What does the cougars dissaperance have to do with soil erosion in the Zion National Park?

Answer 1

The general disappearance of cougars from a portion of Zion National Park in the past 70 years has allowed deer populations to dramatically increase, leading to severe ecological damage, loss of cottonwood trees, eroding streambanks, and declining biodiversity.

A new study by researchers from Oregon State University found that cougars in Zion National Park have a profound impact on other aspects of the ecosystem, primarily by controlling deer populations and the ecosystem alterations related to deer browsing.

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."

Answer 2

Like the absence of organ cactus. People killed the varmints that ate the rodents the ate the seeds. No varmints, many rats, no seeds, no cacti.
No cougars, many small animal and herbivores that eat the foliage and the seeds that hold the earth together and prevent erosion.