Some species threatened by climate change could be moved to new ecosystems, says biologist
April 5, 2010
Camille Parmesan's new, big idea in conservation biology—the "assisted colonization" of species threatened by climate change—is a product, in roughly equal parts, of cynicism, experience and hope.
Parmesan, an associate professor of integrative biology, wasn't cynical at all when she first got involved, in the mid-1990s, with the United Nations' Intergovernmental Panel on Climate Change (IPCC). An expert on the responses of butterflies to climate change, Parmesan was brought in to help assess how climate change was affecting species' ranges on a global scale.
What she found was frightening. Even though the planet hadn't yet seen much man-made warming—less than a degree Centigrade increase in global temperatures—the data was already indicating enormous changes in species' ranges. With a projected warming, over the next century, of 4-6 degrees Centigrade, the future was looking like a scary place for the wild kingdom. Although many of the affected species would be able to migrate away from, or adapt to, warmer conditions, many others, particularly species "endemic" to a particular ecosystem or geographic region, would not. They would, instead, go extinct. Depending on the rate of increase in emissions, in fact, it was estimated that 20-40 percent of the earth's species were likely to go extinct.
For Parmesan, whose work on range shifts in butterflies had first helped demonstrate the effects of climate change, the coming changes weren't just global, they were personal. Some of the species she'd been following for years—like the Quino checkerspot butterfly, which is native to California—were already in serious danger of extinction.
"One reason why I'm more radical than a lot of conservation biologists is that I work on species sensitive to climate change," she says. "I've already watched populations go extinct. A lot of people haven't seen much change within their systems. To them it's a thing that's far away, maybe 100 years from now, but I can see that it's not 100 years from now. It's right now."
Still, Parmesan was hopeful. The data seemed powerful, and the human race certainly had the means, and (just barely) the time, to change. Relatively soon, however, Parmesan began to notice that while a lot of people were talking a good game about dealing with climate change, nobody seemed to be doing very much. By 2001, when the IPCC issued its Third Assessment Report, Parmesan had grown even more cynical about the willingness of people—particularly the American people—to alter their habits in response to climate change.
"In terms of actual reduction of carbon dioxide or other greenhouse gases, what had happened?" says Parmesan, who was one of the lead authors of the Third Assessment. "Very little. At the same time, the amount of greenhouse gases being emitted just kept going up and up and up. In fact, we kept exceeding our predictions. It radicalized me."
Parmesan began to entertain the idea of rescuing certain species from climate change by moving them to new ecosystems. It was simple enough, in theory, but for years Parmesan kept the idea mostly to herself. Restoring a former habitat was one thing, but adding a species to an ecosystem which hadn't historically been its home was a notion that cut radically against the grain of conservation biology. It wouldn't go over well, in particular, with colleagues who studied invasive species, and therefore knew intimately the extraordinary damage that could be done to an ecosystem by the arrival of a non-native species.
Parmesan also held on to some residual hope that the public would begin to take the threat of warming seriously, particularly in reaction to the increase in dramatic weather events.
"I thought that the 2003 heat wave in Europe, followed by hurricanes Rita and Katrina, would change the mind of the American public," she says. "It seemed like for a few months it did, and then that consciousness just went away again."
Over the last few years, Parmesan and a small but growing contingent of fellow biologists have finally brought the assisted colonization idea out of the closet. The threat of climate change, they've concluded, is simply too great, and too novel, not to entertain radical ideas.
"In traditional conservation, conservatism is a good thing," says Parmesan. "Why be risky? But climate change is so different. It's having such a huge impact all over the globe that you've got to be willing to do something that's a little more risky. Doing nothing is risky too. There is no no-risk option."
In the summer of 2008, Parmesan and her colleagues made the case for assisted colonization in an article in Science magazine. The article, "Assisted Colonization and Rapid Climate Change," was respectful of the anticipated objections from conservationists, and guardedly optimistic about the degree to which traditional conservation measures could help ameliorate the impact of climate change. It was blunt, however, in its assessment of the most likely outcome of climate change.
"We must contemplate the possibility," they wrote, "that some regions of the Earth will experience high levels of warming (greater than four degrees Centigrade) within the next 100 years, as well as altered precipitation and ocean acidity. Under these circumstances, the future for many species and ecosystems is so bleak that assisted colonization might be their best chance."
In order to try to balance the risk of doing nothing against the risks of moving species to new habitats, Parmesan and her colleagues proposed a "decision framework" for when to move forward with assisted colonization.
