Sonja Wipf of the Swiss Federal Institute for Snow and Avalanche Research and colleagues from the University of Zurich and the University of Potsdam in Germany examined plant species at 12 Swiss ski resorts. They found that, compared with off-piste plots, there were 11% fewer plant species on ski pistes, with woody plants and early-flowering species being most badly affected.
Machine grading of ski slopes caused most damage to vegetation, with machine-graded slopes having five times more bare ground than ungraded pistes. And, say the researchers, this damage is long lasting. They found pistes that had been machine graded as long as 30 years ago and re-sown with plant seed had still not recovered. "Machine grading constitutes the most drastic vegetation disturbance on ski pistes. It should be avoided wherever possible, as it causes lasting damage that cannot be overcome by revegetation measures, particularly at higher altitudes," they say.
They also measured the impact of artificial snow on vegetation and found that this causes changes in species composition, with snowbed and late-flowering species increasing in abundance while wind-edge and early-flowering species declined. This is due to delayed snow-melt in areas covered with artificial snow, and the fact that artificial snow is made from river and lake water which contains more minerals and other chemical compounds than natural snow.
The findings are particularly important as ski resorts begin to feel the heat of climate change, developing higher altitude runs and using more artificial snow to keep skiers hap py. As this happens, Wipf and her co-workers want ski resorts to become more environmentally sensitive.
"We recommend that environmental goals should be established in ski resort management. In particular, we recommend carefully recording the vegetation in a specific area before any intensification of use as a ski piste, and complete avoidance of areas with vegetation of articularly high conservation value," they say.
Some alpine ecosystems are extraordinarily rich in species, but they are also sensitive and susceptible to changes in land use and climate.