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Thursday, Nov. 14, 2002

NATURAL SELECTIONS

Mammals get early warning on climate change


President George W. Bush and the U.S. government might not be in denial of climate change these days, but their position is little more responsible than the cowboy stance Bush assumed on first coming to power. Climate change is happening, but hell, there's nothing to be done about it, they say.

"Adapting to a changing climate is inevitable," states the U.S. Climate Action Report, published in June. "The question is whether we adapt poorly or well." The report appeared on the Web site of the Environmental Protection Agency ( www.epa.gov) -- a government body that, under the current administration, should think about changing its name.

That fatalistic attitude was reflected last month at the latest round of climate-change talks in New Delhi, where the declaration on global warming failed to even mention the Kyoto Protocol.

While the politicians and oilmen point fingers and refuse to sign on to agreements, scientific evidence of the consequences of climate change is mounting. This week in Nature, scientists show, for the first time, that climate change can cause population fluctuations in different mammal species -- on a continent-wide scale.

The paper compares long-term data on the climate system known as the North Atlantic Oscillation with comparable data from Greenland on the population dynamics of caribou and musk oxen. Both animals are large mammals adapted to breeding in the Arctic.

"The Arctic can provide useful early-warning signals for the rest of the world because the species that live in this sensitive region are expected to be among the first to show the effects of the Earth's changing climate," said Eric Post, an author of the paper and assistant professor of biology at Penn State University, Pa.

"Here we have a very simple system with a very clear signal: Two species on opposite sides of a continent, that never mix, never compete for food and have no common predators, yet their population dynamics are synchronized. The only thing they have in common is the large-scale climate system that influences weather throughout the northern hemisphere," Post commented.

Post and coauthor Mads C. Forchhammer, associate professor of ecology at the University of Copenhagen, studied seven herds of caribou and six herds of musk oxen in Greenland, where the two species live on opposite coasts and are separated by an impassable, continent-wide ice sheet spanning 1,000 km at its minimum width.

The study is the first one using both local and global weather data to show synchrony in species that have no direct contact with each other and that share nothing in common, except for the effect on their local weather of a large-scale climate system -- the North Atlantic Oscillation.

"The North Atlantic Oscillation can be pictured as a fluctuating pressure corridor that squeezes and channels the westerly winds between North America and northern Europe, influencing the direction and speed of the winds and affecting temperature and precipitation on both sides of the North Atlantic Ocean," Post said.

In order to gauge the extent to which the North Atlantic Oscillation affects local weather conditions on the coasts of Greenland, where the musk oxen and caribou live, the researchers compared records of each herd's local weather history with the NAO index -- a measure of the condition of the North Atlantic Oscillation that has been in use from 1864 to the present day. They then compared each of the caribou herds with each of the musk oxen herds, looking at the degree of their geographical separation, the timing of their population fluctuations, the weather conditions affecting each herd and the degree of the North Atlantic Oscillation's influence on the herd's population dynamics.

"We found that whenever the NAO had an approximately equal effect on the population dynamics of two herds, these fluctuations were more synchronized, even though the herds were on opposite sides of the subcontinent of Greenland," Post said. Similarly, the researchers found that whenever the North Atlantic Oscillation exerted opposite effects on herds of the two species, their population dynamics were out of phase with each other -- one thrived while the other declined.

"The physical isolation of the caribou and musk oxen populations by the continent-wide ice sheet in Greenland, along with their lack of shared competition for food and their lack of shared predators, greatly simplifies the analysis of the role of climate in synchronizing their population dynamics," Post said.

Simplifies it so much, in fact, that even presidents might be able to understand. Here we go: Climate change affects the numbers of mammals of different species, at the same time.

But that's not all. Post and his colleagues have conducted similar studies in areas with climates milder than that of Greenland. Their results have shown that climate changes influence the dynamics of many species of large mammals, birds and plants throughout the North Atlantic region.

"What does this tell us about the potential ecological consequences of future climate change?" Post asked. "At the very least, it should make us wonder whether climate trends might bring into synchrony the ups and downs of populations of species that currently are fluctuating independently," he said.

Those in the developed world might adapt poorly or well to climate change, but a large part of the human population has no such luxury. Animals and plants, however, can hardly adapt as well as us.. The latest research shows what many scientists suspected: that many species might simultaneously face rapid changes. This might be the last early warning that we get.

E-mail Rowan Hooper welcomes comments at rowhoop@gol.com


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