[Pollinator] Assisted Species Migration

[Ladadams at aol.com]

http://www.nytimes.com/2007/01/23/science/23migrate.html?ref=science

January 23, 2007
A Radical Step to Preserve a Species: Assisted Migration

By CARL ZIMMER

The Bay checkerspot butterfly’s story is all too familiar. It was once a 
common sight in the San Francisco Bay area, but development and invasive plants 
have wiped out much of its grassland habitat.
Conservationists have tried to save the butterfly by saving the remaining 
patches where it survives. But thanks to global warming, that may not be good 
enough.
Climate scientists expect that the planet will become warmer in the next 
century if humans continue to produce greenhouse gases like carbon dioxide. The 
California Climate Change Center projects the state’s average temperature will 
rise 2.6 to 10.8 degrees Fahrenheit. Warming is also expected to cause bigger 
swings in rainfall.
Studies on the Bay checkerspot butterfly suggest that this climate change 
will push the insect to extinction. The plants it depends on for food will shift 
their growing seasons, so that when the butterfly eggs hatch, the caterpillars 
have little to eat. Many other species may face a similar threat, and 
conservation biologists are beginning to confront the question of how to respond. The 
solution they prefer would be to halt global warming. But they know they may 
need to prepare for the worst.
One of the most radical strategies they are considering is known as assisted 
migration. Biologists would pick a species up and move it hundreds of miles to 
a cooler place.
Assisted migration triggers strong, mixed feelings from conservation 
biologists. They recognize that such a procedure would be plagued by uncertainties and 
risk. And yet it may be the only way to save some of the world’s biodiversity.
“Some days I think this is absolutely, positively something that has to be 
done,” said Dr. Jessica Hellmann of the University of Notre Dame. “And other 
days I think it’s a terrible idea.”
Conservation biologists are talking seriously about assisted migration 
because the effects of climate change are already becoming clear. The average 
temperature of the planet is 1.6 degrees Fahrenheit higher than it was in 1880. Dr. 
Camille Parmesan, a biologist at the University of Texas, reviewed hundreds of 
studies on the ecological effects of climate change this month in the journal 
Annual Review of Ecology, Evolution, and Systematics. Many plant species are 
now budding earlier in the spring. Animals migrate earlier as well. And the 
ranges of many species are shifting to higher latitudes, as they track the 
climate that suits them best.
This is hardly the first time that species have moved in response to climate 
change. For over two million years, the planet has swung between ice ages and 
warm periods, causing some species to shift their ranges hundreds of miles. 
But the current bout of warming may be different. The earth was already 
relatively warm when it began. “These species haven’t seen an earth as warm as this 
one’s going to be in a long, long time,” said Dr. Mark Schwartz, a 
conservation biologist at the University of California, Davis.
It’s also going to be more difficult for some species to move, Dr. Schwartz 
added. When the planet warmed at the end of past ice ages, retreating glaciers 
left behind empty landscapes. Today’s species will face an obstacle course 
made of cities, farms and other human settlements.
Animals and plants will also have to move quickly. If a species cannot keep 
up with the shifting climate, its range will shrink. Species that are already 
limited to small ranges may not be able to survive the loss.
In 2004, an international team of scientists estimated that 15 percent to 37 
percent of species would become extinct by 2050 because of global warming. “We 
need to limit climate change or we wind up with a lot of species in trouble, 
possibly extinct,” said Dr. Lee Hannah, a co-author of the paper and chief 
climate change biologist at the Center for Applied Biodiversity Science at 
Conservation International.
Some scientists have questioned that study’s methods. Dr. Schwartz calls it 
an overestimate. Nevertheless, Dr. Schwartz said that more conservative 
estimates would still represent “a serious extinction.”
Many conservation biologists believe that conventional strategies may help 
combat extinctions from global warming. Bigger preserves, and corridors 
connecting them, could give species more room to move.
Conservation biologists have also been talking informally about assisted 
migration. The idea builds on past efforts to save endangered species by moving 
them to parts of their former ranges. The gray wolf, for example, has been 
translocated from Canada to parts of the western United States with great success.
When Dr. Jason McLachlan, a Notre Dame biologist, gives talks on global 
