Humans as 'predators' impacting thousands of species: Global study co-authored by N.S. researcher

With more than eight billion humans on the planet, a team of international researchers has now quantified the population’s significant impact on other species.

The study, published in in the journal Communications Biology, examines the effects of humans as global predators, rather than just inhabitants, on other living things.

“We're just so out there in terms of our use of wildlife,” says Boris Worm, Dalhousie University marine ecologist and one of the co-authors of the study.

After crunching the numbers, the team found humans use far more species for their own purposes than any other animal on earth.

“Assessed over equivalent ranges,” the study says, “humans exploit up to 300 times more species than comparable non-human predators.”

“About one in three species, 15,000 vertebrates (species with a backbone) are affected by human use,” says Worm. “And in 40 per cent of those, that human use is considered a threat.”

Humans, he explains, are unique in their development of culture and trade, which results in the use of animals for everything from pharmaceuticals to fashion.

“We have culture, we have very elaborate social behavior,” he says, “(and) we have trade, we have commercial goods, and (that) drives the exploitation of a lot of species.”

While most of nature’s predators hunt primarily for sustenance, the study found humans do not.

“About 74 per cent of species, almost three in four, that are used by people on land, are used also or exclusively for non-food uses,” Worm explains.

From pangolins driven towards extinction for their scales to exotic birds hunted down for their feathers, Worm says predation for personal pleasure is also singular to humans.

The study also found the capture of wildlife as pets is surprisingly significant.

“On land, there was twice as many species were used for pets, compared to (those) used for food,” says Rob Cooke, study co-author and ecological modeler at the U.K. Centre for Ecology and Hydrology.

“There's the caged bird industry, fish in aquariums, and reptiles and amphibians, there's huge demand,” he explains.

Cooke says there have been cases in which people have recognized the negative effects of overconsumption on a species, developing regulations in response.

“Often with fishing you have quotas,” he says. “And (when) you fish below the quota, the population can continue reproducing and keep sustaining itself.”

Cooke says using community-based, sustainable methods, in a “decentralization of our interaction with nature”, makes a difference.

“We need to think more about the longevity of these industries, if we're going to have sustainable use of animals, and maybe there's species of animals where we don't need to use them,” he says.

“Our interest in a species can actually wipe them out from the face of the earth for no good reason,” says Worm. “And I think we are smarter than that.”

Worm says when a species becomes extinct, it has a proven ripple effect on entire ecosystems. He and the other authors consider their work both a warning and a call to action, to take a hard look at how humans use animals, to prevent “profound consequences.”