C-BLUES will advance knowledge of blue carbon ecosystems (BCEs) such as seagrasses, tidal marshes, mangroves, and macroalgae. It aims to: 1) develop scientific knowledge to reduce uncertainty and improve UNFCCC blue carbon reporting, 2) provide input for revising the 2013 IPCC Wetlands Supplement to better include coastal wetlands in GHG inventories, and 3) promote the role of blue carbon in global climate policy with international partners. C-BLUES will produce spatial maps, best practices, quantify carbon sequestration, model GHG budgets, assess management impacts, review legal frameworks, and address integration barriers. Targeting the Atlantic/Arctic, Baltic, North Sea, Mediterranean, Black Sea, Dutch Antilles, and Southern China coast, it will engage stakeholders to disseminate knowledge, raise awareness, and influence climate policy to include BCEs in reporting and management actions.