Seagrass meadows, which rarely draw the attention given to coral reefs or mangrove forests, perform a steady but important task: they help hold coasts in place.
The plants anchor themselves in sediment through dense root systems that bind the seabed, similar to how forests stabilize soil on land. Oscar Serrano Gras, a researcher affiliated with the Blanes Center for Advanced Studies in Spain and Edith Cowan University in Australia, told Mongabay contributor Sean Mowbray that these underwater meadows can form a natural barrier against erosion. Their structure also allows them to capture and store large amounts of carbon dioxide.
As climate change strengthens storms and extends their duration, many coastlines are facing more frequent flooding and infrastructure damage. The loss of seagrass reduces a layer of natural protection. Dense meadows slow water movement, reducing wave energy before it reaches shore. Heidi Nepf, a civil and environmental engineering professor at the Massachusetts Institute of Technology, explained that the leaves create resistance to flowing water, weakening waves as they pass through the vegetation.
The details matter. Larger species with broader leaves interact more strongly with moving water. Neptune grass, common in the Mediterranean, can blunt waves far more effectively than smaller varieties such as dwarf eelgrass. At the same time, the plants stabilize sediments and gradually build them up. A study published in Nature in 2024 suggested that widespread loss of Neptune grass could lead to markedly higher water levels along parts of the Mediterranean coast.
Even so, scientists caution against treating seagrass as a standalone defense against storms. Maike Paul of Leibniz University Hannover, in Germany, said evidence linking seagrass to large-scale coastal protection remains incomplete. Engineered defenses will still be necessary in many places.
Yet the meadows deliver benefits that extend beyond shoreline stability. They host dense marine communities whose shells contribute sand to nearby beaches. They also filter sediments and pollutants from the water, improving conditions for ecosystems such as coral reefs.
Despite their value, seagrasses are declining. About 30% of global meadows have disappeared since the 19th century, largely because of coastal development, dredging and polluted runoff. Climate change is now adding further pressure. Marine heat waves in Australia have wiped out large stretches of seagrass meadow, releasing millions of tons of stored carbon and depriving animals such as dugongs of feeding grounds.
Restoration efforts are expanding, though they remain slow and costly. Scientists and volunteers often plant hundreds of seeds per square meter in painstaking trials. New approaches, including mechanical seeding devices and experiments with heat-tolerant strains, may help. Even so, the first priority is clear enough: preventing the remaining meadows from disappearing.
Banner image: Cymodocea nodosa seagrass in Spain, also known as Little Neptune grass. Restoring and protecting seagrass can have climate and coastal protection benefits. Image courtesy of Liam McGuire/Ocean Image Bank.
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