Blue carbon has become one of the most promising intersections between climate action, nature restoration and sustainable finance.
Mangroves, saltmarshes and seagrass meadows can store significant amounts of carbon while supporting fisheries, protecting coastlines, improving water quality and sustaining biodiversity. For project developers and carbon-credit buyers, this creates an attractive proposition: one investment can potentially support climate mitigation, nature recovery and community resilience.
But there is an important caveat.
A carbon credit does not automatically prove that an ecosystem is thriving.
A coastal project may have a credible carbon methodology while still offering limited evidence about broader ecological health, biodiversity outcomes or long-term resilience. As buyers become more sophisticated, the market will need better ways to distinguish between projects that simply quantify carbon and those that demonstrate genuine nature-positive impact.
Environmental DNA—often called eDNA—could become part of the answer.
What is environmental DNA?
Environmental DNA refers to genetic material that organisms leave behind in water, soil, sediment or air.
Fish, plants, invertebrates, birds and other species shed cells, scales, tissue and other material into their environment. By collecting and analysing samples, researchers can identify species present in an ecosystem without relying only on visual surveys, trapping or physical capture.
For coastal and marine ecosystems, this has major potential.
Traditional biodiversity surveys can be expensive, seasonal, geographically limited and difficult to repeat at scale. eDNA offers a complementary way to detect biodiversity changes over time, including the presence of species that may be hard to observe directly.
For blue-carbon projects, it could help move measurement beyond a narrow question—how much carbon is stored?—towards a more complete one: is this ecosystem becoming healthier, more diverse and more resilient?
Why biodiversity evidence matters to buyers
Carbon-market buyers increasingly want evidence of co-benefits. But “co-benefits” can easily become a marketing label unless they are measured consistently.
A buyer considering a mangrove, seagrass or saltmarsh project should want to understand:
Is the project restoring or protecting a functioning ecosystem?
Is biodiversity improving, stable or declining?
Are local livelihoods and fisheries benefiting?
Is the ecosystem resilient to storms, heat, pollution and sea-level rise?
Are the carbon outcomes dependent on ecological conditions that may be weakening?
What monitoring takes place, how often and by whom?
Better biodiversity evidence improves more than storytelling. It can change investment quality.
A project that demonstrates measurable gains in ecological condition may be more resilient, more defensible and potentially more valuable to buyers with nature-positive commitments, TNFD-aligned strategies or biodiversity-finance objectives.
The opportunity for blue carbon
Blue-carbon projects are especially well suited to integrated measurement because coastal ecosystems deliver multiple forms of value.
Mangroves can store carbon, reduce erosion, support fisheries and provide protection from storm surges. Seagrass meadows can support marine biodiversity, stabilise sediments and improve water quality. Saltmarshes can buffer flooding and provide habitat for birds and other wildlife.
However, projects must be assessed carefully. Ecosystems vary significantly by location. Carbon-storage estimates, restoration success, tenure rights, local engagement and permanence risks can differ widely.
This is why buyers should avoid treating “blue carbon” as a single asset class.
The quality of the project, the methodology, the governance arrangements and the monitoring system all matter.
eDNA could improve monitoring—but it is not a shortcut
eDNA is promising, but it is not a replacement for rigorous project design or carbon accounting.
Results need to be interpreted with expertise. Sampling design, laboratory quality, seasonal variation, reference databases and the relationship between detected DNA and ecological abundance all affect reliability.
The best use of eDNA is therefore likely to be within a wider monitoring framework that combines:
Carbon-stock and greenhouse-gas measurements.
Remote sensing and habitat mapping.
Field-based ecological surveys.
Water-quality monitoring.
Community and livelihood indicators.
Transparent reporting and independent verification.
The goal is not to create another layer of complexity for its own sake. It is to produce evidence that reflects the full climate and nature value of a project.
A new premium for measurable nature value
As biodiversity becomes more relevant to investors, lenders and corporate strategy, projects able to demonstrate ecological outcomes may attract stronger demand.
This could lead to greater differentiation within blue-carbon markets.
Projects with robust carbon accounting but weak biodiversity evidence may remain valuable for carbon buyers. Projects with rigorous, independently verifiable evidence of carbon storage, ecosystem recovery and social safeguards may command a stronger premium from buyers seeking climate and nature outcomes together.
That would be a positive development—provided the market avoids overstating early-stage science or creating claims that go beyond the evidence.
The focus should remain on integrity: clear methods, transparent limitations, credible governance and honest communication.
What buyers should ask now
Before purchasing blue-carbon credits or entering a long-term offtake, buyers should ask:
What ecological baseline was established before the project began?
How are carbon outcomes measured and verified?
How are biodiversity outcomes monitored, and what role could eDNA play?
What permanence risks arise from storms, erosion, sea-level rise or ecosystem degradation?
What rights, safeguards and benefit-sharing arrangements exist for local communities?
Are climate and biodiversity claims clearly separated and substantiated?
Blue carbon can become a powerful example of climate action that restores nature rather than treating it as a side benefit.
But the next stage of market maturity will depend on evidence. Carbon accounting is necessary. For genuinely nature-positive projects, it is no longer sufficient.