Open-source seagrass and blue carbon mapping in support of the nationally determined contributions Seagrasses are one of the world’s most productive ecosystems, playing an important role in climate change mitigation and adaptation. They are vast natural carbon sinks which have important yet underestimated implications into national climate agendas. Precise knowledge of seagrass distribution and site-specific in-situ carbon data is crucial for global seagrass carbon storage, but is limited to a few well-studied sites. Within the context of the Global Seagrass Watch project, funded by DLR and supported by the GEO-GEE program, we aim to develop open country-scale seagrass maps and related carbon stocks in support of the Nationally Determined Contributions of the Paris Agreement. We process open Sentinel-2 multi-temporal data within the open cloud computing platform of the Google Earth Engine to quantify seagrass and associated carbon stocks. Our generated data inventories will support interdisciplinary scientific research and management efforts within a regional and global climate action context. Track – Use cases & applications Topic – FOSS4G implementations in strategic application domains: land management, crisis/disaster response, smart cities, population mapping, climate change, ocean and marine monitoring, etc. Level – 1 - Principiants. No required specific knowledge is needed.