An Ancient Parallel : Many scientists who believe that global warming has already arrived, say Alaska may see a repeat of effects that devastated the region at the end of the last ice-age. : Science File / An exploration of issues and trends affecting science, medicine and the environment

If the global warming caused by the notorious greenhouse effect shows up first--as expected--in the polar regions, Alaska may see a repeat of effects that devastated the same region at the end of the last ice age.

Indeed, many scientists believe that global warming has already arrived here.

Gunter Weller, director of the University of Alaska’s Geophysical Institute, says mean annual temperatures have warmed around the world in recent decades, and “in Alaska, this trend is even more startling,” especially in the winter.

From 1961 to 1990, Weller says, the mean winter temperature for the arctic rose 1.44 degrees Fahrenheit. That may not seem much in a region where a typical winter day may see temperatures of 60 degrees below zero, but it is enough to have some effect and it is expected to rise.

“If you extrapolate this for a hundred years or so, you can see that we are talking about temperature increases between 3.6 and 10.8 [degrees] or more over much of Alaska,” he said.

The ice pack that blankets the Arctic Ocean is already thinner and breaks up earlier in the year, suggesting that ice formation is being impeded, he said.

One of the most troubling signs is a gradual warming of the permafrost that underlies most of Alaska. Geophysicist Tom Osterkamp has found that vast areas of permafrost--land that is permanently frozen--just north of Fairbanks have been thawing in recent years.

That causes the land to sag, destroying highways, pipelines and structures, and it also releases additional carbon into the atmosphere, possibly accelerating the greenhouse effect.

There is some evidence that the tree line, expected to move farther north, is already marching into the Brooks Range, a barren chain of jagged peaks just south of the arctic plain.

“If you get up into the Brooks Range now, you can find happy little birch trees,” John Bryant, professor of ecology at the university, told scientists attending a recent conference here on global change.

As it is in most places, the ecology of the arctic is extremely complex, with widely different species dependent upon each other for survival. A slight change in weather patterns can cause a shift in vegetation that could wipe out some species while nourishing others. Even an increase in clouds can make a difference.

“In 1983 and 1985, we had very wet and cloudy summers,” Bryant said. “It was so cloudy that horses were dying of nitrate poisoning because the cloud cover was so thick plants didn’t grow very fast. They accumulated nitrate, horses ate it and they died.”

Bryant and several colleagues have studied the “paleoecological” record, frozen and preserved in the tundra of Alaska, and fear they have found an ancient parallel to what is happening now.

“We had a warming event 10,000 or so years ago” at the end of the last ice age, he said. The record shows that during that warming trend, the grasslike plants that cover much of the far north were gradually replaced by shrubs and dwarf birch.

Most large grazing animals, such as caribou and musk ox, would rather die than eat birch. Caribou feed mainly on lichen in the winter and cotton grass the rest of the year, and those resources are in dire jeopardy.

“Cotton grass is declining rapidly. So one of the major herbs of our arctic tundra is disappearing. Birch is increasing,” Bryant said. “This does not look too different from what you see in the paleo record” of the warming trend 10,000 years ago.

Cotton grass provides protein, which is directly linked to caribou reproduction. If a female caribou does not receive enough protein shortly after dropping her calf, she will not conceive the next season, according to research at the university.

“This is a period when you need a fair amount of protein if you happen to be a cow caribou,” Bryant said. “Birch is simply not eaten very much. So a decline in cotton grass means the cow caribou loses its major source of protein right at the time it needs it, and is faced with something that it really doesn’t want to eat.

“So it doesn’t look good for a caribou.”

The effect of warmer weather could be at least as disastrous for the old spruce trees that now blanket millions of acres in Alaska. Bryant blames the current bark beetle infestation on warmer weather.

Insects thrive in warmer temperatures, particularly the bark beetle that kills the tree by ringing it with bore holes. The same insect has killed thousands of pines in California forests, but its presence in Alaska is recent.

A healthy spruce can put up a good fight, but Bryant believes Alaska’s spruce trees are growing weaker. Global warming is expected to produce an increase in overall rainfall, with occasional droughts, leading to root rot and a stressed tree that is unable to fight off the beetles, Bryant said. A healthy tree, he said, can generate enough sap to literally push the beetle out of its bore hole, but a stressed tree does not contain the water to produce enough sap to accomplish that.

Bryant expects to see vast forests of standing dead spruce trees, just waiting for the right bolt of lightning. If that happens, he says, fires probably will rage for years over much of northern Alaska.

“We will have firestorms to go with our beetle storms,” he said.

That will denude the hillsides and valleys of the forest canopy, enabling birch trees to continue their march across the state.

And in the far north, where thousands of caribou and musk ox thrive on grasses that are already declining, life will become grim indeed.

Of course, Bryant is the first to admit he could be wrong.

“Nobody really knows what’s going to happen,” he says. “But my gut feeling is that we are going to see a repeat of the birch epoch of 10,000 years ago.”

He says the paleo record for that period also shows it to have been a time of mass extinctions, reinforcing his fears about the future of the far north.

And he and his colleagues believe the future has begun.

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Permafrost and Tree Line Changes

Scientists fear that global warming will have devastating effects on Alaska and the far north. The rise in temperature will shift the tree line and permafrost line farther north, jolting the ecological balance. Shown here are projected movements over the next 100 years, but some experts say the warming trend has already begun to affect Alaska.