When the sixth extinction comes, as far as the oceans are concerned, larger sea creatures are more likely to die before their smaller counterparts. Why? Human influence.
In a recent study, a group of scientists led by Stanford University paleobiologist Jonathan Payne found that because of various human activities such as damaging habitats, spreading invasive species and diseases, hunting, poaching and driving global temperatures up, we could soon be on the cusp of an extinction event, and when it comes, larger sea creatures will be the first to go. This sixth extinction event will be the first caused by humans, as opposed to the past five mass extinction events, which were all caused by natural events.
How did they reach this conclusion? By checking out which marine animal groups are currently most at risk.
The study, published in Science, details how the team identified which marine animals are currently at risk of extinction by checking the the International Union for the Conservation of Nature's list of threatened species. From there, they cross-referenced these animals with fossil records of sea creatures that died out in previous extinction events.
The result? Contrary to extinction events in the past, sea creatures that were most at risk also happened to be on the larger side. Specifically, a tenfold increase in body mass corresponds to a 13-fold increase in the threat of extinction.
"We've found that extinction threat in the modern oceans is very strongly associated with larger body size," Payne said in a news release. "This is most likely due to people targeting larger species for consumption first."
Simply put, this means that whales are more likely to die off than crabs. And unfortunately, whales dying off would have dire consequences for local ecosystems as a whole. For example, in the whales' absence, the populations of other creatures that were once kept in check would rise to new levels, potentially having adverse effects in the area. Similarly, whales are known to keep nutrients moving through their marine environments as they feed and excrete waste.
This isn't the first time that a study has found a correlation between hunting by humans and the fate of various sea animals. In 2014, researchers found that some animals evolved to become smaller so that they would be deemed as a less desirable target for hunters.
In the meantime, while the revelation of larger sea creatures being more likely to die off first is certainly a scary prospect, there's still some hope — so long as we act.
"We're not screwed," says Boris Worm, a marine conservation biologist at Dalhousie University. By discovering that human actions are driving larger sea creatures to extinction, we now can work on protecting them by rethinking fishing methods and regulations.
"We're really at a point where we need to make a decision," Worm says, about whether we allow the destruction continue or reverse it. "And we have the power to reverse it."
