1 Introduction Grassland degradation in China's northem steppe has been a major and increasingly serious problem affecting the productivity and sustainability of pastoral systems.The economic and property rights reforms in the early 1980s dramatically modified grazing management and resource institutions in the area.Livestock were privatized,but most of the pastures were jointly used by all herding households or small groups within villages.When a seemingly accelerating deterioration of grassland condition was observed through the 1980s and 1990s,numerous research and government reports suggested that the reform had created the classic problem of resource degradation from privately owned animals grazing on common land (Hardin 1968).At the same time,pastures allocated to and actually controlled by individual households also were subject to overexploitation caused by perceived institutional uncertainties (Longworth and Williamson 1993).
展开▼