People are being urged to help measure the scale of Britain’s butterfly bounceback after last summer’s dramatic decline with this year’s launch of the world’s biggest insect survey.
The Big Butterfly Count asks volunteers to spend 15 minutes in a local green space counting the butterflies and day-flying moths they see. Results of the survey, which takes place from 18 July to 10 August, can be logged on the Butterfly Conservation charity’s website or via its free app.
Naturalists say it has been an “outstanding” summer for butterflies and other flying insects but the Big Butterfly Count will determine whether it has been better than average or simply a return to normal after the dismal, butterfly-less summer of 2024.
Fine and sunny weather in April and May ensured caterpillars prospered and there have been large and unusually early emergences of midsummer butterflies including peacocks, gatekeepers and marbled whites. Butterflies have also been seen farther north than ever before as a result of global heating, with the booming purple emperor spotted in North Yorkshire and the white-letter hairstreak – which only reached Scotland in 2017 – now found in Dundee.
“It’s an outstanding year for most, but not all, butterflies and many other winged insects,” said Matthew Oates, a naturalist and butterfly expert. “It’s all the more remarkable after last year’s insect nadir, which was by far the worst insect trough in my experience of nearly 70 years of butterflying. I was seriously worried.”
Butterfly Conservation declared a “butterfly emergency” after last summer’s Big Butterfly Count revealed the lowest numbers in its history. The UK Butterfly Monitoring Scheme, the gold standard of scientific butterfly surveying, which has been collecting data since 1976, also reported the second-lowest numbers of common butterfly species in 2024 since records began.
Dr Richard Fox of Butterfly Conservation said this year was much more encouraging but warned of “shifting baseline syndrome” whereby people became used to lower numbers of butterflies and so considered what might actually only be a moderately good or average summer to be an abundant one.
“I’ve been in Cornwall and there were loads of butterflies around – red admirals, peacocks, gatekeepers, and the whites are doing well,” said Fox. “There are two big ‘buts’: a better summer for butterflies does not redress the 50 years of decline, and we know that drought isn’t good for butterflies or moths or anything that eats plants. The impact of this year’s dry weather will be on the next generation of butterflies, and drought is not good news.”
The sunniest spring on record and continued sunny weather through the summer have been a boon for many species, and in many regions there has been just enough rain to prevent caterpillar food plants shrivelling up and dying.
Many species have emerged as butterflies earlier than ever this year. The brown hairstreak, which is usually an August butterfly and the last species to take to the wing as a butterfly each summer, was spotted in Surrey and Sussex in June. Lepidopterists expect that some species, such as the white admiral and the small pearl-bordered fritillary, may have unusual second or third broods this summer because they emerged so early.
But a few of Britain’s 59 native species of butterfly have not fared well this year, including the rare large blue and common species such as the ringlet. The large blue is susceptible to dry springs, while the ringlet requires damp conditions for its grass-feeding caterpillars, and struggles in dry summers. The once-ubiquitous small tortoiseshell continues its baffling disappearance from southern Britain, where it has become a rare butterfly.
Up to 100,000 citizen scientists who take part in the Big Butterfly Count each summer provide “quality data about how butterflies are doing beyond the nature reserves that are monitored every week”, said Fox. “Taking that 15 minutes just to spend time in nature, to stop worrying about the day-to-day grind and focus on things of beauty, we know is good for our brains and it’s good for mental wellbeing. It’s something that everyone can do and it gives us a bit of agency when faced with these huge threats to our precious natural environment.”
