Similar pattern of butterfly decline in urban and semi-natural alpine areas

Abstract Urbanization and landscape homogenization are main drivers causing biodiversity loss. The transformation of natural habitats into agro-environments and settlement areas causes the vanishing of many species across the globe and leads to faunal homogenization. In this study, we analyse changes in land-cover and habitat configuration and test for changes in species richness and community composition of butterflies. For this, we analysed historical aerial and recent satellite pictures, and studied the butterfly fauna for two areas in northern Austria, the urban Salzburg areas 'Gaisberg´ and the EU-protected 'Bluntautal´ area. For analyses of landscape and butterfly diversity changes in the respective area, we consider the period 1946–2018. The obtained data show that the proportion of settlement area and forest increased. Sizes of field copses increased, small-scale connectivity decreased and subsequently landscape complexity decreased. In parallel, butterfly species richness decreased and species community composition changed considerably in both areas, particularly in the nature reserve Bluntautal, during the past two decades. For both areas we found severe losses of specialist and xerothermophilic species, relying on open extensively used ecosystems. These trends underpin that the reduction of landscape complexity and subsequent landscape intensification drive the extinction of many species and lead to faunal homogenization. This trend is particularly observable in the Bluntautal, where a large proportion of species diversity has disappeared in recent years despite the protection status of this area. This study underpins that efficient management in protected areas is needed to preserve high habitat quality over long time periods.