Some UK butterfly species drop to lowest recorded numbers amid ‘human impact’

Red Admiral numbers have been increasing in the UK (UKBMS/PA)

Conservationists have recorded their lowest ever count of some butterfly varieties in Britain amid concerns about human impacts on the environment.

Last year saw a mixed picture for 58 butterflies, with some species soaring in numbers while others saw worrying declines, according to findings from the annual UK Butterfly Monitoring Scheme (UKBMS).

Volunteers and environmental organisations recorded data on 3,316 sites in 2023 as part of the annual scheme that monitors changes in insect populations.

The Small Pearl-bordered Fritillary saw its lowest ever count in 2023 (UKBMS/PA)

The results, published on Wednesday, showed that Small Pearl-bordered Fritillaries and Small Tortoiseshells hit their lowest numbers in 48 years of monitoring.

The two species have seen a decline of 71% and 82% respectively since the UKBMS began in 1976, the data suggests.

Small Tortoiseshells, which are common in gardens, had their worst year on record in England, second worst in Wales and joint fifth worst in Scotland in 2023, the findings show, although they saw their second best year in Northern Ireland.

Other species which saw counts decline last year included the Cryptic Wood White, Grizzled Skipper, Pearl-bordered Fritillary, Grayling and Scotch Argus.

The Green-veined White and Ringlet also had a poor year, with conservationists saying this could be due to the ongoing effects from a drought in 2022.

Meanwhile, warming temperatures mean Red Admirals, a migratory species that have begun to spend winters in Britain, saw their highest ever count last year and were common in all habitats including gardens.

Species that flourished last year include the Brimstone butterfly (Matt Berry/PA) — Brimstone butterflies were among the species that appeared to flourish in 2023 (UKBMS/PA)

These butterflies have now increased by 318% at monitored sites since 1976, according to UKBMS data.

Elsewhere, conservationists say efforts to restore the Large Blue, which was reintroduced to the UK after becoming extinct in the 1970s, have been successful with numbers hitting a record high in 2023.

Other species that flourished last year include the Chequered Skipper, Brimstone, Brown Argus, Marbled White, Comma, Black Hairstreak and Holly Blue.

Butterfly monitoring and conservation work remains essential amid the ongoing challenges posed by climate change, according to the organisations behind the UKBMS – the Butterfly Conservation, the UK Centre for Ecology & Hydrology (UKCEH), British Trust for Ornithology (BTO) and the Joint Nature Conservation Committee (JNCC).

Dr Marc Botham, a butterfly ecologist at the UKCEH, said butterflies are an “indicator species” to the wider health of the environment.

He said this makes the UKBMS data “invaluable in assessing the health of our countryside and natural world in general”.

A female Large Blue butterfly which had a great year after conservation efforts. (Pete Withers/UKBMS) — A female Large Blue butterfly, which had a great year in 2023 after conservation efforts (UKBMS/PA)

“The mixed results this year emphasise the need for continued monitoring and conservation efforts to protect these important species and their habitats,” he said.

Dr Richard Fox, Butterfly Conservation’s head of science, said: “Butterfly numbers fluctuate naturally from year to year, largely due to the weather, but the long-term trends of UK butterflies are mainly driven by human activity, including habitat damage and destruction, pesticide use, pollution and climate change.

“By monitoring long-term butterfly trends we can learn about the impact of climate change and other factors on our native wildlife.”