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The health of any ecosystem starts with razor-like teeth and an appetite for meat. The “apex” predators — big carnivores like bears and wolves at the top of the food web — keep things in balance, OSU researchers have found in study after study in the western United States.

Now, the findings have been confirmed on a larger scale: the entire Northern Hemisphere. When big predators are wiped out, as wolves were in the American West during the last century, herds of plant browsers balloon, according to a survey of 42 studies from Canada, Alaska, the Yukon, Northern Europe and Asia. The elk, moose and deer — fearless in the absence of the furry lurkers — linger longer in riparian zones, trampling riverbanks and gobbling up young trees and other plants that sequester carbon, shade streams and shelter countless other animals, say William Ripple and Robert Beschta of the College of Forestry. Biodiversity plummets.

“The preservation and recovery of large predators may represent an important conservation need for helping to maintain the resiliency of northern forest ecosystems, especially in the face of a rapidly changing climate,” they add.