Identifying and analyzing ecosystem service bundles and their socioecological drivers in the Three Gorges Reservoir Area

A comprehensive understanding of ecosystem service (ES) bundles and their socioecological drivers is vital for ecological management and policymaking. However, the underlying mechanisms are still unclear due to less attention being paid to their historical dynamics. Taking the Three Gorges Reservoir Area as a case study, this study used Pearson parametric correlation analysis, k-means clustering analysis, and redundancy analysis to investigate how the ESs and their interactions have changed over time, and to identify historical spatial patterns of ES bundles and their associations with socioecological drivers. Results showed that: (1) most ESs improved over time but soil retention, water yield, and habitat provision showed slightly decreasing trends; (2) intensive agriculture and advances in technology diminished potential ES trade-offs related to food production, while the decrease in soil retention led to a decline in its synergistic relationships with water yield and nitrogen retention; (3) three ES bundles were identified at the watershed scale. The trajectory of each ES bundle could be attributed to the common effects of ecological projects and rapid urbanization. In particular, ecological projects have promoted the transformation of the ES bundle to the direction of high supply and low trade-off, yet trade-offs between ESs have not significantly improved because of constant urban expansion in a major city and its surrounding area; (4) the socioecological drivers determining ESs and ES bundles were also time-dependent, with the ratio of forest to land, slope, and population density being the major drivers. However, other random drivers (e.g., climate change) should also be highlighted as they generate great uncertainty for predicting future ES bundles and further ES management. Overall, our results advocate the historical assessment of the relationships between multiple ESs and socioecological drivers and emphasize the necessity of embracing a historical dynamic perspective in the sustainable management of ESs.