How much CO2 can blue carbon ecosystems remove?

Blue carbon ecosystems (coastal wetlands such as mangrove forests, seagrass beds, and tidal marshes) are widely distributed along the coastlines of all continents except Antarctica, and account for more than half of biological carbon captured worldwide [1]. 

It is estimated that the key marine habitats of mangroves, seagrasses, and tidal marshes collectively store more than 30 gigatons of carbon [2]. The combined actions of protecting and restoring these ecosystems have the potential to stop 3% of annual global emissions from fossil fuel combustion [2]. Moreover, the power of blue carbon habitat protection and restoration to help tackle climate change can be orders of magnitude larger if seaweed and other emerging stores are included.

On the other hand, when coastal wetlands are degraded, lost, or converted for development, their large carbon stocks are exposed and released as carbon dioxide (CO2) into the atmosphere and/or ocean, with effects such as rising temperatures and ocean acidification. Current rates of blue carbon ecosystem loss may result in 0.7 gigatons of CO2 being emitted annually [3] — which is about 15 times the amount China emits each year. This is the reason why the work of communities, individuals, and organizations to prioritize protection and restoration of these habitats matters a great deal.

1. Duarte C. M., Middelburg J. J., & Caraco N. (2005), Major role of marine vegetation on the oceanic carbon cycle. Biogeosciences, 2(1):1-8. Doi: 10.5194/bg-2-1-2005.
2. Macreadie, P. I., Costa, M. D. P., Atwood, T. B., Friess, D. A., Kelleway, J. J., Kennedy, H., Lovelock, C. E., Serrano, O., & Duarte, C. M. (2021), Blue carbon as a natural climate solution. Nature Reviews Earth & Environment, 2(12), 826-839. doi: 10.1038/s43017-021-00224-1.
3. Pendleton, L., Donato, D. C., Murray, B. C., Crooks, S., Jenkins, W. A., Sifleet, S., Craft, C., Fourqurean, J. W., Kauffman, J. B., Marbà, N., Megonigal, P., Pidgeon, E., Herr, D., Gordon, D., & Baldera, A. (2012), Estimating Global ‘Blue Carbon’ Emissions from Conversion and Degradation of Vegetated Coastal Ecosystems. PLOS ONE, 7(9): e43542. doi: 10.1371/journal.pone.0043542.

About the author

Vasiliki I. Chalastani is a PhD candidate at the Laboratory of Harbour Works, National Technical University of Athens (NTUA), Greece. Her thesis, “Optimization Approaches for Marine Spatial Planning,” aims to develop tools for optimal use of the marine environment through reconciliation of human activities and conservation features. Previously, following her undergraduate studies as a civil engineer at NTUA, Chalastani pursued her MSc, “Water Air Pollution and Energy at Global and Regional Scales,” at École Polytechnique, Paris, France. While in France, she has completed an internship at the Laboratoire Océanographique de Villefranche and at École Normale Supérieure on ocean-based solutions. From 2018 to 2019, Chalastani acted as a consultant for the Alternate Minister of Maritime Affairs and Insular Policy of Greece, Nektarios Santorinios. In 2018, she worked for the Institute for Sustainable Development and International Relations (IDDRI), Paris, with Alexandre K. Magnan, on the issue of climate change adaptation. In 2019, Chalastani worked for the Saudi Red Sea Project, developing a preliminary marine spatial planning initiative, under the supervision of Carlos M. Duarte. She is a member of the National Chamber of Engineers and the United Nations Sustainable Development Solutions Network (UN SDSN), Greece.