The decline of large predators such as lions, wolves and bears is threatening the Earth's delicate ecosystems - changing the face of landscapes from the tropics to the Arctic, scientists have warned.
The analysis of 31 carnivore species shows for the first time how threats such as habitat loss, persecution by humans and loss of prey combine to create global hotspots of carnivore decline.
More than 75 per cent of the 31 large-carnivore species are declining, and 17 species now occupy less than half of their former ranges, researchers said.
Southeast Asia, southern and East Africa and the Amazon are among areas in which multiple large carnivore species are declining, researchers said.
With some exceptions, large carnivores have already been exterminated from much of the developed world, including Western Europe and the eastern US.
"Globally, we are losing our large carnivores," said William Ripple, lead author of the paper from 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," he said.
Ripple and colleagues called for an international initiative to conserve large predators in coexistence with people.
The researchers reviewed published scientific reports and singled out seven species that have been studied for their widespread ecological effects or "trophic cascades." This includes African lions, leopards, Eurasian lynx, cougars, grey wolves, sea otters and dingoes.
Ripple and co-author Robert Beschta have documented impacts of cougars and wolves on the regeneration of forest stands and riparian vegetation in Yellowstone and other national parks in North America.
Fewer predators, they have found, lead to an increase in browsing animals such as deer and elk. More browsing disrupts vegetation, shifts birds and small mammals and changes other parts of the ecosystem in a widespread cascade of impacts.
Studies of Eurasian lynx, dingoes, lions and sea otters have found similar effects, researchers reported.
Lynx have been closely tied to the abundance of roe deer, red fox and hare.
In Australia, the construction of a 3,400-mile dingo-proof fence has enabled scientists to study ecosystems with and without the animals, which are closely related to grey wolves.
In some parts of Africa, the decrease of lions and leopards has coincided with a dramatic increase in olive baboons, which threaten farm crops and livestock.
In the waters off southeast Alaska, a decline in sea otters through killer whale predation has led to a rise in sea urchins and loss of kelp beds.
The study was published in the journal Science.
