[Comprehensive Ecosystem Service Changes and Their Drivers in the Middle Reaches of Jinsha River]

Hydropower development is an important starting point for China to implement the dual carbon strategy in the energy field in the new era, and the influence mechanism of a large-scale hydropower development mode with ecological priority on watershed ecosystem service has become complicated. Therefore, exploing the ecosystem services change under the influence of hydropower development is highly important. As one of the frequent anthropogenic activity areas in southwest China, the investigation on the impact of hydropower development on ecosystem service is developing from single factor and single process to multi-factor comprehensive ecosystem service functions. This study conducted a multi-scale analysis in the middle reaches of Jinsha River, a hydropower development base in southwest China, to quantitatively evaluate the spatio-temporal characteristics of water yield, carbon storage, and habitat quality before （2000） and after （2020） hydropower development using the InVEST model； to assess the three ecosystem services based on a comprehensive ecosystems service index （CESI） from the perspective of balanced development； and to investigate the mechanism of CESI change under hydropower development. The results indicated that： ① At the watershed level, water yield showed a decreasing trend （by 18.22%）, whereas carbon storage （by 0.26%） and habitat quality （by 0.45%） showed a subtle increasing trend from 2000 to 2020. ② The three ecosystem services in the sub-watershed with different levels of hydropower development exhibited different changing characteristics： the three ecosystem services in sub-watersheds with higher levels of hydropower development decreased, whereas carbon storage and habitat quality in sub-watersheds without hydropower development increased. ③ The CESI showed a downward trend （by 8.13%）, and pinpointed regions of increasing CESI were in the up and down reaches of the regions, whereas those of decreasing CESI were in the middle reaches of the regions. The sustained hot spots of CESI were located near the left side of the upstream and downstream of the main stream, and the sustained cold spots were mainly distributed in sub-watershed 21 and 23. ④ The △CESI were comprehensively influenced by the climate, land use, landscape pattern, and socio-economic changes, with the change in annual precipitation and the PD of water being the key drivers of △CESI, and the contribution rates were 89.4% and 3.2%, respectively. Moreover, the gross domestic production （GDP） change was found to be positively associated with the △CESI. We proposed to improve the comprehensive function of ecosystem services by reducing interference with sustained hotspots, considering the continuous cold point area as a priority for hydropower development, maintaining intensive urban development, and cultivating more concentrated arable land. This study provides support for the hydropower development planning of ecosystems.