National Trust to create UK sanctuary for endangered butterfly

A beautiful wooded valley on the Devon coast is to be the focus of a project to save the UK’s most endangered butterfly – the high brown fritillary.

Conservationists believe changes to woodland management, such as the abandonment of coppicing, and climate change have contributed to the steep decline of the large, powerful, fast-flying butterfly over the last 50 years.

The National Trust has been given £100,000 by the People’s Postcode Lottery to improve 150 acres of lowland heath and wood pasture at Heddon Valley on the north Devon coast as a habitat for the butterfly.

Other butterflies including the heath fritillary, and birds such as the nightjar and the Dartford warbler will also benefit.

Matthew Oates, a National Trust nature expert and butterfly enthusiast, said: “We’ve witnessed a catastrophic decline of many native butterfly populations in recent decades but initiatives like this can really help to turn the tide.”

The high brown fritillary (argynnis adippe) is usually seen flying swiftly over the tops of bracken or low vegetation in woodland clearings or resting on flowers such as thistle and bramble. It has orange and black wings and distinctive orange ringed “pearls” on the underside of the hindwings.

It was once widespread in England and Wales but since the 1950s has undergone a dramatic decline and is now only found at about 50 sites. As well as Exmoor, other strongholds include Dartmoor in Devon and outcrops of limestone at Morecambe Bay.

High brown fritillaries overwinter as eggs, which are laid singly on leaf litter – often dead bracken – on dog violets or among moss growing on limestone outcrops.

The larvae hatch in early spring and spend long periods basking on dead bracken where there is little grass cover or in short, sparse vegetation.

The temperatures in these microhabitats can be 15 to 20°C higher than in surrounding grassy vegetation, allowing the larvae to develop quickly even in cool spring weather. The larvae have feathered brown spines, giving them the appearance of dead bracken fronds.

To make Heddon Valley even more butterfly friendly, more scrub will be cleared and pathways cut through the bracken to allow the butterflies to move through the landscape.

Another technique to help the butterfly is swailing – controlled burning of the heath. The butterflies need a relatively large area to flourish and are often found feeding more than a mile from breeding spots.

Jenny Plackett, Butterfly Conservation’s senior regional officer, said: “Heddon Valley supports the strongest population of high brown fritillary in England, but even here the butterfly remains at risk, and ongoing efforts to restore habitat and enable the butterfly to expand are crucial to its survival.”

Other National Trust projects that are being supported by new funds from the People’s Postcode Lottery include restoring wildflower meadows along the Durham coast to help ground nesting birds such as skylarks and lapwings.