In the east, annual precipitation is about 700 mm but falls to about 100 mm in the west. As such, the plateau is an extremely harsh environment and in many areas too cold and arid to support cultivated agriculture of forests. Rangelands dominate the landscape of the Tibetan Plateau. The fact that many of the grazing lands on the Tibetan Plateau have supported nomadic pastoralism for thousands of years while sustaining a unique flora and fauna underlies the existence of a productive and remarkably resilient rangeland ecosystem of which, unfortunately, little is known. Some of the Tibetan rangelands also represent one of the last examples on earth of a grazing land ecosystem relatively undisturbed by mankind.
Tibetan rangelands are complex environments and appear to function as highly dynamic ecosystems.
Across much of the Tibetan Plateau there is large variations in annual rainfall and forage production. Periodic severe winter snowstorms add to the dynamic nature of the ecosystem and present special challenges for survival of wildlife and nomads and their livestock. Some of these species are among the least known wildlife species in the world and a number of them are endangered. Tibetan nomads, who have been grazing livestock on the plateau for thousands of years, maintain milking and non-milking herds of yaks, sheep, and goats. Here, in what is undoubtedly the harshest pastoral area on earth, Tibetan nomads still thrive.