Sharks are known to be predatory, but they just might be human beings’ close ally in mitigating the effects of climate change.
According to a new study published in the journal Nature Climate Change on Sept. 28, the killing of sharks and other top predators may lead to the instability in the natural food chain of the ocean, resulting in the releasing of carbon from the sea floor into the earth’s atmosphere.
The team behind the new research includes collaborators from Utah State University, Florida International University, Deakin University, University of Queensland, the University of Western Australia, the University of Technology Sydney, Griffith University and Swansea University.
The study claims there is sufficient evidence that “intact predator populations are critical to maintaining or growing reserves of ‘blue carbon,’” which is carbon stored in coastal or marine ecosystems.
“Sharks and other apex marine predators continue to be harvested unsustainably throughout the world," warned Utah State University scientist Trisha Atwood, the paper’s lead author, adding there are "far-reaching consequences" of the loss of these animals on carbon cycling and the human ability to counter the effects of climate change.
Peter Macreadie, lead researcher of the project at Deakin University, said that changes to food web structures, specifically due to loss of sharks and other top predators, can alter the function of the ecosystem.
"In science, the consequence is what is known as a trophic meltdown. With the loss of around 90 percent of the ocean's top predators from around the globe, the occurrences of trophic meltdowns are now widespread,” he explained.
Macreadie illustrated the effects in “blue carbon” ecosystems.
"In the case of sharks and turtles, sharks eat turtles, which in turn eat seagrasses. But when sharks disappear, the turtles have a tendency to run wild and the seagrass ecosystems cannot sustain the turtle populations,” he warned, citing that turtles overgraze, leading to huge reductions in seagrass carbon stocks.
The researchers called for improved policy and management to reflect these realities.
In Sydney, more than 70 experts gathered on Tuesday, Sept. 29, for the shark summit to discuss new safety measures following a number of shark attacks on New South Wales beaches. Environmentalists and policymakers opposed cruel or inappropriate ways to repel sharks, given scientific warnings on how harming or killing these top predators can exacerbate climate change.
Photo: Steve Garner | Flickr