warming and extinction, “someone will say, ‘It’s not a problem, since we can just 
FedEx them to anywhere they need to go,’ ” he said.
No government or conservation group has yet begun an assisted migration for 
global warming. But discussions have started. “We’re thinking about these 
issues,” said Dr. Patrick Gonzalez, a climate scientist at the Nature Conservancy.
The conservancy is exploring many different ways to combat extinctions from 
global warming, and Dr. Gonzalez says that assisted migration “could certainly 
be one of the options.” For now, the conservancy has no official policy on 
assisted migration.
As Dr. McLachlan began hearing about assisted migration more often, he became 
concerned that conservation biologists were not weighing it scientifically. 
He joined with Dr. Schwartz and Dr. Hellmann to lay out the terms of the debate 
in a paper to be published in the journal Conservation Biology.
Dr. McLachlan and his colleagues argue that assisted migration may indeed 
turn out to be the only way to save some species. But biologists need to answer 
many questions before they can do it safely and effectively.
The first question would be which species to move. If tens of thousands are 
facing extinction, it will probably be impossible to save them all. 
Conservation biologists will have to make the painful decision about which species to try 
to save. Some species threatened by climate change, including polar bears and 
other animals adapted to very cold climates, may have nowhere to go.
The next challenge will be to decide where to take those species. 
Conservation biologists will have to identify regions where species can survive in a 
warmer climate. But to make that prediction, scientists need to know how climate 
controls the range of species today. In many countries, including the United 
States, that information is lacking.
“We don’t even know where species are now,” Dr. McLachlan said.
Simply moving a species is no guarantee it will be saved, of course. Many 
species depend intimately on other species for their survival. If conservation 
biologists move the Bay checkerspot butterfly hundreds of miles north to 
Washington, for example, it may not be able to feed on the plants there. Conservation 
biologists may have to move entire networks of species, and it may be hard to 
know where to draw the line.
Assisted migration is plagued not only with uncertain prospects of success, 
but potential risks as well. A transplanted species would, in essence, be an 
invasive one. And it might thrive so well that it would start to harm other 
species. Invasive species are among the biggest threats to biodiversity in some 
parts of the world. Many were accidentally introduced but some were 
intentionally moved with great confidence that they would do no harm. Cane toads were 
introduced in Australia to destroy pests on sugar plantations, and they proceeded 
to wipe out much of the continent’s wildlife.
“If you’re trying to protect a community of species, you’re not going to 
want someone to introduce some tree from Florida,” Dr. Hellmann said. “But if you
’re someone watching that tree go extinct, you’re going to want to do it.”
Dr. Hellmann and her colleagues do not endorse or condemn assisted migration 
in their new paper. Instead, they call for other conservation biologists to 
join in a debate. They hope to organize a meeting this summer to have experts 
share their ideas.
“There really needs to be a clear conversation about this, so that we can lay 
all the chips on the table,” Dr. Schwartz said.
Other experts on global warming and extinctions praised the new paper for 
framing the assisted migration debate. “It’s certainly on everybody’s mind, and 
people are discussing it quite a lot,” Dr. Hannah said. “This paper’s a 
breakthrough in that sense.”
Dr. Hannah for one is leery of moving species around. “I’m not a huge fan of 
assisted migration, but there’s no question we’ll have to get into it to 
some degree,” he said. “We want to see it as a measure of last resort, and get 
into it as little as possible.”
It is possible that conservation biologists may reject assisted migration in 
favor of other strategies, Dr. McLachlan said. But the hard questions it 
raises will not go away. As species shift their ranges, some of them will push into 
preserves that are refuges for endangered species.
“Even if we don’t move anything, they’re going to be moving,” Dr. McLachlan 
said. “Do we eradicate them? All of these issues are still relevant.”



Laurie Davies Adams
Executive Director
Coevolution Institute
423 Washington St. 5th
San Francisco, CA 94111
415 362 1137
LDA at coevolution.org
http://www.coevolution.org/
http://www.pollinator.org/
http://www.nappc.org/

Bee Ready for National Pollinator Week:  June 24-30, 2007.  Contact us 
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