Why an English Butterfly Is a Rare Winner in Global Warming

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Image courtesy of Louise Mair

The brown argus butterfly is benefiting from climate change

Little is expected to benefit from climate change, with the possible exception of air-conditioning manufacturers, Popsicle makers and Canada. But scientists have found at least one species that seems to be better off in a rapidly warming world. In a study published in the current issue of Science, researchers at the University of York report that the brown argus butterfly has increased its range in England northward by about 50 miles over the past two decades. That’s not unexpected — many species have already responded to recent warming by moving — but what makes the brown argus butterfly different is that the change in range has actually benefited the species. “Many species are shifting their distributions northwards as the climate warms, but this previously scarce species has surprised everyone by moving its range at over twice the average rate,” said lead author Rachel Pateman of the University of York in a statement.

(MORE: The New Age of Extinction)

Why has the move north helped out the butterfly? In its caterpillar form, the brown argus feeds off wild geranium plants, but only in warmer summers — which is exactly what’s been happening in England and much of the world thanks to climate change. The butterflies can now move from one patch of host plants to the next, moving rapidly through the landscape, expanding their range generation after generation. Over the past 20 years, the brown argus — which was considered scarce in the 1980s — has spread northward and has flourished in much of southern England.

As co-author David Roy of the Centre for Ecology and Hydrology in the U.K. put it:

The change in diet represents a change to the interactions between species — in this case between a butterfly and the plants that its caterpillars eat — caused by climate warming. Changes to the interactions between species are often predicted to alter the rate at which species shift their distribution in response to climate change; and now we have demonstrated this in nature.

The research wouldn’t have been possible without the work of amateur lepidopterists — butterfly enthusiasts — who’ve kept track of the movements and numbers of the brown argus butterflies for years. That data enabled scientists in the study to confirm that it was indeed the warming from climate change that was causing the change in numbers and range for the brown argus, rather than any kind of mutation. Species can respond to the changes wrought by global warming — some of them, it would seem, quite successfully.

But the brown argus butterfly is likely to be the exception to climate change, not the rule. Past periods of sudden climate change in the earth’s history have led to a reduction in biodiversity and even great extinction waves. If warming keeps up at the expected rate — and we’re doing little to slow it down — far more species will suffer as they attempt to adapt than those likely to succeed, especially since climate change is only one of many other challenges wildlife will face, including habitat loss and degradation. And the big question for 7 billion-plus human beings is: Will we be able to adapt and even thrive like the brown argus, or will we fail?

MORE: Climate Change: How Adapting to Warming Could Make It Worse