Saving the forest for the trees

After saying good-bye to Smokey-the-Bear tactics, forest managers are at loggerheads about how to prevent catastrophic wildfires. Published in California Monthly magazine.

Scott Stephens has experienced firsthand the power of a raging wildfire. First, he says, there’s the incredible heat, so strong it can be felt hundreds of feet from the flames. Then there’s the deafening noise, like a jet engine, roaring and screaming as the flames race up into the crowns of the trees. There’s the thick, heavy smoke and the strong winds created as the fire sucks up air from all around. And, above all, there’s the fear. “Fires are absolutely chaotic. They can change so quickly, especially the big ones,” says Stephens. Around 25 people lose their lives fighting wildfires in the U.S. every year.

Having served on the front lines in firefighting teams, Stephens appreciates better than most the urge to put out wildfires. And yet, as a professor of fire science at Berkeley, he also understands that it is this very practice of trying to extinguish every fire–big or small–that has led to the worst fire seasons in the history of the western United States. In the last hundred years, since that effort began, firefighters have become steadily better at their job. In 2002, they managed to contain 99 percent of all wildfires before they got out of control–yet 7.2 million acres were consumed by fire nationwide, the second worst season on record (surpassed only by the 7.3 million acres that burned in 2000).

These huge fires have also sparked a heated national debate over how best to prevent them. Last September, before the end of the devastating 2002 fire season, the White House put forward its plan–the Healthy Forests Initiative–which proposed “thinning” the national forests to reduce the risk of catastrophic wildfire. Environmental groups like the Sierra Club responded that “thinning” is just a polite word for “logging”; they contend that the careful reintroduction of fire, a natural part of these forest ecosystems, is the right way forward.

According to fire history studies, the forested areas of California used to see frequent wildfires–any given spot in the lower elevations of the Sierra Nevada would experience, on average, one fire per decade. In the days before European settlement, between 5.5 and 16 million acres burned annually in the state. “Fires then were more frequent and more diverse,” says Stephens. “They used to occur for longer periods, sometimes months at a time.” Those fires would regularly burn up “surface fuels”–fallen tree limbs and branches and small shrubs–preventing them from accumulating. These small fires stayed close to the ground, only rarely reaching up into the canopy. But since those small fires have been eliminated over the years by conscientious fire-fighting efforts, surface fuels have increased to dangerous levels–40 or 50 tons per acre in many places, compared with fewer than 10 tons per acre before the era of fire suppression.

The energy stored in those surface fuels is now so great–a single forest contains the equivalent of an atomic bomb–that, when they do ignite, they can set the whole forest ablaze, creating catastrophic wildfires that leave thousands of dead trees in their wake. “Today, the only fires working our landscape are the largest and most severe, with high flame lengths and high rates of spread,” says Stephens. “All the rest have been eliminated. We’ve lost the tremendous variability that used to exist and the low-intensity, low-severity fires. We’ve filtered out all except the really extreme ones.”

In the late 1940s, Berkeley forestry professor Harold Biswell began to suggest reintroducing small fires as a way to prevent more serious fires from taking hold. He demonstrated that even areas with high fuel loads would burn moderately on a cold night, in moist conditions, or out of season. If fuels were reduced by this controlled burning, he argued, then when wildfires did come along they would be much more manageable, returning to their presettlement intensities rather than becoming the catastrophic wildfires we see today.

But Biswell failed to convince most of his colleagues, who thought him crazy for even suggesting the idea. It is said that the dean of the School of Forestry, John Zivnuska, considered Biswell so dangerous he tried to have him fired. Zivnuska was a forest economist and took the view–as did many others in those days–that fire was just a waste of timber and had no place in the forest. A healthy California forest typically contains stands of large, magnificent trees, with quite a bit of space between them. If only they could get rid of fire, those mid-century foresters reasoned, they could increase the number of trees per acre and produce more timber.

By the time Biswell retired in the early 1970s, attitudes toward prescribed burning were starting to shift. The technique had been tested in various national parks, with promising results. And Biswell did manage to get through to many of his students–people like Jan van Wagtendonk, M.S. ’68, Ph.D. ’72, who now oversees a prescribed burning program in Yosemite National Park, and John Mount ’61, who manages all of the forest land for Southern California Edison in much the way that Biswell recommended.

Biswell was the first forestry professor to dedicate himself to the study of fire, but the Berkeley forestry department has since hosted several professors of fire science and has built up a reputation for its expertise in the area. “In terms of its emphasis on fire research, Berkeley was at the forefront, and I think still is,” says Stephens. “It’s produced the largest group of dedicated fire researchers of any university in the West. No other university out here has the kind of fire legacy that Biswell started.”

Their research showed how frequently fires occurred in the past; they also found that Native Americans had used prescribed burning for millennia to protect areas around their homes from wildfire and to stimulate regeneration in the forest to support their livelihoods. As a result of this research, the notion that all fire is bad–what some have called the “Smokey-the-Bear mentality”–no longer prevails in the forestry profession.

Fifty years after Biswell began the discussion, all those involved in the fire debate now agree that fuel build-up is a serious problem and that prescribed fire must be at least part of the solution. Nevertheless, prescribed burning is currently practiced only on a small scale in our national forests.

How much prescribed fire should be employed, and whether other methods of fuel reduction, including thinning, are appropriate, are matters of debate. The Healthy Forests Initiative focuses mainly on physically removing excess fuels and suggests that logging companies should do some of the work in exchange for timber. And the Sierra Nevada Framework (a long-term plan for managing Sierra Nevada forests, signed by President Clinton just days before he left office) was hailed by environmentalists for severely limiting logging in national forests, but is now being amended to include some logging to pay for the cost of these treatments.

