Animal-welfare groups and environmentalists may be loving Yellowstone and other national parks to death, says a Utah State University College of Natural Resources professor.

By holding park managers to a hands-off, let-nature-take-its-course approach to management, the two movements are causing problems for the parks, Frederic Wagner, associate dean of the College of Natural Resources, told a USU Great Issues Forum recently.Illustrating his talk with slides, the head of the USU Ecology Center showed radical changes that have occurred in the Yellowstone National Park landscape as a result of the northern elk herd buildup.

Once-abundant aspen is scant and mixed-age stands of that tree are found principally in enclosures which keep out the elk.

Outside the enclosures, elk nip off the shoots as new plants sprout upward from the root systems. The elk also strip bark when food sources are low, sometimes girdling mature trees and causing their death.

Willows, found in important riparian zones along rivers and streams, are also being decimated by the burgeoning elk population, Wagner said. Even conifers, which provide few nutrients, have been damaged by wildlife feeding on whatever browse they can reach in harsh winters.

These changes have effects on a variety of wildlife and insect species, Wagner said.

He said wildlife is concentrated in national parks and monuments by fences or de facto fences.

"Yellowstone is fenced by guns," Wagner said, referring to hunting pressure outside that holds animals inside park boundaries. And, urbanization around parks creates fences that retard seasonal migrations.

The Yellowstone elk buildup has occurred because wolves have been eliminated, mountain lions are limited and humans no longer control animal numbers. Other changes affecting parks include water pollution and the introduction of foreign plants into the biota, Wagner said.

Environmentalists have had a role of rising importance - much needed - but there have been side effects, the ecologist said. The "natural regulation" policy fostered by the philosophy that nature is good and can balance itself has removed management, Wagner said.

The animal welfare movement is concerned with humane treatment of animals, but the scientist suggested that these groups are overlooking the welfare of the species.