The researchers looked at 35 species of butterflies and found that 22 had either died out at the southern end of their ranges, or spread beyond their former northern boundary, or both. Of the rest, most had not moved, while two species had extended south. The butterflies' ranges had moved 20 to 150 miles. Europe is 1.4 degrees warmer than it was 100 years ago, and the average temperatures experienced by butterflies then can now be found 75 miles farther north. Temperatures are expected to increase an additional 4 to 8 degrees in the next century because of the greenhouse effect.
Butterfly enthusiasts in Sweden, Finland and Estonia can now find certain butterflies farther north.
In some cases, they are seeing species new to the country. For example, Heodes Tityrus, the sooty copper butterfly, has disappeared from its southern sites in Spain but established itself in Estonia. The researchers studied butterflies because they are known to be sensitive to the climate and have been followed by naturalists for a long time. Migratory butterflies and those strongly affected by other changes in the environment, like pollution and farming, were excluded from the study. Camille Parmesan, an ecologist at the University of Texas, organized the project, which was aimed at detecting large-scale shifts in response to climate change.