Conservation and Restoration Can Offset over Half of the Carbon Emissions from Wetland Conversion in China

Wetland conversion and restoration substantially reshape the terrestrial carbon cycle. However, due to limited large-scale sampling and long-term wetland distribution records, their impacts on soil organic carbon (SOC) remain poorly known. Here, we integrated a nationwide wetland SOC density database, multitemporal wetland maps, and related geospatial environmental data sets and applied a random forest model to map China's wetland carbon pool and quantified SOC losses and gains associated with conversion and restoration between 1980 and 2020. The results showed that the mean SOC density of top 1 m in China's wetlands was 23.10 kg C m-2 over the study period, with pronounced spatial heterogeneity. We found that SOC density declined markedly within the first decade after conversion of wetlands to agriculture, with an average reduction of ∼19%. The rate of decline then slowed and gradually stabilized. Over the four decades, conversion to agriculture led to a cumulative loss of ∼574.66 Tg C, equivalent to ∼10.6% of the national wetland carbon pool. By contrast, wetland restoration promoted SOC recovery, although levels remained below preconversion baselines. Conservation and restoration can offset over half of the carbon emissions from wetland conversion. Among them, restoration contributed 186.36 Tg C (∼3.43% of the wetland carbon pool), offsetting ∼32.4% of conversion-induced losses. Overall, from 1980 to 2020, SOC losses from conversion gradually decreased, while restoration-driven gains gradually increased. These results highlight the critical role of wetland conservation and restoration in reversing carbon losses and advancing climate change mitigation toward carbon neutrality.