Comprehensive evaluation and scenario simulation for determining the optimal conservation priority of ecological services in Danjiangkou Reservoir Area, China

• Seven pending scenarios are simulated based on the relationships of multiple ecosystem services. • New indicator system was built for identifying the optimal priority of ecosystem services conservation. • We used analytic hierarchy process to visualize the process and quantify the results for the identification. • The temporal and spatial heterogeneity of trade-offs and synergy among ecosystem services is investigated. The identification of conservation priority for ecosystem services (ESs) holds paramount importance in harmonizing environmental sustainability with human well-being and bolstering sustainable resource management. However, the utilization of a singular evaluation indicator and the employment of ambiguous methods for delineating conservation priorities have resulted in deviations in the decision-making processes. This study focused on the Danjiangkou Reservoir Area (DRA), the originating point and primary water source for the middle route of the South-to-North Water Transfer Project, and employed the InVEST model to quantify five key ESs, including carbon storage (CS), habitat quality (HQ), water yield (WY), water purification (WP), and soil conservation (SC) for the period spanning from 2000 to 2020 to simulate seven pending priority scenarios by utilizing the ordered weighting algorithm (OWA). Additionally, it incorporated the analytic hierarchy process (AHP) to formulate an evaluation indicator system that combines spatial distribution rationality, conservation efficiency, degree of trade-off, and policy compliance to quantify the scores for each pending scenario, thereby facilitating the determination of the optimal conservation priority. The results indicate a gradual temporal decline in these ESs. Spatially, CS, HQ, WP, and SC show strong synergies, while WY exhibits significant trade-offs with them. The optimal conservation priority, with a total area of 0.35 × 10 4 km 2 and primarily located in the high mountainous and hilly regions in the southern and central parts of DRA, is covered by forest and grass land. It exhibits both high conservation efficiency and spatial distribution rationality, which are based on the policy compliance and effectively coordinates relationships among various ESs. This study offers new insights into the quantification and visualization of the identification of optimal conservation priority. The outcomes serve as a reference for informing the protection and management strategies of water source areas and regions with a high supply of ESs.