In world-first research, Edith Cowan University researchers and an international team of collaborators have accurately quantified the amount of greenhouse gasses – or 'blue carbon' – being absorbed and emitted by Australian marine ecosystems.

Published in Nature Communications, the paper shows Australian seagrass, mangrove and salt marshes absorb 20 million tonnes of carbon dioxide each year, which remains locked up in their soils for millennia.

That's about the same as the annual emissions of more than 4 million cars.

Worryingly, the research shows damage to the same ecosystems is causing 3 million tonnes of carbon dioxide to be released back into the atmosphere each year as a result of human development, severe weather and the effects of climate change.

This quantification of Australia's blue carbon is the most accurate of any country and paves the way for conservation and restoration of these ecosystems to be counted toward the country's commitments to emissions reductions such as the Paris Agreement.

The research also provides a financial baseline for investors looking at blue carbon projects to offset emissions.

Major impact on climate change

The research paper's lead author, Dr Oscar Serrano from the Centre for Marine Ecosystems Research in ECU's School of Science, said blue carbon ecosystems play an enormously important role in climate change mitigation and adaptation.

"When these ecosystems are damaged by storms, heatwaves, dredging or other human development, the carbon dioxide stored in their biomass and soils beneath them can make its way back into the environment, contributing to climate change," says Dr Serrano.

Globally, vegetated coastal ecosystems are being lost twice as fast as tropical rainforests despite covering a fraction of the area.

"These ecosystems are also important as habitats and nurseries for fish and other marine life, helping prevent coastal erosion and improving water clarity."

Making a splash for cash

The research shows there is money to be made in the restoration and protection of blue carbon ecosystems in Australia.

Based on a carbon trading price of $12 per tonne, the authors see potential for blue carbon projects worth tens of millions of dollars per year in payments from the Australian Emission Reduction Fund and voluntary carbon markets.

"Those projects could take the form of replanting seagrass meadows, restoring mangroves by reflooding or by preventing expected losses through environmental management," Dr Serrano said.

"These more accurate measurements of blue carbon providemore certainty on expected returns for financiers looking at investing in blue carbon projects."