( The general disappearance of cougars fr...)Cougar predation key to ecosystem health

This "trophic cascade" of environmental degradation, all linked to the decline of a major predator, has been shown in a new study to affect a broad range of terrestrial and aquatic species, according to scientists from Oregon State University.

The research was just published in the journal Biological Conservation ?and, like recent studies outlining similar ecological ripple effects following the disappearance of wolves in the American West ?may cause land managers to reconsider the importance of predatory species in how ecosystems function.

The findings are consistent, researchers say, with predictions made more than half a century ago by the famed naturalist Aldo Leopold, often considered the father of wildlife ecology.

"When park development caused cougar to begin leaving Zion Canyon in the 1930s, it allowed much higher levels of deer browsing," said Robert Beschta, an OSU professor emeritus of forest hydrology. "That set in motion a long cascade of changes that resulted in the loss of most cottonwoods along the streambanks and heavy bank erosion."

"But the end result isn't just loss of trees," he said. "It's the decline or disappearance of shrubs, wetland plants, amphibians, lizards, wildflowers, and even butterflies."

Until recently, ecologists had a poor understanding of how the loss of an important predator, such as wolves or cougar, could affect such a broad range of other plant and animal species. But the evidence is now accumulating that primary predators not only have direct effects in influencing the population sizes of native grazing animals such as deer and elk ?they also have indirect
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Source:Oregon State University