Saturday, May 31, 2008

BUTTERFLIES ARE IN DECLINE. . . AND WHY THAT MATTERS A LOT

NATIONAL WILDLIFE FEDERATION - Worldwide, many butterfly species have begun to falter and even disappear. In this country, the U.S. Fish and Wildlife Service has designated 23 species as endangered or threatened.

Butterflies play a key role in plant reproduction, transporting pollen from flower to flower. They provide food for birds and other insects. "People may say, ‘Why care about butterflies? They're just insects.' But butterflies are bellwethers for ecosystems, and we're seeing butterflies at risk across the U.S.," says Scott Hoffman Black, executive director of the Xerces Society, an Oregon-based national nonprofit that campaigns for invertebrate conservation. "Everywhere you look, there are butterflies in decline. That really tells us something is wrong."

Butterflies suffer from the same ills that plague all wildlife these days: habitat loss, pollution, invasive species and global warming. But experts say the insects also face unique hurdles. Their dizzyingly complicated life cycles may take one or two years to complete. They spend long periods as vulnerable larvae and pupae. And they form complex interdependent relationships with entire suites of other animals and plants.

In addition, many butterflies have extremely exact needs that may vary depending on life stage. In California, home to 15 of the federally protected species, larvae of the endangered San Bruno elfin, for example, prefer the leaves of sedum, a succulent. Later larval stages feed on the plant's flowers, while adults are believed to sip nectar from manzanita, huckleberry and other plants. The endangered Smith's blue, native to sand dunes of California's central coast, has mouthparts that exactly match the depth of buckwheat flowers. "Since their life cycles can be so complex, it's not enough to just set aside land or to save one host plant," explains John Shuey, chair of the conservation committee of The Lepidopterists' Society and director of conservation science for The Nature Conservancy's Indiana office.

Further complicating butterfly conservation, the biological details of their lives often remain murky. In many cases, scientists do not even know what a species' caterpillar looks like or what the adult eats. Take Southern California's Laguna Mountains skipper: When scientists gathered at a recent conference devoted to the species, they realized they still did not know which nectar plants it uses for food or whether it produces one or two broods a year.

Even intact habitats can be risky places for butterflies. Since the insects spend long periods as soft, slow-moving caterpillars, or as immobile pupae busy metamorphosing into butterflies, activities such as "hiking and horseback riding, even crews removing invasive species, can wipe out an endangered colony," says Hoffman Black.

Global warming also threatens to wreak havoc on butterflies. In North America, butterfly experts report that some cool-loving species seem to be moving to higher elevations as their native habitats get too hot. "We're clearly seeing climatic effects where species are moving upslope," says Shapiro. A 2005 study in Spain showed that 16 butterflies have shifted their ranges upward 700 feet over the last 30 years.

A handful of conservation biologists are floating the idea of "assisted migration"-taking butterflies from places where they are threatened and moving them to more congenial locales. The critically endangered bay checkerspot, for example, could be whisked from its native San Francisco Bay Area-becoming too developed and too warm-north to a cooler, more rural place. But the issues are complex: Do you just move the butterfly? Or do you have to move its host plant and other elements of its habitat? And how do you know if a butterfly will integrate smoothly into its new habitat without disturbing the natives?