Conservationists in the United Kingdom report that butterfly populations in the nation are at a historic low, likely because of punishing weather conditions including the coldest spring the UK has seen in half a century and an abnormally wet summer last year.

David Attenborough, renowned conservationist and president of the non-profit Butterfly Conservation, said the wet weather of 2012 was disasterous for butterflies and that there are "probably fewer butterflies in the UK than at any point in my lifetime." Attenborough is 87.

"Butterflies are vitally important," Attenborough said. "Their presence acts as a barometer of the health of our environment. Their ongoing decline tells us that all is not well in the British countryside."

Part of the work of tracking the butterfly count in the UK is done by the public, who use material provided by the Butterfly Conservation to account for nearby butterflies.

The Conservation provides "citizen scientists" with charts detailing 19 types of common garden butterflies and two types of moth and asks people to see how many of the species they can spot in 15 minutes.

When the citizen survey was conducted last year, 220,000 butterflies were counted, with 15 of the 21 species on the list showing a decline compared with the previous year's survey, the BBC reported. 

A recent spate of hot weather in the UK may be a boon for butterfly populations after the unusually cool spring stalled the emergence of the insects.

"This summer heatwave is the perfect tonic for Britain's beleaguered butterflies," said Butterfly Conservation's survey manager Richard Fox.

Fox said hot, calm conditions are idea for butterflies to emerge, mate and lay eggs.

"We hope that their populations will start to recover and people can once more enjoy a profusion of butterflies in their gardens and the countryside."