Narrator: This is Science Today. For the last one hundred years, the United States pursued a policy of fighting wildfires through fire suppression. Scott Stephens, a professor of fire science at the University of California, Berkeley, explains the dangers of a zero tolerance policy for wildfires.
Stephens: But in many areas in the West or in places that had frequent fires, you stop fires there for a hundred years, dramatic changes occur, now they're very hazardous and they can burn really outside their range of normal variation.
Narrator: To deal with this problem the Forest Service has started using controlled burns, or fighting fire with fire, to clear out dangerously thick forests. Controlled burns from last year are credited with slowing some the recent blazes in Colorado and Arizona.
Stephens: So we're on a trajectory to do more fire use in the United States. When you look though, at the historical amount of fire that used to occur in many of our ecosystems in western United States, it was really millions and millions of acres. We're going to have to get creative because fire use alone with urbanization, air quality and other constraints, fire alone is not going to be the only answer we can use.
Narrator: For Science Today, I'm Larissa Branin.