Experts are left baffled by falling butterfly numbers
THE populations of some species of butterfly in Scotland have declined by nearly 70 per cent in less than 40 years, and conservationists are not sure why.
However, others have been prospering, the latest Scottish Biodiversity Indicator has reported.
In Scotland, butterflies are monitored through the UK Butterfly Monitoring Scheme. Volunteers walk fixed routes weekly from April to September each year. The latest indicator describes trends for 20 of the 34 regularly occurring butterfly species in Scotland at 436 sample locations.
The majority of Scottish butterflies can be conveniently classed as specialists or generalists. Scotland’s specialist butterflies have declined by 67 per cent since 1979, with small pearl bordered fritillary (over the past 10 years), large heath and grayling declining significantly.
Generalists like small skipper and Essex skipper are benefiting from climate change and have expanded their range into southern Scotland.
And three generalist butterflies show climatedriven, significant, longterm population increases – peacock, speckled wood and orange-tip.
Regular migrant butterflies, including the red admiral, are also growing in number.
Dr Tom Prescott, species conservation officer with Butterfly Conservation Scotland, said the health of butterflies was important:
“Butterflies are the canaries of the countryside.
“They have annual life cycles and are very quick to respond to changes in the natural world, whether for the good or bad. The fact that this report has just used Scottish data is important because it is often UK data used, and we tend to think things are better in Scotland than south of the border.
“But this has clearly shown three species in Scotland are obviously suffering.
“We now need to look at why that is. I still see small pearl bordered fritillary around, so this has come as a bit of surprise to me.
“There is obviously an issue across Scotland.”
Dr Prescott added there were many possible reasons for the contrasting fortunes of different species, from the climate to change in land management practices.
“A huge amount study is needed,” concluded. of he