Humans can have a high impact on the species composition. Especially urbanisation and agriculture affect the natural habitats of species.

Many species found today in the alpine region were not originally distributed at higher elevations. This mainly concerns animals with wide ranges, like the large carnivores bear, wolf, lynx and eagle in the Alps. Extensive urbanisation and roadwork have fragmented their natural habitat and built barriers. The consequence has been the retreat of these species to the less disturbed and more natural areas which are found at higher elevations in the mountains. The ancient distribution of the brown bear (Ursus arctos) in Switzerland demonstrates this trend.

On the other hand, humans can also contribute to the spreading of species. Especially the disruption of the forest belt by agriculture and tourism have given many species from alpine steppes opportunities to colonise lower altitudes. The example of common voles (Microtus arvalis) has already been discussed. Marmots (Marmota marmota) also show extended altitudinal ranges where forest aisles are present.

Humans can also change species composition by introducing species to a region where they are not native. The red fox (Vulpes vulpes) in the Snowy Mountains of Australia is an example of such an introduced species. It was introduced to Australia in 1845 for sport hunting and within 50 years spread over the whole continent.

The introduction of wild animals can have severe negative effects:

• Loss of biological diversity - introduced species may displace native animals because the new species do not have the natural control (predators, diseases, ecological barriers) they have in their region of origin.



• Disease and parasites - introduced species may bring along new diseases and parasites to native fauna, that have no natural protection against them.

Reintroduction of species to regions where they have become extinct is a further way humans influence species composition. In the European Alps, several species have recently been re-introduced, including Lynx (Lynx lynx), Bearded vulture (Gypaetus barbatus) and, in some regions, Ibex (Capra ibex).

3a, b and c - Lynx (Lynx lynx), bearded vulture (Gypaetus barbatus) and ibex (Capra ibex) are species that have been re-introduced in the European Alps after extinction. Photo a: K. Robin (85K), b: 112K, c: 172K

29 August 2011
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