Colorado brown.

LAKE CITY, COLORADO-At first it was a just vague impression, something working uncomfortably at the edge of consciousness as I drove along the twisty roads and mountain highways of Colorado--my first tour of the Front Range since I left it behind after a two-year sojourn that ended in 1949. I had not been back since then and naturally had no vivid memory of the particulars, 42 years being not exactly yesterday. Then on the way to Lake City, which is about 50 miles south of Gunnison, l saw a whole mountainside of it. The trees were no longer green. They were brown.

In the days after that, of course, I saw it everywhere--the Colorado brown--for I began looking for it. Still everything seemed normal when I arrived at Lake City, a little Victorian village nestled in a remote valley. I spoke to a young Forest Service seasonal worker who was dispensing wilderness advice and handing out trail maps in a storefront ranger station. I told her what I had seen up near Gunnison. "Trees look pretty good here," I ventured.

"Yeah, now," she replied. She was still a girl, at least from the standpoint of my years. But a big backpacker kind of girl, blond and healthy and good looking with an open honest face.

"But it's coming. It's all around us. Coming in from the north, especially, and from the east and west, too." "What is it, exactly?" I asked.

"Bugs," she said. "A big damn plague of bugs."

She had not yet learned to be a cool Forest Service professional, not to sweat what you can't do anything about and to talk ecology to discourage the civilians from asking stupid questions. Instead, she told me she was terrified because the mountains are turning brown all around her. She gave me some maps. I could hike all day long around Lake City, she said, and not see any damage at all. Left unspoken was the suggestion that I'd better hurry up.

Back on the other side of the Continental Divide, in Lakewood, I got the ecology explained to me by one of the chief bug experts of the Forest Service's Rocky Mountain region, R.D. Averill, a forest entomologist who heads up a task force dealing with what "it" is that is changing the colors in the Colorado mountains. R.D. is a Rocky Mountain version of a good ol' boy, an exGyrene who fought in 'Nam and who now sports cowboy boots, a luxurious moustache, and a Ph.D. from Michigan State University. He is a second-generation Colorado forester: His ranger dad roamed the mountains with the great ones of a generation ago--such men as the militant wilderness advocate Robert Marshall, who was one of the elder Averill's best friends.

Averill told me that there are two bugs doing the damage. First comes the spruce budworm which doesn't just fancy spruces but quite a few other trees, especially Douglas-fir. The female budworm moth, said Averill, warming to his subject, "is a real egg factory. She'll lay several egg masses a day, with 20 to 40 eggs in each mass, on the tender shoots of a host conifer. When the eggs hatch, about 20 days after they're laid, the young larvae look for a place to spend the winter. So they climb under a bit of bark. Then they wait there until the next spring. When it warms up--about the time the buds are expanding--the larvae become active and go into the bud and start feeding." And then the tree dies?

"Not that simple. After the spruce budworms work for a while, weakening the stand, they're followed by the Douglasfir bark beetle," said Averill. "In the conventional view as it's given in the Forest Service literature, the bark beetle does not build up into a large population. Theoretically, the beetles are only a minor component, and outbreaks only last a couple of years. They're not a very threatening type of insect--weaL not an aggressor." R.D. paused to let me catch up with my notes.

"Unfortunately," said Averill, "the bee-ties we've got in this region haven't read the book, and they don't know how to behave. So in the past 10 or 12 years we've experienced much higher losses that we should."

As for the spruce budworm, R.D. noted that infestations are visible on about 300,000 acres in Colorado, but he added that the number of acres involved may understate the severity of infestation since the outbreaks are concentrated in the lower elevation areas of the Front Range.

One of the interesting things about the spruce budworm, said Averill, is the random way it moves from place to place. When evening comes, the female spruce budworm moth rises up on warm air currents. If the air is moving, a whole population, said R.D., "can just migrate out of an area even if it's laid only 20 percent of its eggs. When the air cools down, the moths come down, wherever they happen to be, and then they lay the rest of their eggs."

So. The spruce budworms infest the forest in their immutably random way, the beetles come in after the budworms weaken the trees, and because of that the Douglas-fir bark beetles have become killer bugs, boring into host trees by the thousands to carve their galleries and raise their families, in the course of which they choke off the transport of water and nutrients and sugars needed for cellular growth and import a deadly fungus into the bargain. They are not, it turns out, the mild-mannered fellows they were believed to be.

But back to first causes: How come there are so many spruce budworms to begin with?

Although there's a difference of opinion among the experts on how bad Colorado's current budworm-beetle infestation is, they are pretty much agreed on the basic cause which, not to put too fine a point on it, is us-or at least our forebears.

As is often the case, natural disasters obtain because humans have, as George Perkins Marsh put it more than a century ago, "rearranged nature's original balances." In his classic, Man and Nature, Marsh explained how it is that trees won't grow any more on the Aegean hillsides, which have been browsed off into hard dry rockiness by a thousand years of Grecian goats. Paradoxically, the Colorado Rockies have just the opposite problem. The trees are dying because in the last 100 years the hillsides have been growing too many trees.

This dramatic change in the physical geography of the Front Range has been the preoccupation of Thomas Veblen, chair of the geography department at the University of Colorado. I sought out Veblen in order to discuss the rearrangement of nature's original balances.

"In the vast majority of cases," he explained during a visit to his cluttered office in Boulder, "humans are implicated in one way or another. But when you set out to prove that humans are doing something that results in forest decline, it's very, very tricky.

