Butterfly Numbers Are Declining, Yet Five Species Are on the Rise

Over the past 50 years, milder and sunnier conditions, partly due to climate change, have benefited certain British butterfly species. However, the broader trend reveals a concerning decline in many of the UK’s iconic butterflies, as highlighted by the UK Butterfly Monitoring Scheme (UKBMS). This extensive project, which has amassed over 44 million records from 782,000 volunteer surveys since 1976, stands as one of the longest-running citizen science initiatives tracking insect populations.

Among the 59 native species monitored, 33 have seen population drops, while 25 have shown improvement. One species remains inconclusive due to limited data. The Red admiral, for example, is now overwintering in the UK as warming temperatures allow it to thrive. Comma butterflies, noted for their irregular wing patterns, have rebounded since the survey’s start. Orange tip numbers have surged by more than 40%, and the Black hairstreak, once critically rare, is recovering due to targeted conservation efforts. The Large Blue, which vanished in 1979, has also seen a resurgence thanks to habitat restoration.

Yet, the data underscores a growing disparity between adaptable butterflies and those dependent on specialized environments. Species that survive across diverse habitats—such as farmland, parks, and gardens—generally fare better. Warmer conditions, linked to climate change, are extending their ranges and breeding seasons. Prof Jane Hill, a butterfly specialist at the University of York, calls the dataset “extraordinary,” noting its role as a global benchmark for wildlife tracking. She emphasizes that butterflies, being cold-blooded, benefit from rising temperatures, enabling them to expand further north into Scotland and northern England.

“Most British butterflies reach their northern range limit in the UK, so they have opportunities to expand further north into northern England and Scotland,” said Prof Hill.

Conversely, specialist butterflies—like those reliant on woodland clearings or chalk grasslands—are struggling. As these habitats shrink from land-use changes and environmental stress, such species face steep declines. The white-letter hairstreak, whose caterpillars emit a glow under UV light, has plummeted by 80% since the survey began. The pearl-bordered fritillary, which feeds exclusively on violets, has also lost 70% of its population.

Prof Richard Fox, head of science at Butterfly Conservation, observes, “Just as we have lost family-run shops and traditional skills from the nation’s high streets, we’ve lost variety and diversity in the butterfly communities that can exist in our damaged and simplified landscapes.”

The scale of the dataset reflects a massive public commitment. Volunteers have logged over 932,000 miles across 7,600 sites, providing critical evidence for conservation strategies. Steve Wilkinson, director of the Joint Nature Conservation Committee, stresses, “Without this evidence timeline, we would be flying blind.” He adds that the consistency of volunteer contributions is essential for pinpointing where conservation efforts succeed and where they need strengthening.

Conservationists focus on preserving and expanding habitats that support butterflies, especially amid intensified farming and environmental degradation. Challenges persist, however, as some species and their larvae depend on narrow dietary choices—like the Duke of Burgundy on primroses or the purple emperor on willows. Butterfly Conservation’s Magdalen Hill Downs reserve exemplifies this work, maintaining varied ecosystems to sustain multiple species.