Should Species be Relocated to Prevent Extinction?

WASHINGTON (ISNS) -- As temperatures rise in the mountains of the Western United States, the chinchilla-like American pika is paradoxically freezing to death. A warmer climate means  less snow during the winter months, which burrowing animals depend on to for insulation against life-threatening cold snaps. Over a third of the pika populations living in the Great Basin have disappeared, and the U.S. Fish and Wildlife Service is reviewing the latest data to decide whether the animal should be listed as an endangered species.

The population of the pika -- as well as the density of other species -- is thought to be in decline due to climate change, according to discussions that took place last week at a meeting of the Ecological Society of America in Albuquerque, N.M. The scientists considered the pros and cons of moving groups of these creatures to more hospitable locations -- including ecosystem's outside a species normal inhabited areas. The idea -- called "assisted migration" or "managed relocation" -- is a controversial strategy that some consider hubris, and others deem an unfortunate necessity to ensure some species' chances of survival

"Moving things around is not that new," said group member Jessica Hellmann, assistant professor of biological sciences at the University of Notre Dame in South Bend, Ind. "The new reason to talk about it is the climate change angle."
 
"The timescale of climate change and the amount of climate change we're talking about means that we're going to have to move quickly from science to practice," she added.

An estimated million species worldwide could face potential extinction as a result of climate changes predicted to occur in the next 50 years, according to a 2004 report in the scientific journal Nature. "That's being ultra-cautious, taking our lowest estimate," said ecologist Alison Cameron, who helped author the report and is now at the Max Planck Institute of Ornithology in Munich.

In Madagascar, for example, dozens of species of reptiles and amphibians have been spotted moving to higher altitudes in search of cooler climes. The Quino checkerspot butterfly, once the most populous butterfly in Southern California, is now listed as an endangered species thanks to a combination of climate change, wildfire spread, and urban development. And the disappearance of the golden toad, which has not been seen in the forests of Costa Rica since 1989, has been linked to a drier climate.

When a species is threatened -- by an invasive species, for example, or habitat destruction --  conservation biologists are faced with a choice. They can try to preserve its habitat, breed it in captivity, preserve tissue samples, or attempt a managed relocation to a new habitat.

Traditionally, relocated species are moved to a region that they are known to have once inhabited. In 1994, for example, the U.S. Fish and Wildlife service transported 150 gray wolves from Canada to Yellowstone National Park to establish a new population. This led to the gray wolf's removal from the endangered species list in 1998.

But even with historical data in hand, moving a species is not an easy task, said Daniel Ashe, science adviser to the director of the U.S. Fish and Wildlife Service. "It's politically complicated, socially complicated, scientifically complicated, ethically complicated," he said.

Assisted migration adds an extra layer of complexity by looking forward, using ecological data and computer models to predict new areas that will be suitable for a particular species decades from now.

"Right now our ability to study that is very rudimentary," said group member Dov Sax, an ecologist at Brown University in Providence, RI. "We can say here's where a species lives now, here's where we expect that climate to be in the future … but there are lots of other things besides climate that are important. There's a whole slew of basic science that needs to be done before we can fully understand whether to a species would be just fine where it is or that it needs to be moved, " said Sax.

Still, the first attempts at managed relocation are already being made with plants and invertebrates, which are easier to move and governed by fewer regulations than animals.

In a small-scale experiment published this year, for example, biologist Stephen Willis moved two species of butterfly from southern England to regions in the north identified as suitable habitats by a climate model. A decade later, the new insect colonies are flourishing and growing at the same rate as their cousins in the south.

The most recognized assisted migration project to date may be the Torreya Guardians. This network of conservationists, which includes botanists and ecologists, is trying to save the Torreya taxifolia, an endangered evergreen that grows to 60 feet in height. The group has transplanted dozens of trees from the Florida panhandle, where it is rapidly disappearing, to sites in North Carolina that are thought to have a suitable climate.

"Plants are so much easier to replicate than pandas," said Rob Nicholson of the Botanic Garden at Smith College in Northampton, MA. "Torreya roots easily … and you could start knocking them out by the tens of thousands if you wanted to."

The U.S. Fish and Wildlife Service has yet to actively consider relocating a species because of global warming, said Ashe, but is "starting to think about that concept of movement as we think about changing climate."

One of the biggest worries in assisted migration, though, is not whether a species will be successful in its new environment, but whether it will be too successful and become an invasive species -- such as kudzu, the gypsy moth, or the giant nutria that have overrun parts of Louisiana.

"We're recognizing right from the get-go that our history of moving plants and animals around the landscape is a checkered one," said Ashe.

Some scientists believe that our ability to predict whether an introduced species will turn invasive has been improved by lessons of the past. "Thanks to the art of species distribution modeling, we're able to predict pretty well where a species will become an invasive species," said Cameron.

"You probably wouldn't want to do an assisted migration if you knew something was a voracious predator, for example," said Sax.

Other studies have shown that isolated environments -- like lakes or oceanic islands -- may be more vulnerable to invasive species. The distance that an animal is relocated may also play a part; relocating a species from one continent to another appears to be a riskier move than relocating between states.

Mark Schwartz, group member and ecologist at the University of California, Davis is less than optimistic. He argues that the uncertainties in the models are still too large to predict whether a species will become invasive. "If we start moving species around, we're likely to create as many problems as we solve," he said.

In 1963, for example, the Newfoundland Wildlife Service introduced red squirrels into forest that had been squirrel-free for 9,000 years. They were meant to be food for a local wolverine-like predator on the decline. Instead, the squirrels devoured the cones of the local spruce trees, driving the local crossbill birds who fed on these seeds extinct by 1988.

"Behind habitat loss, invasive species are listed as the second most damaging thing to our biodiversity," said Schwartz. "We're likely to create new invasive species."

To help move the debate forward, the working group recently published its recommendations for how to deal with the uncertainties and risks of assisted migration. They suggest that policy-makers assess and balance the benefits for the species being moved, the potential impact on the new ecosystem, the feasibility of the move, and the social acceptability of the decision. 

"The one thing we all agree on is that there is a policy void that needs to be filled," said Schwartz. "We're getting the ball rolling so that five years from now, 10 years from now, when people are really starting to think about moving species around, we're in a better position than we are today."

Inside Science News Service is supported by the American Institute of Physics.