Big Butterfly Count in UK begins with eyes on declining numbers

Citizen science survey should aid knowledge of populations, including that of small tortoiseshell ‘missing’ from buddleias

The apparent alarming absence of butterflies feeding on buddleia flowers this summer will be tested by the launch of the world’s largest insect survey.

People are being urged to take part in the Big Butterfly Count today to help discover if anecdotal reports of a lack of butterflies reflect a wider reality across Britain this summer.

A record number of people last year submitted more than 150,000 butterfly counts, each lasting 15 minutes. But they recorded the lowest average number of butterflies – nine per count – since the citizen science survey began in 2010, following the previous record low of 10.66 butterflies per count in 2020.

“There seem to be more and more people getting out and doing the count but fewer and fewer butterflies for them to see,” said Zoe Randle, senior surveys officer for Butterfly Conservation, which coordinates the count.

Half of Britain’s 58 resident butterfly species are listed as “threatened” or “near threatened” with extinction, according to the latest Red List, while common species such as the small tortoiseshell are also becoming less abundant. Butterflies are declining more rapidly in urban areas than in the countryside.

This year, many nature lovers, including the scientist Dave Goulson, have been sharing observations of insect-bereft buddleias, although others report an unchanged picture. Buddleias are often not festooned with butterflies until late summer when other nectar is scarcer.

The recent declines in butterfly abundance recorded by the Big Butterfly Count may be due to species emerging significantly earlier in the summer because of global heating, and dying or disappearing into hibernation by the time the three-week count begins in late July.

After this year’s count, Butterfly Conservation scientists will analyse 13 years of count data alongside the UK Butterfly Monitoring Scheme to see if the citizen science observations tally with seasonal variations picked up by a longer-term, scientific count, which extends across the summer. Randle said that in future the Big Butterfly Count could be moved to earlier in the summer to pick up the earlier emergence of high summer butterflies.

One buddleia-feeding butterfly experiencing big declines is the small tortoiseshell, which has declined by 79% since 1976.

Randle said there was now a distinct pattern in the data showing it doing much better in north Wales, Northern Ireland and Scotland than in southern England.

“Why that is we don’t really know but all this data that’s gathered through the Big Butterfly Count can be used to help us understand why that may well be happening,” she said. “It could be phenology – with the butterfly emerging earlier in the south and so being between broods when the count takes place.”

As well as contributing to a scientific understanding of butterfly populations, Butterfly Conservation is also stressing the benefits for people taking 15 minutes out of their day to observe and record butterflies in a park, wood or garden.

Dr Amir Khan, an ambassador for Butterfly Conservation, said: “Spending time in nature is hugely beneficial to our mental health. Just a short amount of time spent in the natural world can alleviate stress, and connecting with nature can help us feel happier and more energised.

“Watching butterflies for just 15 minutes can be a wonderful and calming experience. It is good for you and benefits butterflies by helping Butterfly Conservation gather the important data they need to understand how to better protect these special insects. It is truly a win-win situation for all of us.”


Patrick Barkham

The GuardianTramp

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