Impacts of Land Use Change on Carbon Storage and Future Projections in the Yangtze River Delta Urban Agglomeration Under SSP-RCP Scenarios

Carbon storage (CS) is a critical ecosystem service for climate mitigation. CS in urbanizing areas is being squeezed by climate-driven capacity decline and human-induced stock loss. Focusing on the Yangtze River Delta Urban Agglomeration (YRDUA), we integrated the InVEST CS module with climate projections under SSP-RCP scenarios to quantify CS dynamics during 2000–2020 and project trajectories for 2030–2070, while attributing CS changes to land use change (LUC). The findings indicated that: (1) From 2000 to 2020, the share of cropland decreased from 54.72% to 49.60%, while the share of construction land increased from 6.05% to 12.55%. (2) Regional CS ranged from 2829.46 to 2941.96 Tg C and exhibited a persistent spatial gradient, decreasing from south to north. (3) CS is projected to increase under SSP5-8.5, to rise and then decline under SSP1-1.9, and to decrease overall under SSP2-4.5. (4) From 2000 to 2010, the conversion of cropland to forest made the largest positive contribution to CS changes, while the conversion of water to cropland dominated from 2010 to 2020. Conversely, cropland expansion into construction land was the primary driver of negative CS changes throughout the 2000–2020 period. For the future period (2030–2070), under all scenarios, the conversion of grassland to forest is expected to be the dominant driver of positive CS gains, whereas the conversion of grassland to cropland will consistently lead to the largest CS losses. These findings highlight the need for scenario-specific and spatially differentiated land-management strategies to sustain regional carbon sinks and enhance long-term climate resilience in agglomerations.