草原退化;砂漠化;過放牧;草原農業政策;経営請負制;コモンズの悲劇;生態環境保護;生産責任制, Degeneration of Steppe;Desertification;Overgrazing of Grassland;Agri. Police for Steppe Areas;Household Contract Farming System;Common's Tragedy;Conservation of Eco-System
土壌浸食;環境悪化;草原の砂漠化;長江流域;黄河流域;退耕還林;黄砂, Soil Erosion;Deterioration of Environment;Desertification of Grassland;Drainage Area of Yangtze River;Drainage Area of Yellow River;Returning land for Farming to Forestry