A Butterfly Conservation report has revealed that some of the UK's most threatened butterflies are thriving at National Trust sites.

The study revealed that species like the Marsh Fritillary are bucking nationwide declines, with some habitat specialists seeing their numbers grow at National Trust sites since 1992.

The findings follow decades of work by National Trust advisers and rangers to protect the specialist habitats demanded by struggling butterfly species like the Duke of Burgundy and Pearl-bordered Fritillary.

Butterfly Conservation researchers used results from the UK Butterfly Monitoring Scheme (UKBMS) 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% on National Trust land since 1992.

Overall, scarcer butterflies have declined by 25% in the UK countryside in the last 25 years.

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.”

 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."

The report revealed  that the Marsh Fritillary has seen its numbers grow by 5% year-on-year at National Trust sites over the last 25 years. 

In The Chilterns, Duke of Burgundy numbers are stable on National Trust land compared to a moderate decline elsewhere and have benefitted from a 20-year effort by Trust rangers and partners to manage chalk grassland at Ivinghoe Hills and Dunstable Downs.

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. 

Widespread species such as the Meadow Brown, Large White and Small White were 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 Trust will work closely with Butterfly Conservation to better manage butterfly sites and to monitor progress on these ambitions.