Here’s how ‘blue carbon’ could be even better than rainforests at helping to save the planet

“It’s the mud that gets scientists excited,” says Chris Gillies, who is driving  the most extensive wetlands carbon sequestration project in South Australia’s history.  

The Nature Conservancy (TNC) Oceans Program director is talking about blue carbon — the natural process of storing carbon in coastal and marine ecosystems, which scientists believe will help to reduce Earth’s out-of-control CO2 levels.

In SA, plans are afoot to restore up to 2,000 hectares of mangroves, salt marsh and sea grasses across 700 kilometres in the Saint Vincent and Spencer gulfs.

“It’s a really powerful way of trapping and drawing down carbon from the atmosphere,” Dr Gillies said.

He said coastal wetlands worked by collecting “mobile carbon” such as dead leaves and plants before they flowed out to the ocean, and before bacteria had a chance to break it down into methane and carbon dioxide.

“They capture it there at the wetland and then the combination of mud and salt water prevents the bacteria from breaking it down further and, as more mud accumulates on top of that, it gets pushed down,” he said.

Dr Gillies said the carbon could be observed as the dark matter visible in soils and mud, which was likely to be a mix of carbon, sand and other fine grain materials.

Carbon might account for 30 to 40 per cent of the matter in terrestrial soils, but in wetland muds it could account for between 60 and 80 per cent.

A $1.2m partnership

SA’s $1.2 million blue carbon project was announced this month in a partnership between TNC, the SA government, and the European-based COmON Foundation — a philanthropic organisation dedicated to restoring degraded landscapes worldwide.

COmON chief executive officer John Loudon said coastal wetlands could absorb and store carbon in concentrations up to four times greater than land-based forests.

At the same time, however, he warned Australia was losing the equivalent of 700 soccer pitches in blue carbon wetlands annually.

Even protected mangrove swamps such as those based at St Kilda, north of Adelaide, have not been safe from disaster. An adjacent salt mining company reinstated a pump against the terms of its tenancy in 2020 and hypersaline water leaked from gypsum ponds into the wetlands.

Some 10ha of nearby mangroves are now considered completely dead, along with 35ha of salt marsh, although researchers believe evidence of stressed or dead vegetation can be seen in an area spanning  almost 200ha.

Wetlands insurance on radar

Dr Gillies said the blue carbon project would investigate using insurance models to protect more than 1 million hectares of existing blue carbon ecosystems.

By way of example, Dr Gillies said the world’s first coral reef to be insured was in Mexico’s Yucatan Peninsula in 2019. The policy was established by the State of Quintana Roo with participation from TNC, the tourism industry, the local science community and the international insurance industry.

The policy was triggered by hurricanes in 2005 that hit Mexico’s Caribbean coast, causing $US8 billion in damages to the coastline and closing hotels and businesses.

Authorities noticed that some hotels and beaches in Puerto Morelos had been relatively protected from the wildest seas by a stretch of the Mesoamerican Reef.

With coral reefs able to reduce up to 97 per cent of a wave’s energy before it hits the shore, the Mexican community banded together to insure the reef.

“So if it ever got hit by a hurricane or degraded, then that insurance would essentially pay for the restoration of the coral reef to protect the beach,” Dr Gillies said.

He said an insurance program in SA could protect all of the existing carbon stored in its wetlands.

“You wouldn’t be left saying, ‘How are we going to fund the restoration and recovery of thousands of hectares of wetlands?’.”

Universities explore potential

SA Environment Minister David Speirs said the blue carbon project complemented about $600,000 in partnerships with Flinders University, the University of Adelaide, and Green Adelaide, which were delivering four projects to explore the value of carbon stored along Adelaide’s coastline.

The project would also be used to leverage further funding from the Commonwealth via its Emissions Reduction Fund, which required an assurance that carbon would remain safely sequestered for a minimum of 25 years.

Dr Gillies said that in the same way land-based sequestration of carbon required forest trees to remain healthy and alive to prevent CO2 being released again, so too did coastal sequestration.

“The idea is to not disturb them, but what we’ve done over the last 100 years is drain a lot of those wetlands, we’ve put roads on them, we’ve blocked the ocean, we’ve blocked saltwater on top of those wetlands.”

Dr Gillies said negotiations were underway with a landowner about 50 kilometres north of Adelaide to begin the first blue carbon project.