Rich Guyette knows fire. He’s studied it for more than thirty years and the samples he’s collected and analyzed have helped to create a historical record of fire in North America spanning 400 years.

Till recently, he approached research like most fire scientists, focusing on the fuel source, thinking about local management questions and publishing research studies such as “Fire in the pines: a 341 year fire history of Big Spring, Ozark National Scenic Riverways” or “Fire history of an Indiana oak barren.”

Now his research is going on a diet—a vegetation free diet for fire analysis. The approach is called the Physical Chemical Fire Frequency Model (PC2FM), and its purpose is to understand how climate constrains and drives fire regimes across the continent by focusing on two variables: temperature and precipitation.

The equation, which Guyette has developed with colleagues over the last eight years, can assign a fire frequency to any square kilometer in North America. It integrates disparate fire histories across the continent to formulate a single set of historical fire frequency estimates based on the physical chemistry of climate.

Mapping History to Predict the Future

Historic (1650-1850 CE) MFI estimates for the presence of fire in all or part of an average 1.2 kilometers squared area.

For much of the continent, fire history isn’t available. Creating fire histories requires substantial field work, trudging through brush, paddling canoes to remote locations and extracting old trees out of river banks for analysis in the laboratory. In the eastern U.S. fewer samples exist given the generally moist climate of the region that causes rapid wood decay.

With Guyette’s predictive model, based on a hundred years of experimental chemistry and hundreds of years of fire scar history, researchers can make broad-scale characterizations of past and future fire regimes and assess sensitivity of the fire regime to climatic changes.

“It’s difficult to get the chemistry of combustion off the laboratory bench into something as complicated as an ecosystem, or a forest or grassland,” Guyette said. “What we provide is a bridge between the basics of chemistry and the basics of ecosystems and we use chemistry, physics, ecology and statistical modeling to do this. The chemistry is at the molecular level —whether it’s a giant fire in Colorado or the fire at the end of the cigar. It’s still a similar process, albeit on vastly different scales. It’s still carbon atoms and oxygen and they’re hitting each other and the carbon atoms separate and release energy.”

Guyette’s model can make predictions of fire frequency where vegetative data are unavailable or might differ from historical or future vegetation—limitations of vegetation-based studies.

By the end of August 2012, more than 7.72 million acres had burned across the U.S.—the most on record for a single year. Missouri, which normally experiences its highest wildfire frequency fall through spring, saw a record-setting summer, with more than 6,000 acres burned, 1,000 acres above the yearly average—in Mark Twain National Forest alone.

“People see the fires and destruction caused,” Guyette said. “We see that too, but fire scientists see carbon bonds breaking and decades of solar energy being released; it’s the oxygen content, like a bellows in a blacksmith shop.”

A fire scar on an oak tree.

From May through June, the Missouri Department of Conservation reported a 150 percent increase in the number of reported fires in Missouri. Guyette’s PC2FM equation predicts a 148 percent increase under the conditions for that period—encouraging results for the ability of the equation to accurately forecast fire frequency.

Nationally the model predicts a 40 percent increase in the likelihood of a fire in a one square kilometer area in a year’s time with a 10 degree Fahrenheit rise in temperature. However, averages can be misleading, Guyette says. The likelihood of a fire stays near one percent in many very dry and cold ecosystems. In other more moderate temperature and precipitation environments such as in Oregon, Colorado, and Washington, the likelihood of a fire occurring in a one square kilometer area in a year can increase 60 percent with the same 10 degree Fahrenheit rise in temperature.

“Temperature is a huge contributor to activation energy of reactions. The hotter it is, the easier it is to start your campfire.”

Keep the Bellows Blowing

Rose-Marie Muzika, MU professor of forestry, with a red pine remnant with eight fire scars in Pennsylvania.

Though the PC2FM equation is a breakthrough in connecting fire regimes to climate, Guyette stresses that field work is still critical to further fire science. There’s an immediate need to gather fire scar data, especially from eastern North America where preserved stumps decay quickly and disease and insect pressures and “old age” have reduced the number of trees with significant fire histories, he said.

Natural resource managers, scientists and the general public can use fire histories and models such as the PC2FM to make informed decisions on the ecology of fire, both in better understanding its past and predicting its future.

Several collaborators contributed to the fire equation, including: Michael Stambaugh, MU research assistant professor of forestry; Daniel Day, research scientist for the U.S. Forest Service, Rose-Marie Muzika, professor of forestry and Joseph Marschall, research associate at MU and Oak Woodlands and Forest Fire Consortium Coordinator.