LAST summer provided a welcome boost to butterfly populations, according to the latest survey.

In their best year since 1997, just over half of UK species showed higher numbers in 2019 compared with 2018, making it the eighth best year in the 44-year series.

Butterflies most likely benefited from an usually warm and wet summer.

Summer flying species benefitting included the marbled white, which had its best year in the series with annual abundance up by 66 per cent, ringlet (second best year, up by 23 per cent), dark green fritillary (third best year, up 51 per cent), and meadow brown (fifth best, up 38 per cent). The rare Lulworth skipper, restricted to the Dorset coast which has been in free fall in recent years rallied with its annual abundance up by a whopping 138 per cent.

It wasn’t all good news for summer flying butterflies though as the common blue dropped by 54 per cent, adonis blue by 40 per cent, green-veined white by 43 per cent and large white by 40 per cent with all four species having below average years.

Of particular concern is the rare heath fritillary, which is restricted to a tiny number of sites in southern England. It fell by 34 per cent, raising fears for the long-term future of the butterfly whose numbers have fallen by 91 per cent due to the ending of traditional management.

However, 2019 was an excellent year for two of our three regular migrant butterflies which undergo periodic influxes, with red admiral annual abundance up by 195 per cent (making it the fifth best year in the series) and painted lady numbers up by a massive 1993 per cent (third best year in the series).

Other well-performing species included several spring flying species such as the chequered skipper which was up by 175 per cent, orange-tip, up 63 per cent, and brimstone, up 32 per cent, all of which had their best year on record. The threatened Duke of Burgundy also bounced back to log its 8th best year. These species were all likely to have benefited from warmer than average spring weather, whilst the Duke of Burgundy is benefitting from targeted efforts.

The survey comes from the annual UK Butterfly Monitoring Scheme led by Butterfly Conservation, the UK Centre for Ecology & Hydrology, British Trust for Ornitholog and Joint Nature Conservation Committee.

Prof Tom Brereton, associate director of monitoring and research at Butterfly Conservation said: “The results from 2019 are really encouraging and provide evidence that the overall rate of decline of butterflies is slowing and for some species being reversed. Reasons for this include positive conservation through agri-environment schemes, increased woodland cover, climate warming, increases in grazing levels by wild animals and a slowing in the rate of agricultural intensification.

“The long-term situation for butterflies in general does remain a cause of concern though, with more species declining than increasing since the 1970s.”

Dr Marc Botham, of the UK Centre for Ecology & Hydrology, said: “The analysis shows a wide range of species benefited from a couple of warm summers. In addition to record numbers of spring species such as orange-tip and brimstone, it was also encouraging to see annual increases in garden favourites such as peacock and small tortoiseshell, after some poor years recently.”

“Despite this, some wider countryside species such as Wall and Small Skipper remain at low levels compared to what they used to be.”

Sarah Harris, Breeding Bird Survey (BBS) National organiser at the British Trust for Ornithology, said: “It is great to see some good news from our natural world, with over half the butterfly species monitored showing higher population levels compared to 2018 - a welcome respite for some.

“It is thanks to volunteers that we are able to monitor butterfly populations and the BTO/JNCC/RSPB Breeding Bird Survey (BBS) is proud to contribute to the UKBMS via the Wider Countryside Butterfly Survey, whereby BBS volunteers revisit their bird recording squares to survey butterflies, moths and dragonflies.

“We are grateful to all the volunteers contributing to this project, allowing us to track the long-term changes faced by our butterfly species.”

Anna Robinson, Monitoring Ecologist at JNCC said: “The UKBMS provides an excellent evidence base to help us understand how butterflies are faring. This evidence is important to help inform environmental policy to take better account of biodiversity.

“We are really grateful for the input of the thousands of volunteers who have contributed from 1976 until today, and without whom the scheme would not be possible.”

The UKBMS has run since 1976 and involves thousands of volunteers collecting data through the summer. Last year 3,014 sites were monitored across the UK, with this record level exceeding 3,000 sites for the first time.