"The major change in the Front Range forest is fire suppression. Under preWhite settlement conditions, we had relatively frequent burning of low-elevation forests--the open-woodland, ponderosapine forest. But with fire suppression over the last 70 to 80 years, there have been two results. First, an expansion of the forest area into places where the forest did not exist before; and second, at a slightly higher elevation, formerly open stands that have now become very dense stands with a lot of Doug fir in them, which then are susceptible to spruce budworm attack."

Veblen summed it up this way: "In these relatively low-elevation forests, we had fire frequencies at 20- to 30-year intervals. Now with complete fire suppression, we're getting an entirely different kind of stand structure." Meaning that instead of open ponderosa pine woodlands, or meadow, the slopes are now dense with shade-loving firs that are irresistible to spruce budworms.

After the budworms weaken the stands (they sometimes kill their hosts after many years of infestation, but not always), the bark beetles move in and finish the job. lf there's plenty of moisture about--which has not been the case in the Rockies, now going through some extremely dry years--the host trees can literally dislodge the bark beetle by concentrating a flow of sap to flush the invader out of the hole he is boring to create a colony. But in dry times, and dry places, the beetle succeeds in penetrating the bark, and in short order--a year or two--the trees die.

Well, one wants to know, how about playing Indian and setting some fires? In fact, Veblen took the question seriously. "The trouble is that by this time, we've got such an accumulation of fuel that we can't just let the natural lightning ignition continue. If we did, we'd have very catastrophic fires, whereas previously we had low-intensity surface fires. If we want to re-institute natural fires into this ecosystem, we'll have to remove fuels mechanically, and that's a very expensive proposition."

It would seem, then, that if you need to pin the blame on someone, you might start with Thomas Jefferson, who was so eager to move the nation westward and sent Lewis and Clark to scout it out in 1803. Jefferson thought it might take 40 generations to settle this far country. As it turned out, it took about four, and within that time, with tree-cutting and clearing and fire suppression, we humans changed the forest's composition forever.

To demonstrate the point, Veblen has searched out old photographs of various spots around the Front Range. Most are prints dating to the turn of the century. Then, with the help of a graduate stu[Incomplete Text in Original Pubication] which the old pictures were taken, whereupon he took one of his own. In pair after pair of these matched pictures, the mountainsides are sparsely wooded with big trees in the old prints, and lushly forested with smaller trees in Veblen's modern slides.

To be sure, there have always been insect outbreaks along the Front Range. Studies of tree tings have revealed severe infestations of spruce budworms even in pre-settlement days. So despite the changed composition of the forest, aren't the brown patches in the mountains of Colorado simply part of a natural cycle? A good many of the dozen or so experts I interviewed along the Front Range believe that is true. This is a comforting thought, right enough, and one that I was holding onto myself. But then I ran into Ann Lynch, a research entomologist at the Forest Service's Rocky Mountain Forest and Range Experiment Station in Fort Collins.

A few years ago, Lynch and a colleague from the University of Arizona, Thomas Swetnam, decided to trace the long-term history of budworm outbreaks in the Rockies of Colorado and northern New Mexico, pulling together all the tree-ring data they could find.

Lynch summarized the very elaborate research she and Swetnam conducted. "Prior to European settlement," she said, "you'd have an outbreak in a small area--say in the mountains where the Carson National Forest is now. Then five or 10 years later it would be somewhere else. Widely separated and irregular. Then Europeans came in and grazed the area and controlled fire and cut out preferentially the shade-intolerant species. So the forest changed toward the shadetolerant species, the preferred hosts for spruce budworm."

So far, she had only recapped the conventional wisdom. "But now," she went on, her voice rising to keep me focused on the importance of what she was saying, "when you have outbreaks, they tend to occur over vastly larger regions and all at once." To demonstrate this unsettling finding, she showed me a graph she and Swetnam had prepared. On it were plotted spruce budworm outbreaks in 10 locations from the year 1700 to 1980.

"See how scattered they are early on?" she said, pointing to the graph. "Then look what happens after European settlement." She explained that the relatively long gaps after 1800 were because of logging operations. But after cutting all the big pine out, she said, when what you've got is mainly Douglas-fir and white fir, then you begin to see the outbreaks becoming more frequent and more widespread. "Look how the last two outbreaks have hit every stand." And there they were, lined up like phalanxes of Roman troops invading Gaul.

Synchronicity is the word Ann Lynch used for this phenomenon. But it seemed to me to be synchronicity with a vengeance, self-potentiating, with each event becoming more frequent, more widespread, and, some believe, more virUlent.

"Well, maybe that's as it should be," said Terry Shaw, who heads up the forest pathology work at Ft. Collins, and like many who are witness to great natural forces is inclined to take the long view. "Some ecologists argue that the budworm dieback is just what should happen--to restore the original forest composition and area."

But meanwhile, the climate warms, changing at a rate 100 times normal, according to Stephen Schneider at Boulder's National Center for Atmospheric Research. The trees might have a difficult time adapting to that, and then, in some nightmare scenario, nothing would come back, like the browsed off Mediterranean basin, ruined for the millennia by mercenary Greeks.

The words of the young woman at the Forest Service's storefront office in Lake City echoed in my mind. "Terrified," she had said. She was no ecologist, of course. Such language is not an acceptable part of the jargon in that particular trade. The budworm population may "crash" as they say. It happens. Or all the female moths may rise up on a summer's evening, never to return. Or perhaps as a survival strategy, the opportunistic bark beetle will evolve to a less destructive form before the fir-tree larder goes completely bare. Or, terrible thought, a vast conflagration will solve the problem for everybody.

But meanwhile, the mountains are turning brown, and the inexorability of an unsatisfactory outcome is strongly suggested by Ann Lynch's chart. For the moment then, maybe "terrified" is just the right word for it.