Are habitat changes driving the decline of the UK’s most threatened butterfly: the High Brown Fritillary Argynnis adippe (Lepidoptera: Nymphalidae)?

We describe how a landscape-scale approach has been adopted to conserve the UK’s most threatened butterfly Argynnis adippe. Only 37 populations now remain, with 38 extinctions occurring since 1994 (51% loss). The butterfly has disappeared from most of England and Wales and is now confined to just four landscapes. Since 2005 management in these landscapes has been targeted at improving habitat quality within and connectivity between both occupied and unoccupied sites in the same networks. Conservation advice has been provided on 80% of occupied/former sites and over 270 ha management implemented across 53% of occupied/former sites. Where management was undertaken, significant increases in abundance compared to the national trend were recorded for some site networks or some populations. (Re)colonisations have occurred in response to management/advice on 16 sites, all within 1 km of the nearest population. However, responses to management in one landscape have been mixed, with overall abundance continuing to decline and further extinctions occurring. Habitat condition assessments on five sites in this landscape reveal significant changes between 2004 and 2016, with declines in Viola spp. cover, increased grassiness and less P. aquilinum litter/standing trash on some sites. We discuss potential drivers of both A. adippe population dynamics and habitat condition change. Our research suggests an urgent need to review the butterfly’s ecological requirements and current management recommendations designed to meet them, so that new prescriptions or techniques can be developed and tested which can increase the quality and longevity of A. adippe habitat.