Scientists race to track what’s left of shrinking sea meadows store more carbon than forests
- 08 Apr 2021
Hundreds of miles from the nearest shore, ribbon-like fronds flutter in the ocean currents sweeping across an underwater mountain plateau the size of Switzerland.
A remote-powered camera glides through the sunlit, turquoise waters of this corner of the western Indian Ocean, capturing rare footage of what scientists believe is the world’s largest seagrass meadow.
Human activity is helping destroy the equivalent of a soccer field of these seagrasses every 30 minutes around the world, according to the U.N. Environment Programme (UNEP). And scientists are now racing to take stock of what remains.
Seagrasses play a large role in regulating ocean environments, storing more than twice as much carbon from planet-warming carbon dioxide (CO2) per square mile as forests do on land, according to a 2012 study in the journal Nature Geoscience.
Countries that hope to earn credit toward bringing down their CO2 emissions could tally their seagrasses and the carbon they store, a first step toward accrediting carbon offsets for eventual trading on an open market.
The grasses also curb the acidity of surrounding waters -- an especially important function as the ocean absorbs more CO2 from the atmosphere and becomes more acidic.
SEAGRASS AS CLIMATE ALLY
While most seagrasses fringe coastlines around the world, the shallowness of Saya de Malha allows sunlight to filter to the seabed, creating an aquatic prairie in the Indian Ocean that provides shelter, nurseries and feeding grounds for thousands of marine species.
The bank’s isolation has helped protect it from coastal threats, including pollution and dredging. But even such remote stretches of international waters face increasing incursions from shipping and industrial fishing.
With the boat bobbing for days above the plateau, the researchers gathered bits of grass floating in the water, tweezering them into bottles for analysis back on shore.
Seagrass meadows are believed to be retreating around 7% per year globally, according to the most recent seagrass census published in a 2009 study in Proceedings of the National Academy of Sciences. It notes the estimate was based on incomplete data available at the time.
If still intact, these could have supported around 400 million fish and stored up to 11.5 million tonnes of carbon -- equivalent to 3% of Britain's CO2 emissions in 2017, the study said.
This year, Seychelles began assessing its coastal seagrass carbon stock for the first time, and at least 10 countries have said seagrasses would play a part in their climate action plans, according to UNEP.
Seychelles and Mauritius, which have joint jurisdiction over the Saya de Malha’s seabed, should count up and care for the wealth of seagrass on their shared doorstep, said James Michel, who served 12 years as president of the Seychelles until 2016.
