Would you mind living next door to a top predator? It’s a question I’ve asked you before. It seems that when it comes to bears, lions or wolves, we humans, as a whole, can’t get rid of our four-footed, predatory neighbors fast enough.
Those top predators, however, have far more to fear from us than we from them. And, indeed, so does any other species that humans deem a food source or a trophy to hang on the wall. According to a new study, we are the Earth’s “superpredators,” with methods so devastating that they disrupt global food chains, shrink fish sizes and alter the course of other species’ evolution or even completely drive them to extinction.
Do you think there’s a possibility that we could learn to commercially produce food and hunt in a way that is more sustainable and more like the way the planet’s other large predators harvest prey? Or are our ways too deeply entrenched to hope for change?
The danger of us
Any traveler to Africa may have seen this scenario unfold: a lion approaches a group of zebras, and, if it’s lucky, manages to take down a single animal that is weak, young or very old. In contrast, typically when humans hunt, they search for the biggest, strongest or most charismatic animal, usually choosing one in its prime reproductive years.
This fundamental difference makes us the most devastating predator on Earth. In a study, which was published on August 21, 2015, in the journal Science, 2,125 interactions between predators and their prey were examined. Results showed that worldwide, humans kill carnivores at an average annual rate that is nine times higher than the pace at which carnivores kill each other: while large predators such as bears, lions and wolves kill about 2 percent of their populations annually—usually during competition for dominance—we kill 18 percent of the carnivore population.
Interestingly, humans kill the same proportion of large herbivores (such as deer, elk or moose) that other carnivores do: 5 percent for other carnivores and 6 percent for humans. But things get worse again when it comes to the world’s fish populations: commercial fisheries catch adult fish, such as cod and tuna, at 14 times the rate that natural marine predators do.
The study’s lead author, Chris Darimont, the Hakai-Raincoast professor of geography at the University of Victoria in British Columbia, says that we consider our focus on targeting adult fish sustainable because it supposedly allows smaller, juvenile fish to have greater access to food and then to grow large enough to also be caught. But in some cases when the large adults are killed, only smaller ones reproduce. That can mean they lay fewer eggs, and the fish that do hatch are smaller. This way of managing fish populations also removes nutrients—in the form of large, dead fish—from the ecosystem. It’s one of the reasons why there is less biomass in the ocean now than there used to be. In fact, many fish species and entire fisheries have become depleted in recent years.
Our industrial-scale fishing also results in a large amount of bycatch, or the killing of not just targeted fish but other fish species, as well as birds and sea turtles. That makes us a more destructive predator on top of it and likely the only one that commonly and at very high rates kills animals we don’t intend to.
Likewise, when we target an animal’s reproductive age class and especially the larger, more fecund animals, we significantly decrease the reproductive capacity of that population. If you kill an adult animal, it will take years for another to grow up and take its place. But if you kill a juvenile, it will take only until the next breeding season to produce a replacement. And because the top predators we target naturally don’t face much predation themselves, they have not evolved ways to successfully avoid humans or reproduce fast enough to make up for human-induced losses.
Learning from them
The study also suggests that there’s hope for bringing declining populations back from the brink—if we learn to act more like the predatory animals we’ve been harvesting. That means sparing the adults and going after the young, and lowering our fish catch rates.
For example, some nets allow fisheries to define the entrance size, very easily allowing the exclusion of larger fish, the ones best left to reproduce. Fishing quotas could be readjusted to more closely align with the numbers taken by natural predators. Instead of allowing trophy hunting of large, land carnivores, countries could promote the just-as-lucrative business of wildlife ecotourism. According to Jeff Flocken, North American Regional Director of the International Fund for Animal Welfare, in Africa legal trophy hunting is measured by the millions it contributes to the economy, while nonlethal nature viewing is measured by the billions. Nature tourism generates 13 to 15 times more revenue than trophy hunting.
Some say, however, that these tactics would never work. Ray Hilborn, a professor in the School of Aquatic and Fishery Sciences at the University of Washington, Seattle, and an expert on sustainable exploitation, says that even though humans may take more fish than any one predator, our haul makes up only 40 percent of the total natural predation on fish—a reasonable amount given the need to provide food for the human population. He doesn’t believe that we can fish less and still supply enough food for the world. In Asia alone about 300 million people rely on fish as their primary source of protein. With continued population growth around the world, those numbers will only increase.
And given that the biggest fish earn the biggest bucks, focusing on juveniles would yield less money per ton of fish caught—something fisheries most likely wouldn’t support. Furthermore, quotas would have to be dramatically reduced to bring them closer to fish-predation rates from nonhuman predators.
Whether or not you believe with the study’s hopeful conclusions, it’s clear that we would need significant cultural, economic and institutional changes in order to limit human predation and bring our rate of killing more in line with the rate at which natural predators harvest prey if some species of wildlife are to survive.
Do you think it’s possible that we superpredators could go back to acting more like normal predators? Is an overhaul of the systems we use to relate to the animals we eat and hunt even possible?
Here’s to finding your true places and natural habitats,