More than 75 percent of the 31 large-carnivore species are declining, and 17 species now occupy less than half of their former ranges, the authors said in an analysis published Friday in Science.
"Globally, we are losing our large carnivores," said William Ripple, lead author of the paper and a professor in the Department of Forest Ecosystems and Society at Oregon State University in Corvallis.
Southeast Asia, southern and East Africa and the Amazon are among areas in which multiple large carnivore species were found to be declining. With some exceptions, large carnivores have already been eliminated from much of the developed world, including Western Europe and the eastern United States.
"Many of them are endangered," Ripple said. "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."
An international group of researchers reviewed published scientific reports and highlighted seven species that have been studied for their widespread ecological effects, including African lions, leopards, Eurasian lynx, cougars, gray wolves, sea otters and dingoes.
Ripple and colleagues from the United States, Australia, Italy and Sweden have called for an international initiative to conserve large predators in coexistence with humans.
Where large carnivores have been restored -- such as wolves in Yellowstone or Eurasian lynx in Finland -- ecosystems have responded quickly, Ripple said.
"I am impressed with how resilient the Yellowstone ecosystem is," Ripple said. "It isn't happening quickly everywhere, but in some places, ecosystem restoration has started there."