"In general, the conclusions we make in here are what all the fire ecologists say every year, except that usually people don't quantify it," said Kieran Suckling of the Center for Biological Diversity, a Tuscson-based advocacy group that helped pay for the study.

"And usually people don't start saying this until three months after the fire season."

A chief author of the new study, forest ecologist Peter Morrison, said it suggests some changes in the nation's fire-fighting policies.

In addition to prescribed burns and allowing other fires to continue burning, Morrison would target forest-thinning operations to areas adjacent to rural and urban areas where people live, which tend to be lower-elevation "dry conifer" forests.

These were among the first forests logged in the late 1800s and early 1900s, in part because they were the most accessible.

In the decades that followed, many regenerated into unnaturally dense stands of spindly trees, largely because fires that once naturally thinned the forests were systematically fought by the U.S. Forest Service and others. Much of this land is in private hands.

The timber industry is likely to reject these conclusions.

"Do they really care or are they trying to spin something?" asked Keith Olson, executive director of the Montana Logging Association. "I think they're environmentalist groups with an agenda, and their agenda is to downplay the devastating consequences of this fire season and downplay how an administration fiddled while Rome burned."

Allowing forests to burn while demand for paper and other wood products increases is foolish, Olson said.

"We're going to double the population, we're not going to log, we're going to burn forests?" he said. "I have a problem with that."

Morrison, though, said fire is natural while logging is not.

"Logging isn't going to do it. Loggers like to think that's a solution, but that doesn't replicate fire and it doesn't prevent fire," Morrison said. "Our studies show that logged areas burn readily and burn ferociously in many cases."

Fire, Morrison said, is natural to all Western forests, although it is much more frequent in some than in others. In the higher, moister forests, fire is likely to occur less often.

But as decades pass with no fires, lots of dead limbs and trees accumulate on the forest floor. So when fires do start, they tend to burn intensely and often wipe out whole stands of trees.

At lower elevations, in the dry conifer forests, fire was more likely under pre-logging conditions to sweep through relatively frequently at ground level. This cleared out accumulated underbrush and killed off small trees while leaving larger ones alive.

Under natural circumstances, fire acted "like a gardener that determined what grows in the garden," Morrison said.

It was also a sort of weed-and-feed operation. In addition to killing off small trees and underbrush, fire recycled nutrients back into the soil from dead or dying vegetation. The trees that remained got a shot of fertilizer.

"It keeps these ecosystems as vibrant, healthy ecosystems," Morrison said. "Without fire, it's like a person who never cleans up their room, never sweeps its, never takes the garbage out, never does any of that.

"It's not a very healthy place to live."

The PBI study coming out today follows the recent release of a separate study by the Congressional Research Service concluding that large reductions in timber-cutting have had little or no effect on the frequency of fires.

"The acres burned in any particular year appear to be at most weakly related to the volume of timber harvested," the CRS concluded.

The amount of timber cut in national forests dropped 77 percent between 1987 and 1999 as Endangered Species Act restrictions kicked in for the spotted owl and other protected animals and plants.

Timber industry officials and their supporters in Congress, including House Speaker Dennis Hastert, have blamed the ferocious fires on the lack of logging under the Clinton administration.

The idea is that with less wood in the woods, the fires would not rage so intensely.

CRS investigators compared the fires that burned when logging was at full throttle to when it was reduced. They reported "fewer acres burned in association with lower timber harvests, contrary to the hypothesis" of those who want to cut down more trees.

"Timber harvesting removes the relatively large diameter wood that can be converted into wood products, but leaves behind the small material, especially twigs and needles," the CRS reported.

"The concentration of these 'fine fuels' on the forest floor increases the rate of spread of wildfires."

This week the Clinton administration will release its strategy for dealing with future conflagrations. A Senate subcommittee plans hearings later this month.

In recent years, Forest Service officials have tried to reduce the threat of wildfire in scattered pockets through thinning and prescribed burns. They targeted areas where they could cover the most acreage with the fewest dollars.

That will have to change, said Chris Wood, a senior adviser to Forest Service Chief Mike Dombeck. Echoing the results of the study coming out today, he said thinning and controlled burning will have to be focused in lower-elevation forests where, biologically, they make the most sense.

Those also happen to be the forests closest to towns and homes.

"There are many who want to turn this into a timber fight," Wood said. "This is not about timber. This is about restoring. Fire is going to burn in fire-adapted ecosystems . . . The key is to try to minimize the damage."