About the Project

Determinants of grassland dynamics in Tibetan highlands

Grassland degradation is a global concern, affecting not only wild species and pastoralists who rely on healthy grasslands for their survival, but also non-local people who suffer from resultant hydrological disturbances, dust storms, commodity scarcity, and social consequences of uprooted people. Livestock grazing is the dominant form of land use in Central Asia, and pastures of the Tibetan highlands are located upstream and upwind of roughly 40% of the world’s human population. Grasslands on the Tibetan plateau are usually described as increasingly degraded. 

Steppe rangelands in winter, Gouli

Causes for this grassland degradation are variously attributed to over-stocking of livestock, poor livestock management, historical-cultural factors, alteration of land tenure arrangements, rapid changes in socio-economic systems, climate change, and excessive herbivory and soil disturbance from wildlife. But studies have yet to provide clear support for any putative causative agents, and have not examined interactions and complexity among these factors. As a result, policy choices to reduce or reverse grassland degradation are often made without a clear rationale and are based more on prejudice or convenience than evidence of their effectiveness. 

Our project has examined multiple correlates of grassland status and trends simultaneously, using replicated measurements at permanent plots in a multi-strata design, measuring the strength of evidence for various competing hypotheses. It has linked ecological measurements directly to actions by pastoralists, which in turn are affected by cultural norms, economic incentives, and policies of central and provincial governments. In addition to biophysical attributes of each site, we  quantified livestock density and pasture usage patterns.

A domestic yak in autumn, Stipa grasslands, Gouli

Each site has also been described by the particular grazing strategy employed by the pastoralist managing it, and that strategy, in turn, was related to the complex of economic and policy incentives and historical determinants that pastoralists face. These data will be used to motivate the development of models that link broad historical, policy, economic, and cultural factors to local grassland conditions as mediated by the agency of individual pastoralists which, in turn, may be used to evaluate the implications of different policy interventions.