Sea-grass meadows once wrapped Australia's coastline providing sanctuary and food for dugongs and turtles, habitats for fish to breed and myriad other ecosystem services such as nutrient recycling and sediment stabilization.

Atmospheric carbon dioxide levels are now so high that they risk damaging our ecological life-support systems and sea-grass could play a vital role in helping reverse the earth's dangerous warming trend, said University of Technology, Sydney (UTS) scientist, Dr Peter Macreadie.
"If the amount of CO2 in the atmosphere reaches 450 parts per million, the Intergovernmental Panel on Climate Change - the world's 'climate change referee' - estimates we will only have a 50 percent chance of avoiding the drought, famine and widespread species extinction that is expected from a two degree increase in temperature," Macreadie said.
"What sea-grasses are doing is not complex. They are simply capturing and storing carbon through photosynthesis and by trapping particles in the water column. This process - known as biosequestration - is what created fossil fuels in the first place," he said.
The ability of sea-grass to absorb CO2 could be worth as much as USD 45 billion, based on the current carbon price of about USD 23 per ton, Macreadie said.
It is a conservative estimate based on only one species of sea-grass, Posidonia australis. It is a compelling reason to protect sea-grass meadows around the world, which are under threat from coastal development and nutrient runoff. New South Wales alone has lost 50 percent of its sea-grass, he said.
"The vast majority of carbon in sea-grass meadows is actually stored in the sediment and can remain there for thousands of years," Macreadie said.
"The danger is that by destroying sea-grass not only are we pulling less carbon out of the atmosphere, there is a risk that millennia-old carbon stocks could be released back into the environment.
"We are talking about amounts likely to be in excess of three times Australia's annual greenhouse gas emissions. This would mean sea-grasses would shift from being carbon sinks to carbon sources, thereby accelerating climate change," he added.


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