UK butterflies ravaged by climate change

It has taken 10,000 volunteers, 1.6 million recorded sightings and five years of painstaking research, but the biggest census ever of British butterflies has finally been completed.

It has taken 10,000 volunteers, 1.6 million recorded sightings and five years of painstaking research, but the biggest census ever of British butterflies has finally been completed.

And the results make dismal reading for the prospects of the Northern Brown Argus, or the Pearl-bordered Fritillary Fans.

The Comma, once in decline, can take heart, although its rapid reappearance is almost certainly due to global warming. But the Large Tortoiseshell is now officially extinct.

Researchers for the charity Butterfly Conservation split the country into 10km squares and used an army of enthusiastic lepidopterists to scour an estimated 97 per cent of them. The result is a detailed map of the 60 species of butterfly that inhabit the British Isles.

The butterfly census is the first for 20 years and easily the most comprehensive. The 1979 survey contained a mere 150,000 recorded sightings and took 13 years.

Sadly, the Millennium Atlas of Butterflies, published next year by Oxford University Press, will paint a bleak picture for certain rarer butterflies. An expert says we are sitting on a "biodiversity time bomb" and lists 10 species on the endangered list and facing extinction.

"Something killed off the Large Tortoiseshell," said Richard Fox, Butterfly Conservation's project co-ordinator, "It's really a bit of a mystery. There has been a question mark over the existence of the Large Tortoiseshell in the UK for some time but this survey confirms it no longer exists in this country."

The Large Copper, which for decades struggled to survive the ravages of large-scale farming in the East Anglian fenlands, its natural habitat, is also thought extinct.

Others are in severe danger. The Northern Brown Argus, once thought to be widespread, is confined to a few sites in eastern Scotland. It has disappeared from north Wales and northern England where only a hybrid of the Northern Brown Argus, genetically mixed with the common Brown Argus, exists.

The High Brown Fritillary is another confined to a handful of colonies on Exmoor and Dartmoor and in Morecambe Bay in the north-west. Its decline has been one of the most sudden and severe of all British butterflies.

Destruction of habitat - deliberately or through neglect - is the main cause of declining numbers. But global warming is also playing its part.

Climate change has severely reduced some species and encouraged others to thrive and spread north from natural habitats in the south of England. Mr Fox said: "Butterflies are very closely dependent on the weather."

The Comma is enjoying a rejuvenation. Its range has increased by more than 60 per cent in the past two decades and it looks like returning to Scotland after an absence of more than a century.

"The problem is the ones that are doing well are common already," said Mr Fox.

"On the other hand you have all these species doing very badly - and they are the ones that are much scarcer and restricted because of their habitat requirements. They tend to be confined to nature reserves.

"Ecological theory predicts such populations will become extinct, particularly if neighbouring patches are destroyed or become unsuitable. We are now sitting on a biodiversity time bomb."

To coincide with next year's publication of the census, Butterfly Conservation is pressing for the insects to be adopted by the Government as an official wildlife indicator and measure of the state of health of the environment.

The group is in talks with English Nature, the Government's environmental advisory body, to make butterflies an official barometer.

"The butterfly gives you a good idea of subtle changes in the environment," said Mr Fox.

Butterfly Conservation can be contacted at PO Box 222, Dedham, Colchester, CO7 6EY (tel: 01206 322342).