Quantifying Interregional Flows of Ecosystem Services to Enhance Water Security in the Yellow River Basin, China

Ecosystem services (ES) have complex flow dynamics that operate across distances. However, ES assessments have focused more on their supply. Few studies consider the impacts of interregional flows on ES provision and the spatial and temporal changes of interregional flows are little known. Here, we quantified interregional flows and analyzed their variations by evaluating the interregional dependency of four water-related ES (water yield, flood mitigation, water purification, and soil retention) in the Yellow River Basin, China. The results showed that about one-third of the basin area had 51.3%-98.9% of the ES sourced from interregional flows, and these areas increased by 2.6%-11.9% during 2000-2015. Generally, the upstream regions with contributions of 64.0%-79.7% of water yield, 93.2%-96.9% of flood mitigation, 89.0%-95.3% of water purification, and 53.7%-97.4% of soil retention played an important role in sustaining the human well-being in downstream regions. Our approach offers a reference for building a telecoupled decision-making for other regions based on interregional flows. Moreover, the results of this study provide insights into interregional dependency on and responsibility for the transboundary ES impacts, and can help in sustainable development of watersheds by achieving environmental equality through guiding transboundary management.