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  Yahoo News 24 Oct 07
Extinctions linked to hotter temperatures
By Seth Borenstein, AP Science Writer

Yahoo News 23 Oct 07
Climate change: Fossil record points to future mass extinctions

BBC 24 Oct 07
Climate threat to biodiversity

PlanetArk 25 Oct 07
Global Warming Could Wipe Out Most Species - Study
Story by Michael Kahn

National Geographic 24 Oct 07
Scientists Link Extinctions, Rising Temperatures
Nick Wadhams for National Geographic News

A team of British scientists contends that, within 200 years, the Earth's temperatures may become hot enough to kill off half of all existing plant and animal species.

The researchers from the Universities of York and Leeds in Britain base that dire possibility on a new analysis of the 520-million-year-old fossil record, linking past mass extinctions with cycles of high temperatures that occurred at roughly the same time.

"We could be in the temperature zone in which mass extinctions have occurred by the end of this century, [or] more likely in the next century," said Peter Mayhew, the study's co-author and an ecologist at the University of York.

A Strong Link

Benton and his colleagues laid out their findings in a paper that appeared in the Proceedings of the Royal Society B, the chief biological research journal for the British academy of science.

Measuring in 10-million-year increments, they found a correlation between high temperatures and four of five mass extinctions in Earth's fossil record, dating back 520 million years.

No other research had examined both the entire globe and the entire fossil record, which begins about 540 million years ago. This analysis makes the strongest case yet for a solid link between temperature and changes in the number of species on Earth.

"There have been individual cases where people have shown that some kind of change is detrimental to certain groups," said Michael Foote, a paleontologist and professor at the University of Chicago, who was not involved in the study. "But this is the first time anyone has studied the diversity of animals at a global scale and went back to estimates of temperature over time."

According to the research, the Earth is in a process, millions of years long, of moving from colder to warmer temperatures from the "icehouse phase" to the "greenhouse phase." The Earth will reach the peak of its latest warming phase in the next 60 million years.

It is possible that extinctions don't begin to occur until thousands, or even millions of years after temperatures begin to rise. And the authors were careful to avoid claims about a causal relation between the rising temperatures and the extinctions.

Other things, such as cycles of cosmic rays from space and carbon dioxide, could also have played a role in the past mass extinctions studied.

Still, the authors say it may be possible to avoid some of the future extinctions if man works to control temperatures.

"We don't want to over-extrapolate in our findings, but if they hold, it's quite a scary thing to contemplate," said Timothy Benton, a co-author and professor of population ecology at the University of Leeds.

Beyond the Paper?

The study resists speculation about the present phase of global warming or man's possible role in it. It also notes that periods when species died out were often followed by a stabilization a time when new species would appear.

"You might make a case for the possibility that climate warming could lead to a smaller increase in diversity than you otherwise might have expected," said Foote. "But there was no clear evidence that it would lead to a decrease in diversity."

In interviews, both Mayhew and Benton went beyond the more cautious terms of their paper, saying man-made global warming was accelerating the process.

"The issue here is that we are creating the climate change, and we are creating the climate change at an unprecedented rate," said Benton. "So clearly we are creating the events for a climate-related mass extinction that wouldn't otherwise be happening."

Those statements echo the controversial idea of an imminent massive biodiversity dry-out that has been put forward before. The International Panel on Climate Change, which recently shared the (Nobel Peace Prize with Al Gore, has warned of a possible drop in biodiversity if temperatures rise by three or four degrees.

And last year, experts from 13 countries wrote an article in the journal Nature saying that climate change could push 37 percent of all species to extinction within the next 50 years.

"We are on the verge of a major biodiversity crisis," that letter said. "Virtually all aspects of diversity are in steep decline and a large number of populations and species are likely to become extinct this century.

Other scientists contest that these ideas are flawed or exaggerated.

Richard A. Muller, a physics professor at the University of California, Berkeley, published a piece in Nature in 2005 suggesting a link between changes in climate and changes in biodiversity.

He believes that global warming will devastate the environment, but stopped well short of linking man-made global warming to biodiversity loss, and criticized Mayhew and Benton of going beyond the science of their paper.

"You can't make wild predictions if you can't justify them," said Muller. "If global warming continues at the current pace, I think we will have a tragic future. I think there will be great disruption, but whether humans affect biodiversity in a negative way, I don't think anyone ever really knows."

BBC 24 Oct 07
Climate threat to biodiversity

Global temperatures predicted for the coming centuries could trigger a mass extinction, UK scientists have warned.

