Driving Mr. Lynx
As the climate changes, proponents of 'assisted migration' say it's time to help animals and plants move
ON AN OVERCAST, late-July morning, a five-car caravan of environmentalists arrived at a patch of North Carolina forest in the Smoky Mountains. Armed with shovels and 3-gallon buckets for watering, they unloaded several 2-foot specimens of Torreya taxifolia, a gangly, long-needled pine tree native to North Florida. Only several hundred Torreya pines remain in the wild, clinging to a few ravines by Florida's Apalachicola River, less than 1 percent of the stock a century ago. Most of the survivors are stunted and unable to produce seed.
The most common explanation for the tree's downfall is the repeated disease infestations that set upon it in the second half of the last century. But the people in the caravan that day have their eyes on another culprit: Florida is too hot. The team bought the baby trees from a nursery and ferried them north to a cooler home. They are trying to save the species from global warming.
This mission of the Torreya Guardians, as they are known, represents the first deliberate implementation of a radical conservation idea known as "assisted migration." As the planet warms, many plants and animals are pushing toward the poles, or to higher elevations, in search of comfortable habitat. Similar migrations have unfolded many times before in the planet's long history, but this time there is an obstacle course of human creations - sprawling cities, a skein of highways, and vast swaths of intensive monoculture instead of rich prairie ecosystems. Some species may not be able to find their way over, around, or through all of this to cooler climes, and so some scientists are entertaining the idea of giving them a hand.
A growing number of ecologists worry that conservation-as-usual won't be able to keep up with the predicted pace of climate change. To some of them, assisted migration is a more proactive tool for preserving nature's richness, and possibly the only hope for saving certain species. Others wonder whether it would amount to just the sort of meddling that infested the American South with kudzu and choked Northern wetlands with purple loosestrife. Scientific models are no match for the actual complexities of ecosystems, they argue, and humans have proven inartful at playing God. It is a debate that underlines a broader shift in ecology, as some say the field needs to move into a more activist role - away from simply protecting nature and toward reshaping it.
"The idea that we're going to set aside land and just preserve all
the stuff in it isn't tenable anymore," says Notre Dame ecologist Jessica Hellmann. "Climate change will make these systems much more dynamic, and so we'll have to think about how to meet our objectives in the face of that pressure."
Recent estimates of how quickly things could heat up are driving the debate. Last year, the world's climate scientists reported that the earth's temperature had crept up about 1 degree Fahrenheit in the previous 100 years, but projected an additional warming of 3.2 to 7.2 degrees Fahrenheit by this century's end, depending on future greenhouse gas emissions. While the expected pace and environmental consequences of climate change are debated, one 2004 estimate predicted that global warming could mean extinction for between 15 to 37 percent of the species in six of the earth's most biodiversity-rich regions.
And unlike the last time global temperatures changed this much, when the ice-age glaciers retreated about 10,000 years ago, the escape routes for many species are now blocked by sprawling cities and impregnable monocultures of corn and soybean occupying vast swaths of land, says Dov Sax, an evolutionary biologist at Brown University. Sax cites an endangered "kangaroo rat" that now lives along a narrow stretch of coast south of San Francisco.
"Imagine they need to cross that city to get to a cooler climate, how are they going to do that?" he asks. "Are they going to walk across the Golden Gate Bridge? It's just not going to happen."
While most scientists still urge extreme caution, several now believe that assisted migration will eventually be needed to save certain species, such as Joshua trees or the Spanish lynx. Meanwhile, the National Science Foundation and Boston-based Cedar Tree Foundation have sponsored a working group of biologists, lawyers, economists, and other experts to study the idea's scientific, legal, and ethical ramifications. The working group first met in Milwaukee just days after the Torreya Guardians planted their seedlings. By next fall, they hope to complete a guide on assisted migration for policy makers, an effort to get ahead of global warming - and the next group of well-intentioned citizens taking matters into their own hands.
"What we don't need is 1,000 people each playing Johnny Appleseed for their favorite species," says Steven Hamburg, the Boston-based chief scientist for the Environmental Defense Fund.
For years, conservationists have focused on preventing or undoing the human alteration of nature. They have lobbied to keep wilderness free of subdivisions, battled against clear-cutting forests, argued for tighter controls on invasive species, and pushed factory owners to install smokestack scrubbers. When more active measures were deemed necessary, such as restoring New England's coastal rivers for fish spawning or bringing gray wolves back to Yellowstone, the decisions were preceded by years of scientific analysis, phone-book thick environmental-impact statements, and stakeholder negotiations. In the same conservative spirit, most argued that countering global warming was a matter of cutting greenhouse gas emissions and increasing the size and connectivity of wildlife reserves.
Still, ecologists understand that ecosystems aren't museums in which flora and fauna can be preserved in perpetual equilibrium. When viewed on a geologic scale, even today's most "untouched" wilderness has been in constant flux, with species rising and falling as much as temperatures and sea levels.
This theme was picked up in the first public discussion of assisted migration, a pair of dueling articles published in 2004 by the environmentalist journal Wild Earth about the wisdom of moving the endangered Torreya pines north. Writing in favor was Connie Barlow, a science writer, amateur horticulturalist, and the founder of the Torreya Guardians, along with Paul Martin, a zoologist and researcher of fossilized pollen, seeds, and spores. They argued that the Torreya is not truly native to northern Florida but was pushed south, along with many species, by the last ice age and then was unable to move north again when the glaciers retreated. Thus, they concluded, moving Torreya to North Carolina would actually be a sort of homecoming for the tree.
