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Environmental issues

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Crafty_Dog:
All:

Yes, I know there is a thread of the same name on the Political forum, but I'm beginning to think it belongs here.  So for the moment we will have a thread on each of the forums and see where people tend to post.

I begin with a post of another Nature Conservancy project.  (I am a basic level member of NC btw).  I like NC because of its market, win-win orientation.

Marc
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Farmers and Conservationists Form a Rare Alliance
 Kevin P. Casey for The New York Times
Shorebirds on flooded land in Skagit County, Wash., a sight that could become more common as a result of a “Farming for Wildlife” program.
 
By JESSICA KOWAL
Published: December 27, 2006
MOUNT VERNON, Wash. — The standoff here between farmers and environmentalists was familiar in the modern West.


Lisa Bellefond of the Nature Conservancy and David Hedlin, a farmer, on farmland set to become wetlands.
With salmon and wildlife dwindling in the Skagit River Delta, some environmentalists had argued since the 1980s that local farms should be turned back into wetlands. Farmers here feared that preachy outsiders would strip them of their land and heritage.

This year, though, the standoff ended — at least for three longtime farmers in this fertile valley, who began collaborating with their former enemies to preserve wildlife and their livelihoods.

The Nature Conservancy, which usually buys land to shield it from development, is renting land from the three farmers on behalf of migrating Western sandpipers, black-bellied plovers, dunlins, marbled godwits and other shorebirds.

From private and public funds, including a grant from the federal Environmental Protection Agency, the farmers, David Hedlin, Gail Thulen and Alan Mesman, will together receive up to $350,000 for three years of labor, expenses and the use of 210 acres, said Kevin Morse, the Skagit Delta project manager for the conservancy.

Each man has committed about 70 acres to this project, which is called Farming for Wildlife. A third of that land will be flooded with a few inches of fresh water in the spring, fall and winter. This will create shallow ponds to entice thousands of birds, some of them on their way to and from the Arctic, to stop and snack on tiny invertebrates and worms as they travel along the Pacific flyway.

More than a dozen shorebird species have declined primarily because of the loss of local wetlands, said Gary Slater, research director at the Ecostudies Institute here and a consultant for the Nature Conservancy.

The farmers see the Nature Conservancy’s willingness to pay them as an acknowledgment that they should not be expected to sacrifice their land or their living for wildlife. This approach effectively turns shorebirds into another crop to manage, instead of grounds for a lawsuit.

“The stewardship ethic in this valley is incredibly strong, but it doesn’t trump the bank,” said Mr. Hedlin, 56, who, with his wife, Serena Campbell, grows farmer’s market produce, vegetable seeds, pumpkins, winter wheat and pickling cucumbers on their 400-acre farm.

Mr. Hedlin’s 70-acre Farming for Wildlife parcel has been under water since a heavy November rain breached a dike and flooded the field, in a preview of what environmentalists hope will happen. Edged with wild roses and blackberry bushes, this accidental lake quickly attracted wintering waterfowl like trumpeter swans, coots, and mallard, teal and wigeon ducks.

An hour north of Seattle and an hour south of Vancouver, British Columbia, this region’s glorious tulip farms attract hundreds of thousands of tourists each April. Skagit farmers also produce about 80 crops of commercial significance, including seeds used to grow beets, spinach and cabbage around the world, many of the red potatoes eaten in the United States, and vegetables and dairy products sent to farmer’s markets and restaurants in the Pacific Northwest.

Thousands of years of flooding on the Skagit River deposited a rich layer of topsoil in the “magic Skagit,” as Mr. Hedlin calls the valley. European immigrants flocked here starting in the 1860s and built Victorian houses for their families on the board-flat green fields.

They also constructed an elaborate network of earthen dikes to capture land from the saltwater delta and prevent the rivers from flooding their farms. On this managed agricultural landscape, tens of thousand of acres of farmland were once tidal wetlands, Mr. Hedlin said.

