Partially, it is caused by natural factors, such as topography and climate, and partially it is man-made, such as excessive grazing and the improper development and utilization of water resources, which has caused the withering of oases.

• 有些是自然原因如地形、气候造成的，有些则是人为原因造成的，如草原过度放牧，不适当开发利用水资源造成绿洲萎缩等。