The Impacts of Skiing and Related Winter Recreational Activities on Mountain Environments

Mountain ecosystems consist of alpine zones characterized by rugged, partially vegetated open terrain with snowfields and rocky ridges above montane forests. These alpine grasslands and shrublands, sub-alpine parkland and montane forest habitats are high energy environments characterized by prolonged snow cover, steep terrain, extremes of heat and cold, and intense ultraviolet radiation. With increasing elevation, time for growth and reproduction decreases, environmental conditions become harsher with increasing stochasticity; at the highest elevations, hypoxic conditions add additional energetic living costs. For plants, dispersal of pollen, seeds or ramets may be limited by topography, weather conditions and patchy habitats where access to nutrients may be limited. These factors result in short, intense growing and breeding seasons.

Only a few plants and animals live exclusively in the alpine, while many mountain species breed in both alpine and lower elevation habitats. To cope with their difficult environmental conditions, plants and wildlife living in mountain habitats have adopted a slower lifestyle where they may produce fewer offspring each year compared to populations at low elevations, but many live longer and thus have more years to breed and replace themselves. The compression of several habitat types and variable environmental conditions within small spatial areas often results in high species endemism and biodiversity in mountain areas. High elevation ecosystems are used by migrating wildlife after breeding, a time when mountain habitats offer rich food resources and when productivity in many low elevation habitats has declined. Thus, we need to include life history periods outside the breeding season to accurately evaluate the biodiversity of mountain habitats. Connectivity is a key ecological process for high elevation wildlife populations. Connectivity needs to be maintained (1) among patchy habitat islands for breeding populations, (2) along mountain corridors for north-south migrants, and also (3) between alpine and adjacent lower elevation habitats and valley bottoms for both breeding populations and migrants.

Many European and Asian mountain ecosystems are heavily altered by agriculture, forestry and intense recreational activities such as skiing developments. Although most alpine habitats in North America appear relatively intact, ecological change is also taking place over extensive areas, with some areas showing deterioration due to recreational activities, livestock grazing, mining, and airborne contaminants. Ski area development has dramatically increased in America and Europe. In addition to habitat loss from resort areas and ski pistes, high elevation habitats impacted by ski developments are vulnerable to erosion, with slow recovery of vegetation after such disturbances. On a landscape scale, developed valley bottoms constitute dispersal barriers for wildlife species with seasonal vertical movements. The cumulative impacts of ski developments and climate change increase the challenge of maintaining the key ecological processes for the persistence of flora and fauna in sensitive mountain ecosystems.

Climatic changes are already having a significant impact on snow cover in the European Alps. Several studies from Switzerland, France, Austria, Italy and Germany have noted a general decrease in snow depth and snow cover duration since the end of the 1980s throughout the European Alps. Investigations of snow cover and climate change have revealed that the reduction in snow reliability observed in low and medium altitude ski resorts is mainly caused by warmer winter temperatures. Precipitation becomes the determining factor for a snowy winter only above 2000 m asl. Projected changes in temperature and precipitation are expected to cause further significant decline in the snowreliability of Alpine ski areas. The impacts of these changes, however, are not uniform. They depend on altitude, region and local factors. For example, the impact of climate change is stronger at low altitudes, in inner-alpine dry valleys and on southern slopes, which leads to winners and losers among the different ski areas. The winter tourism industry has already begun to respond to the implications of these observed changes. A range of technological and behavioural measures have been put into practice to offset the adverse impacts. However, adaptation measures, such as the widespread use of snow-making, put new pressures on the ecology of the mountain environment.