Since the mid-1990s, residents have tried to slow development as strip malls and housing subdivisions marched northward from Seattle. Skagit County residents pay extra taxes to buy development rights from farmers, and a charitable group, Skagitonians to Preserve Farmland, warns that “Pavement is forever.”

Many conservationists have also decided that farms are better than pavement, and say they are willing to balance preservation with profitable land use.

Mr. Morse lives here and even volunteered to spend two days last spring selling Mr. Hedlin’s produce at a farmer’s market.

“We don’t know anything about farming,” Mr. Morse told the farmers recently over coffee and sandwiches at the Rexville Grocery. “You guys are the stewards of the land. You tell me what to do.”

For this experiment, each farmer’s 70-acre parcel has been planted with a mixture of clover and grass to enrich the soil. While a third of the land will be periodically flooded for birds, a third will be fenced as pasture for dairy cows, and the rest will be mowed and otherwise left alone.

Farms here are gradually shifting toward organic production because consumers willingly pay much more for organic food. As another incentive to join Farming for Wildlife, the 210 acres will be available for organic use after three years.

Mr. Mesman will start producing organic milk with his 225 Holstein cows next spring. Mr. Thulen sees a big market for organic potatoes.

“In my time, I can see our little valley was farmed very hard,” said Mr. Thulen, whose 2,000-acre farm was begun by his grandfather in 1867. “That pendulum has swung to get the ground healthy again.”

In an ideal world, the Nature Conservancy would love to persuade farmers to add wetlands to their regular crop rotation. To that end, the group’s scientists will analyze soil samples to assess whether shallow flooding might improve soil fertility as much as cow manure and mowed grass do.

In a similar project on the Tule Lake National Wildlife Refuge in Northern California, farmers reported better potato yields and fewer nematodes, a harmful worm, on land that had been purposefully flooded. But scientists say this may not apply in the Skagit Valley, where the soil has a higher clay content.

Whether or not they end up with more productive land, the three farmers seem pleased to try something new without financial risk.

“If 100 years from now,” Mr. Hedlin said, “there are healthy viable family farms in this valley and waterfowl and wildlife and salmon in the river, then everyone wins.”

Crafty_Dog:
Been meaning to post this one for several days now , , ,
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12/12/06 NY Times

by NATALIE ANGIER
Published: December 12, 2006

This was no euphemistic brushoff, no reptilian version of "Sorry, I'll be
busy that night washing my hair." Paddling around in a tropically appointed
pool at the National Aquarium in Baltimore, the husky female Gibba turtle
from South America made all too palpable her disdain for the petite male
Gibba that pursued her. He crawled onto the parqueted hump of her bark-brown
shell. She shrugged and wriggled until he slipped off. He looped around to
show her his best courtship maneuvers, bobbing his head, quivering his neck.
She kicked him aside like a clot of algae and kept swimming.


"I feel sorry for the little guy," said Jack Cover, a turtle specialist and
the general curator of the aquarium. "He's making no progress, she's got
zero interest in him, yet he just keeps coming back for more."

And why not? The male Gibba may be clueless, he may at the moment have the
sex appeal of a floating toupee, but he is a turtle, and, as a major new
book and a wealth of recent discoveries make abundantly clear, turtles are
built for hard times. Through famine, flood, heat wave, ice age, a predator's
inspections, a paramour's rejections, turtles take adversity in stride,
usually by striding as little as possible. "The tale of the tortoise and the
hare is the turtle's life story," said Mr. Cover, who calls himself a
card-carrying member of the "turtle nerds" club. "Slow and steady wins the
race."

