While some species may migrate to cooler regions, others will be unable to move or to adapt.

Other species may find their range reduced, although there will be gains for those able to roam further afield. And conservationists will need new techniques to manage a warmer world.

The warning comes in a report from the UK Climate Impacts Programme, entitled Climate Change and Nature Conservation in Britain and Ireland.

The report, known as Monarch (Modelling Natural Resource Responses to Climate Change), used scenarios prepared by the Hadley Centre for Climate Prediction and the Climatic Research Unit at the University of East Anglia (UEA).

Winners and losers

The authors used computer modelling to predict how animals and plants might react as the climate changes.

They analysed 50 representative species in Britain and Ireland. Some will probably be able to migrate, while others may be driven to extinction.

The authors say warmer weather spreading north-westwards from continental Europe will extend the range of many species. But it will also reduce the range of those already vulnerable, especially in the mountains of north Wales and Scotland.

If they venture further north to escape the rising temperatures, there will be nowhere for them to go.

The report says nature conservation itself will need to change, concentrating more on wildlife management in the wider countryside and not just in reserves.

New techniques that will be needed include the provision of corridors to allow wildlife to migrate. The report's detailed findings include:

• Wales could lose several plants, including the bog rosemary and dwarf willow
• the capercaillie and red-throated diver, birds restricted to northern Scotland, face an increasingly uncertain future
• the mountain ringlet butterfly of the Lake District and western Scotland will probably find no suitable climate anywhere in Britain or Ireland by 2050. But other insects will probably do well
• Scotland will gain as southern butterflies move north
• estuaries are likely to lose many curlews, dunlins and redshanks, though oystercatchers should do better
• beech trees, with their shallow roots, may suffer badly as droughts become more frequent

Limits of tolerance

The large skipper butterfly could colonise most of Ireland and Scotland by the middle of the century. Heaths, bogs, hay meadows and woodlands are all liable to change.

The report also expects changes in marine wildlife, with sea level rises most marked around the southern coasts of Britain and Ireland.

It says increases in sea surface temperatures will affect species currently at the extremes of their temperature tolerance range.

Mike Harley, climate change adviser for English Nature, told BBC News Online: "What we're arguing is that Nature is dynamic. There's been a bit of a failure by nature conservation to recognise that over the last 50 years.

"We have to provide opportunities for those species that want to move on to do so.

"We're in a natural warming cycle, and man's got his foot on the gas pedal. So we have to adapt. It's an exciting challenge. We've got to see adaptation in a positive light."