Warmer temperatures help Ireland’s butterfly population flourish again, but some species still remain ‘at risk’

Warmer temperatures have been helping Ireland’s butterfly population to flourish after a dip in numbers earlier this year, but several species remain on the at-risk list.

Earlier this year, butterfly numbers had been affected by low air temperatures, said Niamh Phelan, biodiversity engagement officer at Biodiversity Ireland.

While the heatwave may have caused alarm among many climatologists, Ireland’s butterfly population has thrived in the heat.

“The numbers were down in general this year due to low air temperatures in the late spring and late summer,” Ms Phelan said

“Butterflies need a minimum of 13C to fly and find a mate/partner. However, with the recent increase in air temperature, the numbers are now back up to what we saw in 2020.”

However, while warmer temperatures may have boosted butterfly population numbers, many species have experienced an overall decline over the past dozen years.

Some species are endangered, and as the insects are a vital part of our food chain, it is imperative they are preserved.

Biodiversity Ireland has been carrying out a five-year Butterfly Atlas survey, producing a detailed map on population changes across Ireland.

In tandem with the Irish Butterfly Monitoring Scheme, Biodiversity Ireland has been tracking the populations of the 15 most common species.

This research has shown that while the populations are growing from the lows of 2016, there are still 0.9pc fewer butterflies than in 2008.

There has been a strong decline in the number of Small Heath butterflies – a 5pc drop at a sample of 50 sites across Ireland from 2008 to 2020.

And there has, according to the Butterfly Atlas, been a 5pc decline in the Green-veined White, the Large White, the Speckled Wood and the Small Copper butterflies across the 50 sites surveyed.

There has been a strong increase in the Peacock butterfly – the species increased by 5pc from 2008 to 2020.

The Marsh Fritillary butterfly, which is rare across Europe, was not observed at all during the 12-year survey.

However, the butterfly with amber, black and yellow markings was spotted separately in a bog in west Offaly in 2017 for the first time in Ireland since 1995, indicating its survival.

The Marsh Fritillary is one of Ireland’s few legally protected butterflies under an EU directive.

“The Marsh Fritillary feeds on Devil’s Bit Scabious, a flowering plant, and this is sometimes abundant in grassland,” Ms Phelan said.

“It is concerning when there’s a reduction in species numbers because butterflies are not only aesthetically pleasing, they also have a cultural value.

“But much more importantly, they are part of the food system. Butterflies provide a food source to animals, including bats and birds.

“When we see a reduction, this gives us an idea of how climate change is affecting our biodiversity.”

The public is also playing a vital role in monitoring butterfly numbers. By joining free Biodiversity Ireland schemes, including the Garden Butterfly Monitoring Scheme, the public have kept watch of Ireland’s butterflies, feeding data back to be recorded.

Biodiversity Ireland noted the average number of butterflies recorded in the garden count is 32pc down on last year for the 10 weeks from May 1. However, numbers appear to be back to 2020 levels, most likely due to the recent warm spell.

Biodiversity Ireland is encouraging more people to get involved in its butterfly monitoring schemes by visiting biodiversityireland.ie.