The Hengduan Mountains of northwestern Yunnan, P.R. China support many rare and endemic species. Several of these species have economic value for horticultural and medicinal uses. This area provides important habitat for high-mountain wildlife populations and is also used as grazing lands for domestic animals. Over the past four years we have documented that herbaceous alpine meadows are contracting as forest treeline advances and alpine shrub biomass increases. Alteration of land management practices and shifts in climate are thought to be the primary drivers of these changes. While the mechanism is unclear, this region of Yunnan appears to be highly sensitive to larger-scale climate forcings. The rate of observed warming since the 1980's (0.06 deg. C yr-1) in the study was double the national average (0.03 deg. C yr-1). Simulation results from the MC1, dynamic vegetation model, under three IPCC-SRES climate-forcing scenarios (Commit, A1B, and B1) show that even modest increases in temperature cause further alteration of these diverse ecosystems. Simulated increases (3.8 deg. C) in average annual temperature in the later part of the 21st century (2070-2099) result in boreal forests shifting to more temperate forest types and loss of alpine meadows. Tree biomass generally increases under all scenarios. Management practices that do not mitigate impacts of climate change will accelerate the threat to indigenous livelihoods and the conservation of biodiversity.