Of the 59 native species of butterflies monitored across the UK, figures show that 33 have declined in numbers and just 25 have improved
Britain’s butterfly species are disappearing because of habitat loss, pollution and climate change, according to 50 years of data from the UK Butterfly Monitoring Scheme.
Since 1976, the world-leading citizen scientist project has built up more than 44 million records into a dataset that indicates how the country’s butterflies are faring.
These have been gathered by 782,000 volunteers who counted species at thousands of sites across the UK over the past five decades. As the scheme marks its 50th anniversary, conservationists warn they are fighting an “increasingly urgent battle” to save the variety and diversity of the UK’s butterflies.
Of the 59 native species monitored, UKBMS figures show that 33 have declined in numbers and 25 have improved, though one mountain-dwelling species has insufficient data.
Species that can survive across different habitats have been better able to cope with changes to the landscape and climate, and some have even spread to new areas, the figures indicate.
For example, the Red Admiral used to be a summer visitor to the UK, but the species is now seen here year-round as the climate warms, with the dataset showing numbers have surged by 330% since 1976.
There have been some exceptions to this trend, such as the small tortoiseshell, which has declined by almost 90% in the last 50 years. On the other hand, butterflies that live in a particular habitat, such as woodland glades or chalk downland, have widely struggled and many are fast declining.
The number of pearl-bordered fritillaries – a vibrant orange-and-black butterfly whose caterpillars only eat violets growing in sunny spots in woodland clearings or bracken-covered hillsides – has decreased by 70% since 1976.
And white-letter hairstreaks, which only lay their eggs on elm trees, have suffered huge declines over the decades after millions died from disease.
But intensive conservation efforts have helped some of these species buck the downward trend, including the silver-studded blue and the black hairstreak.
Richard Fox, head of science at Butterfly Conservation, which is one of the organisations that runs the scheme, called the set of figures “damning”.
“Just as we have lost family-run shops and traditional skills from the nation’s high streets, so we’ve lost variety and diversity in the butterfly communities that can exist in our damaged and simplified landscapes,” he said.
“We have some remarkable species in this country, and we know what we need to do to help them – create more habitat.
“That is what Butterfly Conservation has been doing for more than 50 years, but we are fighting an increasingly urgent battle and we need more help.”
It comes after the organisation’s Big Butterfly Count, which asks members of the public to count species in their local green spaces during a period in the summer, yielded disappointing results last year.
This was despite hopes that the hot record summer – conditions in which butterflies should thrive – might have helped to offset decades of declining numbers.
In 2024, the wet spring and cool summer contributed to the lowest numbers spotted in the count’s 14-year history.
“Last year should have been amazing for butterflies, however we were not treated to a bumper butterfly year – indeed over one-third of species had below average numbers,” Mr Fox said.