Until last month, the National Park Service had been sharply increasing the number of fires set to clear brush and rehabilitate landscapes, tripling the area burned in just four years. That changed when a fire set at Bandelier National Monument got out of control, leading to an inferno that destroyed more than 200 homes in Los Alamos, N.M., and caused hundreds of millions of dollars in damage. Interior Secretary Bruce Babbitt halted all “prescribed fires” by the Park Service in the West indefinitely, saying an investigation found “serious systemic problems in the way the Park Service conducts prescribed burns.” Park Service Director Robert Stanton told a House panel last week that the agency is changing its policies and training to prevent similar problems. It was Babbitt who changed policy in 1995 to encourage use of such fires. He even helped set a prescribed fire in an Idaho national forest in 1998. Congressional critics say federal land managers should rely more on “mechanical thinning” using people and machines to cut down trees and undergrowth. Rep. Helen Chenoweth-Hage, R-Idaho, said the Clinton administration relies too much on prescribed fires because of a “dogmatic, anti-science, anti-technology, anti-people bias.” “Fire alone is not sufficient to the task,” she said. But forestry experts say that when properly monitored, prescribed fires are among the best and cheapest ways to prevent catastrophic wildfires. “As you get away from developed areas, fire becomes a more viable alternative there’s a reduction in cost, and in threats to life and property,” said Park Service fire specialist Tom Zimmerman. ” … We’re just trying to provide the most appropriate and cost-effective treatment.” Last year, the Park Service set a record 326 fires that burned 139,000 acres, according to a computer-assisted analysis of the agency’s fire data. That was a 62 percent jump over the previous year and triple the acreage burned in 1996. But it still represented only 0.2 percent of Park Service land. In all, the Park Service set 3,760 prescribed fires since 1970, burning about 926,000 acres, an area nearly the size of Rhode Island. By contrast, agency workers battled 43,456 wildfires that burned nearly 5.5 million acres during the same period. Some agency officials and outside experts say more prescribed fires are needed to prevent the kind of catastrophic wildfires that blackened 1 million acres of Yellowstone National Park in 1988. “Even when that number (of prescribed fires) is doubled, it’s a drop in the bucket,” said Ronald Myers, director of the National Fire Management Program of The Nature Conservancy, an environmental group. “I hope Congress is patient and lets this thing run its course.” Besides the low cost, prescribed fires can help prime soil for new seedlings and spur the reproduction of species such as giant sequoias, said Nate Stephenson, a U.S. Geological Survey scientist who studies fire in Sequoia and Kings Canyon national parks in California. On the other hand, he said, mechanical treatments produce less smoke and do not leave fire scars on surviving trees. “I think land managers would be shooting themselves in the foot to limit themselves to one tool or the other,” Stephenson said. While the current debate focuses on the West, prescribed fires also are set elsewhere, most notably Florida. The Park Service’s top site for prescribed fires is the Big Cypress National Preserve, which had 388 set blazes since 1980 that burned nearly 534,000 acres an area equivalent to 74 percent of the preserve. “We burn throughout the year, whenever the conditions are appropriate, to remove those hazardous fuels so we don’t get those big, screaming fires we can’t control,” said Larry Belles, the preserve’s fire chief. Second was the adjoining Everglades National Park, where 363 fires that burned 105,244 acres have been set since 1970. Officials at the Florida parks said their ecosystems depend on fires every three to 15 years. “Two hundred years ago, lightning would strike somewhere out in what are now the Miami suburbs, and over the next few weeks the fire would burn into the center of the Everglades,” said Bob Panko, fire manager for the Everglades. “That can’t happen any more, because there’s a Kmart out where the lightning is going to hit. So to respond to that, we’ve been lighting fires to maintain that natural regime of fire in our wilderness.” The Park Service ban does not apply to Florida, but prescribed fires in the state have been suspended because of severe drought. Belles and Panko said they are taking another look at their planning and procedures because of the New Mexico fire. Stanton, the Park Service director, expects to resume using prescribed fires in the West. “We are committed to ensuring that the mistakes that led to it (the Los Alamos disaster) are not repeated, so that we can continue to get the safety and environmental benefits of a prescribed fire program, with no more tragedies of this type,” he said.