How to turn slopes green after skiers go away

"We're in this time of visible climate change," says Jeffrey Clary. "Land uses we once thought were permanent, we're now seeing are likely not. As a land manager, to me, it only makes sense to look at a longer-term picture." (Credit: iStockphoto)

The recovery of an abandoned ski run depends on whether or not it was graded, a new study shows.

Researchers, who report their findings in the Journal of Applied Ecology, evaluated six abandoned ski areas in the Northern Sierra region of California and Nevada. They found that runs that were graded showed no predictable recovery even 40 years after abandonment. With graded runs, heavy machinery is used to remove vegetation, boulders, and, consequently, much of the topsoil and seed bank during construction.

In contrast, “cleared” runs, in which trees and shrubs were cut with their roots left in the ground, consistently recovered to blend in with the surrounding forest. Trees and other vegetation grew back over time, and bare ground and visible soil erosion decreased, protecting water quality.

“As more ski areas become abandoned, there should be some effort taken to actively restore graded ski slopes,” says lead author Jennifer Burt, a University of California, Davis doctoral student at the time of the study and currently a restoration ecologist at AECOM Environment in Sacramento. “These are large land areas in some cases and, as we’re seeing, they don’t recover on their own.”

ski runs
Left: This is what a graded ski run, abandoned 13 years ago at the Iron Mountain ski area, looks like. Right: This cleared ski run at Iron Mountain was abandoned 10 years ago. (Credit: (Andrew Burt, Jessica Hite)

The sites ranged from 10 to 43 years since abandonment and, like many ski areas in the western US, most had operated under special use permit on USDA Forest Service lands. The study included the Lake Tahoe area sites of Powder Bowl, Plavada, Tannenbaum, Edelweiss, Iron Mountain, and Echo Summit.

“We’re in this time of visible climate change,” says coauthor Jeffrey Clary, reserve manager of Stebbins Cold Canyon Reserve in the UC Davis Natural Reserve System. “Land uses we once thought were permanent, we’re now seeing are likely not. As a land manager, to me, it only makes sense to look at a longer-term picture.”

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Abandoned graded runs aren’t all “moonscapes,” Burt says. Aside from some barren patches, the graded lands she studied typically did regrow some trees and other plant life over time. But with a shallower soil depth, the vegetation there was stunted, less robust, and less diverse. The growth there was unpredictable, and the land showed visible signs of erosion compared with formerly cleared runs.

Clearing is the first step in creating any ski run, Burt says. Grading is a second step taken to further smooth the slope, and it is widely practiced in the ski industry.

Grading requires more upfront costs than simply clearing the run. The process also scrapes and compacts the soil, reducing the ability of water to permeate the soil, so ongoing erosion repair is an additional need.

So why do ski areas grade runs at all? It can allow them to open ski runs up to two weeks earlier in the season. Cleared runs need roughly an additional one to two feet of snow before opening to skiers.

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Burt published a related study in 2009 that looked at the negative effects of grading on active, not abandoned, ski slopes.

Both studies have clear implications for land management, including pointing out more desirable methods for constructing ski slopes, and the need for active restoration of abandoned graded ski slopes.

“If you’re going to create a new ski slope, ideally, you shouldn’t grade it,” Burt advises. “If grading is necessary, use a light touch and grade as little of the slope as possible so you don’t destroy the soil function for the long haul.”

The National Science Foundation Graduate Research Fellowship, the UC Davis Department of Plant Sciences, NSF Biological Invasions IGERT program at UC Davis, and a UC Davis Jastro-Shield research fellowship supported the work.

Source: UC Davis