Blue carbon in coastal landscapes: a spatial framework for assessment of stocks and additionality

Efforts to incorporate blue carbon, the carbon associated with marine ecosystems, into carbon accounting and carbon markets are increasing. To fully leverage the capacity of marine ecosystems to sequester carbon requires information to guide prioritisation of coastal landscapes for conservation and regeneration. A comprehensive landscape-scale assessment of mangrove and saltmarsh blue carbon requires information regarding vegetation cover, sedimentological and geomorphological factors. This information should also be integrated with socio-economic factors that alter natural processes of blue carbon accumulation and storage. The purpose of this study was to provide a framework for undertaking a first-pass assessment of blue carbon storage, preservation, generation and permanency in coastal landscapes, and to incorporate socio-economic factors that will influence blue carbon storage in coastal landscapes. This was achieved using readily available datasets that were analysed using a raster-based approach to develop a proxy indication of biophysical and socio-economic factors relevant for mangrove and saltmarsh blue carbon. The approach demonstrated that large catchments were associated with areas highly suitable for blue carbon storage, preservation, generation and permanency. Small catchments associated with mature barrier estuaries had the highest proportional area that provides potential blue carbon ecosystem services and climate mitigation benefits. The qualitative approach used does not replace high-resolution quantitative assessments of blue carbon storage, flux and detailed site-specific assessment of socio-economic factors that may influence blue carbon services; however, it can be used to guide prioritisation of blue carbon landscapes for further assessment prior to conservation and/or regeneration.