'Safe Zone' Method for Wildfires Questioned

One technique for fighting wildfires involves plowing a safe zone around an existing fire. But that seems to invite foreign, flammable plantlife into the plowed zone and can lead to more intense fires in the future.

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JACKI LYDEN, host:

Time now for Science Out of the Box.

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In our weekly segment today, we learn how science can sometimes lead us to the wrong solution. As you've no doubt heard, it's been a terrible fire season in the West. Federal officials say nearly 3 million acres have been scorched so far this year. That's 20 percent more than usual.

Experts blame this increase on everything - from drought to unlucky lightning strikes. But new research suggests there may be another factor - invasive plant species that thrive in the firebreaks that are supposed to slow the fires down.

NPR's John Nielsen has more.

JOHN NIELSEN: Many an inferno has been stopped dead in its tracks by a firebreak. That is a strip of land cleared of all its trees and bushes. This is why firebreaks that stretch for miles are so common out West. But when these same breaks are left to go to sea, they sometimes make fires worse. That's because these firebreaks are often invaded by highly flammable foreign plants. A fire expert with the federal Bureau of Land Management showed my colleague Howard Berkes the case in point a few years ago in Utah.

Sheldon Wimmer led Berkes to a break that was packed with tall, brown grasses once found only in Asia. It looked a little bit like wheat, but Wimmer said its real name was cheatgrass.

Mr. SHELDON WIMMER (State Fire Management Officer, Bureau of Land Management): Bromus tectorum is the scientific name. It is what gets in your socks when you walk through it. Then at that stage, it's almost like gasoline.

NIELSEN: Wimmer said cheatgrass practically explodes when it catches fire.

Mr. WIMMER: And then it goes into the sagebrush and then it goes into the trees, and you have a fire ladder that it takes off and goes up that carries the fire.

NIELSEN: A cheatgrass fire that unfolded in just this fashion killed a firefighter in that Utah break several years ago. At that time, those kinds of blazes were thought of as freak events, but a new report says that is changing. Basically, the new report finds that flammable, invasive plants like cheatgrass are now commonplace in firebreaks all over the West.

Gaze at a forest from a distance and you'll see the proof, says author John Keeley.

Mr. JOHN KEELEY (Biologist, U.S. Geological Survey): You'll see an evergreen landscape with these corridors running through that are tan, golden brown, and that's all the alien grasses.

NIELSEN: Keeley is a biologist with the U.S. Geological Survey. And he's also the leader of a team that surveyed 24 firebreaks in California. The team found that, except at the highest altitudes, foreign plants were common in the breaks, especially in the ones that had already been scorched by a blaze.

Mr. KEELEY: It does seem to have a feedback effect that the more grasses you get into the system, the more fires you get, and the more fires you get, the more grasses you get.

NIELSEN: Keeley says these problems are made worse by the fact that most foreign grasses live fast and die young.

Mr. KEELEY: They have a very short lifespan so they generally dry out before even the native annual plants and so they lengthen the fire season.

NIELSEN: So does all of these mean that we should stop clearing firebreaks? Keeley says no. But he does think it's time to put more money into efforts to slow the spread of plants like cheatgrass. One way to do that is to spray them with herbicides, he says. Another is to cut them by hand.

But in Utah, Sheldon Wimmer of the BLM is fighting back in a more provocative way. He has been bringing in more invasive plants that can resist fire and crowd out the cheatgrass. Wimmer admits that he worries some about whether these new plants will turn out to have unexpected long-term side effects. But in the short-term, for lack of a better phrase, he thinks it's right to be fighting fire with fire.

John Nielsen, NPR News, Washington.

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