Saving The Pine Forest

Wally Covington has shaped the debate and befuddled critics with woodsy charm and the tenacity of a badger

Northern Arizona University Forester Wally Covington has spent 25 years experimenting with how to turn overgrown thickets with 1,200 trees per acre (right) into healthy forests (above) with lots of grass and wildlife.


Northern Arizona University Forester Wally Covington has spent 25 years experimenting with how to turn overgrown thickets with 1,200 trees per acre (right) into healthy forests (above) with lots of grass and wildlife.



Wally Covington


Wally Covington (right) and a colleague measure the diameter of a tree in an experimental forest near Flagstaff. After thinning the plot, the tree’s growth rate increased markedly almost immediately.

Wally Covington, who has spent a quarter century reshaping the debate about forest management, leaned forward excitedly across the boundary between his biggest disappointment and his dearest hope.

On one hand, lush grass and scattered flowers swayed in the dappled sunlight in an open forest dominated by widely spaced, ponderosa pines.

On the other side of a wire fence huddled a dark, thick forest, with the smattering of grand old trees besieged by tangles of spindly saplings — the ground covered by pine needles rather than grass.

The contrast between those two patches of forest underlies his unsettling conclusion that the forests of the Southwest sway at the edge of ecological disaster, which can only be averted by a politically unlikely reinvention of the timber industry to thin millions of acres as a prelude to restoring fire to its rightful role.

The gangling, former medical student and current professor of forestry at Northern Arizona University has spent the last quarter century studying these two patches of forest just outside Flagstaff. His findings have spurred controversy and dominated a high-stakes debate about the future of the ponderosa pine forests of the Southwest.

He has alternatively lambasted Forest Service land management practices, indicted unrestricted cattle grazing and outraged environmentalists — all of it by doggedly pursuing the evidence on the ground.

Tall as a lodgepole pine with big hands, big ideas and the persistence of a badger, Covington has argued tenaciously that the only way to save the world’s largest ponderosa pine forest is to reduce densities from the current 800 to 1,500 trees per acre to the 25 to 50 trees per acre densities of the pre-settlement forest. Fire alone can’t do that, thanks to the degraded condition of the forest today, he says.

If he’s right, then the current Forest Service emphasis on letting low-intensity fires like the recent Milk Point Fire simply burn will likely provide less protection for Rim communities than foresters and residents might hope. Renewed fires without preliminary thinning might not only leave the problematic small trees and debris intact, but could preferentially kill the big trees the forest needs to regain health, concluded Covington, as a result of a 25-year experiment with side-by-side patches of forest.

A child of the ’60s born in 1947, he was raised in Oklahoma by a father who was a forester, prizefighter, radio announcer and barnstorming pilot. His father imbued a hard-headed, reverence for the woods, in the course of years of hunting, fishing and camping — buttressed by readings from Aldo Leopold’s San County Almanac.

After his father died and his mother survived a struggle with cancer, Covington headed off to medical school. But he found the emotional impact of dealing with dying cancer patients too taxing, so he got a master’s degree in biology at the University of New Mexico, then a degree in forestry from Yale.

He has been working tenaciously to understand the unhinged ecosystems of the drought-adapted ponderosa pine forest ever since, with a childlike enthusiasm for discovery, a low-key, woodsy charm, an unflappable sense of proportion and a rare ability to think on the scale of a 300-year-old tree.

Covington’s findings indicted a century of wrong-headed Forest Service management, especially fire suppression, cattle grazing, and to a lesser extent, clear-cut logging. So environmentalists pushing for a return to a healthy, natural forest initially embraced his findings.

But as the data accumulated — especially along this vital fence boundary in the oldest experimental forest in the Southwest — Covington was forced to reluctantly give up the idea that a careful return of fire without preliminary thinning could restore forest health.

Ironically, after having played a vital role in convincing the Forest Service to abandon a simple-minded effort to stamp out all forest fires, Covington now finds himself in an uncomfortable no-man’s-land between advocates of the rapid, widespread return of fire as a management tool and environmentalists advocating a hands-off approach.

The shift has made him the chief proponent for a re-invented timber industry as the only way to prevent the inevitable return of fire from perhaps eliminating ponderosa pines across millions of acres — endangering a host of forest communities in the process.

Covington’s prescription combines hand-thinning followed by restoration of a natural fire regime. Termed the “Flagstaff Model,” that prescription is now being applied in a wide buffer zone around Flagstaff and Rim communities like Payson, Pine and Strawberry. Covington also got research grants from the federal government to test his approach to forest restoration on a huge expanse of dark, crowded forest on Mount Trumbell in the Arizona Strip.

