People are interested in improving production of dairy cattle over the last decade, meanwhile the trend to poorer fertility and longevity is obvious, and a decline in economic has been observed.
近几十年以来，人们对奶牛的选育一直偏重于提高奶牛的产奶量，伴随而来的是奶牛的繁殖能力、使用寿命等性能的恶化，从而导致一定程度上奶牛业经济效益的下降。
People are interested in improving production of dairy cattle over the last decade, meanwhile the trend to poorer fertility and longevity is obvious, and a decline in economic has been observed.
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