Some of Britain’s rarest butterflies are booming at National Trust sites, a new report has found.
The study, led by charity Butterfly Conservation, revealed that rare species like Marsh Fritillary are bucking nationwide declines, with these ‘habitat specialist’ butterflies seeing their numbers grow by a tenth at National Trust sites since 1992.
It follows decades of work by National Trust advisers and rangers to protect the specialist habitats demanded by struggling butterfly species including the Duke of Burgundy and Pearl-bordered Fritillary.
The Trust, which this year pledged to create 25,000 hectares of new ‘priority’ nature habitats by 2025, is also working to restore numbers of farmland butterflies on its land to 1976-levels.
Researchers from Butterfly Conservation used results from the UK Butterfly Monitoring Scheme to compare butterfly numbers at National Trust sites to those under other ownerships. They found that ‘habitat specialist’ butterflies such as the chalk grassland-loving Adonis Blue have increased in abundance by 13 per cent on National Trust land since 1992.
Overall, scarcer butterflies have declined by a quarter (25 per cent) in the British countryside in the last 25 years.
Matthew Oates, National Trust butterfly specialist, said: “Many of Britain’s scarcest butterflies are doing relatively well at our places, with rangers and tenant farmers working together to protect important habitats.
“Nationally, butterflies like the beautiful Duke of Burgundy are experiencing steady declines as a consequence of habitat loss and, most probably, climate change.”
Among the winners identified in the report led by Butterfly Conservation is the Marsh Fritillary, which has seen its numbers grow by five per cent year on year at National Trust sites over the last 25 years. In Ennerdale, Cumbria, the Trust is working with local Lake District farmer Judith Weston, grazing the wet flush grassland habitat with cattle to provide the perfect conditions for the Marsh Fritillary caterpillars.
In The Chilterns, Duke of Burgundy butterflies, whose numbers are stable on National Trust land compared to a moderate decline elsewhere, have benefitted from a 20-year effort by Trust rangers and partners to manage chalk grassland at Ivinghoe Hills and Dunstable Downs.
Professor Tom Brereton, head of monitoring at Butterfly Conservation, said: “The results are highly encouraging and demonstrate that with targeted and tailored habitat management we can turn around the fortunes of many threatened butterfly species.”
Despite concerted effort, a small number of scarce species are still declining on National Trust land. They include the endangered High Brown Fritillary and Heath Fritillary butterflies.
The National Trust’s Matthew Oates added: “We are trying to better understand what’s behind the declines.”
More common butterfly species, such as the Meadow Brown and Large White, were found to be less abundant on National Trust sites than in the wider countryside. The charity’s specialists believe this may be a consequence of rangers managing sites for rarer species.
The National Trust now hopes to boost the number of farmland butterflies on its 200,000 acres of farmed land. The conservation charity has pledged to improve butterfly habitats on land in its care, with the hope of boosting the ranges of rarer ‘habitat specialists’ like Adonis Blue by 50 per cent.
The Trust will work closely with Butterfly Conservation to better manage butterfly sites and to monitor progress on these ambitions.