With its miserly metabolism and tranquil temperament, its capacity to forgo
food and drink for months at a time, its redwood burl of a body shield, so
well engineered it can withstand the impact of a stampeding wildebeest, the
turtle is one of the longest-lived creatures Earth has known. Individual
turtles can survive for centuries, bearing silent witness to epic swaths of
human swagger. Last March, a giant tortoise named Adwaita said to be as old
as 250 years died in a Calcutta zoo, having been taken to India by British
sailors, records suggest, during the reign of King George II. In June,
newspapers around the world noted the passing of Harriet, a Galapagos
tortoise that died in the Australia Zoo at age 176 - 171 years after Charles
Darwin is said, perhaps apocryphally, to have plucked her from her
equatorial home.

Behind such biblical longevity is the turtle's stubborn refusal to senesce -
to grow old. Don't be fooled by the wrinkles, the halting gait and the
rheumy gaze. Researchers lately have been astonished to discover that in
contrast to nearly every other animal studied, a turtle's organs do not
gradually break down or become less efficient over time.

Dr. Christopher J. Raxworthy, the associate curator of herpetology at the
American Museum of Natural History, says the liver, lungs and kidneys of a
centenarian turtle are virtually indistinguishable from those of its teenage
counterpart, a Ponce de Leonic quality that has inspired investigators to
begin examining the turtle genome for novel longevity genes.

"Turtles don't really die of old age," Dr. Raxworthy said. In fact, if
turtles didn't get eaten, crushed by an automobile or fall prey to a
disease, he said, they might just live indefinitely.

Turtles have the power to almost stop the ticking of their personal clock.
"Their heart isn't necessarily stimulated by nerves, and it doesn't need to
beat constantly," said Dr. George Zug, curator of herpetology at the
Smithsonian Institution. "They can turn it on and off essentially at will."

Turtles resist growing old, and they resist growing up. Dr. Zug and his
co-workers recently determined that among some populations of sea turtles,
females do not reach sexual maturity until they are in their 40s or 50s,
which Dr. Zug proposes could be "a record in the animal kingdom."

Turtles are also ancient as a family. The noble chelonian lineage that
includes all living turtles and tortoises extends back 230 million years or
more, possibly predating other reptiles like snakes and crocodiles, as well
as birds, mammals, even the dinosaurs.

The turtle's core morphology has changed little over time, and today's 250
or so living species all display an unmistakable resemblance to the earliest
turtle fossils. Yet the clan has evolved a dazzling array of variations on
its blockbuster theme, allowing it to colonize every continent save
Antarctica and nearly every type of biome nested therein: deserts;
rainforests; oceans; rivers; bogs; mountains; New Brunswick, Canada; New
Brunswick, N.J.

"Turtles can persist in habitats where little else can survive," said Dr. J.
Whitfield Gibbons, a professor of ecology at the University of Georgia in
Athens.

Troubles Foreseen

The iconic turtle likewise has colonized the human heart. People may despise
cats or fear dogs, but practically everybody has a soft spot for turtles.
"Turtles are by far the most popular reptile," said Peter C. H. Pritchard,
director of the Chelonian Research Institute in Oviedo, Fla. "Unlike snakes,
which may threaten you and which move like a flash, turtles are benign and
slow, and you can't dislike or distrust the clumsy."

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(Page 2 of 3)



Yet such warm and fuzzy feelings have proved cold comfort for turtles, and
herpetologists fear that in humans the stalwart survivors from the Mesozoic
era may at last have met their mortician. Turtle habitats are fast
disappearing, or are being fragmented and transected by roads on which
millions of turtles are crushed each year. "There's no defense against that
predator known as the automobile," Dr. Gibbons said.

Researchers estimate that at least half of all turtle species are in serious
trouble, and that some of them, like the Galapagos tortoise, the North
American bog turtle, the Pacific leatherback sea turtle and more than a
dozen species in China and Southeast Asia, may effectively go extinct in the
next decade if extreme measures are not taken. "People love turtles, people
find them endearing, but people take turtles for granted," Mr. Cover said.
"They have no idea how important turtles are to the ecosystems in which
they, and we, live."

