Official Statistics for composite trends of butterflies in the UK between 1976 and 2020 were published on Thursday 16 September 2021, showing how habitat specialists and species of the wider countryside are faring.
Butterflies are considered to provide a good indication of the broad state of the environment because they respond rapidly to changes in environmental conditions and habitat management; occur in a wide range of habitats; and are representative of many other insects, in that they utilise areas with abundant plant food resources.
This Defra statistics release covers two measures of annual butterfly population abundance: the first for habitat specialist butterflies (species strongly associated with semi-natural habitats such as chalk downland), and the second for more widespread butterflies found in both semi-natural habitats and the wider countryside in the UK. Since 1976, populations of habitat specialists have declined significantly, though wider countryside species show no significant change. Habitat specialist species, which are vulnerable to semi-natural habitat loss and fragmentation, have not recovered from declines experienced in the late 1970s. These declines were mainly attributed to the knock-on effects of the drought conditions experienced in 1976.
Additional technical information on the trends can be found in the technical document.
These statistics contribute to a suite of indicators due to be updated in October this year (UK Biodiversity Indicators).
The statistics are based on the UK Butterfly Monitoring Scheme (UKBMS), which is organised and funded by Butterfly Conservation, the UK Centre for Ecology and Hydrology, British Trust for Ornithology, and JNCC. The UKBMS is indebted to the thousands of dedicated volunteers who contribute data to the scheme.