Australia's marine ecosystems, including wetlands and coastal vegetation, are global carbon storage hot spots, absorbing 20 million tons of carbon dioxide each year, the equivalent of taking 4 million cars off the road, a new report has said.

The "world-first research" accurately measured the amount of carbon being absorbed and emitted by seagrass meadows, mangroves and salt marshes, collectively known as blue carbon in Australia, according to the study published on Tuesday in the Nature Communications journal.

The carbon dioxide then remains locked up in the soil for millennia. The study by researchers at Perth-based Edith Cowan University (ECU) said the quantification of Australia's blue carbon "is the most accurate of any country."

However, the study found that damage to the vast carbon sink, due to human development, severe weather and the effects of climate change, are already contributing to climate change by releasing 3 million tons of carbon dioxide back into the atmosphere every year.

"Globally, vegetated coastal ecosystems are being lost twice as fast as tropical rainforests despite covering a fraction of the area," said Oscar Serrano, the paper's lead author. "These ecosystems are also important as habitats and nurseries for fish and other marine life, helping prevent coastal erosion and improving water clarity."

The study said restoring such damaged ecosystems would help fight climate change and bring millions of dollars in carbon credits. Serrano said Australia is home to around 10% of the world's blue carbon ecosystems, which absorb carbon dioxide 40 times faster than terrestrial forests because of their enormous capacity to store carbon in the soil.