Researchers are also impressed by the turtle's many sensory talents. Box
turtles and other forest-dwelling species can spot a lake or pond a mile in
the distance, possibly by detecting polarized light glinting off the surface
of the water. Female sea turtles migrate across entire oceans every breeding
season, unerringly making their way from far-flung feeding grounds right
back to the beach where they were born, and where they are instinctively
driven to lay their own eggs.

Instinctive does not mean inflexible, however. Should a weary wayfarer
arrive at her natal beach in the dead of night and find it has eroded away,
Dr. Pritchard said, she can adapt, swimming down the coast until she locates
a suitably sandy nesting site.

Turtles, it seems, are all ears, all the time. Dr. Ray Ashton, who runs the
Finca de la Tortuga biological preserve in Archer, Fla., has highly
preliminary evidence that some turtle species may communicate subsonically,
just as elephants do, transmitting and detecting ultralow frequency sound
waves as vibrations in the ground.

In their new book, "Turtles of the World" (Johns Hopkins Press), Franck
Bonin, Bernard Devaux and Alain Dupré seek to loft turtles into the
limelight by showcasing the group's diversity - its beauties, its goofies,
its gargoyles.

There is the Indian star tortoise, its shell a vivid basket weave of dark
and light veins that dance like spattered sunlight as the tortoise crosses
the forest floor; and the Matamata turtle of the Amazon basin, with a
flattened, ragged head and neck that look like dead leaves and a bumpy shell
that mimics an old log - just try to spot that Matamata at the bottom of a
stream, awaiting passing prey; and the massive alligator snapping turtle of
the south-central United States, which lures fish right into its open jaw
with a red bleb of flesh on the floor of its mouth that jiggles like a
chubby worm.

Some turtles have serpentine necks twice the length of their shells; others
sport sweet little snorkeling snouts that look like double-barreled cocktail
straws; still others have beaks so fiercely hooked their bearers could
easily serve, in the authors' words, as "adornment of the upper reaches of
Notre Dame."

Among the most common questions leveled at turtle researchers is, What is
the difference between a turtle and a tortoise? It depends on where you
live, researchers reply. In the United States, any reptile with a shell is
referred to as a turtle, and the term tortoise is reserved for those turtle
species that have elephantine feet and live entirely on land, like the
desert tortoise of the American Southwest. In Australia, by contrast, the
word tortoise often applies to aquatic side-necked species - bizarre beasts
with necks that cannot be drawn into the shell for protection but instead
must be tucked on the side, under the shell's eavelike overhang.

Whatever their group identity badge, turtles vary considerably in size, from
the tiny speckled padloper tortoise of South Africa, which in adulthood is
no bigger than a computer mouse, to the great leatherback sea turtle, which
can measure seven feet long and weigh 2,000 pounds.

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(Page 3 of 3)



Menu plans vary as well. Many turtles are omnivores, happily consuming
fruits, leaves, insects, mollusks, fish, frogs, ice cream. Dr. Gibbons told
of a friend whose his pet box turtle would respond to the sound of a spoon
being tapped on a glass ice cream bowl by emerging from behind the couch,
walking over to its owner, rearing up on its hind legs and waiting to be
spoon-fed its just dessert. "Had I not seen this a few times myself," he
said, "I would not have believed it."


A few turtles have highly specialized palates. Green sea turtles prize the
tender tips of sea grass, and will clip away and discard tough, older grass
to stimulate the sprouting of fresh buds beneath. Leatherback sea turtles
dine only on jellyfish, or what they think are jellyfish. "Plastic bags look
like jellyfish," said Dr. Joseph Mitchell, an ecologist and turtle
specialist in Richmond, Va., "and quite a few leatherbacks have stomachs
impacted with plastic bags."

Some turtles, conversely, seek out the world's detritus. Scavenger turtles
that live in the Ganges River devour human corpses, making it possible for
devout Hindus to deposit their loved ones' remains in the waters they deem
sacred.

