Professor studies ecosystem for future wildfires

Wednesday, 14 September 2011 19:03

More than half a million acres of land in Arizona were burned in the Wallow wildfires this summer, according to the U.S. Forest Service.

In Arizona alone, 27 different incidents of wildfires were reported this year totaling over 900,000 acres of land affected. These numbers were taken from the Incident Information System, an interagency risk-management system used by the U.S. Forest Service, the Bureau of Land Management, the Bureau of Indian Affairs, U.S. Fish and Wildlife Service, the National Park Service and the U.S. Fire Administration, among others.

“The Forest Service is fully committed to the recovery and rehabilitation mission in the post Wallow fire environment,” U.S. Forest Service Chief Tom Tidwell, said in a statement on Aug. 17.

The Forest Service has already seeded approximately 80,000 acres of burned land in Arizona as of Aug. 17.  In addition, Tidwell directed his agency to work fast so that any burned timber can be used for higher valued wood products.

Lumber can be made from “fire-killed trees" but only for two years after they are burned, according to the Forest Service.

“Fires were very widespread historically some years and then other years, there would be hardly any,” said Don Falk, an associate professor at the School of Natural Resources and the Environment at the University of Arizona. Falk worked at the Laboratory of Tree-Ring Research at the university for nine years prior to teaching there.

Falk explained that climate conditions, such as El Niño, facilitate fires. “And in particular, what we tend to see is dry winters…that often is one of the antecedent conditions to a big fire season,” he explained.

Because of the work being done at the Laboratory of Tree-Ring Research, scientists have roughly a 500 year history of how widespread and with what frequency fires have occured.  "So it's a pretty long record," Falk said.

While Falk states that the wildfires this year were "unnaturally severe," he does argue that fire plays a "stabilizing beneficial ecological role."

"It helps to keep forests from getting too dense," he explains. "It actually allows forests to adapt to changing resource availability. It helps to recycle nutrients like nitrogen and phosphorus."

Falk's argument is supported by recent research conducted by the U.S. Forest Service which found that intense thinning of forests are the most effective practice to reducing crown fires like the ones we saw this year.

Crown fires refer specifically to the canopy, or crown, of a stand of trees. Crown fires are distinct from surface fires in that they are more severe fires that are typically unnatural and penetrate deeper into the soil that surface fires.

Surface fires burn along the forest floor and are more natural and historically more frequently occuring than crown fires, said Falk. Surface fires can burn for long periods of time before they are eventually extinguished by rain.

The wildfires that ravaged the southwest this year were not all intense crown fires.  "None of these fires are all one thing. They are very very complex events," Falk explained. For example, "the Chiricahua Mountain Range suffered severe localized effects, but they're going to survive."

The local ecosystem adapts itself for fires, Falk explained. Birds, for example, will nest in the openings of burned trees, deer and elk graze on the renewed grass that grows after a fire has cleared old, dried brush.  "Under natural fire conditions, animals either fly away, climb a tree, run around past it, or burrow underground," Falk said.

In the report by the Forest Service, the researchers found that thinning the forests to leave 50 to 100 trees per acre was the most effective practice to reduce the risk of future wildfires. "There are a lot of studies like that. There's no one size fits all prescription," Falk explained. "Numbers like that are fine as long as they're not applied overly broadly. They should be applied in the type of ecosystem that they're developed for."

Photos added to this story on September 21, 2011 courtesy of Don Falk.

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