Blue carbon is carbon captured by ocean and coastal ecosystems and stored in living biomass, dead material and especially waterlogged soils. In practical conservation, the term usually focuses on mangrove forests, seagrass meadows and tidal salt marshes because their carbon stocks can be measured and protected through coastal management.
How coastal ecosystems store carbon
Plants take carbon dioxide from the air or water during photosynthesis. Some carbon becomes leaves, wood and roots; some moves into sediment as plants die or trap organic particles. Waterlogged soils contain little oxygen, so decomposition can be slow and carbon may accumulate for centuries or millennia.
That soil store is crucial. A young restored habitat may begin capturing carbon quickly, but it takes time to rebuild the deep stock of an old, intact ecosystem.
The three best-known blue-carbon habitats
- Mangroves are salt-tolerant trees and shrubs along tropical and subtropical shores.
- Seagrasses are flowering plants forming underwater meadows in sunlit coastal water.
- Salt marshes are intertidal wetlands dominated by salt-tolerant grasses and low plants.
Kelp forests and the open ocean move and store enormous amounts of carbon, but accounting for long-term burial attributable to a specific project is more complex. Not every marine carbon process can be treated as an interchangeable offset.
Benefits beyond climate
Blue-carbon habitats provide nurseries for fish, improve water clarity, stabilise sediment and reduce wave energy. They support fisheries, wildlife, recreation and culture. Protecting them can therefore combine climate mitigation, adaptation and biodiversity goals.
What happens when a habitat is damaged?
Clearing, dredging, drainage and erosion remove plants and expose carbon-rich soils to oxygen. Stored carbon can be released as carbon dioxide, while future capture is lost. Damage also removes coastal protection and habitat.
Good blue-carbon action
The first priority is to protect intact ecosystems and the hydrology that sustains them. Restoration should match the right habitat to the right site, address the original cause of loss and involve local and Indigenous communities. Projects need credible baselines, long-term monitoring, permanence plans and safeguards against shifting damage elsewhere.
Blue carbon complements rapid fossil-fuel emissions reduction; it cannot compensate for unlimited emissions. The restored Save the Wave project shows how Mediterranean habitat knowledge can connect with practical stewardship.
Frequently asked questions
Is all ocean carbon blue carbon?
The phrase can be used broadly, but established coastal blue-carbon accounting usually centres on mangroves, tidal marshes and seagrasses.
Can planting mangroves anywhere create blue carbon?
No. Mangroves need suitable climate, elevation, sediment and tidal flow. Planting in the wrong habitat can fail or damage existing mudflats and seagrass.