20 Apr 2009: Report

As Climate Warms, Species
May Need to Migrate or Perish

With global warming pushing some animals and plants to the brink of extinction, conservation biologists are now saying that the only way to save some species may be to move them.

by carl zimmer

In the gentle hills outside York, England, a controversial experiment is quietly unfolding. It began in the summer of 2000 when Steven Willis, a biologist at the University of Durham, and his colleagues drove to a wildlife preserve called Wingate Quarry. In the back of their car was a cage full of butterflies called Marbled Whites. Willis and his colleagues removed the cage from the car, opened it, and let 500 butterflies flutter away across the scrubby meadows.

Marbled Whites are common in Europe and southern England, but in 2000 the northern edge of their range was 65 kilometers south of Wingate Quarry. Yet Willis and his colleagues suspected that they might do well there. Thanks to global warming, Wingate Quarry might now be mild enough for the butterflies to survive.

Since releasing the butterflies, Willis and his students have returned to
The Wildlife Trusts
The relocation of 500 Marbled White butterflies in York, England offers the first evidence of how managed relocation works.
Wingate Quarry each year. They have walked a transect, counting the Marbled Whites they saw along the way, and have searched the area around the release to see how far they had dispersed. In February, they finally announced the results of their surveys in the journal Conservation Letters. The population of Marbled Whites of Wingate Quarry is steadily growing and slowly increasing its range. “They’re certainly holding their own,” says Willis.

Willis and his colleagues did not move the butterflies purely out of scientific curiosity. A number of studies indicate that global warming will rob many species of their current habitat, pushing them towards extinction. Some conservation biologists argue that the only way to save some species may be to move them to new ranges that they can’t get to themselves.

This strategy — which goes by various names including assisted migration, assisted colonization, and, most recently, managed relocation — only emerged in the scientific literature in 2007. Over the past two years it has attracted widespread interest. A number of scientists are now investigating how they can pick new homes for endangered species and move them safely. Willis’s new paper now provides the first proof of principle that conservation biologists can select new places where species will thrive. Congress may even include funding for research on managed relocation in upcoming climate change legislation.

But managed relocation is also now the subject of a fierce backlash from some leading conservation biologists. In a newly published essay, Daniel Simberloff of the University of Kentucky and Anthony Ricciardi of McGill University call it a game of “ecological roulette.”

By the 1990s it became clear that a number of animal and plant species were on the move because of rising global temperatures. Species in the northern hemisphere were expanding their ranges north; Southern Hemisphere species were moving the other way. Animals and plants that lived on mountainsides were spreading up the slopes. The weight of the evidence pointed towards global warming as the cause of these shifts. A warmer climate opened up new territory that some species could colonize.

While global warming might make new territories suitable for some species, it might also put other territories off limits. The hamster-like
Even if species have clear pathways to new habitat, they may not have time to keep up with the speed of climate change.
American pika, for example, lives on mountainsides and ridges in the western United States. Pikas typically lived at an elevation of 5,700 feet, but in recent decades they’ve moved uphill more than an additional 2,000 feet. There’s only so much further the Pikas can go before they run out of mountain. As a result, the Center for Biological Diversity is petitioning the U.S. Fish and Wildlife to designate the pika as an endangered species due to climate change.

Animals that live in low-lying forests may have an easier time finding a suitable climate, but they may be hobbled for different reasons. The Quino checkerspot butterfly, for example, is an endangered species that lives in southern California and Baja. It appears to have lost some of its southern range to climate change, but it can’t shift north because it can’t survive in the urbanized landscape of San Diego.

“If you are going to migrate from southern California to northern California, you’ve got to get past Los Angeles, and then you’ve got to get past San Francisco,” says Dov Sax of Brown University. “If you can’t, you’re done for.”

Even if species have clear pathways, they may not have enough time to keep up with the speed of climate change. As they creep toward suitable climates, the warmer end of their range may become uninhabitable. As a result, they will become trapped in smaller areas. In 2001, Willis was one of 15 researchers who surveyed 46 species of butterflies in Great Britain and found that three-quarters of them had declined over the previous 30 years — a result consistent with a loss of range due to a warming climate.

Smaller ranges may put some species at greater risk of extinction. While scientists can’t make precise predictions about global warming’s effects on biodiversity, their rough estimates are chilling. In 2004, 19 researchers published a paper in Nature in which they concluded that if mid-range projections of global warming prove right, climate change would shrink the ranges of 15 to 37 percent of all species so drastically that they would be “committed to extinction.”

