1 - High pressure snow making equipment in action.

Global warming affects snow reliability in many winter sports resorts between 1200 and 1800 m in the European Alps. To deal with this problem, tourism managers consider guaranteeing winter sports by intensifying artificial snow-making. However, knowledge of the impact of artificial snow on ecosystems and especially on vegetation is still rudimentary.

A study conducted in Savognin (eastern Swiss Alps), where artificial snow-making has been carried out every year since 1978, has revealed that artificial snow leads to significant changes in the floristic composition of high montane and subalpine grasslands. Figure 2 compares the floristic composition with and without artificial snow.

2 - Composition of nutrient-poor hay meadows that have been sprayed with artificial snow and untreated meadows of the same type.

The cover of species typical of nutrient-rich hay meadows was higher on dry and nutrient-poor hay meadows that are covered with artificial snow in winter when compared to the untreated meadows. On the other hand, the cover of species typical of dry and nutrient-poor meadows decreased in the meadows with artificial snow. This shift of the floristic composition was connected to a decline in the total species number of the meadows sprayed with artificial snow.

3 - A species-rich hay meadow dominated by Bromus erectus and Helictotrichon pubescens in the Savognin region.

4 - Comparison of species richness in nutrient-poor hay meadows

The additional water and ion inputs on the sites sprayed with artificial snow and the prolongation of the snow cover are likely to be the causes of the floristic changes described.

• Water input: In Savognin region, the melting of an artificial snow cover of 60 cm in April and May provides an additional volume of water corresponding to 132 % of the mean precipitation of this period.
   
• Ion input: Compared to the water of natural precipitations, the water of the River Gelgia used for artificial snowing had elevated contents of the macroelements Mg2+, SO42-, Ca2+, K+, and Cl- as well as of Na+.
   
• The prolongation of the snow cover on areas sprayed with artificial snow leads to a delay in the vegetation development ranging from a few days to a maximum of one month.

Each of these factors promotes the faster growing species typical of nutrient-rich, mesic habitats at the expense of weaker competitors such as the species of low-nutrient and drier habitats thereby leading to the vegetation changes observed. In conclusion, artificial snow represents a serious threat to the plant species diversity of low-nutrient and dry grasslands.

5 - Remains of artificial snow in a skiing area in late April.

Compare the phenological development of the vegetation on meadow sprayed with artificial snow to that of an untreated meadow (natural snow) from early May to late June.

29 August 2011
© ALPECOLe 2002-2007