A modeling framework for disentangling the impacts of changing climate and land uses on terrestrial water-carbon balance under SSP-RCP scenarios

The Pearl River Basin (PRB) in South China Understanding impacts of climate and land use changes on terrestrial water-carbon balance is critical for sustainable water-land management and climate change adaptation. Yet attributing responses to individual drivers remains challenging. We develop an integrated modeling framework to quantify contributions of changes in climate and land use and their offsetting effects on key ecohydrological fluxes. In the PRB, we evaluate water and carbon flux responses to climate (precipitation, potential evapotranspiration ( PET )) and land use patterns (e.g., forest and urban) across SSP-RCP scenarios (SSP126, SSP370, SSP585) in the near future (NF, 2021–2050) and far future (FF, 2071–2100). Climate drivers generally exert stronger impacts on water and carbon fluxes than land use drivers across the PRB, whereas land use impacts are non-negligible and spatially heterogeneous. Specifically, urbanization increases runoff ( R ) (up to 34% under NF-SSP585) and reduces net ecosystem productivity ( NEP ) (up to −8% under FF-SSP585), most pronounced in the Pearl River Delta. In contrast, forest expansion reduces R and enhances carbon sequestration especially in Dongjiang River Basin. PET impacts on regional carbon sinks are highly scenario-dependent: higher PET enhances carbon fluxes via increased actual evapotranspiration in the NF, whereas under FF-SSP370 and FF-SSP585, persistently elevated PET induces hot-dry stress that outweighs positive drivers and suppresses NEP . • A framework separates climate vs land-use impacts on regional water–carbon balance • Across SSP-RCPs, climate and land-use changes enhance water yield but diverge in NEP • In humid South China, land-use offsets climate impacts on carbon more than on water