Massive kelp forests off Western Australia have been destroyed in a marine heatwave

Wale sharks in Western Australia. Image: James D. Morgan/Getty

Rapid warming has killed off large kelp forests and turned them into tropical and subtropical marine ecosystems off the western coast of Australia.

The kelp forests covered more than 70% of the area’s shallow rocky reefs between Kalbarri and Perth before an extreme marine heat wave hit the midwest in 2010.

Two years later, nearly half of the kelp forest was gone and it had not recovered nearly five years later.

The area of lost kelp — important because they provide food and shelter for many animals — is calculated at 963 square kilometres.

In the place of the kelp, tropical and subtropical species have taken hold and the kelp is unlikely to return.

The researchers, led by scientists from the University of Western Australia and Curtin University, surveyed marine plants and animals at 65 reefs between 2001 and 2015.

The extent of kelp losses. Image: Science magazine.

The warming off waters off Western Australia is expected to continue with the movement of warm tropical water down the west coast of Australia made stronger by El Niño weather events.

Dr Elizabeth Sinclair at the University of Western Australia says the research documents an alarming change.

“While the Great Barrier Reef has received much recent media exposure in relation to the widespread coral bleaching event this past summer, the impacts of marine heat waves on other marine ecosystems, such as cool water kelps and seagrasses, are just as devastating,” she says.

The research is published in the journal Science.

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