BIOLOGIST Arthur Shapiro has been chasing butterflies since he was a teenager in Philadelphia. He’s netted them in exotic locales from the Alaskan Subarctic to the Andes. But Shapiro, a professor of evolution and ecology at the University of California–Davis, is also an expert on common North American butterflies, those familiar species that breed in home gardens and feed on plants at the edges and in fallow pockets of modern cities, towns and suburbs. For more than 36 years, Shapiro, whose wild graying hair and beard call to mind a frontier mountain man, has regularly walked fixed routes monitoring butterfly populations at ten sites from Suisun Bay to the Sierra Nevada. Lately, his biweekly hikes have inspired mostly questions—and worry.
“I used to be able to walk 15 minutes from my lab and find common sootywing larvae. Now I know of only one permanent colony in the whole county,” Shapiro says. “Butterflies that were once considered utterly common, including willow hairstreak, large marble and West Coast lady, are going into a tailspin, and nobody knows why.”
Other lepidopterists share Shapiro’s concern. Worldwide, many butterfly species have begun to falter and even disappear. In this country, the U.S. Fish and Wildlife Service (FWS) has designated 23 species as endangered or threatened.
Fewer colorful insects fluttering around the garden is more than an aesthetic loss. 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. “There’s a whole world of things we don’t know, things that no one has had the time or money to study yet,” says Jaret Daniels, assistant director of the McGuire Center for Lepidoptera Research at the University of Florida. “Oftentimes, we don’t have the information to make informed decisions about which species are declining.” Daniels and most other researchers point to habitat loss as the number one cause of butterfly declines—and in the United States, perhaps no habitats have been so thoroughly changed as the meadows, grasslands and sparsely wooded prairies, barrens and savanna often favored by butterflies. Since these ecosystems are so easy to turn into subdivisions, farms and industrial parks, they have all but disappeared from most of the lower 48 states. In the Midwest, for example, less than 1 percent of pre-settlement oak savanna remains; in the Northwest, it’s less than 3 percent. With space limitations that severe, it can be difficult to bring a species back from the brink, or even to convince authorities that it is an achievable goal worth the trouble. A decade ago, for instance, John Fleckenstein, a zoologist with the Washington National Heritage Program, conducted a butterfly survey in the grasslands of Puget Trough. “Grasslands have taken a hit from development here,” he says. Fleckenstein ended up capturing two island marble butterflies, a species that had not been seen since 1908. Intensive surveys of more than 200 sites between 2005 and 2007 turned up island marbles at 44 locations. Fleckenstein estimates that the number of individual butterflies is in the low 100s. “The island marble is in trouble,” says Hoffman Black of the Xerces Society, which has teamed up with the Center for Biological Diversity to wage a so far unsuccessful battle to get the species listed as endangered. “With populations this small, just a small fluctuation, a disease or a big storm, can send it spiraling.” 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. On an undulating stretch of sand dunes some 60 miles southeast of Reno, Nevada, a less benign pursuit threatens the Sand Mountain blue, a species found nowhere else on Earth. Though no subdivisions or industries sprawl over the nearly 5,000-acre Sand Mountain Recreation Area, on weekends the dunes become one of the West’s most extreme spots for off-road vehicle enthusiasts. “Off-road vehicles strip the vegetation, including Kearney buckwheat [where the blue feeds and pupates]. So not only is the host plant lost, but the butterflies are run over,” says desert ecologist Daniel Patterson, southwest director of Public Employees for Environmental Responsibility, which has sued for federal protection of the butterfly. As with legions of other creatures, 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. But what happens when there is no more upslope? That situation may soon face the Uncompahgre fritillary, a species that favors tundralike environments above 13,000 feet in Colorado’s San Juan Mountains. The butterfly flits in and out of patches of dwarf willow, a plant that depends on constant watering by year-round snowpack. Before 1995, scientists knew of only two Uncompahgre colonies. Intensive searching by the Colorado Natural Heritage Program revealed more, the last discovered in 1998. But experts now worry that increasing temperatures