Science

Global distribution of blue carbon

There are four main dimensions of coastal blue carbon ecosystems that can be mapped – extent, carbon stocks, rate of carbon accumulation and loss, and species composition. The amount and quality of spatial data available varies for each of these dimensions and each blue carbon ecosystem. Data about the extent of coastal blue carbon ecosystems is currently the most comprehensive.

The United Nations Environment – World Conservation Monitoring Centre (UNEP-WCMC13) datasets have been used to present an overview of the global distribution of mangroves, saltmarshes and seagrasses.

The total global area of mangroves has been estimated as 8.2 million hectares (Hamilton and Casey, Global Ecology and Biogeography, 2016). Tidal salt marshes have been conservatively estimated to cover an area of 5.495 million hectares (Mcowen et al, Biodiversity Data Journal, 2017). The global area of seagrasses is less well defined. Rates of change of mangrove ecosystems have been assessed more frequently than tidal marshes and seagrasses. Further information concerning rates of change in these ecosystems will support refined carbon estimations for inclusion in national greenhouse gas inventories and inform future projects.

Stocks and change

Spatially accurate information is required to inform complete accounting of carbon stocks and to track rates of change. Best practice carbon accounting uses spatially explicit carbon stock and change data to estimate the impact of changed management practices on carbon stocks in an area.

Ongoing research and analysis, including initial carbon accounting at the country and regional level is providing greater insight into the rate of change in coastal blue carbon ecosystem areas, and the drivers of change. As our understanding of coastal blue carbon ecosystems continues to grow, relevant tools and information will also be refined and become more accessible.

Tools, methods and resources

A number of relevant blue carbon tools and methods are available to quantify the carbon sequestration and storage potential of blue carbon projects, a selection of resources can be found here.