Britain’s butterflies are dying out, a report warns, with 33 native species fighting an ‘increasingly urgent battle’ for survival.
New data reveals rare specialist species – including the pearl–bordered fritillary and the small tortoiseshell – have seen their numbers plummet in recent decades.
Some have declined by nearly 90 per cent since 1976, with conservationists urgently sounding the alarm over their dwindling populations.
The UK Butterfly Monitoring Scheme (UKBMS), a citizen science project spanning 50 years, has built up more than 44 million records into a dataset that indicates how the country’s butterflies are faring.
Species that live in a particular habitat, such as woodland glades or chalk downland, have widely struggled and many are disappearing quickly.
Professor 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.’
The small tortoiseshell (pictured) has seen its numbers decline by nearly 90 per cent over the last 50 years
The beautiful pearl–bordered fritillary (pictured) has also seen its numbers plummet in recent decades, the report showed
Of the 59 British species of butterfly monitored by the UKBMS, a total of 33 have declined in number over the last five decades.
In contrast, 25 species have recorded an improvement.
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 per cent since 1976.
But at the other end of the scale is the small tortoiseshell, which has declined by 87 per cent in the last 50 years.
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 per cent 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.
Experts warned that the data for last year highlights the scale of the challenge – as the UK experienced its sunniest year on record, when the animals should thrive, but only recorded average butterfly numbers.
White–letter hairstreaks, which only lay their eggs on elm trees, have suffered huge declines over the decades after millions died from disease
Intensive conservation efforts have helped some butterfly species buck the downward trend, including the large blue
‘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,’ Professor Fox said.
‘Butterfly Conservation can’t control the weather, but working with partners and landowners across the country we can improve the landscape.
‘If we want to see our wonderful specialist species like the high brown fritillary, northern brown argus and Duke of Burgundy recover from 50 years of decline, we need to restore as much of their precious habitat as we can – starting today.’
Intensive conservation efforts have helped some butterfly species buck the downward trend, including the silver–studded blue and the black hairstreak.
The largest increase of any species is the large blue, whose numbers have soared by 1,866 per cent since 1983.
However, this is because – after being declared extinct in Britain – the butterfly has been successfully reintroduced.
Dr Marc Botham, Butterfly Ecologist at the UK Centre for Ecology & Hydrology, said: ‘Butterfly numbers naturally fluctuate from year to year depending on the weather, which is why the UK Butterfly Monitoring Scheme is so important.
‘This invaluable long–term dataset, based on surveys by dedicated volunteers, enables scientists to assess what is actually happening in the countryside over time.’
Steve Wilkinson, Director of Ecosystem Evidence & Advice at the Joint Nature Conservation Committee added: ‘This half–century of data gives us an invaluable window into what is working and what is not – from the spectacular recovery of the Large Blue following reintroduction, to the devastating declines of specialists like the pearl–bordered fritillary.
‘Without this evidence timeline, we would be flying blind.’
The findings mirror last year’s results from Butterfly Conservation’s Big Butterfly Count, which asks members of the public to count species in their local green spaces during a period in the summer.
The charity saw record participation of more than 125,000 people, but participants produced only average numbers of butterflies per count.
