Identifying driving mechanisms and relationships between supply and demand of ecosystem services based on structural equation model in the upstream segment of the Yangtze River.

The upstream regions of the Yangtze River serve as a vital ecological barrier in China, playing a key role in maintaining ecological functions while also supporting regional economic development. The supply and demand of ecosystem services (ESSD) form a dynamic link between natural ecosystems and human society, and their balance is essential for sustaining ecosystem functionality and achieving long-term development goals. However, the spatial distribution and driving mechanisms of ESSD in this region remain insufficiently understood. To address this gap, we first calculated the supply-demand ratio of ecosystem services and assessed the degree of coordination between supply and demand. We then investigated the natural and anthropogenic drivers of ESSD using geographic detectors, redundancy analysis (RDA), structural equation modeling (SEM) based on R, and lag effect analysis. Our results revealed significant spatiotemporal heterogeneity in ESSD coordination at the municipal scale between 2010 and 2020. The total explanatory power of the RDA reached 26.52 %, 38.99 %, and 40.57 % for the years 2010, 2015, and 2020, respectively. SEM results identified precipitation as the most influential driver, positively affecting both the provision and coordination of ecosystem services across the study area. In contrast, human activities, as indicated by factors such as nighttime light intensity and per capita GDP, exerted negative impacts on the ecosystem. Lag effect analysis showed that water yield and soil conservation respond to short-term drivers, while carbon sequestration was influenced by longer-term ecological or institutional factors. This study sheds light on the underlying drivers of ESSD dynamics and provides critical insights for improving regional ecosystem management and developing targeted sustainability policies.