A new paper, ‘The decline of butterflies in Europe: problems, significance, and possible solutions’, part of a special feature on ‘The Global Decline of Insects in the Anthropocene’ has just been published in the Proceedings of the National Academy of Sciences of the United States of America and features major contributions from both Science and Conservation staff at Butterfly Conservation.

The lead author is Dr Martin Warren, currently Head of Development at Butterfly Conservation Europe but previously Chief Executive of Butterfly Conservation, while Sam Ellis (International Director), Nigel Bourn (Chief Scientist) and Dan Hoare (Director of Conservation) all make significant contributions.

The paper reviews changes in the status of butterflies in Europe, focussing on long-running population data available for the UK, Netherlands and Belgium, based on standardised monitoring transects. In the UK, 8% of resident species have become extinct and overall numbers have declined by around 50% since 1976. In the Netherlands, 20% of species have become extinct and overall numbers in the country have declined by 50% since 1990. Distribution trends showed that butterfly distributions began decreasing long ago and between 1890–1940 distributions declined by 80%. In Flanders (Belgium), 20 butterflies have become extinct (29%) and overall numbers declined by around 30% between 1992 and 2007.

A European Grassland Butterfly Indicator from 16 European countries shows that there has been a 39% decline of grassland butterflies since 1990. The 2010 Red List of European butterflies listed 38 of the 482 European species (8%) as threatened and 44 species (10%) as Near Threatened (note that 47 species were not assessed). An analysis at the country level indicates that the average Red List rating is highest in central and mid-Western Europe and lowest in the far north of Europe and around the Mediterranean.

The causes of the decline of butterflies are thought to be similar in most countries, mainly habitat loss and degradation (including grassland abandonment and lack of woodland management) and chemical pollution in the form of pesticides and herbicides. Climate change is allowing many species to spread northwards while bringing new threats to susceptible species.

The paper also describes examples of possible conservation solutions. In the UK, Butterfly Conservation is undertaking a comprehensive landscape-scale conservation programme.

The Duke of Burgundy is one of the UK’s most threatened species and more than 60% of its colonies became extinct between the 1980s and 2012. Concerted efforts to reverse its decline began in 2003 with a programme of landscape-scale conservation of targeted emergency habitat management, with the rotational cutting of scrub and the fencing of sites to reduce grazing pressure. This has brought about recovery of the butterfly’s population to the point that between 2007 and 2016 numbers increased by 90%. The paper also reports on a very successful conservation project in southern Belgium under a LIFE+ project funded by the European Union. Rides and glades have been enlarged and humid grasslands restored or created to increase the area of suitable habitat. In total, the project helped restore over 600ha of habitat. After just three to four years, numbers of the target species (Marsh Fritillary, Large Copper and Violet Copper) increased and several other threatened butterflies either colonised or increased, including Pearl-bordered Fritillary, Heath Fritillary, Dark Green Fritillary and Purple-edged Copper.

Dr Nigel Bourn, Chief Scientist

The decline of butterflies in Europe: problems, significance, and possible solutions. (2021) Warren, M. S., Maes, D., van Swaay, C. A. M., Goffart, P., Van Dyck, H., Bourn, N. A. D., Wynhoff, I., Hoare, D. and Ellis, S., Proceedings of the National Academy of Science, 118, e2002551117..