Predicting water ecosystem services under prospective climate and land-use change scenarios in typical watersheds distributed across China

Water-related ecosystem services (WES) underpin water security but are increasingly threatened by concurrent climate change and land-use change. Yet reliable, generalizable attribution evidence remains limited, because most studies are single-basin and do not explicitly separate climatic and anthropogenic drivers. Here, we implement a scenario-based attribution framework that uses controlled scenario contrasts (climate-only, land-use-only, and coupled scenarios) to quantify and compare the relative contributions of climate and land-use change to two key WES (i.e., water yield and water purification services), and to project WES trajectories for 2020-2100. Using the InVEST Annual Water Yield and Nutrient Delivery Ratio modules, we estimate annual water yield and total nitrogen (TN) export across 17 representative watersheds in China spanning diverse hydroclimatic and landscape settings, and assess WES responses across scenario types. Results show a clear contrast in dominant drivers: climate change affects water yield more than water purification, whereas land-use change affects water purification more than water yield. Climate change contributed >90% to water yields in 15 out of the 17 watersheds; it was 79.4% in the Hei River and only 11.2% in the Yarkant River. For TN export, climate change had a larger influence than land-use change in eight watersheds, exceeding 95% in the Min and Mintuo rivers. For TN export (water purification), climate change had a larger contribution than land-use change in 8 of the 17 watersheds ( >95% in the Min and Mintuo rivers), whereas land-use change dominated in the remaining 9 watersheds ( >95% in the Dongting Lake and Hei River basins). These cross-watershed attribution results identify where climate adaptation versus land-use management is likely to be most effective for sustaining water yield and water quality under future change. The aim of this study is to provide cross-basin attribution evidence that helps target climate adaptation and land-use management to sustain water yield and water quality under future change.