The final major human cause of desertification is soil salinization resulting from over irrigation.

造成土地沙漠化的最后一个主要人为因素在于人类过度灌溉导致土壤的盐碱化。

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

导致沙漠化的主要因素有四个：过度种植，过度放牧，过分砍伐，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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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'

Over the next few decades, as the irrigation policy continued, fishing villages that had once been situated right on the coastline found themselves in the middle of a desert landscape.

NPR: Book Takes Wide-Angle View of a Changing Planet

It will take strong institutions at both the national and international levels to satisfy competing demands and defuse tension when it arises, such as over proposals for shale gas extraction, mass irrigation or dam construction.

UNESCO: Open Access to Scientific Information