The impact of high-altitude ski pistes on ground-dwelling arthropods in the Alps

The development of winter sport resorts above the timberline may affect every ecosystem component. We analyzed the effect of ski-pistes on the abundance and species richness of arthropods (namely carabids, spiders, opilionids, and grasshoppers) trapped in grasslands adjacent to the ski-run, on ski-pistes and at the edge between these two habitat types. Our results showed that diversity of brachypterous carabids, spiders, and grasshoppers decreased significantly from natural grasslands to ski-pistes. This was not true for the macropterous carabid guild, which included species with contrasting ecological requirements. The analysis of indicator species (IndVal) showed that most of the species (some of them precinctive to restricted areas in the north-western Alps) had clear preferences for natural grassland and few taxa were limited to ski-pistes. Generalized linear models suggested that the local extent of grass and rock cover can significantly affect assemblages: the low grass cover of ski-pistes, in particular, was a serious hindrance to colonization by spider, grasshopper, brachypterous, and some macropterous carabid species. The results obtained, support concerns over the possible disruption of local ecosystem functionality and over the conservation of arthropod species which are endemic to restricted alpine areas. In order to retain arthropod ground-dwelling fauna we suggest that: (i) new, environmentally friendly ways of constructing pistes should be developed to preserve as much soil and grass cover as possible; (ii) existing ski-pistes should be restored through management to promote the recovery of local vegetation.