By 2050 Warming to Doom Million Species, Study Says
National Geographic News, July 12, 2004
By 2050, rising temperatures exacerbated by human-induced belches of carbon dioxide and other greenhouse gases could send more than a million of Earth's land-dwelling plants and animals down the road to extinction, according to a recent study.
"Climate change now represents at least as great a threat to the number of species surviving on Earth as habitat-destruction and modification," said Chris Thomas, a conservation biologist at the University of Leeds in the United Kingdom.
Thomas is the lead author of the study published earlier this year in the science journal Nature. His co-authors included 18 scientists from around the world, making this the largest collaboration of its type.
Townsend Peterson, an evolutionary biologist at the University of Kansas in Lawrence and one of the study's co-authors, said the paper allows scientists for the first time to "get a grip" on the impact of climatechange as far as natural systems are concerned.
"A lot of us are in this to start to get a handle on what we are talking about," he said. "When we talk about the difference between half a percent and one percent of carbon dioxide emissions what does that mean?"
The researchers worked independently in six biodiversity-rich regions around the world, from Australia to South Africa, plugging field data on species distribution and regional climate into computer models that simulated the ways species' ranges are expected to move in response to temperature and climate changes.
"We later met and decided to pool results to produce a more globally relevant look at the issue," said Lee Hannah, a climate change biologist with Conservation International's Center for Applied Biodiversity Science in Washington, D.C.
According to the researchers' collective results, the predicted range of climate change by 2050 will place 15 to 35 percent of the 1,103 species studied at risk of extinction. The numbers are expected to hold up when extrapolated globally, potentially dooming more than a million species.
"These are first-pass estimates, but they put the problem in the right ballpark ... I expect more detailed studies to refine these numbers and to add data for additional regions, but not to change the general import of these findings," said Hannah.
Writing in an accompanying commentary to the study in Nature, J. Alan Pounds of the Monteverde Cloud Forest Reserve in Costa Rica, and Robert Puschendorf, a biologist at the University of Costa Rica, say these estimates "might be optimistic."
As global warming interacts with other factors such as habitat-destruction, invasive species, and the build up of carbon dioxide in the landscape, the risk of extinction increases even further, they say.
In agreement with the study authors, Pounds and Puschendorf say taking immediate steps to reduce greenhouse gas emissions is imperative to constrain global warming to the minimum predicted levels and thus prevent many of the extinctions from occurring.
"The threat to life on Earth is not just a problem for the future. It is part of the here and now," they write.
The researchers based their study on minimum, mid-range, and maximum future climate scenarios based on information released by the United Nation's Intergovernmental Panel on Climate Change (IPCC) in 2001.
According to the IPCC, temperatures are expected to rise from somewhere between 1.5 and more than 4 degrees Fahrenheit (0.8 and more than 2 degrees Celsius) by the year 2050.
"Few climate scientists around the world think that 2050 temperatures will fall outside those bounds," said Thomas. "In some respects, we have been conservative because almost all future climate projections expect more warming and hence more extinction between 2050 and 2100."
In addition, the researchers accounted for the ability of species to disperse or successfully move to a new area, thus preventing climate change-induced extinction. They used two alternatives: one where species couldn't move at all, the other assuming unlimited abilities for movement.
"We are trying to bracket the truth," said Peterson. "If you bracket the truth and look at the two endpoints and they give the same general message, then you can start to believe it."
Outside of the small group of researchers working directly on the impacts of climate change to species diversity, "the numbers will come as a huge shock," said Thomas.
The researchers point out that there is a significant gap between the low and high ends of the species predicted to be on the road to extinction by 2050. Taking action to ensure the climate ends up on the lowend of the range is vital to prevent catastrophic extinctions.
"We need to start thinking about the fullest of costs involved with our activities, the real costs of what we do in modern society," said Peterson.
Thomas said that since there may be a large time lag between the climate changing and the last individual of a doomed species dying off, rapid reductions of greenhouse gas emissions may allow some of these species to hang on.
"The only conservation action that really makes sense, at a global scale, is for the international community to minimize warming through reduced emissions and the potential establishment of carbon-sequestration programs," he said.Warming May Threaten 37 Percent of Species by 2050
The Washington Post, Jan. 8, 2004
In the first study of its kind, researchers in a range of habitats including northern Britain, the wet tropics of northeastern Australia and the Mexican desert said yesterday that global warming at currently predicted rates will drive 15 to 37 percent of living species toward extinction by mid-century.
Dismayed by their results, the researchers called for "rapid implementation of technologies" to reduce emissions of greenhouse gases and warned that the scale of extinctions could climb much higher because of mutually reinforcing interactions between climate change and habitat destruction caused by agriculture, invasive species and other factors.
"The midrange estimate is that 24 percent of plants and animals will be committed to extinction by 2050," said ecologist Chris Thomas of Britain's University of Leeds. "We're not talking about the occasional extinction -- we're talking about 1.25 million species. It's a massive number."
The study marks the first time scientists have produced a global analysis with concrete estimates of the effect of climate change on habitat. Previous work -- much of it by the same researchers -- focused on smaller regions or limited numbers of species.
Thomas led a 19-member international team that surveyed habitat decline for 1,103 plant and animal species in five regions: Europe; Queensland, Australia; Mexico's Chihuahuan Desert; the Brazilian Amazon; and the Cape Floristic Region at South Africa's southern tip. The study is being published today in the journal Nature.
The five regions encompass 20 percent of Earth's surface and "include a fair range of terrestrial environments," Thomas said in a telephone interview from Leeds. "Obviously, it would be valuable to expand the scope, but there's no reason to think that doing so would change our results tremendously."
