The loss of carnivorous predators such as lions, wolves, and bears is posing a global conservation problem, according to a new study published Friday in the journal Science. More than 75 percent of the existing 31 large carnivore species are declining due to threats such as habitat loss, human persecution, and loss of prey.
“Globally, we are losing our large carnivores,” said William Ripple, lead author of the paper and a professor with Oregon State University. “Many of them are endangered. Their ranges are collapsing. Many of these animals are at risk of extinction, either locally or globally. And, ironically, they are vanishing just as we are learning about their important ecological effects.”
Large predators play a key role in ecosystems. For the new report, researchers reviewed published scientific studies on trophic cascades, or the ecological effects of large predators. In particular, they studied research on 7 species: African lions, leopards, Eurasian lynx, cougars, gray wolves, sea otters, and dingoes.
One example of a predator’s role in the ecological community is that of the documented impacts of cougars and wolves in Yellowstone and other national parks. Ripple and Oregon State’s Robert Beschta, a co-author of the study, have documented the impacts of these large predators on the regeneration of forests and vegetation in the parks.
They found that a decrease in predators leads to an increase in browsing (similar to grazing) animals like deer and elk, which in turn leads to a higher loss of vegetation. Increased browsing disrupts birds and small mammals and changes parts of the ecosystem through a range of impacts. Studies of other large predators such as lynx, dingoes, lions, and sea otters have found similar effects.
Other examples include the decrease of lions and leopards in some parts of Africa, which as lead to a large increase in olive baboons that threaten crops and livestock. A decline in sea otters off the coast of southeast Alaska has led to increased numbers of sea urchins and loss of kelp beds.
“Human tolerance of these species is a major issue for conservation,” Ripple said. “We say these animals have an intrinsic right to exist, but they are also providing economic and ecological services that people value.”
In addition to 75 percent of large carnivore species declining, 17 species now occupy less than half of their former natural ranges, the study notes. Multiple large carnivore species are declining in certain areas including Southeast Asia, southern and East Africa, and the Amazon. Many large carnivore species have already been wiped out in much of the developed world, including the United States.
“Nature is highly interconnected,” said Ripple. “The work at Yellowstone and other places shows how one species affects another and another through different pathways. It’s humbling as a scientist to see the interconnectedness of nature.”
The study was conducted by researchers from the United States, Australia, Italy, and Sweden. According to an Oregon State University press release, researchers have “Called for an international initiative to conserve large predators in coexistence with people.”
In the United States, wolves are constantly being targeted. The federal government’s proposal to discontinue protection for the gray wolf could impact not only wolves but other species as well. Last month, a group of scientists authored a paper questioning the US Fish and Wildlife Service’s (FWS) proposed rule to declare habitat unsuitable for an endangered animal based on threats to the land.
Scientists said the FWS “conflated threats with habitat suitability” by stating that former wolf habitat is no longer suitable because of human encroachment and intolerance of the animals.
“The Fish and Wildlife Service is supposed to detail what the threats are and, if they’re substantial enough, they’re supposed to list a species and put in place policies to mitigate the threats,” said Jeremy Bruskotter, lead author of the paper and a professor with The Ohio State University.
“Here, they’re saying that they recognize the threat of human intolerance and instead of mitigating the threat, they’re just going to say the land is unsuitable.” By this reasoning, Bruskotter said, “Anytime the US Fish and Wildlife Service finds that something is in the way of a species’ recovery, they can just say the habitat is unsuitable for the species and disregard the threat altogether.”
The Endangered Species Act of 1973 protects US species in danger of or threatened with extinction throughout their ranges. In November, conservative Senators introduced a bill to dismantle existing environmental protections provided by the Act.