The number of catastrophic wildfires in the U.S. has been steadily rising. The nation has spent more than $1 billion annually to suppress such fires in eight of the past 10 years. In 2005 a record 8.7 million acres burned, only to be succeeded by 9.9 million acres in 2006. And this year is off to a furious start. To a great extent, the increase in fires stems from a buildup of excess fuel, particularly deadwood and underbrush. Forests harbor more fuel than ever in large part because for decades, land management agencies, including the U.S. Forest Service, have followed a policy of trying to quickly put out every fire that starts. Fires, however, can clear out debris, preventing material from accumulating across wide areas and feeding extremely large, intense fires that become impossible to fight. Even in the absence of such a policy, firefighters find themselves compelled to combat many blazes because people continue to build homes further into wildlands, and those structures require protection. Exacerbating the problem, spring snowmelts have been occurring earlier, extending the number of weeks every year when forests are exposed and dangerously dry.