“Personally, I think the Healthy Forests Initiative is all about, ‘Let’s cut more timber,'” says wildlife biologist Reginald Barrett, Ph.D. ’71, a Berkeley professor in the division of ecosystem sciences (and a former student of Biswell’s). Barrett favors prescribed fire over thinning for most national forests. “There are certainly some places where you’d have to do some thinning first,” he says. “But unless we start burning at some point I think we’re never going to get on top of the situation.”

On the other hand, David Bischel ’73, president of the California Forestry Association, welcomes the new White House plan. “Logging is one of an array of tools available to forest managers to reduce the risk of catastrophic wildfire,” he says. “Clearly, fire has to be a part of the solution. But we also need to be spacing trees to optimize their growth, their resilience to fire, and to create forest stands that are much more indicative of presettlement forest stands.” And if some of those trees happen to be worth some money, so much the better, he argues. “It’s a win-win situation. You remove that material that has some commercial value and generate revenue to help offset the cost of material that doesn’t have commercial value. All in all, you end up being able to treat more acres.”

Stephens, while not against logging on principle, says that the focus must be on surface fuels–the debris that really get fires going. If those flames reach high enough, they can ignite saplings and smaller trees–the ladder fuels–which channel fire up into the crowns of larger trees, killing them. “You can use thinning to go after ladder fuels and crown fuels, but the real problem is, what are you going to do with the residues? If you leave them on site, you could have a situation that’s bad and make it worse,” says Stephens. “I get real nervous when people say we’re going to thin the forest to save it, because no one talks about surface fuels. It’s an afterthought.”

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No one can say for sure just which strategy is best–burning, thinning, or some combination of the two. But Stephens and Barrett are currently attempting to answer that question at UC’s Blodgett Forest Research Station, one of 13 sites around the country performing essentially the same experiment. “Our experiment is tied so well into the debate, I wish we had it done already and had some definitive answers,” says Stephens.

In contrast with previous studies, the ones at Blodgett and its sister sites are looking at the effect of fire (and the lack of it) on the ecosystem as a whole–what happens to large and small mammals, birds, insects, disease, and soil nutrients. Such a comprehensive scope is critical, says Stephens, because the matter of ecosystem health is at least as important as the prevention of out-of-control wildfire.

Fire suppression has led to two separate, but equally serious problems, he explains. While the build-up of fuels can cause some areas to be completely destroyed when wildfire strikes, the total lack of fire in other areas is choking forests that have adapted over thousands of years to burning. The smaller, cooler fires of the past helped some species directly–giant sequoia, for example. When its cones are scorched, they release huge quantities of seed that can germinate only on the bare mineral soil that is left behind after a fire. Other species, like California black oak and Ponderosa pine, need the sunny openings in the canopy created when frequent, low-intensity fires clear away small seedlings and leave a forest populated mostly by mature, well-spaced trees. Modern forests have grown so dense that only shade-tolerant species can survive in them; forests that once sustained five different species of tree are now down to just two. “That has huge ramifications for food webs and the dynamics of insects and disease, and enormous impacts on ecosystems,” warns Stephens.

This summer, Stephens has been investigating a particularly shocking example of the detrimental effects of decades of fire suppression on a forest ecosystem. The San Bernardino mountains in southern California and the Sierra San Pedro Martir mountains in northern Mexico both sustain mixed conifer forests. One hundred years ago, it would have been hard to tell the forests apart, but today the differences are conspicuous. On the Mexican side, where small surface fires occur regularly, there are around 60 trees per acre. On the Californian side, a century of putting out fires has created a density of around 300. Following four years of drought and dry conditions, the trees on the Californian side have fallen prey to infestations of bark beetle. “There are millions of dead trees down there,” says Stephens. “The San Bernardino National Forests are experiencing catastrophic mortality, which is something that we haven’t seen in a hundred years. It’s the highest amount of mortality I’ve seen in my life. It’s absolutely stunning.”

The forest south of the border, in marked contrast, has experienced few tree deaths, despite experiencing the same drought. On the whole, the trees have been able to defend themselves against bark beetles because, with fewer trees per acre, each has enough water to stay healthy, even during a drought. In southern California, the densely packed trees have had to compete for scarce water, with the result that have they all lost out. Could it be, wonders Stephens, that a similar process is behind the alarming outbreak of Sudden Oak Death in northern California? He is currently working to find out whether fire suppression could be playing a role in that epidemic, too.

The Forest Service certainly has some major challenges ahead for the next century–how to deal with the devastation from insects, disease, and wildfire. For the first half of this century, growing timber was all that mattered; it may have taken most of the second half, but preventing dangerous wildfires and restoring healthy forests have now replaced timber as the Forest Service’s highest priorities. In the time it takes to resolve the question of how to achieve those goals, millions more acres are likely to be lost to fire and ecological ruin, including some of the nation’s most treasured forests. With current fuel loads in the Sierra Nevada, all it would take is a hot, dry, windy day in the fall and entire groves of giant sequoias could be lost. “If you had severe conditions, you could have flames that are 100 feet tall. Even a tree that’s 250 feet tall like a sequoia would be absolutely vulnerable,” says Stephens. A year ago, a huge wildfire came within one mile of the Packsaddle Grove in the Giant Sequoia National Monument.

The size of the task ahead may be even greater than anticipated. “The part of this that’s often omitted, but is absolutely essential, is long-term maintenance,” says Stephens. “Once you’ve got a system away from the high severity fires, you then have to have a long-term philosophy of putting fire back into that system every 10 to 12 years. Because if you don’t do that, we’re going to be back in the same place in a hurry. I’m afraid that there’s this notion that, after 20 years of work, we’ll have the problem licked. That’s absurd. You can do some good work in 20 years, but this problem is never going away.”