Changes in Ecosystem Services and Trade-offs/Synergies in the Nanpan and Beipan River Basin

Understanding the complex relationships among ecosystem services (ESs) is crucial for their joint management, particularly in vulnerable karst areas where ES dynamics are intricate. This study, focusing on the Nanpan and Beipan River Basin (NBPRB), examines seven key ESs—food supply (FP), water supply (WS), soil retention (SR), carbon storage (CS), water purification (WP), habitat quality (HQ), and landscape aesthetics (LA)—over 1985-2020, to analyze their spatiotemporal trends and their trade-offs and synergies for sustainable development. This study innovatively introduces a method to identify trade-offs and synergistic effects among services, including the recognition of positive and negative synergies, as well as determining which service reduction leads to the trade-off relationship. Additionally, by constructing land use transition matrices, the research analyzes how changes in land use affect the trade-offs and synergies among services, offering scientific guidance for the implementation of sustainable land management. The results indicate that (1) FP and LA have risen, and SC have fluctuated, and WP and CS have remained stable, though HQ has decreased. Regionally, ESs differ, with the south of NBPRB leading in FP and the north of NBPRB basin excelling in WS, CS, SR, LA, and HQ. (2) Among 21 combinations of ESs, seven exhibit trade-offs and eight synergies. Trade-offs are mostly between provisioning, regulating, and supporting services, with cultural services not involved. Positive synergies occur between FP, WP, and CS, while negative synergies relate to regulating services. Geographically, positive synergies are more pronounced in the east, negative ones in the south, and trade-offs are concentrated in the southern watershed. (3) Land-use changes affect ESs differently. Forests are crucial for CS, and grasslands and shrublands are important for SR. Expanding cultivated land and impervious surfaces can degrade WP and SR but can improve LA and FP. The study offers insights for managing ESs and informs better land-use planning in the watershed.