Last summer, Britain recorded the fifth-worst summer for butterflies. According to the UK Butterfly Monitoring Scheme (UKBMS), the world’s most significant scientific assessment of insect populations, 2024 was the fifth-worst year for butterflies in nearly five decades. For the first time since 1976, more than half of the country’s 59 native butterfly species are experiencing long-term loss. The data offers a dismal picture: Nine species, including once-popular favourites like the small tortoiseshell, little copper, small skipper, large skipper, and green-veined white, had their worst year on record.

When explaining the issue, Dr. Richard Fox, Butterfly Conservation’s head of science, didn’t mince words. “We have destroyed wildlife habitats, polluted the environment, used pesticides on an industrial scale, and we are changing the climate,” he told reporters. These acts have left butterfly populations on the verge of extinction, unable to recover from adverse conditions as they previously did. While Britain recorded the fifth-worst summer for butterflies, the butterfly numbers inevitably fluctuate with Britain’s changeable weather. The UKBMS data tells a deeper, more alarming narrative. 31 of the 59 native species are currently in chronic decline, indicating that the situation is far worse than a bad season.

A Troubling Snapshot of 2024

The UKBMS, which relies on hundreds of volunteers to count butterflies at over 3,000 locations around the country, offers an unmatched view into the health of these delicate creatures. Common butterflies, which may be found in gardens, parks, and hedgerows across the countryside, had their second-worst year since tracking began. A stunning 51 species had their numbers reduced compared to 2023, a year that was already devastating for many. Among the hardest damaged were species long admired for their beauty and abundance. The small tortoiseshell, long a fixture of British summers, has dropped to unprecedented lows following its worst-ever year in 2023. Other garden regulars, such as the little copper and green-veined white, followed suit, and their populations plummeted to historic lows.

For experts, the demise of the little tortoiseshell is particularly perplexing. With its vivid orange-and-black wings, this butterfly was once a common sight darting across flowerbeds and hedgerows. Its caterpillars eat stinging nettles, so common that it’s difficult to envision a food shortage. Despite this apparent abundance, the species has failed to recover. Theories abound—parasitic insects, climatic fluctuations, and habitat fragmentation have all been proposed as causes—but no single theory has solved the puzzle. What is apparent is that the little tortoiseshell’s condition is representative of an enormous catastrophe impacting British butterflies.

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Human Impacts and Climate Change

Dr. Fox and his colleagues at Butterfly Conservation are unequivocal: human activity is causing this loss. Butterflies rely on wildflower-rich meadows, forests, and wetlands, but decades of habitat loss have depleted them. Industrial-scale pesticide use has poisoned their food supply and killed many people. Pollution has deteriorated the air and soil they rely on, and climate change has added unpredictability to their life cycles. Like many other insects, butterflies are extremely sensitive to temperature and meteorological conditions. A damp spring might drown caterpillars or slow their development, but a chilly summer can limit the nectar accessible to adults. Historically, robust populations were able to survive such setbacks. Today’s already reduced numbers suggest there is little margin left.

The summer of 2024 served as an example. The damp start and cool temps were not ideal for butterflies, but the magnitude of the decline reveals more considerable structural difficulties. “With climate change, that unusual weather is becoming more and more usual,” he said. As global temperatures rise, Britain’s summers become more extreme—drought one year, deluge the next—giving butterflies little chance to adjust. For species already on the verge of extinction, these conditions can tilt the balance from struggle to collapse.

Red-Listed Species and Conservation Successes

The 2024 data was not only bad news for common butterflies. Several species previously designated vulnerable on Britain’s “red list” have reached new lows. The grizzled skipper, small pearl-bordered fritillary, and chalkhill blue—all rare and habitat-specific—had their worst years ever. These butterflies, which are generally limited to specific locations or habitats, are especially vulnerable to habitat loss and climate change. The grizzled skipper, for example, flourishes in short-grassed environments such as chalk downlands, which have been decimated by agricultural development and neglect.

Despite Britain recorded fifth worst summer for butterflies there are glimmers of hope. Conservationists have achieved tremendous progress in recent decades, rescuing some of Britain’s most endangered butterflies. The great blue, which returned after extinction in the 1970s, is currently thriving in well-managed grasslands. The high brown fritillary, another red-listed species, has made localised recoveries due to deliberate habitat restoration.

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Call to Action: Let the Grass Grow

Butterfly Conservation is now motivating the public and municipal governments to take a simple but impactful step: stop mowing. Last year’s research proved what many ecologists suspected: gardens with tall grass attract more butterflies and have a higher species diversity. Individuals and councils can provide instant havens for these insects by leaving lawns uncut between April and September. “By far, the best thing we can do to help butterflies is to create more habitat,” Fox told the crowd. “This simple act can make a real, immediate difference to butterflies, moths, and other wildlife.”

The logic is obvious. Long grass offers caterpillars shelter, breeding grounds, and food plants, and unmown wildflowers supply nectar for adults. This shift could alter the landscape for insects in a country dominated by groomed lawns and tightly clipped verges. Butterfly Conservation’s campaign has already gained speed, with some municipalities agreeing to reduce mowing in parks and along roadsides.

Looking Ahead

The collapse of Britain’s butterflies is a harsh reminder of the toll of human activity on the natural world. Last summer’s terrible results were not an outlier but part of a decades-long trend that shows no signs of easing. The clock is ticking for the little tortoiseshell and its ailing family members. Without immediate efforts to restore ecosystems, limit pesticide usage, and moderate climate change, more species may join the ranks of the endangered—or disappear entirely.

However, the solution is within our grasp. By embracing wilder gardens and greener public areas, Britain can recreate the patchwork of habitats that butterflies need to thrive. The UKBMS will continue tracking these vulnerable groups year after year, providing both a measure of loss and a road map for recovery. The message is clear for now: if we want to see butterflies dancing through our summers again, we must take action and let the grass grow.

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