Western Australia's Shark Bay seabeds are a ticking carbon time bomb, says scientist

More than a quarter of seagrass meadows at Shark Bay were lost in a marine heatwave in 2011. (Supplied: WAMSI/Nick Thake)

Australia’s zero greenhouse gas ambitions could be set back if a vast reserve of carbon stored in a seabed off Western Australia is released into the atmosphere, according to a leading marine ecologist.

World Heritage-listed Shark Bay has the planet’s largest reserve of seagrass meadows, but more than a quarter were lost in a marine heatwave in 2011.

Only 10 per cent has recovered and research shows the massive carbon deposits under the exposed areas are at risk of release during heavy storms.

Marine ecologist Gary Kendrick, professor of marine biology and plant ecology at the University of WA’s Oceans Institute and School of Biological Sciences, has been studying Shark Bay since 1982.

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He said the organic carbon captured under seagrass was 10 times greater than that stored under a rainforest of equivalent size and restoration of the lost seagrass meadows at Shark Bay was urgently needed.

“We lost over 1,300 square kilometres of seagrasses in the system that were capping all that organic carbon in the sediment, so now when storms come they disturb the sediment [and] release all of that buried carbon,” Professor Kendrick said.

“So you have a CO2 pulse going into the atmosphere.

“That’s not industrial, not human-derived and that’s not calculated in the Australian government’s calculation of our annual production of carbon dioxide. It’s extra.”

Professor Kendrick recently completed a 1-hectare trial restoring seagrass using sand-filled hessian tubes to stimulate growth.

He is frustrated a fully-funded plan to expand this work to 100 hectares has been unable to get WA government approval.

Disappearing dugongs

BHP is supporting the proposed $2 million project, which would be undertaken by divers from Shark Bay-based Indigenous sea cucumber company Tidal Moon.

Professor Kendrick said BHP recognised the potential for offsetting greenhouse gas emissions with marine-based “blue” carbon.

He said there was also huge potential for ongoing corporate and government funding for ecosystems services because the restoration would have a positive impact on Shark Bay’s globally important biodiversity and commercial fisheries.

The project funding was locked in more than a year ago and an application lodged with the state government nine months ago. It had been revised three times without consent granted.

“This is so urgent it should have been done two years ago,” he said.

A marine charter operator at Monkey Mia is also frustrated with the WA government’s slow response to seagrass restoration.

Greg Ridgley’s charter company, Perfect Nature Tours, helped the initial University of WA restoration trial.

He is keen to expand the work to a commercial scale with the help of corporate and private sponsorship.

“We’re not interested in making money at all — all we want is to get the grass growing out here,” Mr Ridgley said.

He said his company was only permitted to do research-scale restoration, but the lost seagrass meadows were already affecting populations of marine creatures, including dolphins, sharks and stingrays, which attract tourists.

“The particular bank we want to work on is probably the best dugong feeding bank on the planet,” he said.

“Well it was, and we used to go out there and look at … 40 or 50 dugongs around the boat. Now you’re lucky to have three or four or five.”

Flow on benefits for jobs, sea cucumbers

A WA government spokesperson said several restoration and recovery trials were being assessed.

“Any approval for ongoing restoration will be based on monitoring results of the trial and the proponent’s effective demonstration of capacity to deliver on their project’s objectives in an environmentally and socially acceptable way,” the spokesperson said.

The chief executive officer of Tidal Moon, Michael Wear, said the potential for ongoing funding could provide much-needed training and employment for the Malgana people of Shark Bay.

He said research in Tanzania showed a symbiotic relationship between seagrass and sea cucumbers.

If University of WA studies proved the same closed-loop relationship in Shark Bay, it could open the potential to expand his company’s sea cucumber wild harvest to a sustainable sea ranching operation, he said.

Mr Wear also believes fewer young people would have to leave their traditional country for employment opportunities.

“The whole purpose of what we’re trying to do is create that middle class and you can only do it with jobs — jobs and employment training opportunities,” he said.

A prominent Perth businessman said it was time for the WA government to support private philanthropy to fill scientific gaps at Shark Bay.

Jock Clough headed the construction giant Clough Engineering until his family sold the business in 2005.

He then studied marine biology and is now chair of the University of WA’s Oceans Institute and owns property in Shark Bay, which was used as a base for marine scientists.

He said Shark Bay was unique because it was where temperate and tropical systems merged.

He said a lack of development and the bay’s near-pristine condition made it perfect for studying the impacts of climate change.

“This is going to be my biggest private investment and I want to lean on my mates to get involved as well,” Mr Clough said.

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