Coastal seagrass could store more carbon than forests and could therefore be a vital part of the solution to climate change, according to new research.
The study, published in the journal Nature Geoscience, found that coastal seagrass beds could store up to 83,000 metric tonnes of carbon per square kilometre – mostly in the soils beneath.
This is compared to a typical terrestrial forest which stores about 30,000 metric tonnes per square kilometre – mainly in the form of wood.
The study also estimated that, although seagrass meadows occupy less than 0.2% of oceans worldwide, they are responsible for over 10% of carbon buried annually in seas.
It is the first global analysis of carbon stored in seagrasses and gathered results from 3,640 observations of 946 distinct seagrass meadows across the globe.
Seagrasses not only store carbon but also filter out sediment before it reaches the oceans, protecting the coastlines from flooding and storms.
They are also an area of high biodiversity – supporting many juvenile fish species, as well as crabs, sea urchin, seahorses, shrimp and prawns. Sea turtles and manatees also depend on the meadows for a primary source of food.
Human activity, however, puts these meadows under threat – from pollution and oil spills, and boat propellers and cargo which rake through the seagrass.
Around 29% of historic seagrass meadows have been lost – mainly from dredging and ruined water quality – and a further 1.5% is expected to be lost annually.
By conserving and restoring seagrass meadows, say the researchers, greenhouse gas emissions could be reduced and carbon stores increased – while delivering key ecosystem services to coastal communities.
Read the full paper here.