Loss Of Large Predators Disrupting Multiple Plant,Animal and Human Ecosystems

The enormous decline of large, apex predators and "consumers" ranging from wolves to lions, sharks and sea otters may represent the most powerful impacts humans have ever had on Earth's ecosystems, a group of 24 researchers concluded today in a new report in the journal Science. The decline of such species around the world is much greater than previously understood and now affects many other ecological processes through what scientists call "trophic cascades," in which the loss of "top down" predation severely disrupts many other plant and animal species.

Such disruption is sufficiently severe that it now affects everything from habitat loss to pollution, carbon sequestration, wildfire, climate, invasive species and spread of disease, the scientists said. It is also a driving force in the sixth mass extinction in Earth history, which the researchers said is now under way.

"We now have overwhelming evidence that large predators are hugely important in the function of nature, from the deepest oceans to the highest mountains, the tropics to the Arctic," said William Ripple, a professor of forestry at Oregon State University, co-author of the report and an international leader in this field of study as director of OSU's Trophic Cascades Program.

"In a broad view, the collapse of these ecosystems has reached a point where this doesn't just affect wolves or aspen trees, deforestation or soil or water," Ripple said. "These predators and processes ultimately protect humans. This isn't just about them, it's about us."

Historically there has been little appreciation of how large predators affected so many other species, the researchers said, and too often such processes were studied one plant or animal at a time in a small area, failing to appreciate the larger disruption under way.

Based on the new understanding that is emerging, the scientists argued that the burden of proof should now be shifted, to assume that top predators have major effects on ecosystems until proven otherwise.