A new Red List assessment of the extinction risk of butterfly species in Great Britain has been produced by Butterfly Conservation.
Red Lists highlighting species at risk of extinction have played an important part in nature conservation at global, continental and national levels for over 50 years. The Red List process developed by the International Union for Conservation of Nature (IUCN) sets the global standard for assessing extinction risk. Although extinction risk is not the same as conservation priority, Red Lists also frequently act as starting points for conservation action.
Regular reassessment of extinction risk and revision of Red Lists is vital during the current biodiversity crisis. The last Red List of British butterflies was published in 2010, but was based on an assessment several years earlier using trends up to the year 2004. Given this, and the ongoing rapid changes in butterfly populations over the past decade, it is timely to revisit the Red List.
So, over the last year, we have used data from the UK Butterfly Monitoring Scheme and Butterflies for the New Millennium recording scheme to assess butterfly species that have bred in Great Britain (England, Scotland and Wales) against the objective IUCN criteria. The resultant new Red List categorises 28 species as threatened (45% of the 62 species that met the assessment criteria), an increase on the 23 species previously listed as threatened. These 28 threatened species in the new Red List include four species that are classed as Regionally Extinct in Britain, eight species that are Endangered and 16 that are Vulnerable. A further five species are classed as Near Threatened, which leaves the remaining 29 species as Least Concern.
Duke of Burgundy, copyright Darren Chapman, from the surfbirds galleries
Many species previously listed as threatened have retained their places on the new Red List, although some have moved to lower risk categories because their abundance and distribution trends have improved in response to the great conservation work undertaken over the past two decades. Examples include both of the species formerly listed as Critically Endangered, High Brown Fritillary and Large Blue, which move to Endangered and Near Threatened respectively. Duke of Burgundy and Pearl-bordered Fritillary have also been assessed at lower risk this time, while remaining on the Red List, both moving from the Endangered category to Vulnerable.
In addition, several species that were not deemed at risk in the 2010 assessment are now included in the Red List, such as Swallowtail, Silver-spotted Skipper, Small Heath, Adonis Blue and Chalk Hill Blue, which have all moved from Near Threatened to Vulnerable, and Wall, which has moved from Near Threatened to Endangered.
The process, results and implications of the new Red List will be published in due course as a scientific paper, but in the meanwhile a full listing of species and their Red List categories can be found at https://doi.org/10.5281/zenodo.5710786.
It must be remembered that the Red List categories are not the same as conservation priorities. Butterfly Conservation’s priority species can be found in our UK Conservation Strategy and equivalent documents for the English regions, Northern Ireland, Scotland and Wales.
Many thanks to Natural England for guiding and supporting the new Red List of British butterflies.