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We review changes in the status of butterflies in Europe, focusing on long-running population data available for the United Kingdom, the Netherlands, and Belgium, based on standardized monitoring transects. In the United Kingdom, 8% of resident species have become extinct, and since 1976 overall numbers declined by around 50%. In the Netherlands, 20% of species have become extinct, and since 1990 overall numbers in the country declined by 50%. Distribution trends showed that butterfly distributions began decreasing long ago, and between 1890 and 1940, distributions declined by 80%. In Flanders (Belgium), 20 butterflies have become extinct (29%), and between 1992 and 2007 overall numbers declined by around 30%. A European Grassland Butterfly Indicator from 16 European countries shows 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). A country level analysis 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 and chemical pollution. Climate change is allowing many species to spread northward while bringing new threats to susceptible species. We describe examples of possible conservation solutions and a summary of policy changes needed to conserve butterflies and other insects.

1. Over the last century butterflies have undergone substantial changes in abundance and range in Great Britain and monitoring has improved markedly. These changes, together with a major revision of International Union for Conservation of Nature (IUCN) criteria, render previous Red List assessments outdated. 2. A new Red List assessment of all 62 resident and regularly breeding butterfly species in Britain was undertaken. The current IUCN criteria were applied for the first time to British butterflies using data from the Butterflies for the New Millennium recording scheme and the UK Butterfly Monitoring Scheme. 3. The state of knowledge and nature of the data available from these two schemes enabled assessment to be based upon two quantitative IUCN criteria: A2 (rate of population decline) and B2 (area of occupancy). 4. Twenty-three species (37% of the total) qualified as Regionally Extinct (RE) or threatened: 4 species were listed as RE and 19 as threatened (two Critically Endangered, eight Endangered and nine Vulnerable). A further 11 species were classified as Near Threatened. The remaining 28 species (45% of the total) were classified as Least Concern. 5. In comparison with previous assessments, we show that the number of species classified as threatened has increased. This is likely to be due to a combination of refined assessment criteria, improved data, and a real increase in the extinction threat as a result of human impacts. 6. The results confirm butterflies as a highly threatened group of insects in Great Britain and the Red List provides an important foundation to define conservation priorities.