An Iconic Feature

Whether they wrest it from sea grass, shellfish or Häagen-Dazs, all turtles
need a substantial amount of calcium in their diet, to sustain the structure
that marks them as turtles and that remains among the most extraordinary
architectural achievements in vertebrate evolution: the shell. A number of
invertebrates have shells, of course, and so, too, do a few vertebrates,
most notably the armadillo. But whereas the armadillo's shell is built of
bony segments slapped down over its muscle tissue and is distinct from the
mammal's underlying skeletal frame, in the turtle the skeleton has become
the shell.

During embryonic development, the bones of the turtle's rib cage grow
straight out, rather than curving toward one another as they do in other
vertebrates. Those ribs, spinal vertebrae and other skeletal bones are then
fused to form the upper shell, called the carapace, the lower shell, or
plastron, and the bony bridges that join upstairs with down. In many turtle
species, the bony shell is in turn plated over with tough fingernail-like
structures called scutes.

As a result of the osteotic overhaul, not only can a turtle not crawl out of
its shell, it has trouble crawling, period. "Its legs stick out at bizarre
angles, and the only reason it can walk at all is through sheer strength,"
Dr. Pritchard said. "The turtle has enormously strong muscles and extremely
thick leg bones." A clumsy gait proved a small price to pay, however, for
the acquisition of body armor that protects adult turtles against a panoply
of jaws and claws.

Geneticists have proposed that the turtle shell may have appeared quite
suddenly in the distant past, rather than emerging slowly through modest,
mincing modifications of pre-existing structures. They suggest that the
dramatic innovation could have arisen from just a few key mutations in
master genes like the so-called homeobox genes, which help specify an animal's
basic body plan. If the shell did burst on the reptilian stage more or less
fully formed, they said, that would explain the lack of "intermediary"
fossils or prototurtles in the paleontological record.

The shell very likely helps explain the turtle's elongated storyline. It
takes time to consolidate a large, thick shell, but upon reaching adult
stature, the turtle is close to invulnerable. At that point, it can
compensate for its Darwinically unproductive youth with a very prolonged and
zealously fecund adulthood. A female turtle will continue laying eggs until
she dies, and a male turtle will just as mulishly pursue her.

Crafty_Dog:
LA Times

Rooftop oases find growing enthusiasm
Plants take root on a college building in Pasadena and elsewhere as cities see economic and environmental benefits of going 'green.'
By Mira Tweti, Special to The Times
December 28, 2006


As you lie in the tall Pacific dune grass, amid grasshoppers and butterflies, it's all blue sky and San Gabriel mountains as far as the eye can see. The sounds of the city are a distant murmur.

Here, in an industrial section of Pasadena, it is hard to imagine a more unlikely oasis: nearly 14,000 square feet of transplanted meadow four stories above ground — on a roof.


Atop the Art Center College of Design's downtown campus, this roof is covered in 6 inches of soil bearing native grasses and shrubs. More than a garden, it is an ecologically designed green space that cools the building in summer by absorbing heat — much like an urban park does — and insulates it from cold in winter.

The Art Center's roof is one of hundreds that have been planted in the Los Angeles area and in major cities around the country. Among the first were a handful of "green"-roofed buildings erected in the 1930s at New York's Rockefeller Center.

Living roofs have a long history. The Vikings grew sod on their homes for insulation. The hanging gardens of Babylon were planted rooftops. Europeans have cultivated green roofs for decades. After World War II, Germany made them mandatory in all major cities to prevent rainwater from washing into aging sewer systems.

In modern cities, the roofs are a way to recreate the Earth's natural footprint that has been displaced by buildings. The roofs replicate the outdoors in a variety of ways, from manicured lawns to unruly meadows.

Experts say such roofs retain storm water, decrease the cost of greenhouse gas reduction and lessen the need for interior building insulation. They also help to bring fauna back to inner city areas by attracting insects and birds, just as a backyard would.

