Study led by OSU professor finds decline of most large carnivores

Scientists warn of grave implications for the ecosystem



The big, charismatic — some say scary — carnivores that roam the earth are slipping slowly into extinction, and the rest of us will miss a lot more than their dramatic turns on nature shows.

A study in Science magazine published Friday has found that three-fourths of the largest carnivores on Earth — a group that includes lions, tigers, bears and wolves — are in decline, with most of them officially recognized as threatened. A majority have lost greater than half of their historic geographical range.

The lead author on the study, “Status and Ecological Effects of the World’s Largest Carnivores,” is Oregon State University forest ecology professor William Ripple.

A dozen scientists from the United States, Australia, Italy and Sweden spent two years synthesizing studies in order to document all of the earth’s carnivores (minus a few big sea-going mammals) that weigh greater, on average, than 33 pounds.

The problem is not just the loss of species, but the degradation of the ecosystem after they’re gone, the scientists concluded.

“What’s ironic is we’re just beginning to find out what (the carnivores’) ecological effect and benefits provide as they’re declining,” Ripple said Thursday.

The scientists documented two differing “webs of impacts” when an animal at the top of the food chain goes missing.

The first is, when big carnivores disappear, large-bodied herbivores (deer, elk, moose) populations tend to explode.

The herbivores devour plant life, including willows, aspen and cottonwood.

“If the number of large herbivores gets high enough,” Ripple said, “they will eat themselves out of house and home. If the plants can’t flourish, that impacts a lot of different animals that depend on the plants.”

The second effect, when an apex predator disappears, is an explosion of the next-biggest carnivore on the food chain.

They, in turn, are liable to wipe out the animals they feast on.

“Wherever we’ve looked, similar patterns have emerged,” said Euan Ritchie, an ecologist at Deakin University in Australia, who was featured in a discussion of the study Thursday on the Science magazine website.

When dingoes, wild dog-like creatures, are missing from the Australian countryside, for example, the populations of red foxes and feral cats grow out of control, Ritchie said.

The fox and feline most likely contributed to the extinction of small marsupials (pouch-bearing mammals) and rodents across the continent, the study found.

Wolves are another example.

When they’re not there to eat elk, the elk chomp down plants in the habitat, hurting the birds that rely on those plants.

Coyotes are expanding their range into the Eastern United States, Ritchie said, and that’s tied to the fact that wolves have been removed from large swaths of the country.

“We know that wolves have a large effect on coyotes,” he said.

“They keep their numbers low.”

In parts of Africa, the affected species include people. When lions and leopards are driven away, a species of baboons grows dramatically.

“You think, ‘Big deal. There’s a few more baboons around,’ right?” Ritchie said. But children in those communities can’t go to school because they have to stay home and help their parents protect the crops from baboons, he said.

Such changes to the webs of life across the globe are a “very serious concern,” Ripple said. “Most of the attention goes to issues like climate change, but this is (also) a major global concern.”

Humans sometimes stand in the way of a solution.

The large carnivores invoke either terror or fascination in our species — when what’s really needed is human tolerance, the scientists said, to establish a harmonious coexistence.

A long-standing detente, for example, exists between Romanian sheep farmers and the region’s bears and wolves, Ritchie said. That’s because farmers have retained the tradition of protecting their flocks with shepherds and sheep dogs.

“In many parts of the world, we’ve forgotten how to do that or we’ve chosen not to do that — and that’s had consequences,” he said. “If we actually reconsidered those approaches, we could actually maintain predators with humans in the same landscape.”