Some people may think global warming is a myth, but butterflies seem to know better. In today's Nature, scientists report that many butterfly species have shifted their range northward by hundreds of kilometers in the past century.
Three years ago, ecologist Camille Parmesan from the National Center for Ecological Analysis and Synthesis in Santa Barbara, California, discovered that an American butterfly species, Edith's checkerspot, appeared to be shifting its North American range to higher latitudes. As the butterfly founded new colonies at its northern edge, it would disappear in the south. Parmesan turned to Europe to look at butterflies on a grander scale. "We have so much more historical data here," says co-author Brian Huntley of the University of Durham in the United Kingdom.
Teaming up with a dozen European colleagues, Parmesan worked her way through some 250 museum and amateur butterfly collections from both Northern and Southern European countries. They jotted down the dates and localities on the labels of 35 different species and made maps showing the distribution in consecutive decades. They found that during the 20th century, 11 species had stayed put, two had shifted to the south, but a whopping 22 had moved northward. The trend "came out very strongly," says Huntley.
The data suggest that Europe's modest warming over the last century--less than 1 degree centigrade--has had a substantial ecological impact. Huntley points out that butterflies can stay ahead of climate change because they can found new colonies quickly in response to regional weather changes. But snails and beetles, for instance, are not so mobile and are probably suffering extinctions, he says.
"It's a great paper," says ecologist Sarah Gilman of the University of California, Davis. She notes that the study could not have been done without the data from old-fashioned butterfly collectors, whose hobby many molecularly minded scientists consider passé. "They're hugely important for this whole question," she says.