Butterfly species come back from the brink of extinction
Hope amid the gloom. Six of Britain's rapidly declining butterfly species have started to recover in numbers because of intensive conservation efforts.
They are bucking the trend of dwindling populations being seen in three-quarters of Britain's 60 types of butterfly, which is depressingly confirmed in a new study published today.
The six showing signs of a comeback include Britain's fastest disappearing species, the heath fritillary, as well as the high brown fritillary, the wood white, the silver-spotted skipper, the adonis blue and most remarkably of all, the large blue - which 25 years ago was extinct.
The large blue disappeared from Britain in 1978, partly because of its specialised life cycle - the caterpillar spends much of its life in an ants' nest - but it was reintroduced from continental Europe in the 1980s. Careful management has allowed it to flourish on 10 sites in the west of England, and at the last count there were 7,000 adults.
But this sort of success story is the exception rather than the rule, according to the new study, The State of Butterflies in Britain and Ireland, which is published by the charity Butterfly Conservation, in association with the Centre for Ecology and Hydrology.
The report, which includes much new detail on population trends and distribution, reinforces earlier research in indicating that 76 per cent of our butterfly species are dramatically shrinking both in numbers and range. Seventeen species have gone from 40 per cent of the sites they were found in 30 years ago.
British butterflies are declining much faster than either birds or wild flowers, largely because they are more sensitive to environmental change. Many need specialised habitats, such as short-grazed turf or coppiced woodland (in which the trees are cut in rotation, leaving open glades) and if traditional farming management falls into disuse or is replaced by agricultural intensification, the butterflies tend to disappear.
Recent research also indicates that butterflies cannot survive habitat fragmentation - that is, if they end up in colonies only on widely-separated islands of habitat in the landscape, they will die out. They need networks of sites between which they can freely move to replenish different local populations.
However, in the past decade, growing scientific knowledge of butterflies' life cycles and habitat requirements has led to much more accurately targeted conservation measures. These have been put into practice not only on nature reserves, but more importantly on farmland, via new agri-environment schemes, which all farmers can now join (and receive extra support payments for doing so).
The schemes, designed to maintain or reinstate agricultural practices which allow butterflies in flourish, are now starting to show success. The silver-spotted skipper, for example, had by 1982 shrunk in numbers to a mere 68 colonies in the UK because of ploughing-up or neglect of its habitat, the chalk downland of southern England.
Now green farming schemes which encourage grassland grazing to provide the short turf it needs have led to an increase in individual numbers of 1,500 per cent and to nearly 270 colonies. The brilliantly coloured adonis blue has enjoyed a similar success.
"What the increases in these six species show is that conservation measures are beginning to reverse the really severe declines our butterflies have been suffering from," said Martin Warren, Butterfly Conservation's chief executive. "To have some success in halting that is quite an achievement.
"But we need a lot more of it because we have a lot more species to turn around as well."
Five others on the road to recovery
* HEATH FRITILLARY Melitaea athalia
One of Britain's two fastest-declining butterflies, with population down by 73 per cent over the past 20 years, and now mainly confined to a few sites on Exmoor and in Kent. Carefully targeted habitat management in Kent's Blean Woods has brought its numbers back up, and there are early signs of a similar increase on Exmoor.
* WOOD WHITE Leptidea sinapis
A delicate species that lives in woodland rides and has suffered from the decline in traditional woodland management. In Britain it has declined by more than 60 per cent over 30 years, but in the past decade has staged a comeback, with a recent increase of about 10 per cent. It has responded well to habitat management in Herefordshire, Shropshire and Warwickshire,.
* SILVER-SPOTTED SKIPPER Hesperia comma
A very rare butterfly that is on the way back. A survey in 1982 found just 68 populations in Britain but by 2000 these had increased to 257. Improvement of its chalk grassland habitat by livestock grazing and climate change may help. Warmer temperatures increase its breeding habitat.
* ADONIS BLUE Pollyomatus bellargus
A species that has disappeared from 20 per cent of its sites over the last three decades, but which shows a much more positive recent trend, up more than 60 per cent in numbers in 10 years. Like the silver-spotted skipper, it has benefited from better management of chalk downland, and possibly from climate change also.
* HIGH BROWN FRITILLARY Argynnis adippe
The other most rapidly declining species, having disappeared from nearly 80 per cent of known breeding sites in recent decades. Still in real danger of extinction - but positive habitat management has led to substantial increases in a few places, in particular on the Morecambe Bay limestones of north Lancashire.
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