To burn or not to burn—that has been the age-old question for forest managers.
Nearly a decade ago the federal government relinquished its century-old policy of suppressing all forest fires in favor of using fire management techniques such as thinning and controlled burns. And that was a step in the right direction, says wildfire expert Mark Cochrane, senior scientist at the Geospatial Sciences Center for Excellence and professor of natural resource management.
“Trying not to let things burn,†Cochrane says, increased the number of the trees and the amount of fuel available when a fire did occur.
The Black Hills, for instance, once experienced many low-intensity grass fires. The area now has fewer fires, but they end up being what Cochrane calls “very high-intensity forest fires that are more destructive to trees and humans.â€
In August 2000, the Jasper Fire burned 83,508 acres in the southern Black Hills in less than 10 days. Experts blamed not only the dry conditions but also the abundance of fuel on the forest floor for the fire that devoured nearly 90 percent of the land at Jewel Cave National Monument.
Dry conditions and devastating wildfires in California spurred Congress to pass the Healthy Forest Restoration Act, which President Bush signed into law in December 2003.
Using fire management treatments
One type of fuel treatment, thinning, involves removing either large or small trees to improve the health of the forest.After the Jasper fire, for instance, forest managers thinned the trees throughout unburned portions of the Black Hills, Cochrane says, “to get something closer to a natural system.â€
Those trees large enough to be used as timber were removed from burned areas, a process called salvage logging.In the winter, the piles of debris were burned.
Another technique, mastication, calls for grinding the brush, lower limbs and smaller trees and leaving them on the forest floor, Cochrane explains.
Use of a prescribed burn can clear the forest of potential fuel; however, this technique requires a delicate balance. Conditions must be dry enough to burn and windy enough to disperse the smoke away from where people live, Cochrane explains.
In April 2013, a prescribed burn at the Dakota Prairie National Grasslands near Lemmon in northwest South Dakota burned more than 14,000 acres. It was designed to treat only 130 acres, but winds gusting up to 30 miles per hour pushed it beyond the fire lines.
“To manage fire, your fire prescription will never be more accurate than your weather forecast,†says Cochrane.
Essentially over the last decade forest managers have used every method in every forest type, Cochran explains. “What we’ve ended up with is different types of fires.â€
The changing climate is also an important piece of the puzzle when it comes to wildfires. “Looking at how these fire regimes change as a function of climate,†Cochrane predicts “these types of fire will get worse over time.â€
Determining effectiveness of treatments
“Not all land covers are created equal,†says Cochrane. Land managers want some direction so that they can devote resources to the treatments that will accomplish their goals most efficiently.
Through research projects funded by NASA and the Joint Fire Protection Sciences Program, Cochrane and an interdisciplinary team of experts from geography, biology and statistics set out to determine which fuel management treatments are effective in which areas. More than 20 students ranging from postdoctoral researchers to undergraduates did field work, data collection, data processing and statistical analysis for the projects.
Cochrane’s doctoral student Chris Moran of Rapid City, who has worked on these projects, recently received a NASA Earth and Space Science Fellowship to determine how long these fire management treatments are effective.
The research also involves experts from the U.S. Forest Service and the U.S. Geological Survey Center for Earth Resources Observation and Science (EROS).
First, the researchers gathered data on hundreds of large wildfires over the last 10 years through a project at EROS that monitors the severity of these fires. Then Cochrane and his team spent several years calling U.S. Forest Service managers to collect statistics and spatial data on what types of treatments were applied in the burned areas and when. This allowed them to document burn severity for thousands of treatments applied to areas affected by more than 630 wildfires nationwide during the last decade.
“Fires are so variable,†Cochrane says. “We needed enough statistical power to say something more quantitative.â€
In addition, Cochrane and senior scientist Michael Wimberly visited selected burn sites to compare treated and untreated landscapes— side by side.
“We could see the treatment and measure how different the fire severity was,†says Cochrane.
Based on this work, Cochrane and his team will be able to provide regional guidance as to which types of treatments work better than others and how long they will function. This is crucial information for forest and land managers.
“We can provide information on which tools in their tool box are working best to achieve their goals,†Cochrane explains.
Simulating wildfires
However, the researchers still couldn’t say for certain that a specific treatment actually helped prevent the spread of fire. To do that, they used the data on the fuels, landscape, treatments and weather conditions along with the physics of how fire burns to construct a computer simulation of the actual wildfire.
“We get a simulation to mimic the real fire fairly closely, and then we take the treatments out of the landscape and run the same simulation,†Cochrane says. He and his team run up to 60 simulations of a single fire with and without treatment, even taking into account sparks that ignite spot fires.
Through this modeling, the researchers can describe how a specific treatment in a particular area changed the probability of a fire happening, Cochrane explains. “If treatments are strategically placed, we can protect areas of value.â€
This wildfire research will help forest managers allocate their resources wisely to produce healthier forests, support wildlife and protect human beings.
Christie Delfanian
