The Wolf Preservation Blog

This is the observation made by scientists in a new report published in the  journal Biological Conservation.

For the first time in 70 years, the young aspen and willow trees are not  being eaten before they have a chance to flourish and grow by the elk  populations in northern Yellowstone, thanks to the introduction of wolves back  into the park. The elk are beginning to decline and are also beginning to fear  wolf predation.

As such, trees and shrubs are recovering along some streams, which in turn  provide improved habitat for beaver and fish, and provide more food for birds  and bears.

“Yellowstone increasingly looks like a different place,” said William Ripple,  a professor in the Department of Forest Ecosystems and Society at Oregon State  University, and lead author of the study. “These are still the early stages of  recovery, and some of this may still take decades. But trees and shrubs are  starting to come back and beaver numbers are increasing. The signs are very  encouraging.”

The findings released in the report are based on a recent analysis conducted  by Oregon State University researchers as well as a review of several other  studies.

The report outlines four streams that were studied in the Lamar River basin.  100 percent of the tallest young aspen sprouts were being browsed in 1998, but  that number has dropped to just 20 percent in 2010. As a result of the total  browsing by elk, the new aspen trees were unable to grow and expand, grinding to  a halt in the mid to late 1990s. And all because the wolves weren’t around to  snack on the snackers.

This is the observation made by scientists in a new report published in the  journal Biological Conservation.

Among the observations in this report:

• Since their reintroduction in 1995-96, the wolf population generally  increased until 2003, forcing changes in both elk numbers and behavior due to  what researchers call the “ecology of fear.”

• The northern range elk populations decreased from more than 15,000  individuals in the early 1990s to about 6,000 last year, and remaining elk now  have different patterns of movement, vigilance, and other traits.

• By 2006, some aspen trees had grown tall enough they were no longer  susceptible to browsing by elk, and cottonwood and willow were also beginning to  return in places.

• Improved willow growth is providing habitat that allows for a greater  diversity and abundance of songbirds such as the common yellowthroat, warbling  vireo and song sparrow.

• The number of beaver colonies in the same area increased from one in 1996 to  12 in 2009, with positive impacts on fish habitat.

• Increases in beaver populations have strong implications for riparian  hydrology and biodiversity – Wyoming streams with beaver ponds have been found  to have 75 times more abundant waterfowl than those without.

• The coyote population decreased with the increase in wolf numbers,  potentially allowing more small mammals that provide food for other avian and  mammalian predators, such as red foxes, ravens and bald eagles.

Evidence of improved ecosystem health following the return of wolves is “becoming increasingly persuasive,” the scientists said in their report, though  they also note that an increasing population of bison is continuing to impact  young woody plants in the Lamar Valley.

“The wolves have made a major difference in Yellowstone,” said Robert  Beschta, a professor emeritus of forestry at OSU and co-author on the study.

“Whether similar recovery of plant communities can be expected in other  areas, especially on public lands outside national parks, is less clear,” Beschta said. “It may be necessary for wolves not only to be present but to have  an ecologically effective density, and mechanisms to deal with human and wolf  conflicts also need to be improved.”

“Predation and predation risk associated with large predators appear to  represent powerful ecological forces,” the researchers concluded in their  report, “capable of affecting the interactions of numerous animals and plants,  as well as the structure and function of ecosystems.”