Carbon control
Studies have revealed that seagrass can store twice as much carbon as forests

Seagrasses only take up a small percentage of global coastal area, but they’re a dynamic ecosystem for carbon transformation
Seagrasses only take up a small percentage of global coastal area, but they’re a dynamic ecosystem for carbon transformation Thinkstockphotos/ Getty Images

Conserving and restoring seagrass meadows may reduce greenhouse gas emissions and increase carbon stores, according to a new study. Per unit area, seagrass meadows can store up to twice as much carbon as the world’s temperate and tropical forests, said researchers.

The study is the first global analysis of carbon stored in seagrasses and the results demonstrated that coastal seagrass beds store up to 83,000 metric tons of carbon per square kilometre, mostly in the soils beneath them.

As a comparison, a typical terrestrial forest stores about 30,000 metric tons per sq km, most of which is in the form of wood. The research also estimates that although seagrass meadows occupy less than 0.2 per cent of the world’s oceans, these are responsible for more than 10 per cent of all carbon buried annually in the sea.

"Seagrasses only take up a small percentage of global coastal area, but this assessment shows that they’re a dynamic ecosystem for carbon transformation," said James Fourqurean, the lead author of the paper and a scientist at Florida International University and the National Science Foundation’s (NSF) Florida Coastal Everglades Long-Term Ecological Research (LTER) site.

"Seagrasses have the unique ability to continue to store carbon in their roots and soil in coastal seas. We found places where seagrass beds have been storing carbon for thousands of years," said Fourqurean. The research was led by Fourqurean, in partnership with scientists at the Spanish High Council for Scientific Investigation, the Oceans Institute at University of Western Australia, Bangor University in the United Kingdom, the University of Southern Denmark, the Hellenic Centre for Marine Research in Greece, Aarhus University in Denmark and the University of Virginia.

Seagrass meadows, the researchers found, store 90 per cent of their carbon in the soil — and continue to build on it for centuries. In the Mediterranean, the geographic region with the greatest concentration of carbon found in the study, seagrass meadows store carbon in deposits many metres deep.

Seagrasses are among the world’s most threatened ecosystems. Some 29 per cent of all historic seagrass meadows have been destroyed, mainly due to dredging and degradation of water quality. At least 1.5 per cent of Earth’s seagrass meadows are lost every year. The study estimates that emissions from the destruction of seagrass meadows can potentially emit up to 25 per cent as much carbon as those from terrestrial deforestation.

"One remarkable thing about seagrass meadows is that, if restored, they can effectively and rapidly sequester carbon and re-establish lost carbon sinks," said paper co-author Karen McGlathery, a scientist at the University of Virginia and NSF’s Virginia Coast Reserve LTER site.

Seagrasses have long been recognised for their many ecosystem benefits: they filter sediment from the oceans; protect coastlines against floods and storms; and serve as habitats for fish and other marine life. The finding was reported in a paper this week in the journal Nature Geoscience. — ANI