Projected Hotspots of Carbon Sink Loss under Urban Expansion in Southeast Asia by 2050

Rapid urbanization across developing regions is driving extensive land-use and land-cover change, profoundly affecting ecosystem productivity and terrestrial carbon cycling. However, the spatially explicit identification of future urban expansion and associated hotspots of carbon sink loss remains limited, constraining the development of targeted land-based strategies for climate mitigation and ecosystem resilience. Here, we project urban expansion across Southeast Asia to 2050 under Shared Socio-economic Pathway (SSP1–SSP5) scenarios by integrating and validating multiple global urban growth models. We combine projected urban growth areas with spatial forest aboveground carbon stocks and fluxes to characterize carbon sinks. Focusing on sixty major cities selected based on socioeconomic characteristics and built-up extent in 2020, we identify spatial hotspots of carbon sink loss relevant for urban land management. We find that future urban expansion is most likely to occur in landscapes already exhibiting low carbon sequestration, often reflecting fragmented or degraded habitats. Across Southeast Asia, total potential carbon sequestration losses during 2020–2050 range from 241.81 to 242.93 Tg C yr⁻¹ under SSP1–SSP5. Aboveground carbon stock losses range from 21.91 to 21.94 Gt C, equivalent to approximately 80.46 Gt CO₂, representing about 16–20% of the remaining global carbon budget since 2020. Spatial hotspots of carbon sink loss are most pronounced in Indonesia, Malaysia, Viet Nam, and Thailand, with distinct patterns emerging at the city scale. Our transferable methodology enables application across diverse regions and delivers spatially explicit, actionable evidence to support place specific land-based interventions for reducing future urban heat risk and enhancing the resilience of human settlements.