Large marine animals are now more likely to go extinct than smaller ones — a situation that is apparently unprecedented on the planet — owing to the overfishing of the world’s oceans by humans, new research has found.
Marine animals of larger-size have in the past not been killed at a rate so notably higher, or higher at all, than smaller marine animals, as is the case now. This is owing to the preference of commercial fisheries for larger specimens (more money), and to the general scale of modern fishing (overfishing).
Owing to these circumstances, there are likely to be a great many distinct types of marine animals that go extinct over the coming decades.
“We’ve found that extinction threat in the modern oceans is very strongly associated with larger body size,” stated Jonathan Payne, a paleobiologist at Stanford’s School of Earth, Energy & Environmental Sciences. “This is most likely due to people targeting larger species for consumption first.”
And also no doubt to greater precariousness that one finds oneself in when at the top of the food chain (as most larger animals are).
The new research focused on vertebrates and mollusks — a substantial portion of the animals in marine environments, whether extinct or not — and examined the links between extinction threat level and body-size. This work involved data focused around the last 500 years, and also ancient pre-human times — as far into the last as 445 million years ago (with an emphasis on the last 66 million years).
“We used the fossil record to show, in a concrete, convincing way, that what is happening in the modern oceans is really different from what has happened in the past,” commented study co-author Noel Heim, a postdoctoral researcher in Payne’s lab.
“What our analysis shows is that for every factor of 10 increase in body mass, the odds of being threatened by extinction go up by a factor of 13 or so,” Payne continued. “The bigger you are, the more likely you are to be facing extinction.”
As noted by the researchers involved, this selective elimination of larger marine animals will likely end up seriously affecting ecosystem functioning within the world’s oceans. Even more so than it already is, that is. When large animals go extinct, whether keystone species or otherwise, whole ecosystems are forced to rearrange substantially, and are generally diminished greatly, if they persist at all.
The program director at the National Science Foundation’s Division of Earth Sciences, Judy Skog, commented: “These results show that larger marine animals are poised to disappear from the seas faster than smaller ones. Studies of the fossil record indicate that this trend didn’t exist in the past — it’s a new development in today’s world.”
In addition to the simple fact that a large number of whales, orcas, dolphins, sharks, turtles, dugongs, rays, tuna, swordfish, grouper, etc, are likely to go extinct over the next 100 years, as are other animals, the loss will very likely lead to a surge in the prevalence of jellyfish in the oceans — as earlier research has linked overfishing and increasingly large jellyfish blooms.
Commenting on the implications of the new work, Payne stated: “We can’t do much to quickly reverse the trends of ocean warming or ocean acidification, which are both real threats that must be addressed. But we can change treaties related to how we hunt and fish. Fish populations also have the potential to recover much more quickly than climate or ocean chemistry. We can turn this situation around relatively quickly with appropriate management decisions at the national and international level.”
That’s the optimistic take on things. The reality is that commercial fishing is something that much of the globe now relies on for nutrition — both directly, and with regard to derived fertilizers made from by-catch. A real solution to overfishing, would be similar to a real solution to deforestation… to cascading extinction numbers… and to anthropogenic climate change. That would a solution of reduced scale, and halted growth. There is such a thing as over-growth, even if it’s taboo to say so in the modern world.
The new research is explained further in a paper published in the journal Science.