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对土壤退化有各种估计,根据Kovda在1977年的估算,目前世界每年流失可利用土地面积达五～七百万公顷,到本世纪末,可能增加到一千万公顷.
There are various estimates of soil degradation. According to Kovda’s estimates in 1977, the world currently has an annual loss of 5-7 million hectares of usable land and may increase to 10 million hectares by the end of this century.