downtoearth-subscribe

Butterfly effect

in what experts are calling the first direct biological consequence of global warming, a delicate species of butterflies is being driven north through California to escape rising temperatures, Santa Barbara, a researcher at the University of California has found.

Known as Edith's checkerspot butterfly, the insect is prized by collectors for the distinctive orange and black patterns on its wings which folded together are the size of a pair of postage stamps; and by ecologists because it is especially sensitive to subtle changes in climate. The butterfly is rarely noticed among the hillside snapdragons and figworts on which it feeds, but it can be found at sites from Mexico to Canada, often living and dying confined to a habitat no larger than a few hundred square yards.

Camille Parmesan, a research fellow at the university's National Center for Ecological Analysis and Synthesis surveyed 151 locations throughout western North America where the butterfly traditionally flourished. She found that rising temperatures were killing off the butterfly at the southern extremes of its range, while at the same time allowing it to expand into cooler climes to the north. Populations in Mexico were four times as likely to be extinct as those in Canada, Parmesan discovered.

She also found that in those southern areas where the butterflies persisted, the insects had shifted to higher elevations, where temperatures would be slightly cooler. "It is an excellent climate- sensory canary in a coal mine,' said Stanford University ecologist Paul Erlich.

There is broad agreement among scientists that the Earth has gotten warmer by at least one degree during the past century. But there is considerable controversy over what, if any, effect it has so far had on the flaura and fauna.

Speaking on the biological effects of climate change, John Harte, an expert at the University of California, Berkeley, said the study appears to confirm the prevailing theory of how global warming will alter wildlife. Harte, however, believes that most plants and animals rely on too many local factors, from soil microbes to air quality, to simply shift northward. "If her study is true, it really points to the validity of the conventional and, to my mind, implausible picture of how plants and animals will respond to climate change,' he said. "I think it is an exciting and thought-provoking work.'

Related Content