Coastal wetlands are important for sequestering carbon. They cover globally only 0.2 % of the ocean surface but contribute 50% of the total amount of carbon buried in marine sediments. Despite their importance, very little data on the extent and type of coastal wetlands (salt marshes in the south and, e.g., reed belts in the north) exists in the Baltic Sea area. This project utilized satellite imagery to map reed belts in pilot areas in Finland, and Sweden and validated them against in situ data. In addition, a roadmap for extending the analysis over the whole Baltic was formulated. The results are available in this Report and in this Storymap.