Grazing lands cover about one third of the world's land surface. They include many areas in arid and semi-arid regions, as well as mountainous and high altitude zones which are too steep or too hot, too cold or too dry for intensive cultivation. These lands have low productivity per unit area, and are inherently fragile.
In China 870,000 square kilometres of grassland areas have been degraded due to over- pasturing, reclamation for agricultural use and damage by rodents. An area of 3.67 million square kilometres has been eroded by water and wind.