New research shows that over one third of all vertebrate species on Earth are used by people and this is causing disproportionate impacts on ecosystems and the beneficial services that nature provides humans.
An international study led by the UK Centre for Ecology & Hydrology (UKCEH) and the University of Victoria in Canada analysed data for most known fish, mammals, birds, reptiles and amphibians. It found humans have up to 300 times more prey species than comparable predators over the same geographic ranges and are having a broad impact on biodiversity, estimating that almost 40% of exploited species are now threatened with extinction.
Unlike other predators who hunt prey for food, humans have a wide range of other uses for animals, such as pets, food, clothing, for research or trophy hunting. The study authors were surprised to find that capturing terrestrial animals for the pet trade outnumbered food uses almost two to one.
UKCEH ecological modeller Dr Rob Cooke, co-lead author of the study, which has been published in Communications Biology, says: “The unnatural selection of animals by human predators could lead to a range of repercussions across ecosystems. From the potential loss of large seed-dispersers such as the Helmeted Hornbill, to megaherbivores such as the Black Rhino, to migratory predators such as large sharks.”
The research team says there is an urgent need for policies and conservation action to protect vertebrates and have identified species that are overexploited and also play unique roles in ecosystems. The scientists say that we could learn much from examples of long-term relationships between humans and their prey, such as the fishing of Pacific Herring, which was sustainable for thousands of years before industrial overexploitation.
The study analysed data for 45,000 vertebrates and found humans are using 15,000 of these species, of which around 6,000 are threatened with extinction. Humans use many times more species than other comparable predators. For example, a Jaguar has nine prey species compared to 2,700 species used by humans over the same geographic range, while a Barn Owl has 462 prey species compared to 11,400 species used by humans over the same range.
“Humans have emerged as the planet’s most extraordinary predator, doing things that other predators do not, killing or capturing for reasons other than feeding themselves, as well as endangering thousands of prey species simultaneously,” says co-lead author Professor Chris Darimont of the University of Victoria.
“Over millennia, human beings have gradually occupied a super-sized ecological niche and our ability to manage our impacts has not kept pace with that growth,” adds co-author Dr Boris Worm of Dalhousie University, Canada.
The new study also gives new insight into the risks of exploiting species that tend to have different attributes – like large body size and a plant-based diet – compared with other vertebrates. Indeed, the researchers find that humans are using a diverse and ecologically distinct set of species, and losing these animals and the roles they play could cause significant changes to ecosystems.
New international commitments to protect 30 per cent of the planet by 2030 may help make more room for nature. In addition, how to manage or reduce humans’ impacts on species has been the topic of recent negotiations under the Convention on Biological Diversity.
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