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Human activity has affected native
vertebrate populations in many alpine zones, particularly those of large mammalian herbivores.
In some alpine regions large mammalian herbivores have been driven to the verge of
extinction. For example, in parts of the U.S.A. mountain species such as the bighorn sheep
(Ovis canadensis) and elk (Cervis canadensis) have disappeared, though there are now
attempts to reintroduce them in some areas. In other high mountain regions, population densities of
herbivores have increased after the elimination of
natural predators by humans. Elimination of brown bear (Ursus arctos), wolf
(Canis lupus) and lynx (Lynx lynx) in the Alps has caused an increase in ungulate densities,
especially of deer, but also of ibex. At high densities these animals can cause considerable damage
to the vegetation; this is especially true at the treeline ecotone and in alpine grasslands where the
trampling impact can promote erosion due to needle-ice and solifluction.
Furthermore, there is an indirect effect of human activities
on the occurrence and impact of herbivores due to changes of the habitat. The use of the alpine
environment by humans disturbs the normal behaviour and migration of many herbivores and may therefore
change their spatio-temporal patterns of impact. Competition between natural
herbivores and livestock and the transmittance of infections from livestock animals like sheep on
chamois or ibex may reduce the size of the native herbivore populations. On the other hand, the
presence of livestock may result in a change in their behaviour and locally increased impact.
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