Carmel Valley architect Paul Kephart, a pioneer of green roof design, maintains that even roofs as small as 11 square feet can remove 5 pounds of toxic particulate matter from the air every three months, filter and purify rainfall and control runoff. Through evapotranspiration the water is released back into the atmosphere, cooling it. Or it drains slowly into storm sewers.

Experts believe the roofs can reduce the lethal effects of heat waves, such as the one that led to the deaths of 465 people in Chicago in 1995.

Since then, 2.7 million square feet of green roofs have been built in Chicago or are in the pipeline. The first building to get one under the city's green roof program was City Hall. Because the city shares the building with Cook County offices, it could green only its half of the 38,000-square-foot roof. It contains 20,000 plants in 158 varieties.

On a day when ground temperatures reached 95 degrees, the reading on the City Hall side of the roof was 91 degrees. On the county's half, which was covered with black tar, the temperature was 169 degrees. "The city is saving $40,000 a year in air conditioning costs from this 'green' roof alone," said Constance Buscemi, of the Chicago department of planning and development.

In April, the city of Pasadena made green roofs mandatory on all new city buildings of 5,000 square feet or larger, on commercial buildings and residential tenant improvement construction of 25,000 square feet or more, and on all mixed-use or residential buildings of four stories or more.

Alice Sterling, Pasadena's green building coordinator, said there are 800,000 square feet of new building construction on the books in Pasadena that, if completed, will all have green roofs.

Los Angeles Deputy City Engineer Deborah J. Weintraub has submitted a report to the City Council's planning and land use management committee outlining a possible green roof pilot project for one of several city buildings, including two low-rise wings of City Hall.

Construction of a new constituent services building on Central Avenue at 43rd Street near the famed Hotel Dunbar will break ground Jan. 7. The living roof of the $13-million, 7,000-square-foot, city-owned building, which is scheduled to be completed by mid-2008, was a requirement of 9th District Councilwoman Jan Perry. "I thought, why can't we have the amenities of the Santa Monica mountains in South-Central?" Perry said.

The planted roof will hold more than 100 people for special events. "It will help people think a different way about that area. I want it to be a catalyst and template for development that may follow," Perry said.

Green roofs start with a waterproof roof cover called a membrane. Then comes a root barrier, a drainage layer, and finally the growing medium and plants. Many plants native to California are drought-tolerant and need little maintenance

Depending on how the roof is designed, architects say the additional weight, which can equal that of a load of snow, is not unsafe even for older buildings. Greenery can be rooted on roofs that slope up to 60 degrees.

Nancy Goslee Powers, the Santa Monica landscaper who designed the roof at the Pasadena Art Center building, is working on similar projects in Beverly Hills and Century City, where a living roof is being installed on a public parking structure to keep it cool. It will be three-quarters the size of a football field.

Living roofs aren't risk free. One of Powers' earlier projects — at a store on Rodeo Drive in Beverly Hills — sprang a leak and flooded the store, ruining thousands of dollars in merchandise. That was more than a decade ago. Now, experts say, the roofs are stronger and more waterproof than standard roofs, and some manufacturers offer 20-year guarantees.

Powers acknowledged that there is resistance to the roofs on the part of colleagues and customers in the Los Angeles area.

"You have to keep plugging living roofs," she said. "A crew cut on top of a building may not appeal to every architect. And we have a culture of fear when it comes to new ideas.

"So, it's not always an easy sell to clients. We have to remind people we can't survive without plants."

Crafty_Dog:
A green Republican organization recommended by my friend John Spezzano.

http://www.rep.org:80/

Crafty_Dog:
NY Times

By CARL ZIMMER
Published: January 23, 2007
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.

Much of the grassland habitat of the Bay checkerspot butterfly is already destroyed, and studies suggest that climate change will push the insect to extinction. Moving the species is an option, but one that is not without risk.
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.”

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