How blue carbon fits into the Paris Agreement — NDCs, Article 6 trading, national inventories and coastal-wetland accounting — and where kelp stands.
Blue carbon — the carbon stored in mangroves, seagrass, salt marsh and, increasingly debated, kelp and seaweed systems — has moved from scientific curiosity to a live question of international law. Governments now ask: can we count our mangrove restoration toward our Paris commitments? Can we sell coastal carbon abroad? This article is a guided tour of the actual policy architecture: NDCs, the Paris Agreement's Article 6, national greenhouse gas inventories, and where kelp fits — and doesn't — in all of it.
Everything in international carbon policy rests on national inventories — the ledgers countries compile of emissions and removals, following IPCC guidelines. The pivotal moment for coastal ecosystems was the IPCC's 2013 Supplement on Wetlands, which gave governments standardised methods to count mangroves, tidal marshes and seagrass meadows: what to measure (pools in biomass and sediment), how changes in area and condition translate into emissions or removals, and how to account for rewetting degraded wetlands.
Once a country adopts the supplement, its coastal wetlands are no longer outside the ledger. Actions that protect or restore them show up as accountable removals; loss and disturbance show up as emissions. That single integration is the backbone everything else — carbon markets, funding mechanisms, corporate claims — is bolted onto.
Notably, kelp and other seaweed systems are not in the supplement as carbon pools of the same standing; the science didn't (and largely still doesn't, consensus-wise) support inventory-grade accounting. That shapes everything about kelp's policy position below.
A country's Nationally Determined Contribution (NDC) is its climate pledge under Paris. Dozens of countries now mention coastal wetlands or "blue carbon" in their NDCs, typically in one of three ways:
The practical significance: once blue carbon is inside an NDC, national funding, monitoring agencies and subnational governments (states, councils, provinces) have a mandate to act. Councils that want to fund a foreshore restoration can draw on national blue carbon frameworks — which is why our work with governments begins with reading the national inventory practice before the site plans.
Article 6 of the Paris Agreement is the rulebook for international carbon cooperation. Two mechanisms matter for blue carbon:
Countries can bilaterally trade Internationally Transferred Mitigation Outcomes (ITMOs) — verified emission reductions or removals. Critical rule: when one country sells an outcome, it applies a corresponding adjustment, adding the tonnes back onto its own ledger so the removal isn't counted twice. Blue carbon removals from mangrove projects are among the ecosystem types most likely to appear in 6.2 deals involving coastal nations, because the inventory methods exist and the permanence arguments are comparatively strong.
The successor to Kyoto's Clean Development Mechanism, run under UNFCCC supervision. A supervised body approves methodologies; projects generate credits ("A6.4ERs") usable toward NDCs or, controversially, corporate claims. Coastal-wetland methodologies are expected to be among the earlier nature-based candidates; seaweed-carbon methodologies would need measurement maturity the field is still building (see MRV for blue carbon).
Bluntly: at the margins, for now.
This is a moving target. Should export-fraction science mature and IPCC guidance expand — a plausible development over the next assessment cycles — kelp could graduate into the same inventory ecosystem as mangroves, with NDC inclusion and Article 6 eligibility following. That's the policy outcome our own monitoring programme, Canopy Ledger, is structured to support: long time-series data, openly benchmarked methods, and illustrative indicators that the pilot projects our carbon-buyer solutions describe can eventually hand to national accountants.
International frameworks move slowly; domestic policy moves the money. Notable patterns globally:
For practitioners, the lesson is simple: the contract that matters for a given project is usually national or subnational — read the current methods where you plan to work, and design monitoring from day one to match them.
When Country A sells a mitigation outcome to Country B, A adds the tonnes back into its own inventory so the same removal isn't counted toward both countries' targets. It's the double-counting firewall of Article 6.
Via the voluntary market, yes, with the usual caveats about credit quality and evolving integrity guidance (claims frameworks increasingly distinguish "offsetting" from "contribution"). Article 6.4 credits may also become available for corporate use subject to rules and host-country authorisation.
Some countries lack the mapping baseline, the national monitoring capacity, or the political instrument mix to include them; methods existing doesn't equal accounting being implemented. Capacity-building is a live policy gap.
Possible — if the science converges on transfer functions for export and burial that are robust, generalisable and measurable, as happened piecemeal for other ecosystems. Watch successive IPCC assessment cycles and supplement updates.
With the national inventory methods for their country (if any), and with a monitoring design a national accountant would recognise. Partnerships with research institutions help enormously; our methodology overview describes the standards we build around at project scale.
Blue carbon credits fund coastal restoration at scale — when they're done right. Who buys them, who sells them, how the market works, and where kelp fits.
Priya Raman ·
MRV — monitoring, reporting, verification — is the machinery that makes blue carbon credits real. How coastal carbon claims get measured and audited.
Priya Raman ·
Kelp grows as fast as any forest on Earth, but where does its carbon actually go? The genuine science, the real sinks and the honest uncertainties.
Dr. Mara Ellison ·