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The sixth extinction: 4 of the UK's most endangered species

Some 15% of the species in Britain are formally classified as threatened and therefore at risk of extinction. ENDS examines four of the UK’s most at-risk species.

Water vole

Towards the end of the 1990s, a survey of water voles found the aquatic rodents had disappeared from 94% of the places where they had previously been found, “one of the most rapid and serious declines of any British wild mammal during the 20th century”, according to the 2008 edition of Mammals of the British Isles Handbook.

And while most wildlife declines in the British countryside (as with the corn buttercup) are linked to agricultural intensification, a key cause of the water vole’s plight was not Homo sapiens but a much smaller mammal closely related to stoats and weasels, Neovison vison – the American mink.

Mink were brought here – by people, of course – to be farmed for their fur, but accidental escapes, and some deliberate releases, from the 1950s onwards let them loose in the countryside, where they found they were supremely well-adapted to preying on water voles.

READ MORE: The sixth extinction: The UK's most at-risk species and the fight to halt nature's decline


The water voles, meanwhile, found they had precious few adaptations for avoiding this new nemesis. Despite fragmented attempts to eradicate mink through culling programmes, the most recent national census found that water vole populations have continued to contract – by 30% between 2006 and 2015, according to a report published in 2017.

Atlantic puffin

Despite its unofficial title as Britain’s most-loved seabird, the Atlantic puffin’s demise has – until recently – gone largely unremarked. Even now, long-term trends for the UK’s population as a whole are unavailable, but monitoring from certain sites has revealed unmistakable signs of sharp declines.

For example, numbers on the Farne Islands – the archipelago off Northumberland that’s home to a wide range of seabirds – have fallen by 12% over the past five years, while the population on the Isle of May, in the outer Firth of Forth on Scotland’s east coast, fell by a third between 2008 and 2013. Even more dramatically, of some 33,000 birds counted on 20 sites across Shetland in 2000, just 570 were found when a census was done in 2017.

Conservationists believe the main cause is climate change. Increased sea temperatures reduce the abundance of plankton which is the food source for sandeels, the main prey of puffins and many other seabirds.

There are still an estimated 450,000 puffins in the UK – about 10% of the global population (Iceland has more than half of them) – but some conservationists are even predicting the global extinction of the species should sea temperatures continue to rise.

High brown fritillary

Once widespread across England and Wales, the high brown fritillary is now found on just 37 sites, most notably Dartmoor, Exmoor, the Vale of Glamorgan and Morecambe Bay.

Until recently, the loss of traditional livestock grazing and coppicing, leading to the shading out of its larval food plant, wild violets, has been cited as the cause of the butterfly’s decline – a staggering 96% since the 1970s.

But now a new threat has been identified. High brown fritillaries overwinter as eggs in a state of suspended animation known as diapause, with the process of hatching out as caterpillars being kick-started by the onset of spring.

With climate change causing spring to happen earlier, the life cycle of the high brown fritillary is being shunted forward, leading to an earlier winter diapause.

“They therefore have longer to survive until spring conditions are suitable, but with no additional resources laid down with which to do so,” says Dr Callum Macgregor, from the University of York, lead author of the study. “My hypothesis is that survival is lower in the overwintering life stage following an earlier emergence.”

Habitat loss is still likely to be a major driver of the butterfly’s decline, but the impact of climate change may “explain its abundance declines at sites where it has persisted”, says Macgregor.

Corn buttercup

A smaller relative of that most widespread of wildflowers (creeping and bulbous are the most common species), the corn buttercup has alternative local names – devil’s claws and hellweed, for example – because of the apparently vicious two-millimetre spines sticking out of their proportionately large seedheads.

 It was once widespread across south and eastern England, but is now classed as critically endangered in the UK because of rapid declines over the past 60 years. Only a small pocket of the south-west Midlands remains a secure site for the species, though there are scattered records from Cornwall and as far north as Newcastle.

As with many other wildflowers in the UK, its demise is largely put down to the intensification of arable farming that followed the end of the Second World War. In general, there are two main causes: the increasing use of fertilisers and herbicides and the greater density of modern crops, which shut off the light from this smaller species.

In general, the threats to the corn buttercup are similar to those which have seen the UK lose 97% of its wildflower meadows and other species-rich grasslands over the past century.