New research has found that humans prey on 300 times more species than other predators, use more than one-third of all vertebrate species on Earth, and threaten almost 40% of them.
Published Thursday in the journal Communications Biology, these are among the findings of an international team of scientists from 14 institutions, including Dalhousie University.
“It’s the largest study of its kind so far, and it takes a village to do it…When you do a study of this kind that is the first of its kind, you’re always surprised,” Dalhousie University marine ecologist and report co-author Dr. Boris Worm said in an interview.
“What most surprised me about this study was the very large proportion of species that are exploited for non-food uses. Particularly on land, and particularly for birds, reptiles, and amphibians that are primarily targeted as pets.”
While food use is largely behind the exploitation of marine and freshwater fish (72% of species), researchers found the use of land animals as pets is almost twice as common (74%) as food use (39%). Sport hunting and other forms of animal “collection” account for 8% of exploited land species.
“A lot of people profess they love animals. They are fascinated by animals. It’s very easy to get people engaged when you show pictures of panda bears and lions and tigers and all these other charismatic species,” Worm said.
“At the same time, all of these species are threatened. We love them, but because we love them, we tend to take too many of them for our own benefit, our own enjoyment.”
Earth’s super predators
In the study, titled Humanity’s diverse predatory niche and its ecological consequences, researchers analyzed International Union for Conservation of Nature (IUCN) data that shows how humans use and trade about 45,000 vertebrate species. These include most known fish, mammals, birds, reptiles, and amphibians.
They found that hunters, fishers, and other animal collectors prey on about 15,000 species — more than a third of Earth’s vertebrates.
While other predators kill primarily for food — think lions, wolves, and leopards — humans commonly use prey species for pets, medicines, and other products. The researchers said this poses “a key threat to endangered wildlife in many areas.”
“Assessed over equivalent ranges, humans exploit up to 300 times more species than comparable non-human predators,” the researchers wrote. “Exploitation for the pet trade, medicine, and other uses now affects more species than those targeted for food consumption, and almost 40% of exploited species are threatened by human use.”
Worm said we need to recognize that we are super predators.
“We have evolved these elaborate cognitive abilities, we are very social, we engage in group hunting. And we have for tens of thousands of years. That has made us very successful,” Worm said.
“But it also has come with a large price tag in that a lot of species have gone extinct or are threatened with extinction. And this is something we can and need to and, in my view, will reverse. We can deal with those destructive tendencies, but only if we recognize them.”
Two in five vertebrate species threatened by humans
Worm has studied ecological systems for about 25 years. He described predation as “one of the most powerful forces in nature.” He said changes in the predatory regime often result in large ripple effects throughout the ecosystem, and most have been altered by human predation.
“What is our impact collectively as a predator? I think it’s a really interesting question to ask. How does our impact scale to what other species like us do? Like big sharks or lions or hyenas? What do they eat? What do they consume in terms of how many prey items they rely on, and how does it relate to what we do,” Worm said.
“When we crunched the numbers, it just showed how extraordinarily unusual we are. We are the planet’s super predator, if you will. But we’re not just taking a whole lot of stuff. We’re taking a whole lot of species.”
The study’s researchers also found that two in five vertebrate species are threatened by human use.
“That’s not good enough. That’s a pretty poor record for a presumably intelligent species,” Worm said. “You’re not able to sustain your prey populations for two in five populations. We need to do better there.”
Worm said the two in five statistic is “quite close” to the one in three fish populations currently exploited in an unsustainable way worldwide.
In Canada, one in three fish stocks (32.5%) are in the cautious or critical zone, similar to the global average of one in three fish stocks (35.4%) being overexploited.
The Finding Nemo effect
Although he knew the pet trade was a driver of species use and endangerment, Worm said he didn’t realize the scale of it until his team began working on the international research project.
Cultural phenomena also play into human predation. Worm pointed to the Finding Nemo movie, which featured clownfish and other colourful species like the blue tang. The movie’s popularity led to a spike in exploitation of those fish in the wild.
“And it’s ironic, particularly in that case because that was the message, ‘Don’t do that,’” Worm said.
He said the Harry Potter series, in particular the movies, similarly led to a wave of exploitation of owls.
“I know this particularly from places like Indonesia, for example, where owls were taken from the wild to be sold as pets,” Worm said.
“Now a lot of these species are not suitable as pets. They quickly get sick and die. But that’s not the problem of the person who sold it in the first place, right? Once it’s sold, it’s somebody else’s problem.”
With so many humans regularly taking animals for pets, trophies, food, and other uses, the impacts are far reaching.
