UK butterflies suffered their fourth worst year on record in 2016 with the majority of species experiencing a decline in numbers, a study has revealed.
A mild winter followed by a cold spring contributed to conditions that saw both rare and widespread species struggle despite many parts of the UK enjoying a warm and dry summer. The figures have been revealed as part of the annual UK Butterfly Monitoring Scheme (UKBMS) led by the Butterfly Conservation, the Centre for Ecology & Hydrology (CEH), British Trust for Ornithology (BTO) and Joint Nature Conservation Committee.
The decline has been evident here on the Isle of Wight with the number of Glanville Fritillary butterflies down by more than 50% at the main monitoring site of Mottistone Down. In addition, the Wall Brown butterfly saw a decline in number last year at all 5 monitored sites across the Island.
Other butterflies which had a poor year across the Isle of Wight include the Grizzled Skipper, Wall, Grayling, White-letter Hairstreak and White Admiral.
Research suggests that the UK’s increasingly mild winters are having a negative effect on butterflies as they may lead to increased disease, predation or disruption of overwintering behaviour. Cold springs can also cause problems for butterflies by reducing or delaying emergence leading to shortened lifespans.
Some species bucked the trend to record reasonable years. The previously extinct Large Blue, one of the UK’s rarest butterflies, recorded its second best year on record with numbers up 38% on 2015. The butterfly has responded to conservation work to improve the specific grassland habitat that it relies upon to thrive and has showed a significantly increasing population trend since its reintroduction in 1983.
The widespread and migratory Red Admiral recorded a rise of 86% compared to 2015 and the Clouded Yellow, another mainly migrant species, saw its numbers rise by 35%.
Professor Tom Brereton, Head of Monitoring at Butterfly Conservation, said:
“Worryingly, not even the pleasant summer weather of 2016 was enough to help butterflies bounce back from a run of poor years.
“The results show that butterflies are failing to cope with our changing climate and how we manage the environment. As butterflies are regarded as good indicators of environmental health this is hugely concerning for both wildlife and people.”
Dr Marc Botham, Butterfly Ecologist at the Centre for Ecology & Hydrology, said:
“The weather at critical times of species development can cause dramatic changes in population numbers in the short term. What is of greatest concern is the regularity with which these short-term changes in recent years are negative, resulting in significant long-term declines for many species.”
“Furthermore, this is becoming more and more commonplace for many of our most widespread and abundant species equating to large reductions in overall butterfly numbers with knock-on effects to their ecosystems.”
The UKBMS has run since 1976 and involves thousands of volunteers collecting data through the summer. Last year a record 2,507 sites were monitored across the UK.
