The latest Red List of Britain’s butterflies, published this week in the journal Insect Conservation and Diversity, categorises 50% of regularly breeding species as threatened or Near Threatened. Twenty-four species (41%) are listed as threatened (8 as Endangered and 16 as Vulnerable) and a further five (9%) as Near Threatened. The number of threatened species represents an increase of one-quarter on the previous Red List, published in 2010, which listed 19 threatened species.
Butterfly Conservation scientists carried out the new assessment, using decades of volunteer-gathered data from the UK Butterfly Monitoring Scheme and Butterflies for the New Millennium recording scheme.
The results show that extinction risk is increasing for more species than are decreasing, clearly demonstrating that ongoing decline of British butterflies. Species increasing in threat level include Large Heath and Grayling, both moving from Vulnerable to Endangered, and seven species previously listed as Near Threatened which are now considered Vulnerable or Endangered. These include Swallowtail, Silver-spotted Skipper, Small Pearl-bordered Fritillary and Chalk Hill Blue. The species with the greatest increases in threat level are both butterflies of the wider countryside rather than habitat specialists: Wall moves from Near Threatened to Endangered and Scotch Argus moves from Least Concern to Vulnerable.
It is also notable that all four of Britain’s butterfly species that have northerly distributions, reflecting adaptation to cooler and or damper climates, are now on the Red List (Large Heath, Mountain Ringlet, Scotch Argus and Northern Brown Argus).
The revised Red List also offers some encouragement, however, particularly for species that have been the focus of long-term conservation action. Both species previously categorised as Critically Endangered, Large Blue and High Brown Fritillary, have been downgraded – indeed no species were classed as Critically Endangered on the new Red List. Large Blue, which became extinct in Britain in 1979 and has been the subject of a highly successful, ongoing reintroduction programme, is now Near Threatened. High Brown Fritillary, which has been the focus of intensive conservation efforts in its remaining strongholds in south-west and north-west England, as well as at its only remaining site in Wales, is now Endangered. Other conservation programmes have certainly benefitted threatened butterfly species at the landscape scale and are likely to have contributed to the improved status and trends of Pearl-bordered Fritillary and Duke of Burgundy, both of which have moved from the Endangered category to Vulnerable. Ongoing conservation management of priority species will hopefully lead to continued reduction in extinction risk for these and other species (e.g. Wood White) in the future.
The message is clear: sustained, targeted conservation effort can reduce the extinction risk of threatened species. But, with the extinction risk increasing for more species than are decreasing, much more must be done to protect our butterflies from the effects of changing land management and climate change. Without action it is likely that species will continue to be lost from landscapes, but Butterfly Conservation is taking bold steps to reduce the extinction risk of many threatened species. Our new strategy targets at least 65 of the most threatened butterflies and moths in the UK, focuses on improving 100 key landscapes in collaboration with partners, and highlights the importance of developing research into the key drivers of change to inform conservation action and policy solutions.
The production of the new Red List of British butterflies has been led by Butterfly Conservation with input and funding from Natural England, and the full scientific paper can be found here.
Richard Fox is Head of Science at Butterfly Conservation
The opinions expressed in this blog are the author's and not necessarily those of the wider Link membership.
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