Ocean warming is driving reef sharks from their habitats, and it's likely harming both the animals and their ecosystems.
What's happening?
Gray reef sharks in the Chagos Archipelago of the Indian Ocean "spent significantly less time" in their remote coral reefs following stress events, including "the major ocean-warming" 2015-16 El Niño, the Guardian reported. In the most extreme case, the sharks didn't "return to normal residency" for 16 months.
The study tracked 120 of the animals from 2013 to 2020. It showed they were drawn to healthier reefs where bird feces provided fertilizer and invasive rats had been eradicated. The sharks were likely escaping to "deeper and cooler waters" offshore, project lead and Lancaster University zoology lecturer David Jacoby said.
The reef sharks also provide their own nutrient-rich fertilizer, helping other species on the reefs. Lead author Michael Williamson of London's Institute of Zoology said the sharks likely left their homes because of high temperatures but may have stayed away because of the resulting poor health of the reefs.
The researchers also used satellite data to gauge the environmental factors stressing the reefs, including sea surface temperatures and wind and current patterns.
Why is this important?
Coral reefs support 500 million people around the world with food and livelihoods, the Guardian reported. They are threatened by the rising global and ocean temperatures as well as overfishing and pollution.
The habitats host one in four marine fish, though reef sharks have left nearly one in five coral reefs, Jacoby told the Guardian.
"Sharks play such an important role in keeping the reef system in balance," said the University of Essex's Anna Sturrock, who was not involved with the study. "By eating both herbivorous and smaller predatory fish, they help to keep coral from being overgrazed or overgrown by algae. So it is very worrying that sharks were tending to leave during the reefs' most vulnerable times. The hopeful side of it was that not all sharks did the same thing."
What's being done about protecting coral reefs?
Organizations are stepping up, with the Global Fund for Coral Reefs recently providing $25 million for conservation efforts. Researchers have found that cleaning up waste from the seabed can reverse damage to coral reefs, and sound therapy is a surprising avenue that can also help damaged coral reefs recover.
In general, you can take action by reducing your use of dirty energy sources such as coal, gas, and oil. This helps slow the warming of the planet and protect vital ecosystems as well as our health. Try eating cleaner, swapping out energy-hungry appliances, and even changing how you buy clothes.
Join our free newsletter for good news and useful tips, and don't miss this cool list of easy ways to help yourself while helping the planet.
Cool Picks
