UK butterflies rallied during last summer following their worst year on record, but numbers were still below average, according to the latest results from the UK Butterfly Monitoring Scheme (UKBMS).
Some 46 out of the 56 species studied in 2013 recorded an annual increase compared to 2012 – which was the worst butterfly year on record since the UKBMS began in 1976.
Common species such as the Small, Large and Green-veined White, all of which had their worst year on record in 2012, bounced back to above average numbers in 2013 with all three increasing by more than 100%.
Garden favourite the Small Tortoiseshell also rallied after years of decline. The butterfly was up by more than 200% on 2012 as last year’s warm summer saw it record its best year for a decade.
Several rare species revived following 2012 with the Lulworth Skipper up by 162% and the endangered High Brown Fritillary up 133%, as both responded to conservation work.
The warm weather also saw a huge influx of some migrants with numbers of Clouded Yellow butterflies from the Continent up by more than 4,000% compared to 2012.
But, despite the resurgence, overall butterfly numbers were still below average, data gathered by the UKBMS, jointly led by Butterfly Conservation and the Centre for Ecology & Hydrology (CEH), revealed.
"The data show that a number of species have been significantly declining over the last 38 years. This highlights the importance of maintaining long-term monitoring to determine species and habitats of conservation priority."
Dr Marc Botham, Butterfly ecologist, CEH
CEH butterfly ecologist Dr Marc Botham said: “Annual changes are largely associated with the weather. However, the data show that a number of species have been significantly declining over the last 38 years. This highlights the importance of maintaining long-term monitoring, reliant on the immense dedication of thousands of volunteers, to determine species and habitats of conservation priority.”
The very cold spring of 2013 saw some of our most threatened habitat specialists suffer. The endangered Pearl-bordered Fritillary was down 22% compared to 2012, whilst Grizzled Skipper numbers fell by 45% to a series low.
The washout 2012 year took a toll on many butterflies, with populations of rare species such as Duke of Burgundy becoming locally extinct. Many UK species now need a warm spring and summer this year to give them the best chance of sustaining a recovery.
Dr Tom Brereton, Head of Monitoring at Butterfly Conservation, said: “The recovery of butterflies in 2013 was highly welcome but there is still a long way to go before butterflies return to former glories.
“Our ongoing monitoring efforts will be vital in assessing whether we are on track to reverse butterfly declines and rebuild a healthy countryside.”
Butterfly Conservation issued a press release for this story.
UKBMS has run since 1976 and involves thousands of volunteers collecting data every week throughout the summer from more than 1,000 sites across the UK. The scheme is operated by Butterfly Conservation and the Centre for Ecology & Hydrology (CEH) and funded by a multi-agency consortium including Defra, the Joint Nature Conservation Committee, Forestry Commission, BTO, Natural England, the Natural Environment Research Council, Natural Resources Wales and Scottish Natural Heritage.
The UKBMS is indebted to all volunteers who contribute data to the scheme.