DEFRA’s butterflies index, published today, shows that wider countryside woodland species have dropped by 40% in England since 1990, with numbers of wider countryside farmland butterflies falling by 10% over the same period.
Despite fluctuations in numbers due to weather conditions - 2018 was a good year with more than two-thirds of species increasing in abundance - the overarching long-term trend is a downward one, the figures show.
Wider countryside butterflies locked into long-term decline on farmland include: white-letter hairstreak, wall, small tortoiseshell, gatekeeper, small copper, small/Essex Skipper and peacock. Of these, the small tortoiseshell and peacock have also decreased over the short-term since 2013, according to the figures.
Three species - the ringlet, speckled wood and brimstone - increased over the long term but showed no short-term change, according to DEFRA’s data, although the holly blue has increased since 2013.
DEFRA says the long-term decline of woodland butterflies is due to a lack of woodland management and loss of open spaces in woods. Woodland butterflies in long-term decline include: wall, small tortoiseshell, small copper, white-letter hairstreak, small/Essex skipper, gatekeeper, small heath and peacock. Of these, the peacock and small tortoiseshell have again suffered major short-term decline, mirroring their performance on farmland.
DEFRA’s habitat specialist butterfly index, which covers the whole of the UK, has dropped by 68% since 1976, with wider countryside butterflies falling 30% over the same period.
According to the department, habitat specialists are vulnerable to semi-natural habitat loss and fragmentation and have not recovered from steep drops in numbers in the late 1970s. Within this group, those with the sharpest decline include heath fritillary, wood white, Lulworth skipper, pearl-bordered fritillary and grayling, with the Lulworth skipper and chalkhill blue also showing a short-term decline since 2013.
According to the data however, silver-spotted skipper, large heath, dark green fritillary, adonis blue and silver-washed fritillary have seen significant increases over the long term, while the black hairstreak is the only habitat specialist species to show a statistically significant increase since 2013.
A DEFRA spokesperson said: “Nature matters. We recognise its importance and our 25-Year Environment Plan signals a step-change in ambition for wildlife and the natural environment.
“This year’s statistics show that while there have been long-term declines in many butterfly species, there are real points of progress for species such as the Duke of Burgundy on a number of sites - progress on which we can build.
“It is critical that we continue to act, internationally and at home, to ensure that we leave our environment in a better state for future generations.”
The statistics will form part of England’s and the UK’s Biodiversity 2020 indicators, due to be updated in September 2019.