A black bear crosses the road. Photo by Andrea Izzotti/Shutterstock
Feb. 11 (UPI) -- According to a new survey, more than a quarter of all vertebrate deaths on land are caused by humans.
Researchers at the SUNY College of Environmental Science and Forestry analyzed the reported cause of death for 42,755 animals 1,114 published studies. Their research showed humans were to blame for 28 percent of all vertebrate deaths on land.
Scientists published the results of their survey in the journal Global Ecology and Biogeography.
"We all know humans can have a substantial effect on wildlife. That we are only one among over 35,000 species of terrestrial vertebrates worldwide yet responsible for more than one-fourth of their deaths provides perspective on how large our effect actually is," ESF professor Jerrold L. Belant said in a news release. "And that's just direct causes. When you also consider urban growth and other land use changes that reduce habitat, it becomes clear humans have a disproportionate effect on other terrestrial vertebrates."
The surveyed animals deaths were recorded across the globe, in North and South America, Europe, Asia, Africa and Oceania, and featured a wide variety of species, including mammals, birds, reptiles and amphibians. Scientists surveyed necropsy findings recorded between 1970 and 2018. All of the reported deaths involved animals that had been previously tagged or collared.
Of course, not all necropsies are conclusive. Scientists had to survey the reports on 120,657 individual animals deaths to identify 42,000 animals deaths ascribed a "known fate."
While 28 percent of vertebrate deaths were directly caused by humans, it's possible humans were indirectly culpable for a larger percentage. Habitat loss, limited genetic diversity and shrinking prey populations -- all potential human impacts -- can make animals more vulnerable to natural causes.
The new findings echo the results of previous studies which show humans are having a devastating impact on the numbers of large animals. Human predation, pollution and habitat clearing has both shrunk the physical size of animals and the size of their populations.
"Larger animals were more likely to be killed by humans than smaller species," Hill said. "Adult animals were more likely than juveniles to be killed by humans."
Humans already impact 75 percent of Earth's land. As humans continue to cut down forests and human development expands, more animals will face the detrimental effects of humans.
"It's a wake-up call," ESF professor Jerrold L. Belant said. "Consider deforestation rates and the bleaching of coral reefs from increased sea temperatures. This is one more piece of evidence to add to the list, one more example of the effect we're having on the planet."