Every five-years or so, Butterfly Conservation and its partners publish a ‘state of the nation’ assessment of the UK’s butterflies. Drawing from our world-leading recording and monitoring schemes, these influential reports set out the key results for butterfly species, highlight the implications of recent research and policy initiatives, and make recommendations for the conservation of UK butterflies and wider biodiversity.
The State of the UK’s Butterflies 2015 report contains new long-term (since 1976) and 10-year analyses of butterfly trends from the UK Butterfly Monitoring Scheme (UKBMS) and the Butterflies for the New Millennium (BNM) recording scheme. Tens of thousands of volunteers taking part in these schemes, or other projects such as the Wider Countryside Butterfly Survey and Big Butterfly Count that feed into them, ensure a comprehensive and statistically robust evidence-base to inform our assessment of the state of the UK’s butterflies.
Key findings include:
The new analyses provide further evidence of the serious, long-term and ongoing decline of UK butterflies, with 70% of species declining in occurrence (based on the BNM distribution data) and 57% declining in abundance (based on the UKBMS) since 1976.
Overall, 76% of the UK’s resident and regular migrant butterfly species declined in either abundance or occurrence (or both) over the past four decades. By comparison, 47% of species increased in one or both measures. This is of great concern not just for butterflies but for other wildlife species and the overall state of the environment.
Multi-species indicators show that both habitat specialist butterflies and wider countryside species decreased significantly in abundance and occurrence. Indeed, a number of wider countryside species (e.g. Wall, Small Heath) now rank among the most severely declining UK butterflies. The destruction and deterioration of habitats as a result of land-use change (e.g. intensification of agriculture, changing woodland management) are still considered the prime causes of long-term decline among habitat specialist butterflies in the UK. However, the factors responsible for the decreases of wider countryside species are not well understood.
The minority of UK butterflies that have fared well since the 1970s have increased their distributions, most likely as a response to climate change. However, the latest research into UK butterfly responses to climate change suggests that we should no longer assume that southerly-distributed species will necessarily benefit in the future. Species’ responses are much more variable than previously realised and the increasing frequency of extreme climatic events, predicted in many climate change scenarios, may have serious implications for butterfly populations.
Set against this gloomy backdrop are some important glimmers of hope. Trends over the past decade show that the long-term declines of some threatened species have been halted and small recoveries seen in some areas. Examples include the Duke of Burgundy, Pearl-bordered Fritillary and Dingy Skipper. Landscape-scale conservation projects targeting threatened species have proved successful and should be rolled out to cover more species in more landscapes.
Ten-year trends show that 52% of species decreased in abundance and 47% decreased in occurrence. While this indicates a generally improving situation, the declines of some threatened species (e.g. Wood White, White Admiral) show little signs of abating and, worryingly, populations of some common species (e.g. Gatekeeper, Essex Skipper) have dwindled in recent years. Even for those species where declines have recently been halted, population levels and distributions are much smaller than they once were. The conservation of the UK’s butterflies remains an enormous challenge.
Butterflies are the best-studied UK insects by far, providing vital insights into the changing state of wider biodiversity and the ecosystem services that depend upon it, as well as an important opportunity for the general public to engage with conservation, citizen science and the natural world. Restoring butterfly populations across the UK, in gardens, urban green spaces and the countryside, is likely to bring substantial benefits to innumerable other species but also to the health, wealth and well-being of the human population.
The report was written and produced by Butterfly Conservation and the Centre for Ecology & Hydrology.
We thank the British Trust for Ornithology which is a partner in the UKBMS, and Defra, Forestry Commission, Joint Nature Conservation Committee, Natural England, Natural Resources Wales, Northern Ireland Environment Agency, the Royal Society for the Protection of Birds and Scottish Natural Heritage for their financial support of butterfly recording and monitoring in the UK. The Balmain Charitable Trust, Opticron and the Robert Kiln Charitable Trust generously contributed to the costs of producing this report.
