Decline of large carnivores creates dire environmental ripple effect

Encroachment by human development into natural habitat has a negative effect on the world's major carnivores including the puma.
(Photo by William Ripple)
Sea otter
A decline of sea otters can mean the unrestrained growth of the sea urchin population and a corresponding loss of kelp, researchers found.
(Photo by Norman S. Smith)

UC Santa Cruz environmental researchers contributed to an analysis of 31 carnivore species that 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.

"Most of the world's large-bodied carnivores are in decline," said James Estes, UCSC professor of ecology and evolutionary biology. "For a few of the more well-studied species, the ecological consequences of these losses are wide ranging."

Estes and Chris Wilmers, UCSC associate professor of environmental studies, are among the co-authors of  "Status and Ecological Effects of the World’s Largest Carnivores" published Friday, January 10, in the journal Science.

"Globally, we are losing our large carnivores," said lead author William Ripple, professor in the Department of Forest Ecosystems and Society at Oregon State University. "Many of them are endangered," he 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."

The authors report that more than 75 percent of the 31 large-carnivore species are declining, and 17 species now occupy less than half of their former ranges. These changes have serious environmental consequences, they write.

Ripple and colleagues from the United States, Australia, Italy and Sweden called for an international initiative to conserve large predators in coexistence with people. They suggested that such an effort be modeled on the Large Carnivore Initiative for Europe, a nonprofit scientific group affiliated with the International Union for the Conservation of Nature.

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, gray wolves, sea otters and dingoes.

Estes said more research needs to be done. "Most of the remaining species are still so poorly studied that their ecological effects remain unknown," he said.