Butterfly survey reveals worst year since 1976 for small tortoiseshell

The small tortoiseshell butterfly has suffered its worst year on record in England, and has declined by 82% across the UK since 1976, according to the annual count of butterfly populations.

- Helena Horton

The sharp decline in numbers of the once-common garden butterfly has puzzled scientists, but it is thought to be linked to climate breakdown. It had its worst year on record in England, its second worst in Wales and its joint-fifth worst in Scotland in 2023, but did well in Northern Ireland, logging its second-best year.

Results from the annual UK Butterfly Monitoring Scheme (UKBMS), the largest and longest-running scientific butterfly dataset in the world, show a mixed picture for UK populations.

Half the 58 species monitored had a better than average year, while the other half were below average at monitored sites.

Some showed encouraging signs that conservation efforts are working: the large blue, which was reintroduced to the UK in the 1980s after it became extinct in 1979, recorded its best year yet. The chequered skipper, which was returned to England in 2018 after becoming extinct in the 1970s, also recorded its best ever year.