Researchers have investigated recorded sightings of 57 species of European butterfly over the past century, and have found a significant shift of their breeding ranges northwards.
Of 52 species whose movements have been traced in accurate records, two- thirds have moved between 22 and 150 miles farther north over the past 30 to 100 years.
In Britain, the Essex skipper has expanded from the South-East and is now found in the Midlands. The comma, once found in only a few southern locations, now lives throughout most of England and Wales.
One of the most dramatic examples of the migration northwards is the speckled wood butterfly, which, in the early part of the century, lived almost entirely in the South-West. It can now be found up eastern England, into Scotland and as far north as Inverness.
An international team of scientists, led by Camille Parmesan, of the United States National Center for Ecological Analysis and Synthesis in Santa Barbara, California, found that although 65 per cent of species in Europe had moved north in the past century, only 3 per cent had moved farther south.
The often-rapid response of butterflies to a warming climate is evidently helped by their ability to fly distances during the summer breeding season, the scientists report in the journal Nature.
"Given the relatively slight warming in this century, compared with predicted increases of 2.1C to 4.6C for the next century, our data indicate that future climate warming could become a major force in shifting species' distributions," says the research team. "But it remains to be seen how many species will be able to extend their northern range margins substantially across the highly fragmented landscapes of northern Europe. This could prove difficult for all but the most efficient colonisers."
Dr Chris Thomas, a team member and an ecologist at the University of Leeds, said that some rarer, more sedentary species might not survive the growing pressure to migrate.
He added: "This study on butterflies must suggest that vast numbers of species are on the move at least in part due to the human influence on climate."
Brian Huntley, professor of ecology at Durham University, said the study showed that breeding ranges were being stretched. This was a particular problem for mountain species and those that normally live at the northernmost fringes of Europe. He explained: "Ultimately the species of higher altitudes and latitudes will have nowhere to go if the warming continues."