Current status and emerging perspectives of coastal blue carbon ecosystems

Blue carbon ecosystems require conservation and restoration to maximize organic carbon (CORG) sequestration to ameliorate greenhouse gas emissions. Salt marshes, mangrove forests and seagrass meadows are all autotrophic and are considered blue carbon ecosystems. Macroalgae and tidal flats are currently not considered blue carbon habitats. Blue carbon ecosystems contribute globally to climate change mitigation and at local and national scales, especially in the provision of other ecosystem goods and services. Financial investment is constrained by large uncertainties in CORG dynamics and best practices in restoration, rehabilitation and conservation. Several key emerging perspectives include (1) the fact that groundwater discharge of dissolved carbon is a major pathway of blue carbon loss; (2) allochthonous CORG inputs are required to achieve ecosystem carbon mass balance; (3) blue carbon dynamics are enhanced by habitat connectivity and biotic activities; (4) CH4 and N2O emissions reduce blue carbon potential; (5) habitat destruction causes blue carbon stock losses, but variable gas emissions; (6) sediment blue carbon stocks are increasing at the poles; and (7) land-use and land-cover changes (LULCC) drive changes in blue carbon stocks and emissions. Further research is needed to clarify the applicability of these emerging perspectives.