The Ocean Is Doing the Heavy Lifting—But It’s Reaching Its Limits

The ocean absorbs nearly a quarter of global CO₂ emissions each year. In theory, it could take in even more, but not without consequences. Ocean acidification and warming threaten the ecosystems that depend on stable pH levels and temperatures. To protect these systems, we need additional carbon removal pathways that complement natural ocean processes rather than overwhelm them.

Blue carbon ecosystems — mangroves, seagrass meadows, and tidal marshes — cover only about 2% of Earth’s surface yet are responsible for an outsized portion of annual carbon sequestration. They are nearly ten times more effective than terrestrial forests (i.e. forests) and can lock carbon away for hundreds to thousands of years due to their deep, anoxic soils.

But even this “miracle” solution has limits. Mangrove ecosystems can take more than a decade to mature and reach peak sequestration capacity, making restoration long, logistically complex, and expensive. As carbon credit financiers increasingly look to blue carbon as a climate solution, the maturity timeline and long-term maintenance of these ecosystems are becoming critical considerations.

Newly restored mangrove forests also underperform compared to established ones. Even more concerning: degraded blue carbon ecosystems can shift from carbon sinks to carbon sources, releasing centuries of stored carbon from their soils. This makes the preservation of existing intact systems just as important as restoring lost ones.

Mangroves and seagrass store carbon through photosynthesis, similar to land plants, but about 80% of the carbon they capture ends up in their soils — not in their biomass. For terrestrial plants, that ratio is reversed. The soil-based storage is what gives blue carbon ecosystems their unparalleled permanence.

The Unseen Side of Blue Carbon Scalability

Scaling blue carbon CDR is moderately viable and highly dependent on local context. The largest barrier is availability of land. Much of the world’s coastlines have already been transformed for human use. Nearly 40% of the global population lives within 100 miles of the coast, and many of the remaining restorable areas lie in Southeast Asia and other developing regions.

Take Louisiana as an example: roughly 40% of its coastline used to be mangrove forests. Over the last 150 years, wetlands were drained to build homes and infrastructure, pushing communities into vulnerable landscapes. New Orleans,  famously below sea level, now faces escalating threats as sea level rise accelerates. Reverting these regions back to mangrove habitat is often impossible.

This means scalability depends on protecting existing ecosystems and restoring areas where coastal development pressure is lower. Many governments in Southeast Asia recognize this and are actively working to protect and restore mangroves, understanding they serve as their first line of defense against storm surge, flooding, and other climate-driven disasters.

Bridge-Building: Science, Policy & Local Stewardship

Most mangrove degradation in developing countries is driven by subsistence needs – primarily shrimp farming and wood harvesting as a fuel source. This creates a complex challenge: restricting access to resources that support basic survival is both unethical and unrealistic.

Effective restoration requires co-developing solutions with local communities, not imposing them. Without collaboration, well-intentioned policies lead to leakage, where extractive activities simply move to another area outside the project boundary.

Communities need viable, equal-or-better alternatives that allow them to maintain their livelihoods. This is why equitable financing models are essential. Carbon credits can help fund restoration while also providing direct financial support that enables communities to shift behaviors sustainably.

Importantly, revenue from carbon credits should be equitably shared with local stakeholders. Anything less risks perpetuating modern-day colonial dynamics. Community ownership and benefit-sharing increase long-term project success and build genuine partnerships.

Restoration efforts must also honor cultural practices. Many Indigenous communities have used mangroves in culturally significant ways for generations. For example, in Australia, some First Peoples craft didgeridoos from hollowed mangrove stems. These practices are not the source of ecological decline and should be preserved however their communities and cultures deem appropriate. 

Bottom Line: Key Conditions for Effective Blue Carbon

Biotic, ocean-based carbon removal, especially via blue carbon ecosystems, offers significant potential thanks to its efficiency and long-term permanence. But its success depends on the following:

• Availability of intact or restorable mangrove, seagrass, and marsh ecosystems. Not all coastlines are viable, and development pressures limit expansion.

• Equitable, community-led project development. Long-term success requires preventing leakage, respecting cultural practices, and ensuring that local communities directly benefit.

• Strengthened voluntary and compliance carbon markets. Reliable demand and high-integrity crediting frameworks are essential for funding restoration and ensuring permanence.

If you’re interested in diving deeper into biotic carbon pathways, I highly recommend exploring the educational resources available through the AirMiners BootUp program or the Fair Carbon Academy.