Evolution of ecological carrying capacity and its limiting factors in farmlands and grasslands in the Wuding River Basin, China

With the contradiction between limited natural resources and the unlimited demand of humans, realizing the sustainable development of the ecological environment and social economy and maintaining regional ecological security has become a major challenge for humankind. Taking the Wuding River Basin as the study area, this study estimated the carrying capacity and carrying index of farmland and grassland ecosystems in each county from 2000 to 2020 based on the supply and consumption of forage and food nutrition. The ecological carrying capacity and its evolution were evaluated to identify the major constraints, and the limiting effects of water resource supply were further analyzed based on water resource carrying capacity. The results showed that grassland forage supply and consumption in the Wuding River Basin had an increasing trend over the past 20 years, the farmland food supply increased, and per-capita consumption decreased slightly. The grassland and farmland carrying states were optimized. The comprehensive ecological carrying index decreased in 80% of the counties, and the carrying capacity of Hangjin Banner and Southeast counties worsened. Overall, the ecological carrying capacity of the basin was improved, and forage supply was the major constraint. The ecological carrying state of water resources was aggravated in Etoke Banner and Etokeqian Banner, and water resources were the primary limiting factor for agricultural and animal husbandry production in the northern districts. In the future, attention should be paid to ecological protection and repair, including managing the scale of planting and animal husbandry, to reduce pressure on grassland ecosystems.