Morgan Petroski/The Albuquerque Journal/AP
The Las Conchas Fire burns through a canyon June 29 in Los Alamos, N.M. The government sent a plane equipped with radiation monitors over the Los Alamos nuclear laboratory Wednesday as a 110-square-mile wildfire burned at the lab's doorstep, putting thousands of scientific experiments on hold for days.

Los Alamos fire could become the largest in New Mexico history

Big fires have happened before in New Mexico, but scientists see a recent pattern that may be the most severe since the last Ice Age. Among the causes: fuel buildup due to fire suppression, a decline in the annual snowpack, and warmer climate.

The Las Conchas fire, burning its way through the mountains and canyons around Los Alamos, N.M., is about to join Arizona’s Wallow fire as a state record-breaker.

As of noon local time Thursday, the Las Conchas blaze had consumed 92,710 acres near the city of Los Alamos and the Los Alamos National Laboratory, one of the nation's three nuclear-weapons labs. That's roughly 23,000 acres more than the fire had claimed Wednesday. Most of the additional growth in the past day came as the western section of the fire, driven by southerly winds, moved north from the Los Alamos area.

By midday Friday, Las Conchas is expected to capture the dubious title of largest single forest fire on record in the state. The previous record-holder was the Dry Lakes fire, which burned 94,000 acres near the Gila National Forest in southern New Mexico in 2003.

Combined with another fire in the Gila National Forest that ignited this past April and burned nearly 90,000 acres, three of the state's largest forest fires have occurred within the past 10 years, according to data from the forestry division of the state's Energy, Minerals, and Natural Resources Department.

From the standpoint of geological history, "these big, severe fires are not unprecedented" in hot, dry intervals the region has experienced during the past 10,000 years, says Grant Meyer, a geologist at the University of New Mexico in Albuquerque who studies the interaction of climate and weathering processes – which can be affected by wildfires – on the landscape.

"But recent experience down here suggests that what we're looking at in the last few decades is at least as severe and maybe more so than anything we've seen since the last Ice Age," he adds.

A build-up of fuels from forestry practices that emphasized fire suppression is partly responsible, he says.

"But part of it as well – and the data are very good on this – it's climatic warming" as human industrial activity and land-use changes have pumped increasing amounts of carbon dioxide into the atmosphere, he says.

Long-term decline in annual snow pack

A long-term average decline in annual snow pack, which provides the bulk of the region's water, along with rising average temperatures have lengthened the fire season and dried out the fuel.

New Mexico, along with much of Texas (which has had a record fire season), and the southeastern US is in the throes of extreme to exceptional drought conditions, according to data published jointly by the National Oceanic and Atmospheric Administration, the US Department of Agriculture, and the University of Nebraska.

The Wallow fire in Arizona, which has consumed more than half a million acres and is some 93 percent contained, and the Los Conchas fire, are "an indication of what kind of fire season this has been," says Jerome McDonald of the Southwest Area Incident Management Team, an interagency task force overseeing the firefighting efforts.

"Our team was on the Wallow fire as well," he continues. "As firefighters we're seeing extreme fire behavior and the kind of [fire] growth we haven't seen in our careers."

The Las Conchas fire has displayed some of that odd behavior.

'It's really aggressive'

"We have seen fire behavior we've never seen down here, and it's really aggressive," says Los Alamos fire chief Donald Tucker.

Fire crews were hoping to use the burn scars from the 2000 Cerro Grande fire – recolonized with grasses and shrubs that represent less abundant fuel than the Ponderosas and other conifers the fire has fed on so far – to help anchor their fire breaks.

Instead, when the Las Conchas fire reached the burn scar, the grass and shrubs burned, as expected. But the region is so dry – 0.19 inches of rain since Jan. 1 – and the fire has been so hot that it also has reignited the downed, blackened trees that lie around the landscape "like match sticks," Chief Tucker says.

Backfires set to establish fuel-free zones to the south and west of Los Alamos and the national laboratory so far have proven effective, Tucker says.

"Our piece of the puzzle looks good," although areas to the north are not so fortunate, he acknowledges.

To date, firefighters have been able to contain just 3 percent of the fire, which has destroyed 13 homes and damaged 3 others that were in sparsely populated areas.

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