Page last updated at 00:02 GMT, Wednesday, 8 April 2009 01:02 UK

Butterflies hit by damp summers

By Sarah Mukherjee
BBC environment correspondent

High Brown Fritillary (Peter Eeles)
Fewer than 50 High Brown Fritillary colonies exist in the entire country

The torrential rain of recent summers has hit the UK butterfly population hard, say conservationists.

Numbers are at a new low according to data from the UK Butterfly Monitoring Scheme, and the miserable British weather is said to be a key factor.

Wet conditions limit the insects' ability to fly and find food, and also hamper the creatures' breeding success.

Butterfly Conservation says that for 12 species, 2008 was their worst year since records began in the mid-1970s.

Lack of sun

The fluttering iridescence of a butterfly, floating on a gentle breeze, or settling on a flower, is one of the images of summer - and yet conservationists warn that these beautiful creatures may be somewhat rarer this year.

A lot of species can bounce back quite quickly
Dr Tom Brereton, Butterfly Conservation

The Monitoring Scheme data suggest the pouring rain and cold weather much of Britain suffered in June, July and August last year caused butterfly numbers to fall sharply.

"Two things have contributed to last year's decline," said Dr Tom Brereton, the head of monitoring at Butterfly Conservation.

"Firstly, there was a knock-on effect from the previous year, when the weather was also pretty bad. Indeed, this time last year we were saying that 2007 had been the worst for many years, so many species got off to a bad start."

"Secondly, of course, this was followed up by another summer which, although temperatures were not too bad, was wet and lacking in sunny days."

Conditions are key

Dr Brereton said that most species needed sun and an average temperature of 15-16 C to fly. Most species did not really fly in the rain, he explained.

Last year was particularly unfortunate because of the many butterfly-specific conservation projects which have started across Britain - but the butterflies have not been there to reap the benefits.

Small tortoiseshell (Jim Asher)
The Small Tortoiseshell has seen its numbers plummet over the last decade

So will there be any butterflies fluttering by this year?

"A lot of species can bounce back quite quickly," Dr Brereton said.

"We've certainly seen that with butterflies before. A lot of the commoner species, if we get the right conditions, should be OK.

"But for some species which are at a really low ebb - like the Woodwhite and the Brown Fritillary, which are down to a handful of colonies across the country - there's a chance that they could have died out in some areas."

Good news

Dr Brereton added that there was a possibility that some colonies might be wiped out altogether this winter if they had succumbed to factors such as predation by small mammals or other insects.

But, he said, there were some species that actually did quite well in 2008.

"The Ringlet and the Large Heath - which needs to be pretty hardy because it lives in bogs - both had very good years last year." Both species do not mind flying in the rain.

And there are things that the public can do to help the butterfly population along this year.

"Gardens can be important oases for butterflies - sometimes you can see more of them in gardens than on a country walk," Dr Brereton said.

"Ivy's very good as a nectar source in the autumn, and species like the Small Tortoiseshell and the Comma can roost in ivy over the winter. Any colourful flowers are good, and the caterpillars of a lot of British butterflies are grass eaters - so allowing native species of grass to grow a bit longer in the summer will help.

"It's easy to criticise farmers, but we do put chemicals on our gardens as well, and we're not growing a crop - so reducing chemical inputs will also help."

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