Identifying ecosystem supply–demand response thresholds for land use optimization: A case study of the Taihu Lake Basin, China

• A multi-scenario framework identifies thresholds for regulating land use. • Land use, ES supply and ES demand in TLB are simulated under various scenarios. • Response thresholds are identified for managing ES mismatches and trade-offs in TLB. • Grid-scale areas achieving ES balance and synergy surpass those at county scale. Optimized land-use management is a key approach to addressing the supply–demand mismatches and trade-offs in ecosystem services (ESs). This study, focusing on the Taihu Lake Basin (TLB) in China, analyzes climate, socioeconomic factors, land use, and ES demand from 2000 to 2020 and projects changes for water yield (WY), carbon sequestration (CS), and food provision in the 2050 SSP-RCP scenarios (2020–2050). We identify land-use thresholds necessary for ES balance and synergy, with scenario analysis revealing differences in land expansion and degradation patterns. By 2050, forestland and grassland are projected to expand 4.01 % and 7.70 %, enhancing CS by 3.65 % under SSP126, while under SSP585, urban expansion (31 %) may increase CS supply–demand gap to − 18.77 × 10 8 t. Cropland, built-up land, and forestland are central in determining ES supply–demand balance and synergy. Cropland, built-up land, and forestland are central in determining ES supply–demand balance and synergy. For CS, the results show that built-up land use must not exceed 6.75 %, and forestland must cover at least 16.32 % in 2020. In future scenarios, these thresholds, under SSP126, urban land use would increase to 10.39 %, and forestland to 21.73 %; under SSP245, urban land use would stabilize at 6.80 %, with forestland reaching 21.88 %; and under SSP585, urban land use would decrease to 3.85 %, while forestland would increase significantly to 46.07 % by 2050. Comparative analysis of land-use structures and thresholds across scenarios reveals that the proportion of areas achieving balance and synergy is greater at grid scale than at county scale, highlighting the need to consider complexity and diversity in regions to improve these vital characteristics. We give evidence to inform policy and regulation, for sound long-term management of ES mismatches and trade-offs in the TLB.