Climate change and biological invasions in high elevation ecosystems:
Biological invasions are the redistribution of species through human agency into regions outside of their native range. A subset of these species, so called invasive alien species, can have dramatic ecologic and socio-economic effects. Recently, they have been identified as one of the main drivers of global change and loss of biodiversity. Due to the harsh climatic conditions and comparably low anthropogenic pressure, high elevation ecosystems have been perceived as relatively stable to biological invasions and studies show a decrease of alien species richness with increasing elevation. Nevertheless, globally, about 200 alien plant species have been documented in alpine altitudes to date. Most of these species are generalists that have been introduced to lowland regions and ascend up the mountains. Although, many species are still not able to cope with the climatic conditions in high elevation ecosystems, it has been projected, that they will be able to overcome this barrier under future changing climatic conditions. In contrast, native communities in high elevation ecosystems are becoming increasingly destabilized in the course of global change and thus more susceptible to biological invasions. Hence, the combination of several drivers of global change poses a great risk to the native communities in high elevation ecosystems globally. Since there are still few alien species in the high mountains compared to the lowlands, there is a large option space to develop precautionary measures and reduce the combined influence of climate change and biological invasions.