Scientists are urging the public to help them track how British butterflies are migrating north as the climate warms.
Looking at 50 years of data, researchers from the wildlife conservation group Butterfly Conservation, which holds an annual event, Large butterfly countWe found that many species commonly seen in gardens, such as comma, peacock and holly blue, have clearly been migrating northward.
This is the result of climate disruption warming habitats and huge increases in certain species. The migratory red-footed falcon is one example. Normally found in southern England in summer and migrating to Europe in winter, these winged creatures are now in the UK all year round, and their populations have tripled.
Meanwhile, Holly-leafed mahonia has been spotted in Scotland, where its numbers have increased by 34%, reflecting its northward spread, while the distribution of Peacock-leaf mahonia and Speckled-wood mahonia has also increased by 36% and 53%, respectively.
Further reflecting this trend is the Jersey tiger: previously only found in the south-west of England, this day-flying moth has been spotted as far north as London for the first time during the 2021 Big Butterfly Count.
Dr Zoe Rundle, senior research officer at the butterfly conservation organisation, said: “Other species that previously suffered serious declines, such as the perennial butterfly, have also recovered, showing a massive 94% increase in their habitat. These highly adaptable species are able to migrate to new locations as the climate warms, but for species that are endemic to these habitats, these trends are a serious warning sign.”
Options are even more limited for the Scotch argus butterfly, which lives in the moist grasslands of Scotland’s mountains: its distribution has declined by 20 percent since 1979.
“This butterfly was once found in the north of England,” Rundle said, “and as the environment warmed it moved north in search of cooler climates. But how far north can the Scotch Argus get?”
The gatekeeper butterfly, which has declined 42 percent since 1979, is also among those being affected by habitat loss and global warming. The meadow brown has also seen its distribution decline by 22 percent, and the green-veined white has declined by 11 percent.
For Rundle, these figures are worrying: “Food plants can’t move like butterflies. Species that depend on specific habitats can’t move as freely, which means that if climate change continues they could become trapped in isolated fragments of remaining habitat and face extinction.”
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“Often we see these patterns of change in isolation, but we need to remember that all organisms in a habitat are connected, including us humans.”
Butterflies form an essential part of the Earth’s ecosystems – they act as pollinators and are keenly aware of changes in their environment. Up to 80% of UK butterfly species are already showing signs of decline, either in population or distribution, making it essential that we monitor their patterns and protect their habitats.
The Big Butterfly Count asks people to spend 15 minutes in a sunny place this summer and record the number and types of butterflies they see. Last year more than 135,000 counts were carried out across the UK, with volunteers counting butterflies over a total of nearly four years. This information helps scientists understand the status of species, informs conservation efforts and shapes government policy.
