PRAGUE: Butterflies fluttering in central Europe's mountains may be giving a silent warning that the planet is heating up.

That's the conclusion of Czech scientists, who've discovered that at least 12 and as many as 15 butterfly species have since 1950 migrated to higher - and cooler - elevations in the region's mountains.

A research team led by entomologist Martin Konvicka of the Czech Academy of Sciences cited global climate change as "the most likely cause" for the dramatic "uphill shifts" of species such as the Black Hairstreak, White Admiral and False Grayling.

The migration patterns observed over the past 50 years have affected a wide range of butterflies, many of which are rare or endangered in Europe.

British scientists in 2002 found a similar link between global warming and butterfly migration in that country. But the Czech study is the first to describe the phenomenon on the European continent.

Since the Czech Republic's mountains are "situated near the geographical centre of Europe, the patterns detectable there may well represent the continent as a whole", the Czech study concluded.

Konvicka's team looked at native, non-migrating butterflies and conducted the study in a way that attempted to rule out farming, urban sprawl or other types of habitat loss as reasons for the elevation change.

They concluded that the evidence gathered "supports the notion that the shifts (in habitat altitude) were indeed caused by a warming climate".

The researchers found that each of the 15 species examined has gradually moved uphill over the years, with the change in habitat altitude averaging 90 metres above sea level.

The species making the greatest change, the tiny False Heath Fritillary, now makes its home at an elevation 148 metres higher than its previous habitat.

"The shifts were observed on a large scale, in map cells of 11 kilometres by 10 kilometres," Konvicka said. "They reflect pervasive underlaying patterns rather than short- term fluctuations, so even if there are yearly jumps and retractions, the pattern working on a scale of decades is quite clear."

In their study, Konvicka and four colleagues from the University of South Bohemia limited the investigation to butterflies and habitats. They did not discuss reasons for global warming or the implications for humans.

But the researcher voiced fears that the Earth's changing climate could drive some butterfly species to extinction, including species that environmental regulators in the European Union have carefully tried to protect through land conservation programmes.

Konvicka said he is particularly concerned about the future of the Large Copper, which is now extinct in Britain and threatened in Western Europe. This butterfly has migrated 56 metres higher in the Czech mountains in the past few years, the study found.

He's also worried about the effects of climate change on species that historically live around the tops of European mountains, such as the alpine dwelling Mountain Ringlet.

To counteract the threat, Konvicka said more could be done to protect habitats and land "stepping stones" such as railroad corridors and abandoned mines, which climate-stressed butterflies could use in their hunts for new, cooler homes.-dpa