Blue carbon in Australia: what it is, and where kelp fits

What is blue carbon?

Blue carbon is carbon captured and stored by coastal and marine ecosystems. In practice, the term refers to a specific, established set of habitats: mangroves, tidal marshes (saltmarsh) and seagrass meadows. These are the internationally recognised blue carbon ecosystems, and for good reason. They grow in waterlogged, low-oxygen soils that slow decomposition to a crawl, so the carbon their plants pull from the atmosphere gets locked into sediment and can stay there for centuries to millennia.

That combination — fast capture above ground, durable storage below it — is what makes these blue carbon ecosystems so valuable. The carbon is not just absorbed; it is buried and held, which is exactly what climate accounting cares about.

Why Australia is globally significant for blue carbon

Australia punches well above its weight here. The continent holds a large share of the world's blue carbon ecosystems — extensive mangroves across the tropical north, vast seagrass meadows, and saltmarsh along temperate coasts. That gives Australia both a major natural carbon store and an outsized opportunity to protect and restore it.

Policy has been catching up to that opportunity. Australia has been developing blue carbon methodology for years, including a dedicated blue carbon method under the Australian Carbon Credit Unit (ACCU) scheme. That method centres on restoring tidal flow to coastal wetlands — for example, removing barriers like levees and tidal gates so seawater can return to drained land, allowing mangroves and saltmarsh to re-establish and resume storing carbon. It is one of the few places in the world where coastal wetland restoration can generate formal carbon credits.

Kelp, macroalgae and blue carbon — the honest version

Here's where care matters most. Kelp forests and other macroalgae are extraordinary carbon-drawdown machines: they are among the fastest-growing primary producers on Earth, and they pull large amounts of carbon from seawater as they grow. It is tempting to fold them straight into the blue carbon story. But the science doesn't yet support treating kelp carbon as equivalent to mangrove or seagrass carbon.

The reason is storage, not capture. Unlike wetland plants rooted in sediment, kelp grows attached to rock. It doesn't bury carbon beneath itself. For kelp-derived carbon to be durably locked away, a meaningful portion of it has to be exported to the deep sea — sinking below depths where it won't quickly return to the atmosphere. How much of that actually happens, and how reliably it can be measured and verified, is genuinely debated among scientists.

Because of that, methodologies for crediting macroalgae and kelp carbon are still emerging. They are not established in the way mangrove and seagrass methods are. So while kelp restoration delivers real carbon drawdown, it should not be presented as guaranteed, readily creditable sequestration today. Anyone claiming otherwise is getting ahead of the evidence.

Why blue carbon matters to investors and corporates

For companies looking past simple offsets, blue carbon is attractive because it can deliver real, science-based outcomes rather than paper credits. Coastal restoration produces measurable climate benefits alongside biodiversity gains and coastal-resilience co-benefits — wetlands and reefs that buffer storms, support fisheries and rebuild habitat. That substance is exactly what stands up to ESG scrutiny and investor diligence.

• Substance over offsets: tangible ecosystem outcomes, not just a certificate.
• Biodiversity co-benefits: restored habitat supports the species that depend on it.
• Coastal resilience: healthy coastal ecosystems protect shorelines and communities.

Where Ocean Greens fits

Ocean Greens restores kelp forests primarily for their broad ecological value — biodiversity, fisheries, coastal protection — and for the carbon they draw down as they grow. We're deliberately upfront that macroalgae carbon accounting is still developing, and we don't sell kelp restoration as established blue carbon credit. Our case rests on rebuilding living reefs along the Great Southern Reef, with carbon as one benefit among several. You can read our full approach on the kelp forest restoration page, and see how it sits within our broader rewilding Australia mission.