Fighting Fire with Fire

Michael Cannell

This spring, Jim Brenner will lead hundreds of men and women in burning more than 2 million acres of Florida pine forests. See those trees? Whoosh'! They're toast. Those cattail reeds? Sizzle! They're history. That old rotting log? Crackle! Gone. Is Brenner a pyromaniac? Actually, he's just the opposite: As Florida's fire-management administrator, Brenner guards against fires.

So why is Florida's top firefighter torching forests? Brenner is one of a growing number of land managers who believe in fighting fire with fire. By starting their own carefully controlled blazes—a practice called prescribed burning—they hope to put an end to monster wildfires, like the one that ravaged 500,000 Florida acres last summer. "It was hell on Earth," Brenner remembers. "If we'd done more prescribed burning, we could have greatly reduced its damage."

Florida wasn't the only place to fire up headlines in recent years. Mexico, Brazil, and Indonesia have suffered their own catastrophic fires. Are we on the brink of a flammable new era? Scientists warn that global warming (planetary heating caused by greenhouse gases like carbon dioxide) could boost the Earth's temperature by as much as 5 ° F (3 ° C) by 2070. In 1998 the Earth's average surface temperature was the hottest ever recorded, according to the World Meteorological Organization. A warming planet promises more droughts, which in turn makes vegetation drier and more likely to go up in flames.

How are U.S. forest officials responding to this burning threat? Prescribed burning has once again gained wide acceptance among fire ecologists (scientists who study the ecology of fire). They also believe in letting fires sparked by lightning burn naturally when cool, damp weather reduces the risk of runaway flames. Both fire-management techniques, first practiced in the 1970s, are based on the theory that frequent small fires diminish the risk of devastating events, like last summer's Florida firestorm, while keeping the ecosystem healthy.

After the raging 1988 Yellowstone National Park fires, which were ignited by lightning and allowed to burn by foresters, public sentiment opposed let-it-burn and prescribed burning practices. Now, the threat of growing forest debris that can fuel uncontrollable flames has rekindled interest in these fire-management tactics. "Fires are as important to forests as sunshine and rain," Brenner says. "They're simply part of the system—they always have been."

A Burning Issue

Stamping out forest fires as soon as they start was the U.S. Forest Service's sole mission when it was founded nearly a century ago. Over the years, it has developed a highly effective system of two satellites that watch for blazes, 82 planes and 440 helicopters that dump fire-extinguishing chemicals, firefighters that swarm around the flames.

Before the Forest Service interfered, scattered ground fires ignited by lightning cleared the forest floor of accumulating leaves, branches, and needles every 5 to 25 years. These natural fires swept swiftly across the forest floor but left trees intact. The Forest Service has become so skilled at killing these fires, however, that hundreds of millions of acres have gone unburned for the past 75 years, or three natural cycles of fire.

Deprived of fire, landscapes" from New York's Adirondack mountains to Washington's Olympic Peninsula have undergone dramatic changes: Once-grassy clearings close up with trees. Swamps fill with vegetation and dry up. The open area under the tree canopy, "known as the understory, clogs with a thick mass of vegetation. "It's a fire hazard!" exclaims fire ecologist Leon Neuenschwander of the University of Idaho. "It's worse than my daughter's bedroom when she was 15."

The longer vegetation accumulates, the more destructive an eventual fire will be. Years of amassed underbrush lit by lightning or carelessly tended campfires can fuel a much hotter, faster-moving fire than would naturally occur. (The 1994 wildfires near Los Angeles reached a searing 2,552 ° F/ 1,400 ° C, hot enough to ignite highway asphalt.)

These infernos"—known as crown fires—consume" whole stands" of trees at once. Crown fires burn so hot and deep that they destroy the roots of trees. Without roots to anchor" the soil, heavy rains erode topsoil and sweep it into rivers. "We're paying for all those decades that Smokey the Bear suppressed' fires," says Karl Brown of the U.S. Geological Survey.

Let It Burn

To reduce the fire deficit, foresters are lighting prescribed fires. These blazes clear away underbrush and fallen branches, thereby robbing the next fire of hazardous fuel. Flames don't climb to the treetops. Roots are undamaged, and trees survive.

Last year, the Forest Service and other agencies intentionally" burned millions of acres. "It's an art form, not a science," says Jason Greenlee, executive director of the International Association of Wildland Fire in Spokane, Washington. Here's how they do prescribed burns:

Organizers pick a site with a natural firebreak, 'like a road or stream, across which the fire cannot spread. On a dry, windless day, burn crews cross the site in a careful pattern carrying handheld drip torches, oversize watering cans filled with diesel and oil that pass through a wick, or piece of rope that burns with a small, steady flame. The crew drips a trail of fire over anywhere from one to several thousand acres. The no. 1 safety rule: Advance into the wind. That way, if the wind gusts, it will blow the fire back onto the previously burned area, or blackline, where it will fizzle out for lack of fuel.

Of course, prescribed fires sometimes do burn out of control. On such occasions, threatened burn crews can escape into fire shelters, tent-like devices made of foil and glass-cloth laminate that reflect heat. But land managers would rather face small risks now than big risks tomorrow.

After the Fire

While most people still see fires as disasters, the flames actually help forests. Remember the natural fire that roasted more than a third of Yellowstone National Park's 2.2 million acres? Today in the park, 10,000 knee-high lodgepole saplings are growing per acre. "They're growing like grass," says Brown. "A big flush of seeds has rejuvenated the forest."

It's too early to know if the burned areas of Florida will undergo a similar rebirth. In any case, the government says it is committed to its new "fighting-fire-with-fire" policy. As with all natural forces, the trick is to find the right balance. In this case, the benefits of fire are weighed against the need to protect people and property.

Imagine Smokey the Bear with a shovel in one hand and a drip torch in the other.

From Science World February 22, 1999