‘Warning sign to us all’ as UK butterfly numbers hit record low

Butterfly numbers are the lowest on record in the UK after a wet spring and summer dampened their chances of mating.

Butterfly Conservation, which runs the Big Butterfly Count , sounded the alarm after this year’s count revealed the worst numbers since it began 14 years ago.

Many people have noticed the lack of fluttering insects in their gardens. Experts say this is due to the unusually wet conditions so far in 2024. Climate breakdown means the UK is more likely to face extremes in weather, and the natural rhythms of the seasons that insects such as butterflies are used to can no longer be relied on.

The UK had its wettest spring since 1986 and the sixth wettest on record, as an average 301.7mm (11.87in) of rain fell across March, April and May, nearly a third (32%) more than usual for the season. The Met Office has said recent decades have been warmer, wetter and sunnier than those of the 20th century.

Dr Dan Hoare, the director of conservation at Butterfly Conservation, said: “Butterflies need some warm and dry conditions to be able to fly around and mate. If the weather doesn’t allow for this there will be fewer opportunities to breed, and the lack of butterflies now is likely the knock-on effect of our very dreary spring and early summer.”

The extra rain is not the only problem; the charity said 80% of butterfly species in the UK had declined since the 1970s, with habitat loss, climate breakdown and pesticide use being the main causes. Butterfly populations already hit by these issues would be less likely to be able to cope with extreme weather.

“The lack of butterflies this year is a warning sign to us all,” said Hoare. “Nature is sounding the alarm and we must listen. Butterflies are a key indicator species. When they are in trouble we know the wider environment is in trouble too.”

Painstaking work by conservationists has meant that some butterfly species have recovered in recent years.

Results released in April from the annual UK Butterfly Monitoring Scheme (UKBMS), the largest and longest-running scientific butterfly dataset in the world, showed encouraging signs that conservation efforts were working: the large blue, which was reintroduced to the UK in the 1980s after it became extinct in 1979, recorded its best year yet. The chequered skipper, which was returned to England in 2018 after becoming extinct in the 1970s, also recorded its best year.

However, as well as the rain this year, butterfly species are struggling to bounce back from the 2022 drought; they do not mate in wet conditions, but they also need the plants their caterpillars eat to be adequately watered. Species including the green-veined white and the ringlet still have low populations because their caterpillars did not survive the drought. The extremes of climate breakdown mean that as butterflies try to recover from one extreme weather event such as a drought, they are hit with another event like very heavy and sustained rainfall a couple of years later.

Butterfly Conservation said there was still a chance of some butterflies emerging late if the weather got drier and sunnier.

People can help butterflies to thrive by leaving the grass in their gardens to grow. A recent study found wilder lawns boost butterfly numbers. The benefits of leaving areas of grass long were most pronounced in gardens within intensively farmed landscapes, with up to 93% more butterflies found and a greater range of species. Gardens with long grass in urban areas showed an 18% boost to butterfly abundance.

There is one week left of the 2024 Big Butterfly Count, which asks people to go outside for 15 minutes and record the number and type of butterflies they see – and to submit their results even if they see very few or no butterflies.