Fig. 3: Trade-off relationships between ecosystem service value (ESV) and socio-economic well-being across different zones.

Production possibility frontier (PPF) curves for: (a) Abundantly sufficient zone. b Moderately sufficient zone. c Slightly sufficient zone. d High demand zone. e Deficit zone. Red lines represent fitted PPF curves (sigmoid functions with R² > 0.97), with Pareto-optimal points (red) and non-optimal points (gray) shown for each zone. All zones display characteristic trade-off patterns: initial stability in ESV as socio-economic well-being increases, followed by accelerated ESV decline beyond zone-specific thresholds. Curve equations are shown in each panel.