Is Alaska Already Melting? : Record warm temperatures are affecting forests in the far north. Many scientists say the greenhouse effect has begun. : Science File / an exploration of issues and trends affecting science, medicine and the environment

John Bryant needed to look no farther than the spruce tree growing in his own frontyard to conclude that the vast evergreen forests of northern Alaska are in trouble.

Showing signs of environmental stress that made it more susceptible to deadly insects, his tree grew weaker and weaker before Bryant’s eyes. He is a professor of ecology at the University of Alaska and an expert on plant physiology, so he knew there was little he could do to save the tree.

It is dying, he believes, because of changes in the local climate driven by events thousands of miles away.

His tree is not alone. Throughout much of northern Alaska, giant old spruce trees are dying at an alarming rate as bark beetles attack the forests with unmerciful zeal, moving across the landscape like a deadly plague. Beetles and other insects are known to thrive in warmer weather, which undeniably has enveloped this state in recent years.

The beetles hit the spruce-rich lands of the Kenai Peninsula just to the south of Anchorage last year, and they took no prisoners.

“The Kenai Peninsula,” once rich with the dark green foliage of majestic spruce trees, “has been cleaned out,” Bryant says with the resignation of a scientist who believes great changes are taking place in the northernmost lands of North America.

Although the evidence is inconclusive--and will be for many years--Bryant believes that the global warming phenomenon called the greenhouse effect has arrived. And as predicted, it is most evident in the Arctic and sub-Arctic regions of Alaska and Canada.

The greenhouse effect is caused primarily by the release of carbon dioxide from the burning of fossil fuels. The gas traps heat in the Earth’s lower atmosphere, causing a warming trend that many predict will have major consequences for global weather patterns.

For years, scientists have suggested that global temperatures will rise from the greenhouse effect, although they have debated fiercely whether current warming can be blamed on increased levels of carbon dioxide dating back to the beginning of the Industrial Revolution or is just part of a natural warming/cooling cycle.

But here in the far north, where the effect is expected to be the most severe, scientists who are studying every aspect of the problem are less circumspect.

“You are probably going to see the evergreen forest disappearing at a high rate,” Bryant told scientists attending a symposium here on global warming. “And I think that’s happening now.”

His colleagues were a little more conservative in their statements, although all agree that weather patterns in the north have shown a dramatic warming trend over the past three decades.

“Does that have anything to do with global greenhouse?” Gunter Weller, director of the university’s Geophysical Institute, asked rhetorically. “We cannot say.”

But like the other scientists who attended the symposium, sponsored by the Arctic division of the American Assn. for the Advancement of Science, he believes the evidence clearly points in that direction.

Changes are already under way, many contend, and in the years ahead the far north will probably go through a dramatic evolution. Some changes could be disastrous, especially for wildlife, but some could be beneficial. Vast areas of Alaska that are now difficult to develop because of severe weather patterns could become more hospitable to oil and mineral extraction.

And if Bryant’s fears are correct, residents won’t have to worry about the effect on the great herds of caribou that now roam the same lands. They won’t be there.

Most predictions are long term, extending over the next century, but many people believe that some changes are already under way and that the rate of change could be dramatic.

Among the expectations:

* Temperatures throughout most of the far north will rise several degrees, possibly as much as 22 degrees Fahrenheit in some areas, within the next century.

* Increasing temperatures will cause sea ice to melt, or not form at all, thus freeing areas to navigation that are now locked in ice for much of the year. That could permit ship traffic directly from Alaska to Europe and northern Asia, but it would also allow storm surges now mitigated by ice to sweep ashore with possibly devastating results.

* Rising temperatures will bring more rain and more snow to the far north, initially causing Alaska’s thousands of glaciers to grow. But in time they will melt more rapidly than they accumulate snowfall, sending megatons of water down the rivers and into the sea, causing sea levels to rise so much that parts of Alaska--and the rest of the world--will be inundated.

* Alaska’s forests will move farther north, but they will be made up mainly of hardwoods such as birch, not evergreens.

* The small shrubs and grasses that now feed the vast herds of caribou and musk ox will die out with dire consequences for wildlife.

All of these predictions are based on the assumption that the current warming trends, which have broken records throughout Alaska in recent years, are part of a long-term change brought on by the greenhouse effect. If the current trend turns out to be just a peculiar blip in what scientists just a few years ago were predicting--a cooling trend--then the scenario will change dramatically.

Despite the caution most scientists deploy in their pronouncements, the experts attending the symposium in Fairbanks overwhelmingly believe that the greenhouse effect has arrived and that it will be here for a long, long time. As if to punctuate their findings, the temperature outside the meeting rooms broke all-time records on each of the four days of the symposium, turning the normally crisp days of autumn into the balmy days of summer.

Referring to the shirt-sleeve weather outside, geophysicist Juan Roederer of the University of Alaska said:

“Global warming may appear to be beneficial, as it is outside right now, but it could have very detrimental effects.”