Hakai Magazine

Coastal science and societies

a tractor grooms a beach
A clean beach may be pretty, but it’s bad news for the life forms that rely on washed-up seaweed. Photo by Ryan Carter/Alamy Stock Photo

For a Healthy Beach, Leave the Seaweed Alone

Beaches with thick mats of seaweed support more diverse ecosystems.

Authored by

by Samantha Andrews

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For a tourist, nothing ruins a picturesque sandy beach like the sight and smell of rotting seaweed, which is why owners and managers of beaches in many seaside towns use tractors to drag large rakes through the intertidal. Mechanical beach cleaning removes the seaweed, but it also destroys habitat.

“It might look like nothing more than dead and rotting seaweed, but the strandline is an important food source and habitat for much of our coastal wildlife,” says Lissa Batey, a marine policy expert at England-based NGO the Wildlife Trusts. The seaweed masks myriad life forms, such as the golden-brown dune chafer beetle, which travels from nearby dunes to eat rotting seaweed, and the aptly named seaweed fly, which lays its eggs in the decaying algae. Removing the seaweed hurts the whole food web, from microscopic bacteria and humble marine isopods to the shorebirds and small mammals that feed on them.

But the tide continuously brings seaweed to shore; surely communities that rely on it have time to recover. Not quite, says Caroline Griffin, an ecologist who spent several months researching invertebrate communities on cleaned and uncleaned beaches in Scotland and Sweden while studying at Scotland’s University of Stirling. Griffin found that the thicker the layer of seaweed, the greater the diversity of macroinvertebrate life.

Unsurprisingly, ungroomed beaches have, on average, more seaweed and greater diversity of macroinvertebrates than groomed beaches. But even when comparing groomed with ungroomed beaches with similar seaweed covers, she found that the diversity on ungroomed beaches was higher.

Grooming is sometimes put on hold over the winter, during which storms rebuild much of the seaweed cover. However, Griffin found that seaweed-dependent communities do not always fully recover before grooming starts again.

In the United Kingdom, Batey says beach managers are becoming increasingly aware of the importance of leaving seaweed on the beach. But “work is still needed to raise public awareness of the importance of strandlines, as public attitudes towards leaving seaweed on the beach are often negative,” she says.

“The removal of all surface debris creates a sterile, artificial environment and further exacerbates the disconnection between society and our natural environment.”