Biotope use and trends of European butterflies

Europe has undergone substantial biotope loss and change over the last century and data are needed urgently on the rate of decline in different wildlife groups in order to identify and target conservation measures. However, pan-European data are available for very few taxonomic groups, notably birds. We present here the first overview of trends for an insect group within different biotopes across Europe, based on data from the Red Data Book of European Butterflies. The most important biotopes for Europe's 576 butterfly species, including threatened species, are man-made or man-influenced, notably types of grassland or heath/scrub communities. Our results show that butterflies are declining substantially across Europe, with a decline in distribution of -11% over the last 25 years. The distributions of the 25 most generalist species are declining only slowly (-1%) compared to specialist butterflies of grassland (-19%), wetlands (-15%), and forests (-14%). On average, grassland butterflies have declined somewhat slower than farmland birds (annual decrease -0.8% compared to -1.5%), but woodland butterflies have decreased more rapidly (-0.01% to -0.6%) than woodland birds, which are more or less stable. The sensitivity of butterflies to environmental changes and the availability of data across Europe suggest that they are very good candidates to build biodiversity indicators and, along with other major groups such as birds, suitable to monitor progress towards the EU target of halting biodiversity loss by 2010.