From simulated to realized carbon sinks in Zhejiang, China

Terrestrial carbon sinks contribute to climate change mitigation, but their realized magnitude is constrained by carbon cycle processes that are not always fully represented in process-based models, including natural disturbances, forest management, and lateral carbon transport. Here, using Zhejiang Province, China, as a regional case, we estimated land carbon sinks with a multi-model ensemble and compared their magnitude with LUC-related fluxes from a bookkeeping model. Independent estimates of carbon losses from wildfires, wood harvest, and soil erosion were used to clarify the differences between simulated and realized carbon sinks. During 2012–2022, the multi-model ensemble simulated a land carbon sink of -5.01 Tg C yr − 1 in Zhejiang. Separately, the bookkeeping results showed that reforestation was the dominant contributor to LUC-induced gross sinks. Accounting for carbon losses from wildfire (0.11 Tg C yr − 1 ), wood harvest (0.45 Tg C yr − 1 ), and lateral carbon transport from soil erosion (1.06 Tg C yr − 1 ) reduced the simulated sink by roughly one-third, resulting in a realized sink of -3.39 Tg C yr − 1 . These results demonstrate that relying solely on model-simulated sinks may overestimate regional mitigation potential. Our findings highlight the critical role of land use and management, including reforestation, fire prevention, forest management, and soil conservation, in augmenting carbon sinks. This regional assessment can inform land-based mitigation strategies across other regions and support China’s carbon neutrality goals.