Researchers said the wide geographical scope also overcame outside factors that might affect a single region only. "A prolonged drought might cause one instance of a dieback" but be offset by changes elsewhere, acknowledged climate change biologist Lee Hannah, who worked in South Africa. "When you see the broader context, the regional blips drop out."
Although there is little dispute that Earth's temperature is rising, debate over the reasons and speed of change remains contentious. Still, most scientists accept that much of the warming is caused by the cumulative effects of human-produced emissions of carbon dioxide and other "greenhouse gases" -- from power plants and other industries -- that trap and hold heat in the atmosphere.
One skeptic, William O'Keefe, president of the George C. Marshall Institute, a conservative science policy organization, criticized the Nature study, saying that the research "ignored species' ability to adapt to higher temperatures" and assumed that technologies will not arise to reduce emissions.
Climatologists have developed models that describe the temperature changes that specific regions have undergone over periods of as long as 30,000 years. The Nature study used U.N. projections that world average temperatures will rise 2.5 to 10.4 degrees Fahrenheit by 2100.
The trick for the study, Thomas said, was to marry the maps of projected climate change in particular regions with maps describing the habitat -- especially the climate needs -- of plants and animals in the same area.
For this, "we needed to get the people together who knew where the species lived," Thomas said. These were the conservationists on the research team -- ecological experts who study extinctions by looking at traditional culprits: destruction of habitat through agriculture, industry or human settlement; invasive species shoving aside native plants and animals; and hunting and extermination of pests.
"Obviously, plants and animals depend on climate for survival, but we figured that if we protect them in place, they would be all right," Hannah said in a telephone interview from his home in California. "But now we realize that we have to take care of them not only where they are now, but where they might have to go."
The team calculated the effects of climate change on extinctions by using what ecologists J. Alan Pounds and Robert Puschendorf, in an article accompanying the study, called "one of ecology's few ironclad laws" -- that shrinking habitat supports fewer species.
The study considered a range of possibilities based on the ability of each species to move to a more congenial habitat to escape warming. If all species were able to move, or "disperse," the study said, only 15 percent would be irrevocably headed for extinction by 2050. If no species were able to disperse, the extinction rate could rise as high as 37 percent.
"Reality, of course, will fall somewhere in between," Thomas said.
As an example, he cited Britain's comma butterfly, a robust flier that hopscotched 160 miles north from 1982 to 1997, feeding all the way -- in its caterpillar phase -- on stinging nettles. By contrast, the silver-studded blue butterfly needs to move north but cannot, because it needs lowland heath to survive, and the gaps between patches of habitat are too large for this weak-winged flier to overcome. As a result, "it has continued to decline," Thomas said.
Pounds, speaking by telephone from his office in Costa Rica's Monteverde Cloud Forest Preserve, called the study's results "ironclad" and "if anything, too conservative." The adverse effects of natural roadblocks would be compounded by "interaction with other changes" such as agriculture, human settlement or invasive species, he said.
"There are different ways you can lose area," Pounds said. "One is to have the habitat directly destroyed. Climate change does the same thing."
The New York Times, Jan. 8, 2004
An international group of 19 scientists, analyzing research around the globe, has concluded that a warming climate will rival habitat destruction in prompting widespread extinctions in this century.
By 2050, the scientists say, if current warming trends continue, 15 to 37 percent of the 1,103 species they studied will be doomed.
They did not extend their prediction to all species worldwide, but they said that the sample was large enough to show that climate change could be disastrous. In addition to current efforts to create parks and reserves, they added, efforts to decrease global warming will be necessary to reduce rates of extinction.
The analysis is built on layers of computer models of climate change and other models of the ways species become extinct, each having varying degrees of uncertainty. Consequently, the authors say, the numbers cannot be taken as precise. They are described in the paper as a "first pass" at quantifying the extinction threat posed by a global warming trend.
"There's a huge amount of uncertainty," said the primary author of the paper, Dr. Chris D. Thomas, a professor of conservation biology at the University of Leeds in England.
Dr. Daniel B. Botkin, professor emeritus at the University of California at Santa Barbara, an ecologist who has done extensive research on climate change, said the paper was "a valiant effort" to address the effect of warming trends on living things, an area of research he said had been slighted in favor of creating climate models.
And he acknowledged that the authors themselves presented their numbers as a beginning and a spur to further research.
He said, however, that the analysis was based on "a lot of steady state assumptions that lead it to the most pessimistic forecast," including the notion that things will stay as they are in terms of the ways animals migrate and respond to temperature change.
Scientists have been predicting drastic extinctions for years, largely because humans are steadily taking land that other creatures live on and turning it to their own purposes.
By different estimates species are now becoming extinct at rates 100 to 1,000 times as great as would be expected without human interference or a catastrophic event.
The analysis, published Wednesday in the journal Nature, raises the status of global warming from that of contributor to habitat loss to full-fledged force for extinction.
Dr. Thomas said that despite the significant uncertainties, the researchers assessed the raw data on species numbers, current habitats and past extinctions from as many angles as possible. They included species in different terrestrial environments around the world in Central America, South America, Australia and Africa.
They used predictions of increased temperature ranging from mild to extreme and applied three different methods for predicting extinction, all based on the relationship of species disappearance to loss of livable habitat. They also considered two different possibilities for gauging how well the different species would be able to disperse as temperatures at home became uncomfortable.
Although the results vary widely, Dr. Thomas said, even the most conservative estimates show that global warming, which he and most other scientists attribute to emissions of carbon dioxide and other greenhouse gases in the burning of fossil fuels, presents a "very serious risk to huge numbers of species and at least ranks alongside habitat destruction" as a threat.
The paper does not predict that all the extinctions will occur by 2050, but that by that time these species will have reached the point of no return.