Last summer marked the fifth worst butterfly season in Britain in nearly 50 years, with common species experiencing their second-worst summer since records began in 1976. The findings come from the UK Butterfly Monitoring Scheme (UKBMS), the world’s largest scientific insect survey.
For the first time since monitoring began, more than half of Britain’s 59 native butterfly species are now in long-term decline. Nine species recorded their worst year ever, including the small tortoiseshell, small copper, small skipper, large skipper, and green-veined white—species that were once common in gardens and parks.
Dr Richard Fox, head of science at Butterfly Conservation, described the situation as “devastating,” blaming human-driven environmental changes for the widespread losses.
“We have destroyed wildlife habitats, polluted the environment, used pesticides on an industrial scale and we are changing the climate,” he said. “That means that when we have poor weather, these already-depleted butterfly populations are highly vulnerable and can’t bounce back like they once did – and with climate change, that unusual weather is becoming more and more usual.”
The summer of 2024 followed a wet spring and relatively cool temperatures, which contributed to short-term declines. However, experts stress that weather is only part of the story, and the long-term downward trends are much more concerning.
According to the UKBMS, which relies on thousands of volunteers counting butterflies at over 3,000 sites across the UK, 51 of the 59 species saw declines compared to 2023, and 31 species show persistent long-term reductions.
The sharp decline of the small tortoiseshell, once a familiar garden sight, has particularly puzzled scientists. Despite its caterpillars feeding on stinging nettles—a plant still widespread—its numbers have plummeted for two years in a row.
While conservation efforts have helped revive some critically endangered species, even butterflies already on Britain’s “red list,” such as the grizzled skipper, small pearl-bordered fritillary, and chalkhill blue, had their worst-ever years in 2024.
Butterfly Conservation is urging councils to reduce grass-cutting and encouraging the public to let lawns grow wild. Research shows that gardens with long grass significantly boost both butterfly numbers and diversity, offering a practical step toward reversing declines.
“By far the best thing we can do to help butterflies is to create more habitat,” said Fox. “That is why we are calling on people and councils across the UK to pledge to not cut their grass this year from April to September: this simple act can make a real, immediate difference to butterflies, moths and other wildlife.”
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