The steep wooden ladder that connects Mesa Verde’s Balcony House cliff dwelling with solid ground thins the crowd of tourists who make the climb into it every summer. Safeguarding the cultural site from the tread of visitors, however, is much easier than protecting it from fire.

This difficult task falls on the shoulders of Tim Oliverius, Mesa Verde’s fire management officer. For him, the ladder leading up to Balcony House is just one of the fuels around the site that could feed a fire and possibly destroy the priceless structure.

National Park Service officials often use controlled burns to thin vegetation within parks and monuments in order to protect against wildfires, but a controlled burn that blew out of control last month in New Mexico’s Bandelier National Monument and forced the evacuation of Los Alamos proved the danger involved in such fires. Instead of controlled burns, officials at Mesa Verde have been using a mechanical thinning method whereby trees are cut down by hand, removed from the area and burned in a safe area within the park.

Oliverius said that in the future, the thinned areas may be safely burned — a less costly way of controlling fire hazards — but at the moment, chainsaws and bow saws are the safest way to reduce the fuels within the park. It costs between $2,500 and $3,000 to thin an acre by hand, versus between $300 and $400 per acre for a prescribed fire.

Also at risk from wildfires are the $500,000 shelters which cover the ancient pithouses, and are made out of laminated wood beams.

Any wood salvaged from the thinning is sold to park residents and put up for commercial bid in the fall.

The park is estimated to contain 4,500 cultural sites. Most of these are underground and protected from fire, but the study concluded that 600 cliff dwellings and alcoves above ground are at a high risk from forest fire. With record temperatures and ideal fire conditions, the park has a high risk for forest fires this season.

"We have a history of large fires occurring here in the park," said Oliverius. "And the interval between the fires seems to be shortening."

The cliff dwellings and alcoves are at a high risk because of flammable roof materials and the dense mountain shrub and pinon juniper surrounding them.

If an environmental assessment is approved at the end of June, Oliverius and his crew will be thinning forest this summer around some of the 25 cultural sites proposed. Some popular sites may have to be closed to the public while the crews do hazardous work.

These sites include Balcony House, Cliff Palace, Step House, Long House, the Badger House Community on Wetherill Mesa, the sheltered sites along the Mesa Top Loop Road, and the sites of the Far View Community.

Oliverius said that a prescribed burn around these sites would be too risky, even if such fires were not currently banned by the Department of Interior. "Our fire program is very conservative by today’s standards," he said.

Last year the park service thinned around Spruce Tree House, the third largest cliff dwelling in the park. It took a crew of 15 people, working 10 hours a day for five days, to haul out an acre and a half of oak brush and one large Douglas fir from the area.

The sites planned for this summer are three to four miles from the nearest paved roads, so the vegetation will be scattered downslope, a safe distance from the sites, instead of being centrally burned.

Thinning the forested areas in the park became a top priority after the 1996 Chapin 5 fire, which burned close to 4,780 acres and damaged some important cultural sites. Petroglyph Panel on Battleship Rock was destroyed beyond repair.

"We’ve known there has been a need for thinning for a long time," said Oliverius. "But after Chapin 5 we began a proactive program."

The park was granted federal funds to hire an architect and field specialist to do a two-year study and assess the fire hazards around 200 sites within the park.

Ironically, Chapin 5 uncovered a wealth of cultural sites underneath the burnt vegetation. Prior to the fire, the park had recorded 296 sites, and since then archaeologists have recorded an additional 372.

Oliverius said that in order to prevent fires from jumping from tree to tree, a 20-foot open space is cut between the brush. Wildlife trees are preserved, although the habitat has changed for wildlife in the area.

George San Miguel, the park’s resource management specialist, said that habitat for the Western Bluebird and the Cottontail Rabbit has been reduced.

"This [dense vegetation] isn’t a natural situation," said Oliverius. "This forest naturally was probably much more open when the Ancient Puebloans were here, but there is a lot we still don’t know about."

Not only has thinning reduced the risk of fire by 50 percent within the thinned areas, but according to Oliverius, this may allow the incident management teams to safely leave firefighters in the area to fight the fire.

The Environmental Assessment and Assessment of Effect document is available at the park for the public to review.