“I get food use. I eat fish if it’s sustainably sourced, and I think we can and we should to some extent, use nature in that way. We always have,” Worm said.
“But when we stack all these different uses and there’s eight billion of us, if only one in 10,000 of those wants an owl as a pet, that’s too much, right. Because there’s not that many owls out there.”
Numbers likely an underestimate
While many people think of mammals and birds when they hear the word ‘vertebrates,’ Worm said there are more than twice as many fish than small mammals and birds. Most of the vertebrates we consume are fish, and we’re using many ocean and freshwater species.
“We have these problems on land. We have these problems in the ocean. They’re of a similar magnitude, but there’s just more of those vertebrates in the ocean,” he explained.
“While we’re not hunting as much anymore on land as we largely have shifted to agriculture, in the ocean we’re still engaged in hunting. I don’t have a fundamental problem with (eating fish). But we need to work within the capacity of the system to provide for us. And we’re not doing a perfect job so far.”
Worm said the importance of their research is they’re showing where we can do better for the two in five species exploited in an unsustainable way.
“But also for the species that we may not need to exploit after all, because it’s really for luxury goods and entertainment,” Worm said. “Those species have a more important role to play in their ecosystems, and that’s where they should remain, in my view.”
The research paper also notes that while researchers used a trusted and accepted data source, their numbers are likely on the conservative side.
“It may actually underestimate the number, the extent of the biodiversity crisis,” Worm said. “A lot of those species, because there’s so many of them, only get updated every 10 years or so. So some of them may actually be in more dire straits.”
Extraordinarily large global footprint
In some cases, we are doing better. Worm points to large whales and how some populations have started to “come back,” and to the return of some wolf populations.
“I was just back from Germany and we now have wolves again in Germany and they’re thriving because people are protecting them and they’re learning to live with them,” he said.
“That to me is very hopeful. But if you look at our global footprint as a predator, it still is a very extraordinarily large footprint.”
Worm described Atlantic Canada as a very species rich environment. Coastal zones often have the highest number of new and threatened species because biodiversity often spikes at the margins between land and sea.
“I think we want to be aware that we live in a very special place. We need to take care of both the species we see every day, say our migratory birds, and the species we don’t necessarily see,” Worm said. “This would be mainly that large biodiversity in the ocean. And our work has shown that our impacts are particularly pronounced in the ocean.”
Researchers found that regardless of conservation approach, humanity must fully recognize the effects its “outsized” predatory niche exerts on target species and their ecosystems.
“Although humanity’s predatory niche is seemingly unrestricted, exploitation rates need to be constrained if >45,000 contemporary vertebrate species and the ecological processes they support are to be safeguarded,” the report’s authors wrote.
‘We really do have a chance’
In December, Montreal was the site of the Kunming-Montreal Global Biodiversity Framework. Worm described it as humanity’s plan for saving biodiversity by having 30% of land and sea areas protected by 2030.
“Honestly, that was probably the most optimistic sign I’ve seen in my entire lifetime for biodiversity. When that was under-signed almost unanimously by all the signatories to the Convention on Biological Diversity, I thought, ‘You know, we really do have a chance now. We really do,’” he said.
“Honestly, that was probably the most optimistic sign I’ve seen in my entire lifetime for biodiversity. When that was under-signed almost unanimously by all the signatories to the Convention on Biological Diversity, I thought, ‘You know, we really do have a chance now. We really do,’” he said.
“This is going to trickle down and this is going to be a huge change in how we relate to nature and how we treat nature. And so I think our paper is coming out at an opportune time. Kind of giving more support to that plan, that idea, that program. This is something we absolutely need to address. And we are addressing it.”
‘First order survival question for humanity’
While the climate crisis can lead to a sense of hopelessness — particularly in younger generations — Worm said he remains optimistic.
He was recently invited to speak at a local school where teachers were concerned about their students’ feelings of hopelessness over the state of the planet.
I said, ‘You know, I am convinced that when you are my age, you will see a healthier world than the one we live in now. It’s not going to go down. It’s going to go up. It’s going to be better. And you will make that happen along with everybody else.
You will be part of that huge shift that after tens of thousands of years of being a fairly destructive force in nature, we can turn this around. I am absolutely convinced that we will do it because we have to. It’s as simple as that. And when you have to do something, you do it.’
We saw that with COVID. We had to shut down the world for a bit. We did. We can do that. I really do feel we’re on the right track there. But we also need to remind ourselves, and pretty much every day, how important this is. This is not a second order problem. This is a first order survival question for humanity.
We humans are the only species that destroy our fellow creatures and all the living habitat on our planet.