The temperatures are within the range of greenhouse phases early in the Earth's history when up to 95% of plants and animals died out, they say.

Experts examined the link between climate and diversity over 520 million years, almost the entire fossil record.

They found that global diversity is high during cool (icehouse) periods and low during warm (greenhouse) phases.

"Our results provide the first clear evidence that global climate may explain substantial variation in the fossil record in a simple and consistent manner," said Dr Peter Mayhew, one of the paper's co-authors.

"If our results hold for current warming, the magnitude of which is comparable with the long-term fluctuations in the Earth's climate, they suggest that extinctions will increase."

Warmer, wetter

The study by researchers from the Universites of York and Leeds, published in Proceedings of the Royal Society B, compared data sets on marine and land diversity against estimates of sea surface temperatures for the same period.

They found that four out of the five mass extinction events on Earth are associated with greenhouse phases (warmer, wetter conditions) rather than icehouse phases (cold, dry conditions).

These include Earth's worst mass extinction 251 million years ago when some 95% of all species were lost.

"We could - at worst - be experiencing that in the next century - only a few human generations down the line," Dr Mayhew told BBC News.

"We need to know why temperatures and extinctions are linked in this way."

PlanetArk 25 Oct 07
Global Warming Could Wipe Out Most Species - Study
Story by Michael Kahn

LONDON - Rising temperatures could wipe out more than half of the earth's species in the next few centuries, according to researchers who published a study on Wednesday linking climate change to past mass extinctions.

Researchers at the University of York said their study was the first to examine the relationship between climate, extinction rates and biodiversity over a long period.

The findings, published in the Proceedings of the Royal Society, suggest climate change was the cause of large-scale extinctions, said Peter Mayhew, an ecologist who worked on the study.

The study analysed fossil records and temperature changes over 500 million years, and found that three of the four biggest extinctions -- defined as when more than 50 percent of species disappeared -- occurred during periods of high temperatures.

"The relationship is true for the whole period in general," Mayhew said in a telephone interview. "If temperatures went up, then extinctions went up and biodiversity tended to be lower."

The UN Intergovernmental Panel on Climate Change predicts that average global temperatures are likely to rise by between 1.8 and 4 degrees Celsius (3.2 and 7.2 Fahrenheit) by the end of the century, partly as a result of greenhouse gas emissions.

The upper end of the forecast rise would heat the earth close to the temperatures of 250 million years ago, when 95 percent of all animal and plant species became extinct, Mayhew said.

Some of the past mass extinctions happened over a brief few hundred years, providing evidence that present day rapid temperature rises could have the same impact, Mayhew said.

"It does give us an idea of what to expect in the near future," he said. "There is nothing that says it couldn't happen in a short timescale."

Yahoo News 23 Oct 07
Climate change: Fossil record points to future mass extinctions

Global warming could cut a swathe through the planet's species over the coming centuries, warns a study released Wednesday that shows a link between rising temperatures and mass extinctions reaching back half a billion years.

Each of five major eras of declining biodiversity -- including one in which 95 percent of the Earth's species disappeared -- correspond to cycles of severe warming over the 520-million-year period for which there are fossil records.

If emissions of greenhouse gas rise unchecked, the predicted increase in global temperature over the next several hundred years could fall within a similar range as these peaks, said the study, published in a British journal, Proceedings of The Royal Society B.

Previous studies have either looked for patterns in climate change or the causes of particular mass extinctions. But this is the first time the two been paired together to give a perspective over such a long time.

"If our results hold for current warming -- the magnitude of which is comparable with the long-term fluctuations in Earth climate -- they suggest that extinctions will increase," lead author Peter Mayhew said in a statement.

The UN's top panel of climate scientists, which won the Nobel Peace Prize earlier this month, forecasts an average increase by 2100 of between 1.1 C (1.98 F) and 6.4 C (11.52 F), compared to 1980-99 levels.

The trio of researchers, led by Timothy Benton at the University of Leeds in northern England, used sea surface temperatures -- extrapolated from fossilized records of the oxygen and acidity levels -- to determine the fluctuations over tens of millions of years between "greenhouse" and "icehouse" periods.

They then matched this data with changes in the number of plant and animal families inhabiting Earth, also based on fossil records.

The study did not dwell on the likely causes of these bouts of warming, whether natural cycles in the earth's climate or, most recently, to the burning of fossil fuels.

