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

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Main image: Small blue butterfly. © Iain H Leach

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