Four specific activities have been identified as major contributors to the desertification processes: over-cultivation, overgrazing, firewood gathering, and over-irrigation.

四项具体活动已被确定为对荒漠化的主要导致的过程：过度农垦，过度放牧，薪柴采集和过度灌溉。

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Over the last 40 years, only 4 million hectares of new irrigation have been developed, compared to 25 and 32 million hectares for China and India respectively.

过去四十年来，非洲新增灌溉面积仅为400万公顷，而同期中国和印度的新增面积分别为2500万公顷和3200万公顷。

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For decades, central Asia's environment has suffered from over-ambitious Soviet-era irrigation projects.

几十年来，中亚地区的环境因苏联时代的雄心勃勃灌溉计划而遭受了许多破坏。

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But human factors have also played their part, with over-grazing, over-farming, misuse of irrigation and the unsustainable demands of a growing population all contributing to environmental degradation.

CNN: Growing deserts 'a global problem'