“Blue carbon” is defined as the carbon stored, sequestered or released from coastal ecosystems of tidal marshes, mangroves and seagrass meadows.
A great deal of effort has gone into developing a policy framework around avoiding emissions from deforestation and degradation in tropical forests (REDD/REDD+). However, marine vegetated habitats are significant carbon sinks that are being lost at rates exceeding those of some tropical forests. In 2010, a UNEP workshop examined the potential for developing a policy framework around ‘blue carbon’, the carbon stored in marine vegetated habitats. There has been a rapid increase in the number of scientific papers examining marine vegetated habitats for their role in mitigation both from maintaining carbon sinks as well as their mitigation potential of maintaining (primarily) or restoring (potentially) these habitats, and the risk of emissions resulting from their loss owing to human activities. The IPCC estimates that there are currently the equivalent of 47.7 – 60.2 Gt CO2 stored within coastal wetlands (~29.4 Gt CO2 in mangroves; ~2.9 Gt CO2 in tidal marshes and 15.4 – 30.8 Gt CO2 in seagrass meadows); these are median estimates and the broader range from the literature can be found in table
This information is provided to help inform policymakers of the potential need to modify existing policy frameworks around avoiding emissions from the loss of coastal vegetated wetlands. Unlike many forests, a much larger fraction of the carbon in marine vegetated habitats is in the soil, and this carbon can have much greater stability than the carbon in terrestrial soils. Research has shown that avoiding emissions from loss of marine vegetation habitats can be done at reasonably low costs (US$10 per ton CO2) and with fewer of the land tenure and ownership issues often associated with REDD+. There is also potential for sequestering carbon by restoring these habitats. This paper is a review of the published literature on blue carbon, focussing as the 2010 UNEP workshop did, on the potential for including blue carbon within REDD+ and similar carbon markets. It primarily looks at blue carbon from the point of view of reducing emissions from loss.