This study estimates global emissions of carbon dioxide (CO₂) from the conversion and degradation of vegetated coastal ecosystems, including mangroves, seagrasses, and tidal marshes. These ecosystems store large amounts of carbon in sediments, which can be released to the atmosphere when the ecosystems are disturbed. Using available data on global area, conversion rates, and carbon stocks, the researchers estimate that 0.15–1.02 Pg of CO₂ are released annually, several times higher than previous estimates that only account for lost sequestration. These emissions are equivalent to 3–19% of global deforestation emissions and result in annual economic damages of $6–42 billion. The largest uncertainties in these estimates stem from limited data on global area and conversion rates, but further research is needed on the fate of ecosystem carbon upon conversion. Currently, these emissions are not included in emissions accounting or carbon market protocols, but the analysis suggests they may be disproportionately important. The study highlights the need for policies that encourage the sustainable management of coastal ecosystems to reduce carbon emissions and maintain ecosystem services. The findings suggest that coastal ecosystems, despite occupying a small portion of the coastline, play a significant role in global carbon emissions and economic impacts. The study also emphasizes the importance of improving data and understanding of blue carbon stocks and their release to better inform conservation and policy decisions.This study estimates global emissions of carbon dioxide (CO₂) from the conversion and degradation of vegetated coastal ecosystems, including mangroves, seagrasses, and tidal marshes. These ecosystems store large amounts of carbon in sediments, which can be released to the atmosphere when the ecosystems are disturbed. Using available data on global area, conversion rates, and carbon stocks, the researchers estimate that 0.15–1.02 Pg of CO₂ are released annually, several times higher than previous estimates that only account for lost sequestration. These emissions are equivalent to 3–19% of global deforestation emissions and result in annual economic damages of $6–42 billion. The largest uncertainties in these estimates stem from limited data on global area and conversion rates, but further research is needed on the fate of ecosystem carbon upon conversion. Currently, these emissions are not included in emissions accounting or carbon market protocols, but the analysis suggests they may be disproportionately important. The study highlights the need for policies that encourage the sustainable management of coastal ecosystems to reduce carbon emissions and maintain ecosystem services. The findings suggest that coastal ecosystems, despite occupying a small portion of the coastline, play a significant role in global carbon emissions and economic impacts. The study also emphasizes the importance of improving data and understanding of blue carbon stocks and their release to better inform conservation and policy decisions.