An extraordinary dataset of over 44 million records from 782,000 volunteer surveys has revealed what has happened to the UK's butterflies as the national landscape has changed over the past 50 years.Half a century of data from the UK Butterfly Monitoring Scheme (UKBMS) shows that many of the UK’s species are disappearing due to habitat loss, pollution and climate change.Citizen scientists have walked more than 1.5 million kilometres since 1976 at more than 7,600 sites to produce the incredible dataset. That’s the equivalent of walking 40 times around the world – or to the moon and back twice.Of the 59 native butterfly species monitored, 33 have declined, 25 have improved and one mountain-dwelling species has insufficient data.While some adaptable species are coping and even spreading to new areas, specialist butterflies, restricted to particular habitats such as woodland glades or chalk downland, have fared worse – and many are declining at alarming rates.The Pearl-bordered Fritillary, a striking orange-and-black butterfly whose caterpillars only eat violets growing in warm, sunny spots in woodland clearings and bracken-covered hillsides, has declined by 70 per cent since 1976.Some habitat specialists, such as the heathland-dwelling Silver-studded Blue, have bucked the trend, but only thanks to intensive conservation efforts.By contrast, habitat generalists which can breed in farmland, parks and gardens, have coped better on their own - but even for these butterflies there is a mix of fortunes, such as the Small Tortoiseshell which has declined by 87 per cent.The UK Butterfly Monitoring Scheme (UKBMS), jointly run by Butterfly Conservation, the UK Centre for Ecology & Hydrology (UKCEH), British Trust for Ornithology (BTO) and the Joint Nature Conservation Committee (JNCC), has asked volunteers to count butterflies across the country since 1976 and is now marking its 50th anniversary with this concerning set of results.Professor Richard Fox, Head of Science at Butterfly Conservation, said: "What this damning set of figures really shows us today is what type of wildlife is able to survive in the UK’s modern landscapes, and it is not our wonderful specialist species - it is the generalists. 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."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."The White-letter Hairstreak is another charismatic specialist which has suffered massive declines: adults have striking wing patterns and the caterpillars glow in the dark under UV light, however females only lay their eggs on elm trees, millions of which have died from Dutch Elm Disease. The White-letter Hairstreak has declined by 80 per cent since 1976.Among the habitat generalist species that have done well is the Red Admiral, which has rocketed by 330 per cent since 1976. It was once a summer visitor to the UK but as the climate has warmed it is now seen here year-round. With caterpillars that feed almost exclusively on stinging nettles, they are able to survive in many habitats.Some specialist species have done well, such as the Black Hairstreak, which only lays its eggs on blackthorn but has increased by 844 per cent since 1995 - however this is a species which Butterfly Conservation has been doing targeted work to help across the country for decades.The largest increase of any species is the Large Blue, whose numbers have soared by 1,866 per cent since 1983 – but that's because, after being declared extinct in Britain in 1979, the butterfly has been successfully reintroduced.Elsewhere across the country, Butterfly Conservation and partners have done targeted conservation work which has successful slowed the decline of rare species and increased local populations.The UKBMS results for last year in particular highlight the scale of the challenge: despite the UK experiencing its sunniest year on record – weather in which butterflies should thrive – 2025 was only an average butterfly year (20th out of the past 50 years), and not a single species recorded its best year.This mirrors last year’s results of Butterfly Conservation's Big Butterfly Count, which saw record participation of more than 125,000 people but produced only average numbers of butterflies per count.Prof Fox said: "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. 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."Dr Marc Botham, Butterfly Ecologist at UKCEH, 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. Data from the past 50 years show many butterflies are in long-term decline, and knowing which species are struggling and where informs conservation action to support populations."Steve Wilkinson, Director of Ecosystem Evidence & Advice at JNCC, said: "Reaching 50 years of continuous butterfly monitoring data is a remarkable milestone which would not have been possible without the extraordinary dedication of our volunteers. Their consistent and careful work, year after year, has built an evidence base that is unmatched anywhere in the world for insect monitoring. “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. Understanding where conservation efforts are making a real difference and where we need to strengthen efforts, depends entirely on the quality and continuity of data that our volunteers make possible.”Dr David Noble, Principal Ecologist for Monitoring at BTO, said: "Although the results for 2025 are not encouraging, it is critical that these measures of change in butterfly populations are generated from high quality data. The UK BMS is a paragon of biodiversity monitoring generally, being very long-term, uses robust methods, and collected by skilled surveyors, and with the inclusion of WCBS data, fully represents all key habitats across the UK. Importantly, these surveyors are volunteers - for Butterfly Conservation or BTO - and we are hugely indebted to all of them for their dedication, some for many decades." Find out more about joining in with the Big Butterfly Count here.