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World - Why Seagrass Could Be the Ocean's Secret Weapon Against Climate Change

A vast, mostly invisible ecosystem shapes life on Earth, from the food we eat to the air we breathe. And the more scientists learn, the more they say it’s in trouble

Bright sunlight filters down through the clear Mediterranean waters off the coast of Spain, illuminating a lush meadow just below the surface. Blades of strikingly green grass undulate in the currents. Painted comber fish dart among clumps of leaves, and technicolor nudibranchs crawl over mounds. Porcelain crabs scuttle by tiny starfish clinging to the blades. A four-foot-tall fan mussel has planted itself on a rock outcropping. A sea turtle glides by.

This rich underwater landscape has been shaped by its humble covering, Posidonia oceanica. Commonly known as Neptune grass, it is one of about 70 species of seagrasses that have spread, over millions of years, across the globe’s coastal shallows, embracing and buffering continental shelves from Greenland to New Guinea. Seagrasses provide habitat for fish, sea horses, crustaceans and others; food for sea turtles, waterfowl and marine mammals; and nurseries for an astounding 20 percent of the largest fisheries on the planet.

“Seagrasses are the forgotten ecosystem,” Ronald Jumeau, a United Nations representative from the Republic of Seychelles, writes in a 2020 U.N. report. “Swaying gently beneath the surface of the ocean, seagrasses are too often out of sight and out of mind, overshadowed by colorful coral reefs and mighty mangroves.” But, he says, they “are among the most productive natural habitats on land or sea.”

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