A conventional strategy for conserving species — such as setting up a preserve where they live now — may not work against global warming. Trying to save the American pika by protecting mountaintops may be futile if the entire mountain gets too warm for them. So conservation biologists began to wonder if they might have to ship species to new places.

They’d done it before. To bring wolves back to Yellowstone, for example, wildlife managers had imported animals from Canada. But in that case and others like it, animals and plants were returned back where they had once been. Managed relocation would require conservation biologists to move species to places where they might never have dwelled, and that’s never been done before.

Jason McLachlan and Jessica Hellmann of Notre Dame University and Mark Schwartz of the University of California at Davis first broached the possibility in the journal Conservation Biology in 2007. They did not endorse managed relocation, but simply argued that conservation biologists should openly discuss the benefits and risks seriously before anyone started to move species around. In 2008, Hellmann, McLachlan, Schwartz, and Sax established a 30-person Managed Relocation Working Group that is working on a detailed analysis of when and how to resort to the strategy.

Managed relocation has also earned some high-profile endorsements over the past year. In July 2008, a group of leading conservation biologists
Until now, no one had any hard data on how managed relocation might turn out. That has changed.
published a piece in Science in which they argued that there might be little choice but to move some species. “The future for many species and ecosystems is so bleak that assisted colonization might be their best chance,” they wrote. Camille Parmesan, one of the co-authors and a biologist at the University of Texas, has pointed to the American pika as a candidate. The Ecological Society of Australia has endorsed managed relocation as well as a way to help species cope with climate change.

Up until now, however, all the talk about managed relocation to defend against climate change has been in the abstract. No one had any hard data on how such a move might turn out. That’s changed now that Willis and his colleagues have published their results from relocating butterflies. (In the same paper, the biologists also describe how they released 600 small skipper butterflies north of their range in 1999 and 2000, with similar success.)

“We think this is the first test,” says Willis. “And we’ve demonstrated it does have the potential to work.”

But Daniel Simberloff, an ecologist at the University of Kentucky, is not impressed. “It seems like this idea is developing into a bandwagon,” he says. “It’s a thing to do, but it doesn’t have a sound scientific foundation.”

In March, Simberloff and Anthony Ricciardi of McGill University in Montreal published a fierce attack on managed relocation in the journal Trends in Ecology and Evolution. Ricciardi and Simberloff’s concerns stem from their decades of research on biological invasions. Humans shuttle many species from their native habitat to a new home each year. Most of the introductions are accidental. A species may hitchhike across an ocean in the ballast water of a ship. Snakes sneak up the wheel wells of airplanes. People sometimes buy pets smuggled in from other countries and then abandon them. On the other hand, some introductions are intentional. Rabbits were brought to Australia by a bored rancher who wanted something to shoot.

Most of the alien species introduced to new places die off. Some establish small populations that don’t disturb the native ecosystem. And others wreak havoc, driving native populations towards extinction.

Invasion biology is a busy scientific discipline (Simberloff is editor-in-chief of a journal, Biological Invasions, dedicated to the topic). But it’s still too young, according to Simberloff and Ricciardi, to predict what will happen to a particular species introduced to a particular place. “I’m skeptical that we’ll ever be really good at it,” says Simberloff. “There are always going to be mistakes.”

Even carefully planned introductions that seem to pose no risk sometimes go awry. Wildlife managers introduced a North American freshwater shrimp into Flathead Lake in Montana to feed kokanee salmon (that were themselves introduced for fishing). The nocturnal shrimp avoided the diurnal salmon and began gobbling up zooplankton the salmon were eating. The salmon population crashed, and so did the eagle population that depended on it.

It may be hard to imagine an endangered species turning into an ecological monster. Yet a number of animals and plants have undergone exactly this makeover. The Australian Paperbark Tree is endangered in its native Australia, thanks to logging on private land. Around 1900 the tree was introduced into southern Florida, where it has spread aggressively, shutting out native trees from its dense stands and frequently catching ablaze.

Simberloff says he doesn’t have any good solutions to offer in the place of managed relocation. “That doesn’t mean that the best thing to do is try something that either might not work or might have unintended consequences that are even worse,” he warns.

Hellmann thinks that Simberloff and Ricciardi raise some important points, and she herself doesn’t think managed relocation will ever be able to help more than a small fraction of the species that will be threatened by climate change. But she believes that Simberloff and Ricciardi are drawing the wrong conclusions from the situation.

