Prado de ervas marinhas. Crédito: John Mark Arnold/Unsplash

Study: seagrass may be key for carbon sequestration

Researchers discovered that seagrass meadows are the second most efficient ecosystem in storing carbon and show that it is possible to expand the volume of these plants globally

The solution to reducing the volume of greenhouse gases in the atmosphere may lie on the seabed. A study recently published in the scientific journal Nature Geoscience showed the, until then unknown, capacity of seagrasses to capture carbon with extreme efficiency.

In a statement to website Smithsonian Mag, Marianne Holmer, one of the scientific article authors, explained that the research found out that oceanic seagrass meadows are the second most efficient ecosystem in the cycle of carbon storage, only behind tundra and ahead of mangrove forest, restingas and rainforests, such as the Amazon.

In the tundra, the frozen soil - highly efficient in retaining the substance - captures the bulk of the stored carbon. The problem, explains Holmer, is that global warming is thawing the tundra’s ice in many parts of the world and, therefore, releasing carbon back into the atmosphere. Conversely, seagrass meadows are less affected by climate changes and can be spread globally with more ease than tundra.

“Seagrass plants have an excellent capacity for taking up and storing carbon in the oxygen-depleted seabed, where it decomposes much slower than on land. This oxygen-free sediment traps the carbon in the dead plant material which may then remain buried for hundreds of years,” explains the researcher.

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According to the researchers’ calculations, although seagrass meadows are not so common in the Earth’s seas, they account for 10% of all carbon sequestered in the oceans. For every one kilometer square of this ecosystem, the planet stores 83 thousand tons of carbon, almost three-fold more than the 30 thousand tons sequestered every kilometer square of rainforests, for example.

“Seagrasses only take up a small percentage of global coastal area, but this assessment shows that they are a dynamic ecosystem for carbon transformation. Seagrasses have the unique ability to continue to store carbon in their roots and soil in coastal seas. We found instances in which particular seagrass beds have been storing carbon for thousands of years,” said James Fourquerean, one of the article’s authors, to the website Climate Action.

Where and how seagrasses may save the planet

All living organisms, be it animals, plants, algae or bacteria, have carbon in their composition and, presumably, work as substance absorbers. The larger these organisms, the greater their capacity of storing carbon - which is why forests, with huge and populated trees, are great CO2 hosts.

Thus, the more seagrass spread meadows around the world, the more CO2 will be captured by this ecosystem. Currently, the opposite is true: human action along coastlines is putting the ecosystem at risk. According to the researchers, the annual loss of these plants is 1.5% - and this is equivalent to, proportionally, destroying 25% of rainforests, if we consider the subsequent environmental impact.

The good news, according to the article, is that planting vast areas of seagrasses is a very feasible task. The researchers defend that, since these grasses are not algae, but full plants (with flowers, leaves and roots), the seeds can be sowed on the seabed and stimulated by divers.

The team of scientists has already started testing a seagrass sowing project along Denmark’s coastline, and already plans a new project on a large scale. To date, there are 60 seagrass species cataloged; however, the experiment has focused only on the most popular of them, Zostera marina. The conclusion is that it may grow relatively well in temperate areas in the North Hemisphere, but it has potential for growth around the world, except in the Antarctica surroundings.

 

Published 05 December 2018