A Spatial Baseline of China's Blue Carbon Stocks for Improved Monitoring, Management, and Protection

Blue carbon ecosystems (BCEs) exhibit remarkable capacities for organic carbon (C) storage, making them a promising nature-based climate solution. However, the lack of robust, spatially explicit estimates of C stocks in BCEs presents a major challenge to incorporating them into national and global C accounting and climate mitigation strategies. For the first time, we develop spatially explicit estimates of both soil and living biomass C stocks in BCEs across China by integrating open-access remote sensing, climate, and soil property data with 2,899 site measurements using a data-driven method. Our C stock estimates reveal that mean C stocks in BCEs significantly decrease with increasing latitude. We estimate the total C storage within China's BCEs at 121.1 ± 48.4 Tg C, with soil accounting for 90% of the total C storage. Tidal marshes and flats contribute a total of 64.7 ± 8.7 Tg C, while mangroves store a much smaller amount (4.4 ± 1.4 Tg C) due to their limited spatial extent. Seagrasses store a total of 52.0 ± 38.3 Tg C, which is significantly larger than previous estimates. These findings underscore the significant potential of BCEs protection and restoration for China's climate mitigation efforts. Our spatially explicit C stock estimates for China's BCEs provide essential data for national and global C accounting and can serve as baselines for quantifying the impacts of climate change and anthropogenic activities on BCEs C stocks. Additionally, this study offers a practical framework for comprehensively assessing C stocks in BCEs at the national scale.