Butterfly loss in urban landscapes and nature reserves

Abstract

ContextUrbanization and landscape homogenization are main drivers causing biodiversity loss across the globe. The transformation of natural and semi-natural habitats into agro-environments and settlement areas causes the reduction of species diversity, and thus faunal homogenization. ObjectiveIn this study, we analyse changes in land-cover and habitat configuration and test for changes in species richness and community composition of butterflies in an urban area and a nature reserve. MethodWe analysed historical and recent aerial and satellite pictures, and studied the butterfly fauna for two areas in northern Austria, the urban area around Salzburg city and the nature reserve Bluntautal in close geographic proximity. For these analyses we consider the period 1946–2018. ResultsThe proportion of settlement area and forest increased in average by about 5%. Size of field copses increased and small-scale connectivity and thus landscape complexity decreased in both areas. In the same time span, we found a decrease in butterfly species richness for both areas, and in the nature reserve Bluntautal particularly for the past two decades by 50%. The species community composition changed significantly, with severe losses of specialist and xerothermophilic species which rely on open and extensively used ecosystems. ConclusionsThe findings underpin that the reduction of landscape complexity and the intensification of land-use including urbanization drives the loss of diversity of butterflies and changes in species composition, today dominated by some few generalist species. This trend is particularly observable for the nature reserve Bluntautal, where a large proportion of species diversity has disappeared in recent years despite nature conservation. This case underlines habitat management in nature reserves is needed to hold a high level of habitat quality and to preserve the entire species diversity.