Aspen trees disappearing from West

IDAHO FALLS – Groves of aspen – tall, skinny trees with telltale white bark and fluttering, glossy leaves – are unmistakable in eastern Idaho.

But look for the cone-shaped tops of conifers living among the smaller aspen, and juniper trees creeping closer to the perimeter of the grove. It’s not an example of species diversity; it’s a death sentence.

Aspen – the most widespread tree in North America – are disappearing across the Western United States. Eastern Idaho’s aspen community, once estimated to cover 40 percent of eastern Idaho’s forested areas, has declined by an estimated 60 percent in the past 100 years, while Arizona has seen a 90 percent decline during that time, said Aren Eddingsaas, chairman of the science and technology committee for the Eastern Idaho Aspen Working Group and a wildlife biologist for the Shoshone-Bannock Tribe.

“I would consider it a very big issue,” said Ben Dyer, ecologist for the U.S. Bureau of Land Management. “It’s a keystone species and vital to other plant, animal and insect survival.”

A keystone species is one that has a “disproportionately large effect on the communities in which it occurs,” according to Encyclopedia Britannica. “Such species help to maintain local biodiversity within a community either by controlling populations of other species that would otherwise dominate the community or by providing critical resources for a wide range of species.”

Terry Thomas, Idaho Department of Fish and Game regional habitat manager, said eastern Idaho is losing 5,000 acres of aspen each year.

In order to combat that loss, Fish and Game, the U.S. Forest Service, Bureau of Land Management, Idaho Department of Lands, Idaho Department of Parks and Recreation and Idaho Department of Agriculture banded together in 2006 to form the Eastern Idaho Aspen Working Group. The group’s mission is to preserve the species.

Since a number of species benefit from aspen, especially elk and deer, Eddingsaas said, conservation is vital.

“They found that fawn and calves in those areas (with dense aspen groves) are healthier,” he said. “Because of the diversity that aspen provide, it’s just an important community.”

While providing habitat and food for wildlife, they also have a relatively short life span (70 to 100 years). That allows them to decompose and put nutrients back into the forest floor more often than other trees. The minimal canopy of an aspen grove allows snowmelt to drip into the groundwater rather than evaporate as it does on more dense canopies, said Eddingsaas.

Experts agree that the decline of aspen, locally and around the West, largely is the result of two things: lack of fire and encroachment of conifers and juniper.

Because the root system of aspens runs deeper below the ground than most trees, aspens can survive forest fires that competing trees can’t. But as wildfire fighting becomes more prevalent, aspen benefit less.

“When you have juniper encroachment, they have a wide root system and take in a lot more water and can choke out the aspen,” Dyer said.

The trees also are susceptible to sudden aspen decline – a condition that claims entire groves without conifer invasion.

Thomas cites an example of this in a research paper he published on the decline of aspen: from 2005 to 2007, amid the worst drought in 109 years, 338,000 acres of aspen perished in Colorado. While the cause is still being researched, most evidence points toward drought.

The Aspen Working Group spends most of its time working to find ways to protect aspen. The BLM has been removing juniper and conifers in the Tex Creek Wildlife Management Area east of Idaho Falls.

Aspen are higher in fat than many other plants, which make the aspen shoots a vital food source for deer and elk in the winter. Dyer said the Tex Creek area attracts about 6,000 deer and elk in the winter months. The goal of the restoration project is to not only be able to provide the food source for game, but have enough shoots in spring to regenerate the groves in the area.

Another way to help aspen thrive is through controlled burns to reduce the number of competing trees. But that practice can cause other problems.

“People don’t like to see smoke, they don’t like to see black on the hillside up from their property,” Thomas said. “We have a lot of tools in the toolbox; it’s whether or not we get the opportunity to apply those tools.”

The task is not an easy one.

“Considering the loss, and the fact that we don’t have the budget to do as much as we like, we’re not even close to keeping up with the loss of aspen on an annual basis,” Eddingsaas said.