Half of British butterfly species are now threatened with extinction

Butterfly Conservation has revealed that there has been a 26% increase in the number of butterfly species threatened with extinction.

A new Red List has been published in Insect Conservation and Diversity, with 62 UK species of butterfly assessed. Of those, four are classed as being extinct in Britain, with 24 threatened (including eight that are endangered) and five considered to be near threatened.

The four species that are considered to be extinct in the UK are the black-veined white, large tortoiseshell (pictured below), large copper and mazarine blue butterflies.

The data was gathered by volunteers through the UK Butterfly Monitoring Scheme and Butterflies for the New Millennium recording schemes, and assessed by scientists from Butterfly Conservation.

The risk of extinction for these butterfly species is increasing, with the numbers of threatened butterfly species having increased since the last time data was published in 2010, based on assessments up to the year 2004.

The impact of climate change is said to be notable from these findings, with all four butterfly species (large heath, Scotch argus, northern brown argus and mountain ringlet) that are distributed in the north of the UK – and therefore having adapted to cooler or damper climates – having now been listed as threatened or near threatened.

“Shockingly, half of Britain’s remaining butterfly species are listed as threatened or near threatened on the new Red List,” says Dr Richard Fox, head of science for Butterfly Conservation.

“Even prior to this new assessment, British butterflies were among the most threatened in Europe, and now the number of threatened species in Britain has increased by five, an increase of more than one-quarter. While some species have become less threatened, and a few have even dropped off the Red List, the overall increase clearly demonstrates that the deterioration of the status of British butterflies continues apace.”

Some species' statuses have improved. For example, the large blue (pictured above) has moved from critically endangered to near threatened, following a highly successful reintroduction programme and ongoing conservation work. The high brown fritillary (pictured below) is also no longer critically endangered and is considered endangered instead, thanks to intense conservation work. The pearl-bordered fritillary and Duke of Burgundy have moved from endangered to vulnerable.

“Where we are able to target conservation work, we have managed to bring species back from the brink, but with the extinction risk increasing for more species than are decreasing, more must be done to protect our butterflies from the effects of changing land management and climate change,” adds Dr Fox.

“Without action it is likely that species will be lost from Britain’s landscapes for good, but Butterfly Conservation is taking bold steps to improve key landscapes for butterflies and reduce the extinction risk of many threatened species.”

The full Red List compared to the species' previous categories:

Species
New GB Red List Category
Previous GB Red List

Black-veined White
Regionally Extinct
Regionally Extinct

Large Copper
Regionally Extinct
Regionally Extinct

Large Tortoiseshell
Regionally Extinct
Regionally Extinct

Mazarine Blue
Regionally Extinct
Regionally Extinct

Black Hairstreak
Endangered
Endangered

Glanville Fritillary
Endangered
Endangered

Grayling
Endangered
Vulnerable

Heath Fritillary
Endangered
Endangered

High Brown Fritillary
Endangered
Critically Endangered

Large Heath
Endangered
Vulnerable

Wall
Endangered
Near Threatened

Wood White
Endangered
Endangered

Adonis Blue
Vulnerable
Near Threatened

Brown Hairstreak
Vulnerable
Vulnerable

Chalk Hill Blue
Vulnerable
Near Threatened

Duke of Burgundy
Vulnerable
Endangered

Grizzled Skipper
Vulnerable
Vulnerable

Marsh Fritillary
Vulnerable
Vulnerable

Northern Brown Argus
Vulnerable
Vulnerable

Pearl-bordered Fritillary
Vulnerable
Endangered

Scotch Argus
Vulnerable
Least Concern

Silver-spotted Skipper
Vulnerable
Near Threatened

Silver-studded Blue
Vulnerable
Vulnerable

Small Heath
Vulnerable
Near Threatened

Small Pearl-bordered Fritillary
Vulnerable
Near Threatened

Swallowtail
Vulnerable
Near Threatened

White Admiral
Vulnerable
Vulnerable

White-letter Hairstreak
Vulnerable
Endangered

Dark Green Fritillary
Near Threatened
Least Concern

Large Blue
Near Threatened
Critically Endangered

Lulworth Skipper
Near Threatened
Near Threatened

Mountain Ringlet
Near Threatened
Near Threatened

Small Blue
Near Threatened
Near Threatened

Comparison with previous Red List:

Red List threat category
Number of species qualifying in new Red List
Number of species qualifying in 2011 Red List

Regionally Extinct
4
4

Critically Endangered
0
2

Endangered
8
8

Vulnerable
16
9

Near Threatened
5
11

Least Concern
29
28

Total
62
62

Main image: Small blue butterfly. © Iain H Leach