Nonlinear Impact of Socio‐Ecological Drivers on Ecosystem Service Trade‐Offs in the P oyang L ake B asin

Trade‐offs among ecosystem services (ESs) constrain regional ecological sustainability. Existing studies have largely focused on how socio‐ecological drivers influence ES supply; however, the nonlinear relationships and potential thresholds linking trade‐off intensity to its driving factors remain insufficiently explored. Taking the Poyang Lake Basin as a case study area, we firstly identified strong ES trade‐offs with an RMSE‐based approach, then quantified dominant driving factors through the methods of Optimal Parameters‐based Geographical Detector (OPGD) and Multiscale Geographically Weighted Regression (MGWR), and further characterized nonlinear responses and thresholds using the constraint line method. The results showed that strong trade‐offs (RMSE > 0.3) were predominantly observed among ESs related to soil retention and food production, with hotspots mainly distributed in high‐elevation areas surrounding the basin. Terrain factors exerted the strongest influence on ES trade‐off intensity, whereas climatic factors showed comparatively weaker impact. ES trade‐off intensity exhibited distinct nonlinear response to socio‐ecological drivers, which could be classified into three types: (I) a rapid increase followed by gradual stabilization or decline; (II) an initially slow increase transitioning to accelerated growth; and (III) a sharp decrease followed by a slower decline. Several critical thresholds were also identified, including the elevation of 268 m and slope of 2.8°, beyond which abrupt shifts in ES trade‐off intensity occurred. This study explored the nonlinear impacts and threshold effects of socio‐ecological drivers on ES trade‐off intensity, highlighting the significance of targeted and adaptive ecosystem management in the Poyang Lake Basin.