Butterfly Decline: A Complex Picture of Loss and Resilience
Britain’s butterfly populations are undergoing a significant shift, according to the latest data from the UK Butterfly Monitoring Scheme (UKBMS). While fears of a complete “insectageddon” haven’t materialized, a worrying trend of declining diversity is evident. Over the past half-century, 33 of the 58 native butterfly species have decreased in number, even as 25 have seen increases.
The Winners and Losers
The most dramatic increases are being observed in species benefiting from warmer temperatures. The purple emperor has seen a 136% increase, the red admiral a staggering 330%, and the comma butterfly a 178% rise. These butterflies are expanding their range northward as the climate changes.
Although, this positive trend masks a concerning decline among “habitat specialist” butterflies – those reliant on specific environments like woodlands, wetlands, and grasslands. The high brown fritillary is down 66%, the pearl-bordered fritillary has fallen by 70%, and the white-letter hairstreak has plummeted by 80%.
Why the Disparity?
Habitat loss is a primary driver of decline for specialist species. The loss of traditional woodland management practices, such as coppicing, has reduced the availability of the floral-rich, sunny environments these butterflies need. Beyond habitat, pollution also plays a role. Warmer weather combined with nitrogen pollution from vehicles is altering grassland ecosystems, making them unsuitable for certain caterpillars, like those of the wall brown and grayling.
As Richard Fox, head of science at Butterfly Conservation, explains, “The rain is now dilute fertiliser and that’s raining down on our plant communities and causing them to change.” These changes in plant composition and structure directly impact the caterpillars that depend on them.
Success Stories Offer Hope
Despite the overall trend, conservation efforts are proving successful in some cases. The large blue butterfly, once extinct in Britain by 1979, has experienced a remarkable resurgence – a 1,866% increase since its reintroduction in 1983. The silver-spotted skipper (up 300%) and the black hairstreak (up 844%) also demonstrate the positive impact of targeted conservation work.
These successes are largely thanks to the dedication of volunteer citizen scientists who have walked over 1.5 million kilometers monitoring butterfly populations at more than 7,600 sites since 1976.
The Importance of Diversity
The decline in butterfly diversity is a worrying sign, even if overall numbers haven’t collapsed. As Fox notes, “It’s not just that the total number of butterflies has gone down, it’s about the diversity that’s being eroded.” This loss of variety mirrors the decline of traditional businesses and skills in communities.
Prof Chris Thomas, director of the Leverhulme Centre for Anthropocene Biodiversity at the University of York, highlights the value of the UKBMS data, stating, “The fact that 43% of species with data have increased over the last 50 years is fairly remarkable given the rates of environmental change.”
Frequently Asked Questions
Q: What can I do to assist butterflies?
A: Create butterfly-friendly habitats in your garden by planting nectar-rich flowers and host plants for caterpillars. Support organizations like Butterfly Conservation.
Q: Are all butterfly species declining?
A: No, some species are thriving, particularly those that benefit from warmer weather. However, many specialist species are facing significant declines.
Q: What is the UK Butterfly Monitoring Scheme?
A: It’s a long-running citizen science project that tracks butterfly populations across Britain, providing crucial data for conservation efforts.
Q: What is coppicing and why is it important?
A: Coppicing is a traditional woodland management technique that involves cutting trees near the base to stimulate regrowth. This creates a diverse range of habitats beneficial to butterflies.
Did you know? Male purple emperors can travel up to a kilometer to gather in ‘master trees’ to compete for females.
Pro Tip: Binoculars are helpful for spotting purple emperors, as they often feed high in the treetops.
Learn more about butterfly conservation and how you can get involved at Butterfly Conservation.
