Extinction fears grow for rare Scots butterfly after worst year on record
A rare Scottish butterfly described as vulnerable to extinction has suffered its worst year on record, a study has found.
The Scotch Argus declined by 53% in 2022 compared with the previous year, according to the latest report from the annual UK Butterfly Monitoring Scheme (UKBMS).
In addition to the dramatic annual decline, the study shows a “statistically significant” 48% drop in abundance in the red-listed species over the past 10 years.
The Scotch Argus is known as “Scotland’s butterfly” because its UK distribution is almost entirely confined to sites north of the border. In England, it is now found at only two isolated sites in Cumbria.
Although it remains widespread in parts of Scotland, experts fear climate change could drive it further north and it could eventually be lost.
The monitoring scheme has operated since 1976, led by the charity Butterfly Conservation, the UK Centre for Ecology & Hydrology, British Trust for Ornithology and Joint Nature Conservation Committee.
Dr Richard Fox, Butterfly Conservation’s head of science, said: “The study shows clearly that the Scotch Argus had its worst ever year last year.
“After five years when it seemed to be stable in terms of numbers in Scotland, it really fell off the scale and this is comfortably the worst year for the species since monitoring began in 1990.
“The Scotch Argus has had a severe negative trend in the last decade, decreasing in abundance by nearly 50%.
“It’s ‘statistically significant’, which means we can have confidence it is a real change.
“If climate does prove to be the major driver for this species – and there is some cause to think that it might be – then we could be looking at its gradual disappearance.
“There was already a concern that it might be retreating in the face of climate change because it is adapted to cooler temperatures. Climate change doesn’t bode well for any of the northern speciality species that occur in Scotland.”
The report reveals that, overall, 2022 was an “average year” for butterflies across the UK – the 27th best out of 47 years since the UKBMS began monitoring butterfly numbers in 1976.
But, while the heatwave and drought of summer 2022 had a major negative impact on some UK species, Scotland enjoyed a better-thanaverage year, possibly due to less extreme weather.
Species that enjoyed an increase in abundance included the Orange Tip, Wall, Small Heath, Ringlet, PearlBordered Fritillary and Red Admiral.
Dr Fox said: “Of all the UK countries, Scotland is the only one where butterflies are, overall, showing a positive picture. But, while some species had a good year north of the border, others did badly. In particular, habitat specialist butterflies are struggling.”