10 new butterfly species in Scotland thanks to climate change – study

The latest Scottish Biodiversity Indicator, published by NatureScot on Monday, examines the long-term trend for butterflies since 1979.

The report found that from 1979 to 2023 there has been an overall 35% increase across the 20 species analysed but was likely to be impacted by “chaotic” climate events.

Research shows that over the past 40 years, butterflies traditionally found in England and Wales – for example: orange-tip and peacock – have become more common in Scotland, with “climate change and weather being the likely drivers”, according to a report.

But scientists warned that the potential for northward expansion is likely to be limited by habitat availability and regional weather conditions that can affect their survival and dispersal.

Generalist butterfly species, which use a range of habitats, have increased by half, while populations of specialist species, which are limited to specific habitats like heathland, remain stable.

Red admiral butterflies increased 10-fold, with orange tip and speckled wood butterflies increasing three-fold.

But two species: grayling and small tortoiseshell; have suffered dramatic declines. Grayling is a coastal specialist whose 90% decline may be due to changes in habitat.

Small tortoiseshell has fallen by more than 60% with climate change, habitat loss and parasites thought to have affected these insects over the decades.

Across the UK, the distribution of 58 native butterflies plummeted 42% from 1976 to 2019, records show, particularly badly impacting habitat specialists, however, efforts are being made to boost populations in Argyll and the Scottish Highlands.

Areas populated by butterflies and moths provide benefits including pollination and natural pest control, while butterflies and caterpillars are also an important element in the food chain as prey for birds, bats and other animals.

NatureScot trends and indicators analyst, Simon Foster, said: “In recent decades, we’ve seen the damaging effects of climate change on butterflies, with species that fly in the spring emerging earlier.

“But an earlier start to the butterfly season doesn’t necessarily benefit the insects if the plants and flowers they feed on die earlier than they used to.

“Extreme events, such as heavy rainfall and drought, can impact butterflies dramatically, and we see this reflected in how much their numbers vary from one year to the next. Butterflies generally benefit from warm, dry springs and summers, but drought conditions can reduce caterpillar food availability by reducing plant growth or shortening the flowering season.

“On the other hand, cold and wet weather can reduce butterfly activity and affect caterpillar growth and survival.

“As our climate becomes increasingly chaotic, it’s important we take steps now to protect our butterflies in the future. One way people can help is by joining the UK Butterfly Monitoring Scheme (UKBMS) and getting involved with surveys.

“It’s easy, fun and can help us improve our knowledge of what is happening where, giving us the best chance of targeting conservation measures most effectively.

“People can also help butterflies in their gardens by planting flowers that produce lots of nectar and pollen.”

Butterfly Conservation head of conservation for Scotland, Tom Prescott, said: “We are delighted that generalist butterflies like the red admiral are doing so well in Scotland, but it’s deeply worrying that specialists like the grayling are not doing any better than 40 years ago – and some are doing much worse.

“It’s also crucial to remember that this data only shows how species are doing at sites where our fantastic UKBMS volunteers have been surveying, many of which are nature reserves. Across the UK, the distribution of our 58 native butterflies plummeted 42% from 1976 to 2019, and habitat specialists are doing the worst.

“We are doing targeted work in Scotland and across the UK to create and protect habitat for specialists, such as our project planting kidney vetch for the small blue with primary school pupils in the Highlands and working with farmers in Argyll to benefit marsh fritillary – but we still need to do a lot more to secure the future of our fantastic native species.”