Human beings are increasingly making their homes on the coasts of continents, but this demographic shift is taking a toll on a sensitive coastal ecosystem that is often overlooked: seagrass meadows. A new analysis of seagrass abundance around the world found that 27 percent of these meadows have disappeared since 1879, and the rate of loss is accelerating. The study’s authors write: “Seagrass loss rates are comparable to those reported for mangroves, coral reefs and tropical rainforests, and place seagrass meadows among the most threatened ecosystems on earth….. Our report of mounting seagrass losses reveals a major global environmental crisis in coastal ecosystems, for which seagrasses are sentinels of change” [Nature News].
Endangered species expert Susanne Livingstone notes that despite these losses seagrass rarely makes it into the public consciousness. “It’s probably because they’re not as sexy [as corals], they’re not as attractive,” she says. “They’re just as ecologically important if not more so” [Nature News]. Seagrass meadows provide grazing for a variety of marine animals, including the green turtle and the manatee-like dugong. The coastal areas also serve as nurseries for fish; both coral reefs and commercial fisheries would feel the impact if seagrass meadows vanish.
In the study, which will be published in the Proceedings of the National Academy of Sciences, researchers say that nutrients in sewage and run-off from agriculture and industry are the major cause of seagrass death…. These nutrients trigger the growth of algae, plants and animals that grow above or on seagrass, and stop it from getting the sunlight it needs [Australian Broadcasting Corporation].
Seagrasses, which evolved from terrestrial plants, are the only flowering plants that can live entirely in water. They are most closely related to lilies and are very different to seaweeds, which are algae…. Seagrass beds are believed to rival rice paddies in their photosynthetic productivity or the ability to extract greenhouse gas CO2 and convert it into oxygen and stored carbon matter [Reuters]. If seagrass meadows continue to shrink in shallow coastal waters around the world, it will accelerate the pace of global warming, researchers say.
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Image: flickr / jayhem