Hidden underwater prairies are essential to our planet's climate and marine health

Nature · Published 3 October 2026 Swipe more like this →

In short: Seagrass meadows are not seaweed; they are true flowering plants that thrive in shallow coastal waters across every continent except Antarctica. These dense underwater ecosystems act as vital nurseries for marine life, stabilize shorelines, and sequester massive amounts of carbon, yet they are disappearing at an alarming, rapid rate.

Seagrasses are unique marine plants that evolved from terrestrial ancestors, returning to the ocean between 75 and 100 million years ago. Unlike algae, these flowering plants possess true roots, leaves, and seeds, allowing them to anchor into sandy or muddy seafloors. They form dense, productive meadows in shallow coastal zones, estuaries, and lagoons, where they play a critical role in global carbon storage. By trapping sediment in anoxic environments, these meadows prevent the decomposition of organic matter, effectively locking away carbon. Despite covering only 0.1 percent of the ocean floor, they are estimated to store 18 percent of the ocean's total carbon, making them a powerful natural buffer against the climate crisis.

Beyond their climate benefits, these meadows function as essential nurseries for over 20 percent of the world’s fisheries. They provide food and shelter for thousands of species, ranging from juvenile fish and invertebrates like scallops and snails to large herbivores such as manatees, dugongs, and green sea turtles. Their dense blade structures slow water movement, which traps sediment and filters the water column, thereby improving water clarity and protecting coastlines from erosion during storms. This intricate web of life supports biodiversity comparable to that of coral reefs, acting as a vital link in the health of marine ecosystems far beyond their immediate boundaries.

Despite their importance, these ecosystems face severe threats from human activity, including coastal development, dredging, and pollution from agricultural runoff. Excess nutrients can trigger algal blooms that coat seagrass blades, blocking the sunlight necessary for photosynthesis. Estimates suggest that at least 20 percent of the world’s seagrass has already been lost, with some regions seeing the equivalent of a football field vanish every 30 minutes. Restoration efforts are underway, involving techniques like seeding, transplanting sprigs, and using aquaculture to grow seedlings. While these initiatives aim to reverse the decline, the recovery process is often slow, highlighting the urgent need to protect existing meadows from further degradation.

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