“Is the alternative just to forsake a species?” she asks. “I just don’t want to sit back and say, ‘Oh the world is going to hell.’”

POSTED ON 20 Apr 2009 IN Biodiversity Biodiversity Climate Policy & Politics Central & South America North America 


I cannot believe your arrogance! What did the world do without you millions of years ago? Maybe you could have saved the dinosaurs. Relocate a T-Rex to your backyard.
Posted by jeremiah on 21 Apr 2009

Butterflies are hardly going to have much of a problem extending their range by 30 miles to the north.

I thought most research found that animals were extending their ranges north and further up hills, but keeping their southern ranges as well — in a word, expanding their living area. Warmth is much better for life than cold.

But that doesn't seem to be the right political message, does it...?
Posted by T Massingham on 21 Apr 2009

It is not the case that the warmer ranges are staying put. The ranges are contracting from warmer zones and expanding on the cooler side. This is clear evidence that climate change is moving the habitats of species. Studies of mountain species are the most obvious evidence of this.

We are facing a mass extinction event. I am inclined to think that if we move too many species, we will lose more. Moving new species into existing ecosystems that look like they will survive well under warming should be avoided as they may be seriously damaged by such movements.

The marbled butterfly may be doing OK in the Quarry, but what species have they displaced?
Posted by Ricki (Australia) on 21 Apr 2009

Who's monitoring the scientists on this? Who makes sure the "cure" doesn't create problems worse than the ailment? This needs to be approached very cautiously, if it all.
Posted by D Albert on 21 Apr 2009

This is a very important piece of the puzzle of what is happening with global warming, whether the causes are anthropomorphic or not. Ecological systems include all types of plants and animals that are interdependent. If some are relatively mobile and can move quickly to stay in appropriate climatic conditions, that ability to move may still be for naught if the less mobile species on which they co-depend cannot move with them. Rapid climate change will result in widespread ecological system breakdowns until new ecosystems can evolve into relatively stable systems. By then mankind may also be extinct, or at least decimated.

Maybe Jeremiah should reconsider his comment given that food crops also need to migrate to stay in appropriate climates to be productive.
Posted by Henry on 22 Apr 2009

Dr Simberloff et al are comparing apples with oranges. Transcontinental species movements have little bearing on within continental movements. Even if the worst IPC projections were to happen we might be looking at range movements in the order of 1000Km North and South of their range. Most species will initially suffer as their sourthernmost range disappear whilst they spread north more slowly. The problem might be mountain, insular and lake species which have nowhere to go. In these cases we might have to consider translocating entire ecosystems, no just single species without their host plants, predators or parasites. Even then it would happen within their biogeographical areas and the possibility of invasion will be minimal at best. Not to mention that much of biodiversity is contained in these areas, so we would saving many more species than those from plains and rivers.

In any case the loss of butterflies in the UK and climate change is hopeful at best. Many of the lost species span the entire continent but are restricted to Southern England, where sprawl and agriculture have finished off much of the habitat on which these species depend.
Posted by Jason Mate on 22 Apr 2009

"Studies indicate that global warming will rob many species of their current habitat, pushing them towards extinction."

Perhaps they will be pushed towards adaptation. Ever hear of "unintended consequences"? How about "it's not nice to fool with mother nature." What arrogance!
Posted by UncleG on 22 Apr 2009

UncleG, we already have fooled with life support systems.

Standing by and watching the web unravel claiming that intervening would be arrogant is, I'm afraid, hypocritical. Although one may find solace in the ages old "the end does not justify the means" we have to be more pragmatic than this.

Translocation will not be necessary, warranted or even advisable in many cases, but I for many others it is either this or total loss. I am not sure what unintended consequences you may have in mind but it can't be worst than the loss of an entire ecosystem.

Posted by Jason Mate on 22 Apr 2009

What makes this most recent warming the cause of so much death when plants and wildlife flourished during warm periods in the past?

Cold is the killer.
Posted by Ray on 23 Apr 2009

The Endangered Species Act is one of our most important tools for protecting plants and animals imperiled by the climate crisis. The Endangered Species Act has a proven track record of success, having prevented the extinction of over 98 percent of species listed to date, and will work in a complimentary fashion with the beneficial requirements of other existing laws, such as the Clean Air Act and National Environmental Policy Act.

