The preservation, conservation and creation of marine ecosystems such as mangroves, seagrass beds and saltmarshes, which remove and store ‘blue’ carbon from the atmosphere for decades to centuries, provides an important means of mitigating climate change for countries where such ecosystems cover a significant area. Blue carbon ecosystems also make an important contribution to the social and economic development of coastal communities, whose role in the in-situ preservation and conservation of blue carbon is substantial.

However, there are major uncertainties in quantifying the global extent of blue carbon ecosystems. There is even more uncertainty about less conventional blue carbon habitats, such as intertidal sand- and mudflats and kelp beds. Further major unknowns are the mechanisms and extents of offshore carbon export from these systems, and the degree to which it joins medium- to long-term carbon sinks, in the deep-water dissolved organic carbon pool or burial in shelf, slope or deep-sea sediments. Finally, understanding of how climate change influences carbon accumulation in mature and restored blue carbon ecosystems is still lacking. Reducing these uncertainties and knowledge gaps is important to inform valuation of blue carbon ecosystems and thus their inclusion in policy and management scenarios, and is a central objective of the IMBeR BCWG.

In addition to economic value, the social and cultural value of blue carbon ecosystems are important, including how blue carbon facilitates Nature’s Contribution to People and a range of Ecosystem Services in a variety of coastal-marine social-ecological systems. The assessment of current policy and management actions in terms of how well they enable the maintenance and development of the services provided by, and economic value of, blue carbon ecosystems including their use in accounts of natural capital, is important.