Land use optimization based on ecosystem service assessment: A case study in the Yanhe watershed

Regional land use change can significantly change the ecosystem patterns and processes, resulting in changes of ecosystem services supplies. Large-scale ecological restoration programmes have been implemented in China to restore and sustain ecosystem services. We selected the Yanhe watershed on China's Loess Plateau, which has experienced the Grain for Green Programme (GFGP), as study area, and we used specialized models to quantify four ecosystem services (water provision, soil conservation, carbon sequestration, and agricultural production) under land use scenarios relative to actual land use change from 2000 to 2015. These scenarios were set according to slope, land use type and water constraint of the watershed to improve water quantity, carbon sequestration, soil retention, agricultural production, and sub-watershed water sustainability. The results show that from 2000 to 2015, 66% of farmlands converted to grassland, 12% of farmlands converted to forest, and farmland proportion declined from 42.0% to 5.3%, while water provision and agricultural production services declined by 12% and 87%, and soil conservation and carbon sequestration services increased by 13% and 3%. Furthermore, under five specific scenarios that converted all retired farmland to grassland in the water-short area and maintained farmland at 0-10 slope in the water-adequate area, all four ecosystem services improved compared with 2015 levels. By identifying optimized land use scenario of retired farmland, we refined general principles of future analyses and decision making in ecological restoration. Comprehensively analyzing slope, land use type and water constraint of the watershed when choosing land use scenarios for GFGP can effectively resolve trade-offs among multiple ecosystem services and can promote regional sustainable development.