Much of the surface area in mountain regions has been converted to recreational activities in recent decades due to the increasing demand of tourists for winter sports. In general, ski-run construction and management have a great influence on the chemical and physical properties of underlying soils. To create ski-runs the natural landform is often changed to level the surface, thus exposing unweathered parent material or deep soil horizons. Thus the original soil thickness can be reduced, often resulting in a “turbated” topsoil. The result is that soils in ski-runs have an almost complete lack of structure, with subsequent problems of soil compaction and reduction of water and air permeability. Erosion on ski-runs is thus enhanced. One control that is often pursued is artificial seeding. However, depletion of soil organic matter, reduction in soil aggregate stability, and nutrient imbalance may affect plant development. In skirun restoration the improvement of soil organic matter and nutrient status is one of the most crucial tasks. A greater understanding of soil physico-chemical characteristics, plant colonisation and soil microbial activity after ski-run construction is necessary to enhance conservation and restoration of these disturbed pedoenvironments.

Impacts of skiing on alpine and subalpine vegetation are expressed by multiple disturbances: snow is being compacted by skiers and heavy machinery, new ski pistes are constructed by means of machine-grading and, increasingly, artificial snow is being produced by snow-making facilities.

This review compiles studies on ski piste vegetation from more than three centuries and skiing destinations across the world and distinguishes between different types of disturbances and elevations. Skiing in general can exert disturbances in the vegetation because of the changed snow conditions. The compaction of the snow can induce hard soil frost and mechanically damage plants. Machine-grading in summer to create smooth surfaces represents the most drastic disturbance on ski pistes especially at elevations around and above treeline. Artificial snow production has the potential to change vegetation through an input of water and ions and through postponing the time of melt-out.

Restoration measures to re-establish local vegetation after machine-grading have improved considerably in the last decades, however, still the vegetation and soil rarely fully recovers after major disturbance. If constructions are unavoidable, it is vitally important that restoration measures follow restoration guidelines that represent today’s state of the art.

Research on the impact of ski-runs on ground-dwelling arthropods has so far been largely neglected, despite the fact that such invertebrates may provide goods and services that are fundamental for mountain ecosystem functioning, and may be usefully employed as bio-indicators of human-induced environmental disturbance. In this chapter we present the results of previous research carried out in the north-western Italian Alps by pitfall trapping on ski-pistes, in adjacent habitats (i.e. forests or alpine prairies) and at the habitat edge. Research focused mainly on ground beetle and spider assemblages, but several results on other groups of arthropods (harvestmen, grasshoppers) were also provided. Below the tree line, all parameters of diversity (i.e. mean abundance, species richness and Shannon index) of brachypterous carabids (reduced wings or wingless) significantly decreased from forest interior to open habitats (i.e. ski-piste or pasture), whereas those of spiders and macropterous carabids (full-sized wings) increased from forest interior to open habitat. Ski-pistes showed lower values than pastures in all community parameters. Indicator Species Analysis showed that there were fewer species significantly preferring forest ski-pistes compared to those preferring pastures, and that there were very few species which were exclusive to skipistes (mainly generalist/eurieciouos species). Above the tree line, mean abundance and species richness of brachypterous carabids, spiders and grasshoppers decreased significantly from natural grasslands to ski-pistes. This was not true for the guild of macropterous beetles, which was composed of species with contrasting ecological requirements. Most of the species (some of them endemic to restricted areas in the western Italian Alps) had clear preferences for natural grassland and only two species of ground beetles (one being a generalist) had preference for ski-pistes. Both below and above the tree line, generalized linear models showed that the poor grass cover of skipistes is a serious hindrance to colonization by ground-dwelling arthropods. The potential impact of ski-pistes on the functioning of high altitude ecosystems and on the conservation of endemic species is discussed.

