Assessment of Ecosystem Services and Optimization of Their Spatial Patterns in a Mountainous Watershed: A Case Study of the Anning River Basin, China

Assessing ecosystem services, identifying their driving factors, and optimizing their spatial patterns are essential for coordinating ecological conservation and socioeconomic development in mountainous regions. Taking the Anning River Basin in southwestern China as the study area, this study quantitatively assessed ecosystem services from 2010 to 2024, integrated trade-off intensity into the Integrated Ecosystem Services Index, applied a Bayesian network model to identify the driving factors of ecosystem services, and proposed strategies for spatial pattern optimization. The results showed that: (1) the mean values of water conservation and soil conservation in the Anning River Basin were 94.45 mm and 1179.64 t ha−1, respectively, both showing substantial interannual fluctuations. The habitat quality index was 0.83, and the mean carbon storage was 132.68 t ha−1; both habitat quality and carbon storage declined slightly. The mean food production was 0.46 t ha−1, indicating an improvement in the food production function. (2) The trade-off intensity among ecosystem services was 0.33, and the Integrated Ecosystem Services Index was 0.51, remaining generally stable overall. Ecosystem services were mainly influenced by land use, precipitation, population count, and fractional vegetation cover. Their spatial heterogeneity was pronounced, with relatively low values in the Anning River Plain, the Jinsha River dry-hot valley, and the Yanyuan Basin. (3) The identified priority conservation areas for ecosystem services covered 8307 km2 and were mainly distributed within ecological conservation redline areas and regulated zones. The general functional areas for ecosystem services covered 149 km2 and were concentrated in urban construction areas and along major transportation corridors in the basin. Targeted strategies were further proposed to enhance the synergistic improvement of ecosystem service supply. This study provides theoretical and practical support for ecosystem management in the Anning River Basin and other mountainous watersheds.