W. Wallace Covington, a professor of forest ecology at Northern Arizona University, likes to invoke the memory of Aldo Leopold, the naturalist and philosopher who lectured on the importance of undisturbed wilderness.

Of course, there are no more undisturbed wildernesses, and after more than a century of fire suppression, grazing, logging--forest gardening, essentially--even those areas officially designated as "wilderness" are choking on their own prodigious growth, and so full of firewood that they could be incinerated with the next lightning bolt or careless campfire.

Covington's work branches out from his discovery that over the last 100 years, the ponderosa pine forests around Flagstaff have increased in density from around 23 trees per acre to more than 851 trees per acre. And at the same time, the grasses on the forest floor have dropped from more than 1,000 tons per acre to about 112 tons per acre. Studies on the Kaibab Plateau show a similar, if less drastic, change, as well.

Like some vaccination that uses a mild dose of disease to render a body immune, Covington wants to garden the wilderness back to some approximation of nature.

And though it terrifies them to admit it, both the logging industry and the environmentalists, who are by principle at loggerheads on everything, agree with Covington--if for different reasons.

Wally Covington is a tree-size man--six-foot-five--with thick auburn sideburns, and 1970s-style wire-rimmed glasses. On a recent morning, he lumbers through his own experimental forest, just off Highway 180 north of Flagstaff, on the Forest Service's Fort Valley Experiment Station.

Like his idol, Aldo Leopold, who taught right here in Fort Valley, Wally Covington came to Flagstaff with a Ph.D. in forestry from Yale. Since arriving in 1976, Covington has distinguished himself in the academic community; since 1984, he has cultivated more than $2 million in academic grants. This plot was worth $300,000 from the National Science Foundation. And Covington is overseeing another forthcoming $2.8 million in federal funds for a similar, but larger, restoration project on the Arizona Strip west of the Grand Canyon.

Ironically, the Fort Valley Station was set aside in 1906 by Gifford Pinchot, the father of the modern Forest Service, to figure out ways to make the ponderosa pine forests around Flagstaff more productive.

When settlers first arrived in the area in the late 1800s, they found parklike forests with big, yellow-barked pines scattered in clumps across grassy meadows.

The fledgling Forest Service saw those wide-open glades as understocked tree farms and wanted to figure out ways to grow enough trees to make timbering productive and profitable. Little did they know the process had already been set in motion.

The logic of the era said that if you eliminated all predators, there would be plenty of game to be had by humans. And if you eliminated fire from the landscape, there would be more trees to cut.

Before the arrival of European Americans, fires had flashed through the forest nearly every other year, burning off the brushy undergrowth and excess pine seedlings. But by 1876, with the Native Americans newly sequestered on reservations and the railroad chugging through the territory, Arizona settlers filled the landscape with sheep and then cattle, which quickly chewed off the grass, which eliminated the fuel for the frequent fires. And in the absence of fire, the forest grew like never before.

The 1906 Forest Service experiment became a moot point; the tree farm grew by itself. As a reminder, Wally Covington's 1995 study areas are bordered by dog-hair thickets, ponderosa pines packed so tightly that in 85 years they have not managed to grow thicker than four inches in diameter.

If such a forest catches fire, the flames don't just flash along the ground, leaving the big trees untouched as in the prehistoric forest. Instead, the undergrowth and debris serve as kindling and the fires climb up into the crowns of the trees, killing them all. A crown fire can be far more devastating than a clearcut and can set off a succession of ecological events that could take 1,000 years to heal.

Covington wants to cut the forest back to where it was 100 years ago, with the hope that if he does there will still be something left 100 years from now.

One year ago, Covington and volunteer helpers removed most of the smaller, postsettlement pines from an eight-acre plot in Fort Valley. Whereas logging operations leave piles of leaves and branches--called "slash"--on the ground, Covington hauled it away, then raked the combustible pine needles and forest litter, or "duff," from beneath the trees. He burned off the rest with controlled fire, then mowed 14 acres of nearby Hart Prairie, hauled the grass and wildflower clippings up to Fort Valley and spread it over the ground, with the hope that soil will be seeded. Covington plans to set more fires to burn off the undergrowth and try to restore the original fire regime.

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Michael Kiefer