The focus of this chapter is on the effect of ski-pistes on birds and small mammals. We present the results of previous research carried out in the north-western Italian Alps both below and above the tree line. Data from other mountain areas are also incorporated. Ski-pistes below the tree line produce a negative edge effect: forest plots at their edges have lower bird diversity and species richness than those far from edges; conversely, species richness is enhanced when the forest grades into a pasture (positive edge effect). Ski-pistes above the tree line are characterized by low bird species richness and diversity. Moreover, plots adjacent to ski-pistes support a significantly lower bird abundance than plots far from ski-pistes, suggesting these ski-pistes, besides exerting a direct negative effect upon their avifauna, may also exert an indirect, detrimental effect on the number of individuals utilizing nearby areas. Small forest mammals clearly avoid ski-pistes, but open habitat species are able to colonize them. The effects of other skidevelopments (i.e. roads, buildings, car parks, lifts etc.) on ski-resorts are also discussed by considering research on the alpine chough in Italy, the elk in the USA and the mountain pygmy possum in Australia. As a conclusion, considering both the impact of ski-pistes on vertebrates and invertebrates, we urge a new, environmentally friendly way of constructing ski-pistes, such as only removing rocks and/or levelling the roughest ground surfaces (to preserve as much soil and natural vegetation as possible). The creation of a gradual transition from forest to ski-run, the retention of tree islands, and the incorporation of woody debris may be other useful interventions.

With the expansion of resorts for winter sports, the number of ski lifts has increased dramatically. The overhead cables of these structures are dangerous for birds, particularly for grouse and partridges living in the mountains, and cases of collisions are frequently reported. In 1997, the Mountain Galliformes Observatory (OGM) initiated a survey of sections of cables where dead birds had been discovered in all French ski areas in the Alps and the Pyrenees. The aim was to identify avian collision mortality sites in ski areas and to provide recommendations for reducing cable collisions in respective habitats. During the 1997-2009 period, 835 mortality events were identified on 137 of the 225 ski lifts investigated. The collisions involved six species of Galliformes present in the mountains of France. The species suffering the highest losses were the black grouse (Tetrao tetrix) in the Alps and the capercaillie (Tetrao urogallus) in the Pyrenees (capercaillie disappeared from the French Alps early in the decade; black grouse is not present in the Pyrenees). The collisions were mostly due to button lifts. It is possible to reduce mortality by installing marking devices on the more dangerous sections of cable. Collection and analysis of the type of data presented here can facilitate the characterisation and visualisation of potentially dangerous sections of existing and future installations.

Outdoor winter recreation is exerting an increasing pressure upon alpine biodiversity. There is an urgent need to better understand the detrimental effects on wildlife in order to propose targeted mitigation measures. This chapter summarizes the main results of a still ongoing research about the impacts of outdoor snowsports on black grouse, a regionally declining bird species. Black grouse was chosen as a model species because, in the European Alps, it inhabits exclusively treeline ecosystems, where most outdoor winter activities take place. We investigated the physiological (stress and energetics) and behavioural (activity budget) responses of free-ranging radio-tracked black grouse to human disturbance in winter, while assessing demographic effects. We then modelled areas of conflict between black grouse and winter outdoor recreation, which resulted in spatially-explicit prescriptions for mitigating its impacts. We finally discuss various issues around practical implementation of winter refuges for Alpine black grouse conservation.

The efforts in high-altitude restoration on ski runs have changed considerably since the demands for sustainable erosion control arose in the 1970ies. In this study we compare the success of restoration measures dating from the beginnings of high-altitude restoration with that of modern techniques. Vegetation and ecological data suggest that formerly used seed mixtures were less effective for re-vegetation of ski runs than modern seed mixtures, which contain site-specific and regional plant species. The vegetative and generative traits of the site-specific plant species proved to be important for erosion control.

The basic principles for long-term ecological restoration of ski-runs are presented.

Several thousands of hectares every year require restoration in the sub-alpine and alpine vegetation belt of the European Alps. The majority of these areas are used as ski-runs during winter and for agriculture in summer.

Control of erosion and its after effects, like increased surface drainage and dislocation of soil, is one of the most essential tasks when restoring ski-runs at high elevations. Ecological restoration of such areas requires the combination of high quality application techniques and site-specific seed or plant material containing species adapted to the given site conditions. Average slope inclinations of 30% to 45% in the vicinity of skiruns require the additional use of mulch covers to avoid increased surface drainage and noticeable soil losses during the first two vegetation periods. In the long-term, sufficient protection against erosion can only be guaranteed if stable, enduring and ecologically adapted sub-alpine and alpine plant species become established.