Concern over 46% decline of moths in Scotland

The latest research shows that their abundance almost halved between 1990 and 2018 and is continuing to decline while one species has declined by as much as 62%.

Climate change and habitat loss as a result of deterimental land management has been attributed for the decline.

Entomology experts say moths can tell us a lot about the health of our environment because they are found in so many different habitats and have a high sensitivity to environmental changes.

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Research has shown they play a vital role as overnight pollinators of a wide range of flowers and plants.

This not only benefits wild plants but also food crops, which depend on moths as well as other insects to ensure a good harvest.

Experts say public anxiety about the role of our pollinators has focused squarely on bees, while moths have not evoked similar sympathies.

A detailed report showing the number and spread of the insects has been compiled using 1.4 million records from volunteer observers for 290 species of moth.

It reveals the varying fortunes of different species. Numbers of upland Brindled Ochre have declined by 62% between 1975 and 2018, while the distribution of the species also fell 39% between 1990 and 2016.

Mountain Burnet, which occurs at only a handful of sites including Braemar, is also said to be among the most endangered. Other solely Scottish endangered species include Netted Mountain Moth and Choreutis diana, which is only found in Glen Affric.

Volunteers are being trained to monitor their incidence.

In contrast the Frosted Orange, found in grasslands, woodlands and gardens, is expanding in Scotland. This species increased in abundance by 506% between 1975 and 2018 with a 135% increase in distribution by between 1990 and 2016.

Climate change is likely to be an important factor behind the trends, driving the range of some species northward with corresponding increases in occupancy.

At the same time warmer, wetter winters driven by climate change have been shown to negatively impact some moths while other species are suffering population declines as a result of detrimental land management and habitat changes.

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Changes in Scotland which may have negatively influenced moth populations include: commercial afforestation and associated drainage of blanket peat bog, decline in mixed farming, reseeding and overgrazing by livestock and increased extent of built land.

Climate change is likely to be a principal driver of species range expansions.

Simon Foster, NatureScot trends and indicators analyst, said: “Moths can tell us a lot about the health of our environment because they are found in so many different habitats and have a high sensitivity to environmental changes.

“Unfortunately the evidence shows that previously reported declines for moths in Scotland continue to deepen, with climate change and habitat loss likely to be driving this trend.

“Monitoring moths gives us a greater understanding of the specific requirements of individual species, allowing us to work with partners to take action on the ground to conserve those species most at risk.

“At NatureScot we are incredibly grateful to the thousands of dedicated volunteers who have given their time to make such a detailed picture possible.”

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Moths have suffered steep declines in numbers since the 1970s, largely due to changes in land use and the increasing use of pesticides. This is said to have had a knock-on effect for birds that feed on moths, such as the cuckoo and bats.

Tom Prescott, Senior Conservation Officer at Butterfly Conservation, said: “It’s worrying that the data shows how moths are continuing to decline in Scotland and just goes to show the importance of partnership working across nature organisations and the value of the contribution from volunteers.

“This data and analysis is focused on our more common and widespread species and will help determine the species of conservation concern of the future. 

“In the meantime, we are also increasing monitoring of our most rare and threatened species to determine how they are faring.

"This includes training local volunteers to monitor Mountain Burnet a species that only occurs in the UK at a handful of sites near Braemar, as well as other solely Scottish species including Netted Mountain Moth and Choreutis diana, the latter being entirely restricted to Glen Affric.”