Yet one of President Bush’s last acts in office was to issue regulations weakening the protections that the polar bear, endangered by global warming, and other species (like the American pika, once listed) will receive. On the campaign trail, President Obama pledged to revoke Bush’s Endangered Species Act regulations, and Congress then granted his Interior Secretary Ken Salazar a golden opportunity to rescind the rules entirely with no more than the stroke of a pen, but this special authority extends only until May 9th.

Despite President Obama’s campaign pledge, Secretary Salazar has so far refused to say what he intends to do. Please ask him to rescind the damaging Bush Endangered Species Act rules by signing the online petition at www.savethepolarbear.org.
Posted by Kassie Siegel on 23 Apr 2009

"Yet one of President Bush’s last acts in office was to issue regulations weakening the protections that the polar bear, endangered by global warming."

The population of polar bears is at the highest known levels in history. It is not endangered and in fact Canada has increased the number which can and are hunted each year. Putting them on an "endangered" list is a dishonest and abusive way to utilize this act by saying that if the earth warmed further they might be endangered. It is absolute political nonsense when there is no danger to polar bear populations despite the untruths included in Al Gore's movie.

"In the 1950s the polar bear population up north was estimated at 5,000. Today it's 20- to 25,000, a number that has either held steady over the last 20 years or has risen slightly. In Canada, the manager of wildlife resources for the Nunavut territory of Canada has found that the population there has increased by 25 percent."


Please do not give me any quotes from the Western Hudson's Bay which is the only area in the world where polar bear population has declined slightly.

Posted by Dahun on 23 Apr 2009

If polar bears are dependent on ice for survival they are not threatened anyway. Arctic ice has increased to within 1979-2000 levels.

The Endangered Species Act is a political tool being used to curtail development with little regard for wildlife. Polar bears are thriving.
Posted by Ray on 24 Apr 2009

I do not know why we all are so scared from the extinction of some species in the future.

As an environmentalist, does everyone believe in the natural selection working in the ecosystem. Then we are within the field and are affected by these species around us and we are going to affect the species where we can make an impact. So just survive in this planet under the same rule and try not to modify nature for trying to teach this planet how to behave. If you want all the species to follow the principles of ecosytem, then homo sapien should follow the same rule. We humans should not make our own rules teaching the planet how to behave. About 99.5 percent species which came on this planet have become extinct and if we have some more becoming extinct in future, we should accept it.

This planet created the circumstances by itself, without our help to let us inhabit it. This planet is going to get rid of us and would have new species occupy our place in future.
Posted by Dr. Mahmood Anwar on 21 May 2009

Endangered species act is not an act to protect the environment, but it is an excuse to stop any legitimate project started by a developer. a dreamer, a scientist, an innovator. It is being used as an arrogant tool by the government to show its superiority with the help of not so intelligent scientists or environmentalists. All those species which we have saved so far under this law have changed their roles and are being changed by the planet under natural selection. The white spotted owl is being replaced by an other species, and the oaks which were saved under this rule from being harvested are dying due to the tree disease. The alligators number has increased so much that they are eating the joggers in Florida. The bald eagles number has increased so much that they have started to take the roles of vultures instead of being hunters of fish from the water.
Posted by Dr. Mahmood Anwar on 21 May 2009

I think that most species will figure it out themselves.
It's amazing that butterflies migrate all that way without any obvious orientation.
Posted by Wheel Bearings on 02 Jul 2009

Friend! Perhaps everybody accepts that the rich people of the developed countries are the main culprits in the current crisis of global warming but the poor of the undeveloped countries have to suffer the most due to climate change. Other species may migrate to suitable places without the problem of passport and VISA but what about the poor human species?

Posted by Padam Pande on 19 Sep 2009

Plain and simple "nature wll always find a way" so let nature take it's course.

Posted by arlene viera on 04 Nov 2010

I am of the opinion that we are fighting the inevitable. Yes, to an extent we might be able to
rescue some species of plants and animals for a while but what of those that we cannot aid in
relocation? My idea is that Mother Nature will create a balance-some species will definitely become extinct while new ones will emerge as time goes by.

Posted by Janett McFarlane on 14 Nov 2010

Comments have been closed on this feature.
Carl Zimmer writes about science for The New York Times and a number of magazines. A 2007 winner of the National Academies of Science Communication Award, Zimmer is the author of six books, including Microcosm: E. coli and the New Science of Life. He also writes an award-winning blog about science called The Loom. In other articles for Yale Environment 360, he has written about how mass extinctions unfolded in the past and the high-tech search for a cleaner biofuel alternative.



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