Effects of climate-induced habitat fragmentation on high alpine biodiversity (ALPINEFRAGMENTATION)

Alpine biodiversity is especially vulnerable to climate change; warmer temperatures are forecast to cause altitudinal shifts in vegetation zones and vertical advance of the treeline. Such effects will result in a lower area of suitable habitat for high alpine specialists as their optimal habitat becomes increasingly small. In addition, populations on separate high altitude areas will become increasingly fragmented and isolated from one-another as suitable habitat towards the lower end of their altitudinal range becomes unsuitable. For many alpine specialists, mountain tops may be considered as islands separated by unsuitable habitat, and the size and spacing of these can greatly affect the regional occurrence of species. This project addressed the effects of high alpine habitat patch size and isolation on the abundance and species richness of different animal taxa (birds, butterflies and carabids, representing different dispersal abilities). Surveys in habitat patches were carried out, representing a gradient of different sizes and levels of isolation, where patches are defined by the treeline and a range of high-altitude species of open grassland habitats. Effects of fragmentation were examined by analysing the relationship between species abundance/richness and patch size and isolation, and the effects of climate-induced vegetation shifts on high-alpine animal communities. Field work was carried out and habitat data was recorded. Animal distribution patterns were modelled in the relation of environmental variables. Resulting statistical models were used to examine the potential consequences of climate change on alpine communities by considering differing scenarios of altitudinal shifts in vegetation zones. In many cases, there was evidence that both local climate and habitat composition dictated the distribution of species along the altitudinal gradients.

The efficacy of habitat management will depend on the extent to which species are limited by climatic variation within grasslands, which was implied by the models for several species. Thus, the project produced predictions of the effects of habitat fragmentation and therefore enables recommendations about the size and location of any protected areas that are designated to ameliorate climate change effects.