A new study has found that the decline in large predators, particularly wolves, in forest systems across the Northern Hemisphere has triggered major ecosystem disruptions and loss of biodiversity. In a survey of 42
studies conducted over the past 50 years, scientists at Oregon State University (OSU) found that the loss of mammalian predators in forest ecosystems across North America, Europe and Asia — including killings to prevent ranching conflicts — has allowed an increase in populations of moose, deer, and other large herbivore species, which in turn has impaired the growth of young trees. According to the researchers, population densities of large herbivores were six times greater in areas without wolves. The researchers say the presence of predators not only limits the size of herbivore populations but affects their behavior, a factor they call the “ecology of fear.” “There’s consistent evidence that large predators help keep populations of large herbivores in check, with positive effects on ecosystem health,” said William Ripple, a professor of forestry at OSU and lead author of the study, published in the European Journal of Wildlife Research.