Not All Ski Slopes Are Environmentally Equal, Study Concludes

By SINDYA N. BHANOO

Ski resorts are not as fun for the environment as they are for skiers. The damage to forested hills caused by the construction of ski slopes is obvious. Trees are cut down, ground is cleared, and the resulting slopes are maintained as the foundation for a yearly carpet of snow.

Some ski slopes, however, are more environmentally friendly than others, according to a new study. Cleared ski runs, where trees and other tall, woody plants are cut down to open skiing pathways, cause less damage to the natural ecosystem than graded ski runs, which are bulldozed, leaving little or no vegetation or shrubs.

“Cleared slopes are actually more like forests than graded slopes,” said Jennifer W. Burt, the lead author of the study, published in last month’s issue of Ecological Applications. “This was an unexpected result of our research,” said Dr. Burt, who studied ski slope construction as part of her doctoral research. On cleared runs, seed banks are left intact, and small shrubs remain undamaged. Also left intact are the top layers of the soil, which support plant growth and more robust and diverse vegetation, which in turn support wildlife.

Machine-graded runs, on the other hand, remove topsoil and vegetation, significantly damaging the ecosystem.

Dr. Burt studied seven ski areas in and around the Lake Tahoe Basin, including Sugar Bowl, Heavenly, Kirkwood and Northstar-at-Tahoe, which all had both cleared and graded slopes.

Although she says she is the first to study graded and cleared slopes in the United States, a number of studies on ski slope ecology have been done in Europe.

European ski resorts, however, tend to be at higher elevations, where trees do not grow.

“That’s a very important distinction between U.S. ski resorts and the European ones,” said Christian Rixen, an alpine ecosystem researcher at the Swiss Federal Institute for Forest, Snow and Landscape Research. “It’s basically a question of forest or no forest.”

In his work in Europe, Dr. Rixen also found that cleared runs cause less environmental damage, offering better growth opportunities to alpine tundra and other vegetation.

When Dr. Burt asked resort managers why they create graded runs at all, she was told that they are smoother, which means less snow is needed to open a graded run than a comparable cleared run. On average, graded runs opened in the 2006-7 season a week earlier than cleared runs, Dr. Burt said.

“I don’t mind waiting a week or two if that’s what it takes to have much reduced environmental impacts,” said Dr. Burt, an avid skier herself. “I think there are other skiers who would say the same.”

A group called the Ski Area Citizen’s Coalition, based in Colorado, maintains a Web site that grades ski resorts based on their impact on the environment. The group plans to incorporate the results from Dr. Burt’s research into its grading system.

While conservationists might argue against any kind of ski slope, Paul Joyce, the coalition’s research director, pointed out that skiing has considerable economic benefits and offers millions of people a way to enjoy the outdoors.

However, he said, environmental interests are being sacrificed in favor of financial ones.

“In the last couple decades, it’s turned into a giant moneymaking machine, and the Forest Service has become a party to this,” Mr. Joyce said, referring to the fact that many ski resorts operate on United States Forest Service land. “Skiers are out there enjoying the outdoors, often in harsh conditions, and we’d at least like to think of ourselves as green — it’s incumbent on the industry to make this the experience.”