Blue carbon ecosystem restoration (and avoided conversion) are important natural climate solutions. Blue carbon ecosystems accumulate carbon through in situ photosynthesising vegetation (autochthonous) and deposition of sediments during tidal inundation (allochthonous). We debate the treatment of allochthonous carbon (which was not taken out of the atmosphere by the blue carbon ecosystem) in blue carbon projects.

Blue carbon ecosystems (BCEs) remove carbon dioxide from the atmosphere and store significant amounts of organic carbon (OC) in their soils. Consequently, the protection and restoration of BCEs may contribute to net greenhouse gas emissions abatement and help address the global challenges of both mitigating and adapting to climate change. An ongoing debate is whether OC sequestered out with the blue carbon (BC) project and tra...

International policy frameworks recognize the net drawdown and storage of atmospheric greenhouse gases through management interventions on blue carbon ecosystems (saltmarshes, mangroves, seagrasses) as potential emissions offset strategies. However, key questions remain around the “additionality” of the carbon sequestered by these ecosystems, and whether some fraction of the organic carbon (OC) that does not derive from in sit...