Coastal and marine ecosystems store carbon in their soils at high density, and their restoration can generate credits.
Why coastal ecosystems matter
Mangroves, seagrass meadows and salt marshes store carbon in waterlogged soils, where it decomposes slowly. Per hectare they can hold far more carbon than many terrestrial forests. Damage to these habitats releases that carbon, so protecting or restoring them can avoid or reverse large emissions.
Restoration and protection
Blue carbon projects either protect existing ecosystems from loss or restore those that have been degraded, for example by replanting mangroves or reconnecting tidal flows to salt marshes. Credits reflect the avoided loss or the carbon that accumulates after restoration.
Measurement challenges
Soil carbon in coastal systems is hard to measure because it is deep, variable and sometimes lost through erosion. Projects use soil cores, sediment accretion measurements and remote sensing to estimate stocks, and methodologies set conservative assumptions to reflect the uncertainty.
Questions to ask before you rely on these credits
- Are soil carbon stocks measured directly, not just estimated from canopy cover?
- Does the project account for erosion and sea-level change?
- Is the restoration site's baseline based on its actual condition before the project?