may cause the species’ habitat to vanish completely. Rising temperatures can also cause butterflies to get out of sync with the food plants they depend on. Along North America’s West Coast, a study led by Camille Parmesan, a biologist at the University of Texas at Austin, showed that the range of Edith’s checkerspot is contracting. According to Parmesan, who has studied the species for more than two decades, 80 percent of the populations in the southern portion of its range in Mexico have become extinct. The reason, she believes, is that warmer temperatures are causing host plants on which butterflies lay their eggs to dry up before caterpillars hatch. Fortunately, the plight of checkerspots, fritillaries and other butterflies has begun to rally a wide variety of organizations trying to save the insects. Many efforts focus on the obvious goal of restoring habitat, but some butterfly lovers are trying more radical solutions: In many states, scientists from universities, zoos and conservation groups have reared generations of butterflies in captivity so they can be reintroduced. Portland’s Oregon Zoo, for instance, has partnered with The Nature Conservancy and Seattle’s Woodland Park Zoo to raise Oregon silverspots until they pupate, then return them to their native coastal headland habitat. Once common from northern California to Washington, only 57 Oregon silverspots were tallied in 1998. Today, though still imperiled, they number in the hundreds. A handful of conservation biologists are even 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? “We’re going to have to seriously consider assisting species in moving to new habitats—humans have put up too many barriers to expect wildlife to follow changing climate on its own,” says Parmesan. “The biggest questions will be ethical, deciding which species to assist, which areas are okay to invade, and when to let nature take its course, even when that means allowing something to go extinct.” Dozens of zoos and natural history museums, meanwhile, have featured butterfly exhibits to encourage public awareness. Volunteer-based butterfly monitoring censuses like Monarch Watch and the Florida Butterfly Monitoring Network track the health of butterfly populations. In 2001, FWS, along with a coalition of universities, zoos and conservation organizations—including NWF—formed the Butterfly Conservation Initiative to promote habitat restoration, research and public education. Thanks to such efforts, at least a handful of butterflies have been saved from oblivion. In Florida, populations of the showy, black-and-yellow-streaked Schaus swallowtail already had begun to plummet by the 1970s. The pressures of mosquito spraying, overcollecting and decline of the tropical hardwood habitat where the insect lives pushed it onto the endangered list in 1984. Then, in 1992, Hurricane Andrew slammed Schaus habitat, the wild lime and torchwood forests that cover high elevation hammocks of the upper Florida Keys. When the storm surge receded, fewer than 20 of the butterflies survived in the wild. Luckily, the University of Florida’s McGuire Center had just collected 100 Schaus eggs to use in a captive-breeding program. By simulating daily spring rains with a garden hose and hand pairing butterflies, its scientists successfully reared the eggs to adults. For three years, they reintroduced the butterflies at seven sites. Though droughts and hurricanes have brought numbers down from highs of about 1,400 in 1996 and 1997 to some 200 today, scientists say the colonies seem to be self-perpetuating. To the north, Karner blue butterflies once flew over states from Minnesota to Maine, living in grassy, sandy barrens and savannas cleared periodically by natural fires. Then fire suppression and development reduced the insect’s numbers; by 1992, only six states still had Karner blues. The butterfly’s plight inspired a far-flung coalition: federal and state wildlife agencies, universities, zoos and nonprofits that have been rearing Karner blues to reintroduce to the wild. Private landowners in Michigan, Wisconsin and other states have restored habitat, as have military installations and parks. Karner blue reintroductions are now underway in northern Indiana, Ohio and New Hampshire and are being planned for Michigan. Though many populations remain small, they seem to be hanging on. “We’re working our way to recovering viable populations throughout its range,” says Cathy Carnes, the Wisconsin-based Karner blue recovery coordinator for FWS. “People recognize that by recovering Karner blues they’re doing more than saving one species, they are restoring imperiled ecosystems and a host of other species that depend on them.” Heather Millar is a Brooklyn, New York-based writer.
Posts
No comments:
Post a Comment