Climate change is helping the brown argus butterfly expand its range, bolstering a species that was on the wane a few decades ago.
Over the past 20 years, the insect has staked out new territory in Britain, moving 50 miles farther north. Researchers at the University of York say rising summer temperatures have made the little butterfly's journey possible.
As the climate in the United Kingdom warmed and the butterfly inched northward, its caterpillars discovered a new food source: plentiful blooms of wild geraniums.
Some species will be winners and others will lose as the climate changes. The brown argus butterfly has doubled its habitat in the United Kingdom, while its larvae have found new flowers to nibble on. Photo by Louise Mair.
That has helped reverse the fortunes of the once-scarce brown argus, whose population was declining as late as the 1980s. The butterfly has now spread into much of southern Britain, no longer limited by the availability of its traditional food source, the rock rose.
The University of York scientists traced the brown argus' northern march using four decades of observations collected by volunteer butterfly spotters.
The rapid pace of the change is unusual, the researchers reported yesterday in the journal Science, especially for a butterfly long considered to be specialized and sedentary.
"This previously scarce species has surprised everyone by moving its range at over twice the average rate" of species worldwide, said the study's lead author, University of York graduate student Rachel Pateman, in a statement.
Scientists have long warned that climate change is likely to scramble ecosystems, creating winners and losers as different species respond to environmental changes like warming at different rates.
In this case, that appears to benefit the brown argus -- scientific name Aricia agestis. But many other species may not be so lucky.
"Species do not respond to climate change in isolation," Pateman said. "Climate change affects how species interact with one another. In the case of the brown argus butterfly, changes in interactions with its food plants have helped it to respond to climate change very rapidly. However, changes to interactions may hinder other species, potentially putting them at risk of extinction."
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