Wet weather hits butterfly populations for a second year

There had been hopes that butterflies would bounce back after the summer of 2016 – the fourth worst in 42 years of records – with many spring species emerging earlier than usual.

But a cold snap at the end of last April and the gloomy, wet summer that followed affected species which were already struggling from the effects of climate change and the loss of habitat. The combined effects made 2017 the seventh worst year on record, experts warned.

And with the cold and wet conditions this March, there are “no immediate signs” things are going to pick up this year, said Professor Tim Brereton of Butterfly Conservation.

Butterflies need warm, dry weather during periods when they are on the wing in order to feed and mate successfully.

But last year, both grayling and grizzled skippers recorded their lowest numbers since records began – the second year in a row in which they have they have hit new lows, according to the annual UK Butterfly Monitoring Scheme.

Numbers of grizzled skippers, which are found in Wales and the south, were down nine per cent compared to 2016, and their population has more than halved since the 1970s, while graylings, which are native to heathlands and around the coasts, declined by six per cent on the previous year. Its numbers have shrunk by 63 per cent in a decade.

Threatened dingy skippers also saw numbers fall by 22 per cent compared to 2016 and the rare marsh fritillary suffered declines of 12 per cent, according to the survey.

But Prof Brereton said: “There is little comfort in these results for the UK’s hard-pressed butterflies. 2017 was the seventh worst in the 42-year series and makes it five below average years in a row.

“On the positive side, there is much good conservation work happening across the country, which will aid any recovery should we get a helping hand with the weather.”

But many species did better in 2017 than in 2016, with the red admiral seeing numbers rise by 78 per cent, commas up by 91 per cent and the rare and threatened pearl-bordered fritillary up by 57 per cent.

Dr Marc Botham, from the Centre for Ecology and Hydrology in Lancaster, said: “The weather can have a serious impact on individual species’ numbers each year. However, populations can and do bounce back providing suitable habitat is available.”