Trends in populations of selected butterfly species - UK

These indicators on butterflies in the United Kingdom contribute to a suite of indicators in the UK Biodiversity Indicators. Early data availability allows their release ahead of that publication.
Two measures of annual butterfly population abundance are presented: the first for specialist butterflies (species strongly associated with semi-natural habitats such as unimproved grassland) and the second for butterflies found in both semi-natural habitats and the wider countryside. The measures are multi-species indices compiled by Butterfly Conservation (BC), the Centre for Ecology & Hydrology (CEH), and the Joint Nature Conservation Committee (JNCC) from data collated through the UK Butterfly Monitoring Scheme (UK BMS) and the Wider Countryside Butterfly Survey (WCBS).
The indicators use data from butterfly transect sites on farmland and in woodland from the UK BMS and additionally randomly selected farmland plots from the WCBS.