Sierra resorts such as Northstar-at-Tahoe contain both graded and
cleared ski runs, with very different
environmental impacts.
For many, being “green” means finding high-tech – and, by extension, high-cost – fixes for familiar environmental problems.
But sometimes the greenest solutions lie in reviving sensible and economical practices from the past.
Ski run construction presents one clear example.
In bygone days, when skiing operations were smaller in scope, ski runs were mostly created in ways that avoided long-term environmental degradation. In forested areas, ski area operators simply cut down trees and tall shrubs in the path of the new run, creating an open slope through the forest. Skiers flew over unseen snow-buried stumps, small shrubs, and undisturbed soils. Because the soils were left undisturbed, these ski runs were not subject to great erosion, and native plant communities regrew vigorously from the existing seedbank.
In subsequent decades, ski run construction changed dramatically. The predominant practice shifted from clearing to grading, or bulldozing ski runs to create a smooth under-snow surface, stripping the slope of vegetation, stumps, rocks, roots and seeds. The topsoil is scraped and often buried beneath the subsoil, and soils are compacted, creating a harsh environment for plant establishment and growth.
In collaboration with Dr. Kevin Rice, a professor of plant science at UC Davis, I decided to conduct a scientific investigation and analysis of precisely what environmental impacts this change has wrought in ski areas of the Sierra Nevada.
We compared cleared ski runs to nearby graded ski runs across seven ski areas – Kirkwood, Sierra-at-Tahoe, Heavenly, Diamond Peak, Mount Rose, Northstar-at-Tahoe, and Sugar Bowl. All contain both graded and cleared ski runs. Across this wide range of ski resorts, we found that grading causes significant long-lasting environmental damage. Compared with ski runs that were simply cleared, there was much reduced soil depth and soil nutrients and increased soil compaction, exposed bare ground and visible erosion on machine-graded ski runs.
Such impacts to mountain soils are of particular concern in the Lake Tahoe basin, where runoff from degraded upland slopes has been responsible for much loss of lake clarity. Graded ski runs also tend to be sparsely covered by nonnative grass plant communities (introduced by active seeding for erosion control), while cleared ski runs are characterized by more robust plant communities composed of native shrubs and perennial herbs that sprouted from the intact seedbank.
Similarly, my research in abandoned ski areas indicates that cleared ski runs recover and converge more quickly and predictably than graded ski runs, speeding up the process of forest regeneration. By contrast, ski runs that were graded and then abandoned did not return to natural forests as quickly or recover in terms of natural soil structure. Other scientific studies of machine-graded ski runs from around the world also indicate that ski run grading causes negative environmental impacts.
For some people, it may seem counterintuitive that downhill ski runs can be constructed without decimating the local ecosystem. Our research in the Sierra Nevada found that ski runs cleared of only trees and other tall vegetation are ecologically more similar to undisturbed forests than they are to graded ski runs. These cleared slopes actually harbor greater species diversity than undisturbed forests in many adjacent sites.
Ecologists know that disturbance can be a natural component of ecosystem health. Our research showed that clearing trees for ski runs mimics in some ways natural disturbances, such as fires, avalanches and treefalls. While clearing ski runs introduces larger-scale issues of forest fragmentation and crowds of winter (and sometimes summer) tourists in a formerly natural area, the clearing technique reduces overall harm, compared to the more destructive bulldozing.
Nevertheless, machine-grading of ski runs is prevalent worldwide. In the Sierra Nevada and many other parts of the West, the vast majority of ski runs are graded. At Whistler-Blackcomb near Vancouver, British Columbia, where the so-called “Green Olympics” were held, 90 percent of conventional ski runs are graded. Graded ski runs are also common elsewhere in the United States, Europe and Japan.
Why is bulldozing so widespread? Graded ski runs require less snow to open, allowing ski resorts to capitalize on the “shoulder” seasons of early and late winter, when snow coverage is sparser. But a ski area doesn’t need to open all of its runs at once to be open for business.
As an alternative to allow earlier ski run openings, clearing may be done with greater precision and attention to detail so that less snow is required to open the ski run. Large rocks and boulders can be fragmented in place using the same methods used on runs that are later graded. Stumps can be ground down to soil level.
Spot-grading can also be used, if a rock outcrop or other irreconcilable irregularity impedes a workable run. But wherever grading is used, restoration of soil function and native vegetation should be carried out, including planting with appropriate native species after tilling subsoils with wood mulch and redistributing saved topsoil.
The conventional wisdom is that the “green” way of doing things is necessarily more expensive. But clearing ski runs is far more economical in construction costs in both the short and long terms. Clearing trees and breaking up large rocks on a new ski run in a forested area are the first steps of ski run construction, regardless of whether the ski run is then smooth-graded.
Furthermore, graded ski runs have additional inherent upfront costs in that they require both bulldozing and often more mitigation at the time of construction, along with the time and money that are then put into often repeated attempts to establish vegetation on the graded ski runs in the off season. These erosion control practices are generally not necessary on cleared ski runs because the soils and native seedbank are left essentially intact during the clearing process and plants can readily grow in these conditions without active assistance.
Some surveys show that skiers, as a group, are highly committed to environmental protection. So the question becomes: Are resort managers, along with skiers and snowboarders, willing for some runs to open a little later and potentially close earlier so that resorts rely more on clearing instead of grading?
Jennifer Williamson Burt
