Ecosystem Carbon Stocks Assessment and Projection Under Future Developments of the Coastal Greater Bay Area, China

Coastal zones are dynamic land-sea transition systems in which rapid land-use change can substantially alter ecosystem carbon stocks. However, integrated assessments linking historical land-use transformation, carbon-stock dynamics, spatial drivers, future trajectories, and scenario trade-offs remain limited in highly urbanized coastal regions. Taking the coastal zone of the Guangdong-Hong Kong-Macao Greater Bay Area (GBA), China as the study area, this study employed the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model, GeoDetector, the Patch-generating Land Use Simulation (PLUS) model, and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) to assess historical ecosystem carbon-stock dynamics and their spatial drivers, project carbon stocks under four future land-use scenarios, and evaluate trade-offs between development demand and ecological conservation. Results showed that from 2000 to 2020, construction land expanded by 71.29%, whereas cropland, woodland, and salt marshes decreased by 27.01%, 3.25%, and 26.30%, respectively. Total carbon stocks declined from 44.58 million to 44.13 million t (−1.01%). Normalized Difference Vegetation Index (NDVI) was the strongest individual explanatory factor for spatial carbon-stock heterogeneity (q = 0.56), and its interactions with climatic and topographic factors enhanced explanatory power. Among the 2030 scenarios, Ecological Protection (EP) yielded the greatest increase in carbon stocks (approximately 0.13 million t, 0.29%), whereas Economic Development (ED) led to a net carbon loss. Sustainable Development (SD) achieved the highest TOPSIS score (Scon = 0.74), with construction land increasing by 8.16% and carbon stocks increasing by approximately 0.08 million t (0.17%). Overall, SD provided the most balanced pathway for reconciling development demand with ecological conservation, wetland protection, carbon-stock conservation. These findings provide a practical basis for optimizing land-use allocation and strengthening ecosystem carbon management in rapidly urbanizing coastal regions.