His prescription has proven controversial. The drastic reduction in tree densities initially leaves a treated forest looking devastated. Moreover, the logic of his research leads to the conclusion that only a restored timber industry that can make money on millions of small diameter trees can save the forest.

His argument rests heavily on what you see when standing on this boundary between two differently managed patches of experimental forest.

His studies in several experimental forests near Flagstaff have shown that the current forest bears little resemblance to the open, sunny, grassy forest that existed before the arrival of Europeans in the area some 200 years ago. In the Gus Pearson Natural Area, established in 1908, photographs and the meticulous plotting of every old-growth tree, stump and scrap of wood showed a dramatic increase in densities — from 22 trees per acre to more than 1,200. Covington blamed that increase on both fire suppression and cattle grazing, since the cattle removed the grass that could carry the periodic, low-intensity ground fires to which the forest had adapted.

So the researchers decided to “treat” the forest in different ways and compare the results, starting in 1992.

One patch, they left alone as a control sample.

In an adjoining patch, they cut down enough trees to restore densities to 1876 levels, then left it alone to study the result. That involved leaving more than 23 trees per acre, since they left several small trees for each old-growth stump they located, to ensure one would live long enough to replace the missing giant.

In the third patch, they thinned trees, then set ground fires every four or five years to burn off brush, leaves on the ground and returning seedlings. In that treatment, crews also raked away the thick layer of needles and debris that had accumulated at the base of all the big trees during the decades of fire suppression.

The results were dramatic. The remaining trees immediately increased their growth rate, up to 55 percent in most cases. The gains proved especially dramatic during the drought. The leaves of the trees had significantly more nitrogen and tougher foliage, with great resin flow. That resin flow dramatically increased the tree’s resistance to bark beetles, which have killed millions of pine in recent years.

The thinned forests — especially the patch with regular fires — produced six times as much grass, which nearly doubled the number of animal and insect species present — rising from 37 to 66.

Covington then applied that prescription on a wider scale at another, larger experimental forest nearby.

Here, he once again meticulously reconstructed that vanished, old-growth forest. Then his restoration crews removed most of the existing trees, even large trees that were clustered more tightly than the trees of that old-growth forest.

Criticism poured in when people got a look at the severity of the thinning. Some environmental groups even posted photos of the seemingly denuded landscape on Web sites to decry Covington’s approach.

But year by year, the forest recovered, with lush grass and flowers.

Now, that small extent of forest looks like a restoration postcard, in stark contrast to the dark, crowded, huddled forests that surround it.

The restoration of that experimental forest stands as Covington’s dearest hope, since it provides a model for the restoration of an endangered forest he loves.

However, his greatest disappointment still reproaches him from the other side of the fence, a rebuff to his once fiercely-held hope that the forest could be saved with the simple reintroduction of fire.

In that adjoining patch, the Forest Service tried its hand at using fire alone to restore ecological balance. The Forest Service for some 20 years has regularly set fire to that experimental patch of woods, timing the fires for the cool spring and fall conditions that would keep the flames from getting out of control. Foresters hoped the fires would creep through and burn off the brush and saplings, leaving the big trees intact.

Oddly enough, just the opposite happened. The fires often wandered through without consuming the downed logs or even many of the saplings. However, the heat did settle into the mounds of leaves and needles built up over decades around the bases of the big trees.

The intense heat at ground level girdled the trees, cutting off the flow of nutrients and moisture just under the bark up to the leaves above. As a result, the ground fires that burned through without first removing the debris from the base of the big trees left a thick tangle of forest — but preferentially killed the bigger trees, said Covington.

“That was a big disappointment,” he said, “we were really hoping that would work.”

Obviously, it would have made the job of restoring the forest far less costly.

In the fire season just past, the Forest Service has embraced the idea of letting fires burn, including the big fire on Milk Ranch Point.

Burns without preliminary thinning only cost a couple hundred dollars per acre, since crews must simply contain the fire and keep it from spreading toward structures. By contrast, it costs about $1,000 per acre to hand thin the forest, pile up the debris, then burn the slash pile. Forest Service crews have done just that on thousands of acres surrounding Rim communities, but obviously can’t afford to take that approach on the millions of acres of unhealthy forest.

All of which brought Covington to the conclusion that the only remaining hope is to develop a timber industry that can do the thinning work at little or no cost to taxpayers.


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