Earth’s ecosystems suffering due to reductions of large predators

New study says removal of top carnivores is ”mankind’s biggest effect on natural world.”

SANTA CRUZ, CA—Regardless of whether they live on land, in the sea, or in rivers and lakes, large predator species at the top of the food chain have remarkably beneficial influences on the way ecosystems function. According to Jim Estes, lead author of a new paper on the subject published in the July 15 issue of Science, the planet’s ongoing loss of apex predators due to human actions is “arguably humankind's most pervasive influence on the natural world."

The decline of top predators has been most noticeable among wolves and lions, whales and sharks, and large freshwater fish. The loss of “apex consumers” triggers an ecological phenomenon known as a "trophic cascade," a chain of events that can unbalance the entire food chain.  An example of  such a cascade occurred in Yellowstone National Park when wolves were killed off, allowing elk to over-browse streamside vegetation.  Reintroduction of wolves has allowed that vegetation, and the species it supports, to almost fully recover. Similarly, coastal ecosystems that lost key kelp forests when sea otter populations collapsed have recovered with the resurgence of otters, which control populations of kelp-grazing sea urchins.

Estes and co-authors John Terborgh and Michael Soule´, all board members of the conservation group Wildlands Network, agree that their findings have major implications for how ecosystem restoration and protection should be conducted. “The reestablishment of large animals and their ecological effects is fundamental," Estes said, noting that restoring large carnivores can’t be done on an acre of land.  “These animals roam over large areas, so it's going to require large-scale approaches,” he said.

The study confirms a major tenet of the Wildlands Network’s  20-year mission to create large, continental “Wildways” — without connected, protected, and restored habitat between existing protected areas, wide-ranging species that regulate ecosystems will not survive into the distant future, causing ecosystems to unravel.

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CONTACT: Kim Vacariu, Wildlands Network

kim@wildlandsnetwork.org  520-558-0165