This summer's drought-fed wildfires have blackened twice as much acreage as in 1987 and may be driving tourists from America's national parks, but experts say the blazes are enormously important to the forests' ecology.

"Just as the wildlife needs predators, vegetation needs predators to keep the forest evolving," said Jim Olson, a Denver-based resource management specialist for the Rocky Mountain Region of the National Park Service. "Fire is its greatest predator. Fire is a necessary thing to manage forested areas."Naturally occurring fires, usually ignited by lightning, sweep out overgrowth and dead timber, clearing the way for new vegetation to feed animals, Olson explained.

Howard Burnett, special projects forester with the American Forestry Association in Washington, D.C., agrees. "You have to think of the forests not so much as a lot of trees but as an ecosystem, with all the wildlife, the streams, the fish, the soil.

Yellowstone National Park in northwestern Wyoming, the nation's oldest federal park, already is enduring one of its worst summers for wildfires, and August, the most dangerous month, has only begun.

In 1987, wildfires ravaged 1.1 million American acres by Aug. 1, while 2.29 million acres have been devoured so far this year, including 1.5 million acres in Alaska and 120,000 acres in Yellowstone's 2.2 million acres, U.S. Forest Service statistics show.

The rest have been in Western states that included Arizona, Idaho, Montana, Oregon, Washington state, California and South Dakota.

Olson said the 1988 drought has has made forests ripe for wildfires. "The West is five years into a drought cycle, and each year the fire potential has become more severe," he said.

"My own observation, being in the woods for 30 years as a firefighter - I'd say we have the most severe burning conditions as we've had in 30 or 40 years," Olson said. "Because (Yellowstone is) such a large park people don't usually see it, but this year they are."