Seagrass carbon Storage - marine biosequestration could be important for negative emissions

Updated 28 October.

Blue carbon is part of the solution to tackle climate change. So why aren't we talking about it far more?

Blue carbon refers to the carbon sequestration potential of coastal ecosystems: that zone reaching from just above the high tide mark to the coastal shallows. It includes salt marsh, mangroves and seagrass meadow ecosystems.

We need to take care and nurture our coastal ecosystems as they can play a vital role in bio-sequestration of carbon at rates far in excess of forests and soil carbon farming.

Biologists working with seagrasses met to present papers and discuss scientific practices at the 12th International Seagrass Biology Workshop (ISBW) (Conference website) in Wales 16th to 21st October. Just before the conference 122 scientists across 28 countries associated with the World Seagrass Association released a statement on the global importance of conserving and expanding seagrass meadows.

Seagrass projected to drastically decline with sea level rise

To most of us, what is hidden beneath the waves of our coastal environment remains invisible and is little thought about or cared about. Yet seagrass meadows, though hidden from our direct view, contribute valuable ecological services supporting valuable fish nurseries, as food for dugongs and turtles, and as a highly efficient blue carbon sink sequestering carbon.

A new study of the seagrass meadows in Moreton Bay, Queensland found that a significant proportion of valuable seagrass habitats would be lost without action to offset the affects of climate change. "The area of seagrass habitat was predicted to decline by 17% by 2100 under a scenario of SLR of 1.1 m." said the study.

Lead author Dr Megan Saunders from UQ's Global Change Institute said "Seagrass meadows not only help to slow climate change by sucking up a large portion of the world's plant-stored carbon, but they also benefit livelihoods, food security, fisheries, biodiversity, shoreline protection and other ecosystem services,"

Seagrass meadows are key carbon sinks for combatting climate change

May 22 is UNESCO's
 International Day for Biological Diversity which focussed strongly on conserving our marine diversity. One of the important marine ecosystems are the seagrass meadows around the coasts of the world. A new global scientific research study just released has shown that seagrass meadows store significantly more carbon than any land based forest. They are very important as carbon sinks. But they are also suffering a major decline due to pollution from agricultural and mining development and chemical runoff, coastal development changing water turbidity upsetting photosynthesis in seagrass, and increasing sea surface temperatures affecting seagrass growth due to global warming.

The new global study of seagrass meadow ecosystems has found that coastal seagrass beds store much more carbon than can be stored in even the most carbon dense forests, such as the temperate native forests of Victoria. Seagrass meadows can store up to 83,000 metric tons of carbon per square kilometre, mostly in the soils below them. In comparison, a typical land forest stores around 30,000 metric tons per square kilometre mostly as wood. It is the first global study to analyze the carbon storage capacity in seagrasses.

Seagrass meadows support a highly level of biodiversity with many fish species using the seagrass during their juvenile period, as well as providing homes for crabs, sea urchin, seahorses shrimp and prawns. Sea tutles, dugongs and manatees depend on seagrass meadows as a primary food source. As Professor Carlos Duarte points out in an article on The Conversation website, Indigenous cultures new the significance and value of seagrass meadows. Conservation and restoration of seagrass ecosystems provides a unique Submarine Carbon Tax Opportunity! Seagrass meadows are intense, but fragile carbon sinks.

More Information: Seagrass Watch | Global Seagrass Monitoring Network

Coastal ecosystems suffer 100 fold decrease in capacity to store carbon mitigating climate change

The carbon sink capacity of urbanized river estuary and coastal environments to mitigate climate change has reduced by 100 fold according to scientists from the University of Technology Sydney. The Scientists used core samples from Botany Bay in Sydney to reconstruct the sedimentation changes in the past 6000 years, highlighting the changes in the ecology. The plant samples in the sedimentation changed as rapid industrialisation occurred around Botany Bay during the 1950s.

"We have effectively gone back in time and monitored carbon capture and storage by coastal ecosystems, finding a 100-fold weakening in the ability of coastal ecosystems to sequester carbon since the time of European settlement. This severely hampered the ability of nature to reset the planet's thermostat." said Dr. Peter Macreadie, University of Technology, Sydney Chancellor's Postdoctoral Research Fellow.