But whatever the causes, the result has been consistently the same: a more or less severe culling of life on Earth.

The death toll included 47 percent of all marine genera -- the classification above species -- and 18 percent of land vertebrate families.

At the end of the Permian period, some 250 million years ago, the planet's worst mass extinction wiped out 95 percent of all species, including 70 percent of land plants, insects and vertebrae.

"Our results provide the first clear evidence that global climate may explain substantial variation in the fossil record in a simple and consistent manner," the study states.

The same correlation held true for a flourishing of new species as well, with new flora and fauna multiplying during the interstices of "greenhouse" and "icehouse" cycles.

The researchers point out that the time-scale of their study does not help in making short-term predictions.

Yahoo News 24 Oct 07
Extinctions linked to hotter temperatures
By Seth Borenstein, AP Science Writer

Whenever the world's tropical seas warm several degrees, Earth has experienced mass extinctions over millions of years, according to a first-of-its-kind statistical study of fossil records.

And scientists fear it may be about to happen again but in a matter of several decades, not tens of millions of years.

Four of the five major extinctions over 520 million years of Earth history have been linked to warmer tropical seas, something that indicates a warmer world overall, according to the new study published Wednesday.

"We found that over the fossil record as a whole, the higher the temperatures have been, the higher the extinctions have been," said University of York ecologist Peter Mayhew, the co-author of the peer-reviewed research published in the Proceedings of the Royal Society B, a British journal.

Earth is on track to hit that same level of extinction-connected warming in about 100 years, unless greenhouse gas emissions are curbed, according to top scientists.

A second study, to be presented at a scientific convention Sunday, links high carbon dioxide levels, the chief man-made gas responsible for global warming, to past extinctions.

In the British study, Mayhew and his colleagues looked at temperatures in 10 million-year chunks because fossil records aren't that precise in time measurements. They then compared those to the number of species, the number of species families, and overall biodiversity. They found more biodiversity with lower temperatures and more species dying with higher temperatures.

The researchers examined tropical sea temperatures the only ones that can be determined from fossil records and go back hundreds of millions of years. They indicate a natural 60 million-year climate cycle that moves from a warmer "greenhouse" to a cooler "icehouse." The Earth is warming from its current colder period.

Every time the tropical sea temperatures were about 7 degrees warmer than they are now and stayed that way for millions of enough years, there was a die-off. How fast extinctions happen varies in length.

The study linked mass extinctions with higher temperatures, but did not try to establish a cause-and-effect. For example, the most recent mass extinction, the one 65 million years ago that included the die-off of dinosaurs, probably was caused by an asteroid collision as scientists theorize and Mayhew agrees.

But extinctions were likely happening anyway as temperatures were increasing, Mayhew said. Massive volcanic activity, which releases large amounts of carbon dioxide, have also been blamed for the dinosaur extinction.

The author of the second study, which focuses on carbon dioxide, said he does see a cause-and-effect between warmer seas and extinctions.

Peter Ward, a University of Washington biology and paleontology professor, said natural increases in carbon dioxide warmed the air and ocean. The warmer water had less oxygen and spawned more microbes, which in turn spewed toxic hydrogen sulfide into the air and water, killing species.

Ward examined 13 major and minor extinctions in the past and found a common link: rising carbon dioxide levels in the air and falling oxygen levels. Ward's study will be presented Sunday at the Geological Society of America's annual convention in Denver.

Mayhew also found increasing carbon dioxide levels in the air coinciding with die-offs, but concluded that temperatures better predicted biodiversity.

Those higher temperatures that coincided with mass extinctions are about the same level forecast for a century from now if the world continues its growing emissions of greenhouse gases, according to the Nobel Prize-winning Intergovernmental Panel on Climate Change.

In April, the same climate panel of thousands of scientists warned that "20 to 30 percent of animal species assessed so far are likely to be at increased risk of extinction" if temperatures increase by about 3 to 4 degrees Fahrenheit.

"Since we're already seeing threshold changes in ecosystems with the relatively small amount of climate change already taking place, one could expect there's going to be severe transformations," said biologist Thomas Lovejoy, president of the H. John Heinz Center for Science, Economics and the Environment in Washington.

University of Texas biologist Camille Parmesan, who studies how existing species are changing with global warming but wasn't part of either team, said she was "blown away" by the Mayhew study and called it "very convincing."

"This will give scant comfort to anyone who says that the world has often been warmer than recently so we're just going back to a better world," Pennsylvania State University geological sciences professor Richard Alley said.

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