If a given species, for instance, wasn't in short-term danger of steep decline or extinction, then conservation efforts should focus on preserving and restoring their natural habitat, or on creating low-impact "corridors" between a threatened habitat and other suitable habitats within the species' historic range. If a threatened species was simply too expensive or too difficult to transport, then efforts might focus on creating artificial environments—an artificial reef, for instance—in cooler, nearby regions to which the species could migrate on its own. In the worst-case scenarios, scientists might simply have to store seeds, sperm and eggs so that at some future point, when circumstances change, they could try to restore a species to existence.
If assisted colonization proved optimal, after all alternatives were explored, it would be done with the lightest possible footprint. In many cases, it could be as simple as moving a population to a mountain at a higher latitude within the same mountain range.
"We already do something like that, as butterfly biologists, when we're restoring habitats," says Parmesan. "We can take an area that's basically a trash heap, and bring in the soil, bring in the plants, bring in the butterflies, and boom, you've got a population. If the host plants of a given area are right, I can create a population with one egg cluster just by putting it in my pickup truck and driving it there."
Under no circumstances, says Parmesan, would scientists help a species colonize a new region if the risks to the new ecosystem, or to other species native to it, appeared significant.
"We're not going to move polar bears to Antarctica," says Parmesan. "They would cause the extinction of several penguin species. That's not preserving biodiversity."
Parmesan acknowledges that catastrophic scenarios need to be taken into account in assessing the risks of assisted colonization. But the most destructive invasive species, she says, are almost always ones that have traveled from one continent to another, or from one ocean to another, usually as unwanted hitchhikers on planes or boats. Assisted colonization, on the other hand, would be undertaken over much smaller distances, with much greater forethought, and between ecosystems that are much more similar.
"If you confine assisted colonization to organisms that are innocuous in their current communities, and you're not moving them far, I think you've got a very low probability of causing a problem," she says. "If it's only a few hundred miles, in fact, there's a good chance that at some point in their evolutionary history they had contact with this other community."
Not only are such risks manageable, she argues, the truth is that we're managing them already. Every time we blast a mountain to make way for a highway, or clear forest to make way for a housing development, we're shifting the ranges of native species. Sometimes we're just diminishing their ranges, but in many cases we're pushing them to migrate out into new areas. The choice we face, she believes, isn't between intervention and non-intervention, it's between intervening thoughtfully, with preserving biodiversity as the goal, and stepping back and leaving the interventions entirely in the hands of people—developers, governments, farmers—who are changing the landscape already, often without much concern for biodiversity.
"Think about the panda," says Parmesan. "Does it have to live where it lives now? Can we create bamboo forests that will be climatically suitable over the next hundred years? Well, why not? It will mean shifting land ownership and land use, but we do that all the time anyway, and for far worse reasons than saving the panda."
When Parmesan began contemplating assisted colonization, she conceived of it primarily as a rescue operation, and on a limited scale. Even under the best of circumstances, biologists won't be able to save more than a small fraction of species threatened by climate change. The big charismatic carnivores, for instance, like the polar bears and the snow leopards, are probably doomed, along with thousands of other species that aren't suitable for relocation, or that simply won't find a benefactor.
As Parmesan has thought more about assisted colonization, however, she's also begun to believe that change might be possible, on a much broader scale, if we can let go—in the right way—of the expectation that climate change is going to be stopped or slowed significantly. Keep fighting to diminish the emissions of greenhouse gases, of course, but also begin to think radically about how to use our knowledge and skill to alter the natural world for the benefit of species other than humans.
"Where we need to be going, I believe, is toward a real science of ecosystem engineering," says Parmesan. "Can we design habitats, for instance, that are viable for species that don't live together now but that we expect to see come together in a future climate? Can we create new ecosystems that do what we want them to do, whether it's preserving biodiversity or even mitigating climate change?"
Among the more majestic ideas that has, recently, emerged from Parmesan's fertile imagination is that of resurrecting the great American plains. It came to her after reading a study that found that of all the potential biofuel crops, the ones that came closest to being carbon neutral were native American prairie grasses. What if, it occurred to Parmesan, energy companies blanketed the midwestern and western United States with fields of such grass? Since prairie ecosystems need to be managed anyway—in the past, fire and large game grazing (for example, the huge bison migrations) did the trick—the harvests of the grasses would be a win-win-win scenario. They would, at one and the same, make money for the companies, help our nation decrease emissions, and foster massive, native, diverse prairie landscapes that would allow species to move around the whole American west.
"It's not that I think anyone's going to do this," says Parmesan, "but it's exciting to think that there are solutions. If people don't bother to take advantage of them, then that's on their heads."