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Wärtsilä : Sharks on the brink

Climate change is threatening the survival of sharks. And not only are they in danger, but their disappearance could have massive implications for the stability of ocean ecosystems.

Ocean ecosystems rely on sharks to keep the populations of other species in check. Toby Daly-Engel, an assistant professor of Ocean Engineering and Marine Sciences at the Florida Institute of Technology and the Director of the Florida Tech Shark Conservation Lab, is sounding the alarm.

Dr. Toby Daly-Engel

“Big predators like sharks are sentinel species. They’re the canary in the coal mine for climate change, “ she says. “In 2021, a study found that 70% of sharks are already lost in terms of abundance and species. That includes sharks going extinct before they are officially described and named. Of the known species, over a third are close to extinction—that’s a new finding as of 2021.”

Sharks on the brink

Ocean warming 

In a 2021 study conducted by the British Ecological Society, researchers used data from a 16-month field experiment to simulate impacts should the tiger shark, a key apex predator in Western Australia’s Shark Bay, become completely extinct.

The findings were shocking: should tiger sharks die out, the population of sea cows, which tiger sharks primarily feed on, would explode. This would lead to the overgrazing of seagrass, a plant that has already been irreparably damaged by climate change.

Juvenile natural mortality is a hard parameter to estimate, but it can be  done with pop-up archival tags – The Applied Ecologist

Juvenile sharks are especially vulnerable to warming waters. Even massive sharks that are found everywhere and able to swim thousands of kilometers in a season aren’t using their whole range. They return to the same habitats to reproduce, and so are creatures of habit. When climate change affects the shallow reproductive habitats that they use as nurseries, that affects the whole population.

A 2021 study published in Nature has recommended protecting 30% of the world’s land and oceans. This is a good start but those concerned with the ocean’s longevity remain deeply concerned about the future.

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