Developing a butterfly indicator to assess changes inEurope’s biodiversity

Brereton T., Van Swaay C., Van Strien A.

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Abstract:

To monitor progress towards the European Union target to halt the loss of biodiversity by 2010, biodiversity indicators at a European scale are required. Butterflies have been proposed as biodiversity indicators due to their rapid and sensitive responses to subtle habitat and climatic changes and as representatives for the diversity and responses of other wildlife, especially insects. Since the frst butterfly monitoring scheme was established in the UK in 1976, schemes have now been established in over ten European countries. In each scheme, regular butterfly counts are made through the season each year along fxed routes under suitable weather criteria. Here, we used the counts to compile both national and supra-national annual indices for a number of species, in order to develop and test a preliminary European scale biodiversity indicator for the European Environment Agency. A multi-species grassland “European” Butterfly indicator was constructed by combining data from 17 characteristic grassland species, following closely the analytical method developed for the European Bird Indicator. The indicator showed a strong decline in butterfly abundance (of about 40% in 15 years from 1990). The European Environment Agency has subsequently proposed a number of indicators for inclusion in the set of European biodiversity indicators, butterflies being one of the most highest ranked. We hope to update and develop the indicator further (including compiling an indicator for woodland butterflies), make further analytical improvements and extend butterfly monitoring schemes to other countries in order to improve the quality and representativeness of the indicator.