Altitudinal distributions of endangered butterflies in the Austrian Alps

Abstract

In Alpine regions, biodiversity loss is more pronounced in lowland areas intensively used by humans. At higher altitude, topography hardly allows for large-scale agricultural intensification and settlement as observed for the lowland areas. Based on long-term observations of butterflies across Northern Austria, we investigate the degree and trends of endangerment of butterflies, depending on altitude. Our results show that many endangered butterfly species occur mainly at lower altitudes where ongoing habitat loss contributes to their decline. Species relying on oligotrophic grasslands and on wetlands are at particular risk. Butterfly species mainly occurring all over the altitudinal gradient or exclusively at higher altitudes are on average less endangered. The lowland–mountain discrepancy in the proportion of endangered species has increased over the last 30 years. Climate change augments this tendency because common species might keep their thermal niches by altitudinal range expansion while endangered specialists might not find appropriate habitats at higher altitude. The establishing of appropriate lowland nature reserves might counteract these trends.