Rare UK butterfly under threat as elms disappear

A species of rare UK butterfly is under threat after a widespread tree disease caused its only habitat to virtually disappear.

According to research, the population of white-letter hairstreak butterflies has dropped by 96% in the last 40 years.

Experts say over the same period, the UK population of elm trees, the butterflies’ exclusive habitat, has dropped by more than 30 million.

The Wildlife Trust has estimated there are approximately 1,000 mature English elms left in the UK following an outbreak of Dutch elm disease in the 1970s and 1980s.

It said the disease, spread by elm bark beetles, has had a “catastrophic” effect on the hairstreaks - named so because of the characteristic single white stripe across their brown wings.

The State of the UK’s Butterflies 2015 report from Butterfly Conservation and the Centre for Ecology and Hydrology said the species has suffered “very substantial decreases” in both abundance and occurrence over the last four decades.

Ben Keywood, a butterfly specialist at the trust, said: “White-letter hairstreaks are a UK Biodiversity Priority Species as they spend their whole life cycle exclusively on elm trees.

“The eggs will be on the tree for the next couple of months and then the caterpillars will feed on the leaves before pupating and becoming adult butterflies in July.”

The trust’s Rotherham branch has supported a petition by residents in Sheffield to protect a 150-year-old English elm that was found to be home to a colony of hairstreaks.

The tree, in the Nether Edge area, had been earmarked for destruction by Sheffield council and contracted construction firm Amey as part of a street tree replacement programme before the trust made the discovery.

Dr Nicky Rivers, of the trust, said: “We hope that Amey and the council will listen to the local people and they can approve a solution which retains this important tree.

“As well as the butterfly, we also saw bullfinches and other birds using the tree, just on one visit - it would not just be the tree that would be lost, but all the biodiversity it supports.”

The council has promised to reassess its plan to chop down the tree and assured residents it would take the butterfly colony into account.

A spokeswoman said: “We are aware of the tree in question. We are currently working with our contractor Amey to reassess it and other trees as part of our residents’ survey in that area.

“We have also recently been made aware of the findings relating to the butterflies and naturally this will be taken into account as part of this process. Only once all results are in will any decisions be made about the future of this or other trees in the area.

“Trees are only ever removed if they are dead, dying, diseased, decaying or dangerous.”