Opposing them was Mark Schwartz, a plant ecologist at the University of California who has studied Torreya for 20 years and argued that traditional, less risky conservation measures should be given a chance to succeed.
As the Torreya Guardians proved this summer, the reality of assisted migration could be as simple as a group of concerned citizens bringing a species north in their cars. It might mean attempting to grow vast coral reefs outside their current range by placing cultured coral on specially arranged, underwater concrete blocks. It could mean capturing an endangered butterfly and taking it (and maybe the plant it feeds on) to cooler elevations.
Of course, most of these scenarios are speculative, with scientists still trying to understand the implications of shuffling ecosystems. In many cases, for instance, assisted migration would require changes to existing regulations on endangered and invasive species (see sidebar).
Ecologists have also begun to devise guidelines for when to give a plant or animal a helping hand. One of these attempts, published this summer in the journal Science, suggested a "decision framework" based on a species' risk of extinction balanced against its potential to move on its own and the risk of it wreaking havoc on its new home. All of these questions will require extensive research and public consultations with the proposed recipient communities, says Schwartz, who's now a member of the assisted migration working group. "Basically, we're trying to develop strategies for not doing stupid things."
The most obvious risk of moving wildlife to a new home is the potential to overwhelm native species, just as the Nile perch, a large, predatory fish, did to smaller, less aggressive native fish in Lake Victoria after it was introduced for commercial fishing in the 1950s.
"A lot of well-intentioned efforts have led to the introduction of exotic species and created far more problems than they solved," says Hamburg of Environmental Defense.
To evaluate these risks, conservationists are turning to scientists, such as Sax, of Brown, who specialize in the study of invasive species. Sax uses case studies of introduced plants and animals to find out what makes a particular environment "saturated" and another resilient enough to absorb newcomers without major extinctions. In this summer's Science article, the authors concluded that continent-to-continent or continent-to-island moves had historically caused the most trouble.
"This is not the scale of translocation that is being proposed here," they wrote. "We are not recommending placing rhino herds in Arizona or polar bears in Antarctica."
Still, other scientists remain wary. While a warming ecosystem can stress a species and make it more susceptible to predators and disease, so can competition from other species, human encroachment on habitat, or the loss of helpful species such as those that disseminate seed. Moving a species may not help it.
It's not known for certain that climate was a major factor in the Torreya struggles, Schwartz argues. He notes that a few Torreya have been planted in less shaded areas near the visitors center of Northern Florida's Torreya State Park. "They're looking great," he says. "They're doing just fantastic."
And then there's the fact that moving one plant or animal might involve moving others upon which it feeds or that depend on it for their own survival. The implications, says Hellmann, are that "climatically, a species might be able to live further north, but you'd have to move their food north as well." And that food, be it animal or vegetable, has its own ecosystem requirements that would need to be taken into account, and so on.
Any such operation would undoubtedly be neither easy nor cheap. Americans were willing to spend more than $24 million on endangered gray wolves between 1974 and 2008, and we shell out more than $3 million every year for the recovery of Atlantic Coast piping plovers. But how much would we be willing to spend to help the kangaroo rat hop over San Francisco?
With climate change predictions growing more dire, ecologists are confronting the possibility that the deliberative, preservation-oriented conservation measures they've long championed may not be enough to stave off mass extinctions. Serious debates have begun over what were once considered fringe ideas, such as dumping iron into the ocean to promote algal blooms that suck up carbon dioxide or even North American "rewilding" - the reintroduction of large mammals, such as cheetahs and camels, that disappeared from the continent about 13,000 years ago.
The more cautionary members of the conservation community emphasize that nothing need be done immediately at the expense of careful, science-based decision-making. Jason McLachlan, a Notre Dame ecologist, says that when it comes to global warming pressures, "for most species, we probably have decades to work this out."
The Torreya Guardians weren't willing to wait that long. Neither is Camille Parmesan, a University of Texas ecologist. In August, Parmesan made the case to the US Fish and Wildlife Service that it is time to move the endangered Quino checkerspot butterfly, whose wings are a patchwork of brown, red, and yellow. It cannot be moved north, because its range, the sage-brush habitats of Southern California, abuts the Mojave Desert. She believes it should be helped to a higher elevation.
"It's the perfect candidate," argues Parmesan. "It's a very innocuous species, a very small butterfly that doesn't really interact with other butterflies or get abundant enough to severely impact the plant populations it uses. And it's easy and cheap to move around to new places."
Barlow, meanwhile, has fielded inquiries from people interested in following the group's example for the endangered Florida yew, a dark-green needled tree with smooth, purple-brown bark. And similar talk has swirled around the iconic Joshua trees, which are disappearing from the national park that bears their name. But Barlow says that she's just out to save the Torreya and is not trying to set an example for "how to solve the world's biodiversity crises." She says scientists may still be in doubt about exactly what caused the Torreya's decline, but insists she has a personal connection to the tree and knows it doesn't belong in the heat of northern Florida.
"I kept visiting these spindly trees and thinking, nobody understands you but I do," she says. "I made a personal commitment to do whatever it took to save them."
Chris Berdik is the senior writer for Bostonia, the alumni magazine of Boston University.