When Big Carnivores Go Down, Even Vegetarians Take The Hit
January 10, 2014 3:01 AM
WASHINGTON - The decline of large carnivores such as lions, wolves or pumas is threatening the Earth's ecosystems, scientists warned Friday as they launched an appeal to protect such predators.
More than 75 percent of 31 large carnivore species are on the decline, and 17 of them now occupy less than half of their former ranges, says a study published in the American journal Science.
"Globally, we are losing large carnivores. 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," wrote William Ripple, lead author of the study and a professor in the Department of Forest Ecosystems and Society at Oregon State University.
The American, European and Australian scientists who took part in the study said it is time to launch a worldwide initiative to reintroduce these animals into the wild and restore their populations in an effort modelled on the Large Carnivore Initiative for Europe.
The LCI is a non-profit scientific group affiliated with the International Union for the Study of Nature. The project aims to reintroduce wolves, lynx and brown bears in their natural habitats.
Ripple and his colleagues focused on seven species that have been studied for their widespread ecological effects. They are African lions, leopards, Eurasian lynx, cougars, gray wolves, sea otters and dingoes.
The different reports show that a decline in pumas and wolves in Yellowstone National Park led to an increase in animals that feed on tree leaves and bushes, such as deer and elk. This disrupts the growth of vegetation and shifts populations of birds and small mammals, the researchers said.
In Europe, fewer lynx have been tied to overpopulation of roe deer, red foxes and hares, while in Africa the disappearance of lions and leopards has coincided with a dramatic increase in the number of olive baboons, which threaten farm crops and livestock.
In Alaska, a decline in sea otters through killer whale depredation has triggered a rise in sea urchins and loss of kelp beds.
"Nature is highly interconnected," said Ripple. "The work at Yellowstone and other places shows how one species affects another and another through different pathways."
For instance, avoiding overpopulation of herbivores allows forest flora to develop more and sequester more carbon dioxide, the main green house gas responsible for global warming.
But the authors of the study say it will be very hard to convince people to accept a large scale restoration of large carnivore populations. People are afraid of them and have demonized them for centuries, they said.
"We're dealing with the most complicated systems in the universe, and we hardly even know what the moving parts are," said Rolf Peterson a research ecologist at Michigan Tech.
Peterson studies large carnivores, and is among the world's top wolf experts. He and scientists like him are finding that as the number of big predators dwindles, everything around the animals changes. It's like a "cascade" down the food chain. Ecologists call it a trophic cascade, trophic being a term to define any particular level in nature's food chain.
Take cougars and wolves for example. When there are fewer of them, their prey, deer and elk, multiply. More plant eaters means more plants get eaten. And everything that depends on those plants, from birds to butterflies, is affected.
Carnivore biologist William Ripple, from Oregon State University, says even streams are affected. Armies of deer, grown out of control because of a lack of predators that eat them, can devour all the vegetation along stream banks, and that causes erosion along those banks.
"The stream actually changes course," says Ripple. "So we're finding that the predator can actually affect the shape of the stream."
These cascade effects take all sorts of paths. Bears, for example, grab salmon out of rivers and eat them on the banks; the leftovers decay and add nutrients to the soil that help plants grow. "It's just a type of connecting-the-dots in nature," says Ripple. "And it shows the interconnectedness."
Peterson says the wolf has been an especially difficult case. It has made a comeback in the U.S. and Canada, but wolves sometimes prey on livestock. They compete with hunters for deer and elk. Many people have a deep-seated fear of them. Several states now allow the hunting of wolves in places where their numbers seem adequate. That has created enmity — with hunters and ranchers on one side and some environmentalists on the other.
Peterson says people have always had a love-hate relationship with wolves, having bred them into "man's best friend," the dog, while at the same time demonizing them in myth, and hunting them to near extinction.
American conservationists failed to agree on opposing the lifting of federal protection granted to wolves in Montana and Idaho in 2011. This was followed in 2012 by Wyoming, under pressure from ranchers.
Scientists are now calling for a global to organize research on carnivore ecology and, as Peterson points out, to illustrate just how predators have shaped our world. "It was the large carnivores to a great extent that maintained that fabric of life that formed us," he says. The world wouldn't be what it is without them."