Carbon fluxes from urban land-use change in Zhejiang Province, China

• Mapped 30-m annual changes in urban impervious and green surfaces in Zhejiang Province (1985–2022). • Urbanization-related LUC constituted a net carbon source of 0.27–0.77 Tg C yr −1 . • Half of Urbanization-related LUC emissions was concentrated in Hangzhou Bay region. • Urban LUC offsetting 11–30% of LUC carbon sinks during 2000–2020. Urbanization profoundly influences regional carbon dynamics, yet the effects of urban land-use change (LUC) on land carbon sinks remain poorly represented in current regional carbon budgets. Here, we focus on Zhejiang Province, one of China’s most rapidly urbanizing regions, to quantify net carbon fluxes associated with urbanization-related LUC, driven by the expansion of urban impervious surfaces (UIS) and urban green spaces (UGS). Based on multi-source 30 m datasets, we showed that UIS expanded at an average rate of 140 km 2 yr −1 , generating 0.32–0.83 Tg C yr −1 during 1985–2022 in Zhejiang Province. UGS represented by tree cover, expanded at 7.0 km 2 yr −1 over the past four decades and accelerated to 31.3 km 2 yr −1 during the past decade (2013–2022), enhancing the carbon sink to −0.25 Tg C yr −1 . Even after 2020, carbon sinks from UGS growth outweighed UIS-induced emissions. Overall, urbanization-related LUC constituted a net carbon source of 0.27–0.77 Tg C yr −1 , nearly half of which was concentrated in Hangzhou Bay region (Ningbo, Hangzhou, and Jiaxing). Our results indicated that LUC-induced carbon sinks have been overestimated in Zhejiang Province, with urban LUC offsetting 11–30% of LUC carbon sinks during 2000–2020. These findings highlight that while urban LUC drives carbon emissions, urban greening offers substantial mitigation potential for reconciling urban development with climate goals in rapidly developing regions.