NEW YORK (July 20, 2011) – The loss of large predators in the wild may be humankind’s most pervasive influence on nature, according to Wildlife Conservation Society Conservationist Joel Berger.

Berger, author of The Better to Eat You With, is a co-author of the paper “Trophic Downgrading of Planet Earth,” that appears in the July 15 issue of the journal Science.

Until recently in human history, large predators – also known as apex consumer species – have been omnipresent and their influence has often been associated only with species that they directly consume. The study indicates, however, that the removal of these top-tier consumers has more far-reaching consequences than originally thought.

The authors reviewed findings from a growing body of scientific data on the effects of removing apex consumers from nature – a process referred to as “trophic downgrading.” They found that removing these species can cause cascading effects throughout their associated ecosystems, with negative effects reverberating to other species and throughout ecosystem processes.

Berger said, “The disruption of top-down control in an ecosystem is something that much of the public once viewed as good but is now recognizing AS disturbing and expensive consequences that affect all forms of our lives and economies.”

While scientists have long thought trophic cascades are the norm and not the exception when apex carnivores are removed, studies to thoroughly examine this idea have been hindered due to things such as life spans of some species which exceed many human generations and the goal to preserve, rather than disturb, existing ecosystems. Today, however, trophic cascades resulting from removing apex species have now been documented in all of the world’s major biomes and in terrestrial, freshwater, and marine systems.

Moreover, in following a trail of complex cause and effect relationships, the scientists noted unanticipated impacts of trophic downgrading on processes as diverse as the dynamics of disease, wildfire, carbon sequestration, invasive species, and biogeochemical cycles.

In one example presented in the paper, the authors discuss how the reduction of lions and leopards in parts of Africa has led to changes in numbers and behavior of olive baboons which have been drawn increasingly into contact with people. This has led to higher rates of intestinal parasites in baboons and the humans who live in close proximity to them.

Also included in the paper are “before and after" photographs that illustrate stark contrasts in ecosystem conditions occurring due to the presence/ absence of apex species in various land and seascapes. These help demonstrate the urgent need for interdisciplinary research to forecast the effects of trophic downgrading on process, function, and resilience in global ecosystems.

“If we continue with business as usual and lack an on-the-ground presence to reverse the alarming trends, we continue down a path of repeating history, one mistake at a time, rather than benefitting from past mistakes, as egregious as they have been,” said Berger.


Contact:
Stephen Sautner: 1-718-220-3682; ssautner@wcs.org

The Wildlife Conservation Society saves wildlife and wild places worldwide. We do so through science, global conservation, education and the management of the world's largest system of urban wildlife parks, led by the flagship Bronx Zoo. Together these activities change attitudes towards nature and help people imagine wildlife and humans living in harmony. WCS is committed to this mission because it is essential to the integrity of life on Earth.