New Red List shows British butterflies are in trouble
22 October 2010, by Tamera Jones
The number of British butterflies that have disappeared or that are classed as threatened has gone up dramatically since the late 1990s. This new assessment – the most comprehensive yet – confirms butterflies as a highly threatened group of British insects.
A Large Blue butterfly resting on bracken.
More than a third of the 62 butterflies that live in Britain have either already disappeared from the country, or are now considered threatened: four species have gone 'regionally extinct', two are critically endangered, eight are endangered and nine are vulnerable.
Eleven of the 62 species are now classed as near threatened, while 28 are in the least concern category.
The figures are the result of a major re-assessment of the state of British butterfly populations using the International Union for Conservation of Nature (IUCN) Red List approach. Scientists first evaluated the extinction threat to butterflies in the country back in 1987. The second review – and until now the last – took place 10 years later in 1997.
'Butterflies are one of the best indicators of what's going on in the environment. They're the canary in the coal mine to quote David Attenborough.'
Richard Fox, Butterfly Conservation
Two butterfly recording projects allowed this new assessment: Butterflies for the New Millennium, launched by the charity Butterfly Conservation in 1995, and the UK Butterfly Monitoring Scheme, run by both the Centre for Ecology & Hydrology (CEH) and Butterfly Conservation. Both rely heavily on so-called citizen scientists (members of the public and butterfly enthusiasts) to record information about the insects.
'We probably know more about British butterflies than any other insect group in the world. They've been studied intensively. And what we can say is that what's happening to British butterflies indicates what's happening to insects and other invertebrate groups elsewhere,' says Richard Fox from Butterfly Conservation, lead author of the study.
Recent research has revealed that British dragonflies, plants and birds are also in trouble. But this latest research found that compared with butterflies, these other species are less seriously threatened.
'Butterflies are one of the best indicators of what's going on in the environment. They're the canary in the coal mine to quote David Attenborough,' says Fox.
Researchers from Butterfly Conservation, CEH and the Joint Nature Conservation Committee used new IUCN criteria focusing on rate of decline and area of occupancy, or distribution, to compile the new Red List.
They say one of the problems butterflies are facing is destruction of their habitat. Large-scale farming, forestry and woodlands not being managed the way they used to be all contribute. 'There's a real increase in the extinction threat as a result of human impacts,' says Fox.
Add to that their caterpillars' precise requirements and it's easy to see why they're threatened.
Duke of Burgundy.
'The large blue is an extreme example of a fussy butterfly. But others are just as picky. The Duke of Burgundy will only lay its eggs on primrose or cowslip plants growing in very particular situations. A lot of butterflies don't make life easy for themselves,' says Fox.
Fox explains that one reason we're seeing butterflies declining faster than birds, plants or dragonflies is that they have such fast and short lifecycles. 'No butterfly lives for longer than a year, so populations react rapidly to change. Oak trees live for longer, so they react much slower to change.'
They also add that one of the reasons for such a marked decline is that monitoring data is much better than it was ten or 20 years ago, so the drop in numbers might be easier to see.
Not only that, but, 'IUCN criteria have evolved since the 1990s,' explains Fox. When scientists came up with their first assessment in 1987, there were no criteria to show rate of decline. 'The criteria used to be more qualitative, but now it's entirely quantitative. IUCN realised it's the rate of change and not rarity that's important.'
The researchers are keen to point out that none of the species they looked at are limited to Britain. 'They all occur elsewhere,' says Fox. 'But this doesn't mean there isn't cause for alarm. British wildlife is our heritage.'
The new list is likely to be used as a tool to focus conservation efforts. There are many examples of successful butterfly conservation projects: the Large Blue is one. The butterfly disappeared from Britain in 1979, but after being re-introduced to southwest England from Scandinavia and careful tending to its needs, it is now thriving and spreading.
RICHARD FOX, MARTIN S. WARREN, TOM M. BRERETON, DAVID B. ROY and ANNA ROBINSON, A new Red List of British butterflies, Insect Conservation and Diversity, published online 13 October 2010, doi: 10.1111/j.1752-4598.2010.00117.x
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