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The latest results from the annual UK Butterfly Monitoring Scheme (UKBMS) show that 2023 was a mixed picture for butterflies, with some species soaring while others continued worrying declines.

The scheme, which began in 1976, is led by Butterfly Conservation, the UK Centre for Ecology & Hydrology (UKCEH), British Trust for Ornithology (BTO) and the Joint Nature Conservation Committee (JNCC). 

Half the 58 UK butterfly species for which trends were produced had a better than average year while the other half were below average at monitored sites. 

Species that flourished the Large Blue, which was reintroduced to the UK by Natural England and UKCEH after becoming extinct in the 1970s. This species had its best year since 1976, as did Chequered Skipper, Brimstone and Red Admiral, a migratory species that overwinters in the UK as the climate has warmed. Its numbers have increased by 318% at monitored sites since 1976.

Small Pearl-bordered Fritillary and garden favourite the Small Tortoiseshell, recorded their lowest numbers in the 48 years of monitoring, declining by 71% and 82%, respectively, since 1976. Small Tortoiseshell had its worst year on record in England. The Green-veined White and Ringlet both had a poor year, perhaps suffering ongoing effects from the drought the previous summer. 

Scientists involved in UKBMS have thanked the thousands of volunteers who record butterfly species every year at more than 3,000 sites.

Dr Marc Botham, Butterfly Ecologist at UKCEH, said: “Butterflies are an indicator species, meaning they can tell us about the health of the wider environment, which makes the UKBMS data invaluable in assessing the health of our countryside and natural world in general. The mixed results this year emphasise the need for continued monitoring and conservation efforts to protect these important species and their habitats.”

Butterfly numbers fluctuate naturally from year to year largely due to the weather, but long-term trends are mainly driven by human activity, including habitat loss and deterioration, climate change, pollution and pesticide use. 

Data from UKBMS 2023 is available at ukbms.org/official-statistics