Seagrass may help fight climate change

Seagrass may be crucial in the battle against climate change as the humble plant is 35 times more efficient at locking up, or 'sequestering' carbon than rainforests, a new study has found.
Seagrass 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 stabilisation.
Atmospheric carbon dioxide levels are now so high they risk damaging our ecological life-support systems and seagrass 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 per cent chance of avoiding the drought, famine and widespread species extinction that is expected from a two degree increase in temperature," Macreadie said.
"What seagrasses 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 seagrass to absorb CO2 could be worth as much as USD 45 billion, based on the current carbon price of about USD 23 per tonne, Macreadie said.

It is a conservative estimate based on only one species of seagrass, Posidonia australis.

It is a compelling reason to protect seagrass meadows around the world, which are under threat from coastal development and nutrient runoff. New South Wales alone has lost 50 per cent of its seagrass, he said.
"The vast majority of carbon in seagrass meadows is actually stored in the sediment and can remain there for thousands of years," Macreadie said.
"The danger is that by destroying seagrass 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 seagrasses would shift from being carbon sinks to carbon sources, thereby accelerating climate change," he added.