土地荒漠化ppt课件.ppt

土地沙漠化
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荒漠
一种残缺的美…
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荒漠
—美丽背后的忧患
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狭义的荒漠化（即：沙漠化）
在脆弱的生态系统下，由于人为过度的经济活动，破坏其平衡，使原非沙漠的地区出现了类似沙漠景观的环境变化过程。
Desertification in a narrow sense
Under the fragile ecosystem, the environment change process similar to the desert landscape in the former non-desert areas is occurred because of the artificial excessive economic activities, which destroys the balance.
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1992年联合国环境与发展大会对荒漠化的概念作了这样的定义：荒漠化是由于气候变化和人类不合理的经济活动等因素，使干旱、半干旱和具有干旱灾害的半湿润地区的土地发生了退化。
The concept of desertification was defined by the United Nations conference on environment and development in 1992 as the degradation of land in arid, semi-arid and semi-humid areas, due to factors such as climate change and irrational human economic activities.
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成因
人为破坏说：认为过度放牧开垦，砍伐森林和破坏地表植被，以及水土流失是主要原因。
Human destruction: overgrazing, deforestation and destruction of land cover, and soil erosion are cited as major causes
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变暖说：认为在地质时期低纬度沙漠区的雨期、少雨期与高纬度冰期、间冰期的关系模式是，低纬度少雨-高纬度间冰期，低纬度多雨-高纬度冰期。在变暖的间冰期，低纬度地区少雨干燥，沙漠扩展。近年来，国外一些气候数值模拟结果，认为CO2 的温室效应在未来几十年内将使全球气候变暖，导致中纬度地区干旱，其它地区变湿。
It is believed that the relationship between the rain period and the low latitude glacial period and the high latitude glacial period and the low latitude interglacial period and the low latitude pluvial period and the high latitude interglacial period in the geological period. During the warmer interglacial periods, the lower latitudes were drier and the desert expanded. In recent years, some climate numerical simulations abroad believe that the greenhouse effect of CO2 will cause global warming in the coming decades, resulting in drought in the mid-latitude region and wet in other regions.
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海气相互作用说：认为是热带海温异常导致低纬度大气环流异常所引起。
Air-sea interaction theory: it is believed that tropical SST anomalies lead to atmospheric circulation anomalies at lower latitudes.
反馈说：认为干旱开始后，由于植物枯死，土壤水分减少，蒸发大为减少，形成对流性降水的可能性减少；半干旱地区过量放