Even before a record breaking year for wildfires, the use of controlled burns to limit the spread of fire was gaining favor. Training programs in Nebraska are teaching crews how to use them effectively and safely.
Never has Nebraska had a drier year and never has there been a wilder season for wildfires. By the end of 2012 the Nebraska Emergency Management Agency estimates more than 300,000 acres have been blackened by fire.
One method used to reduce the chances and the size of wildfires is the use of fire itself under controlled conditions. These prescribed burns on grasslands and in forested areas have been aggressively promoted by land management experts and ecologists as an effective way to cleanse the landscape of old grasses, plants and trees which can create too much burnable fuel on valuable acreage.
In the past two decades, plans for controlled burns used a blend of new science and old-school knowledge handed down by farmers and Native Americans, who have used the practice for more than a century.
Photo by Bill Kelly, NET News
Jeremy Bailey of the Nature Conservancy lays down the first line of flame for the prescribed burn training.
"The science (involved in fire behavior) is weather and fuel loading and topography," said Jeremy Bailey, the lead trainer for the exercise. "A lot of our firefighters train for years to get the point where they can supervise a burn like this."
(Watch how the controlled burn was carried out in an NET News video below)
After breakfast they gathered on a clear March morning on a ranch south of Gothenburg. Most in the group had some classroom training on ecology or land management. Others were full or part-time firefighters. Their training emphasized how to plan for and implement a safe burn while accomplishing specific goals in an ecosystem.
Bailey hoped to get the burn started earlier in the day, but steady winds meant the crews spent their time getting a refresher course in priming the pumps on a fire truck and making another survey of the landscape.
Finally, at about 4:30 in the afternoon, the weather began to calm. Bailey called the group together. Conditions appeared favorable, but the short timeframe meant a change in plans.
"We've been planning and planning for the past 48 hours, and now we're going to do something different," he told the eager firefighters, who would soon become fire starters.
The decision to proceed would be based on a number of variables, including data collected by the weather specialist in the group. Lou Schnapp, a graduate student completing her ecology studies in Texas, climbed to the top of a hill overlooking the pasture where the fire team assembled around a small armada of fire-fighting equipment.
Rummaging through her backpack, she pulled out an instrument called a "sling" psychrometer . All during the day members of the group referred to getting the latest wind and humidity readings as "slinging weather.” The device used by Schnapp provides the origin of the term commonly used during prescribed burns.
The psychrometer looks surprisingly low tech. Two pieces of metal attached by a chain each have thermometers attached. Schnapp moistened a cotton gauze covering over one of the thermometers with distilled water.
Photo by Bill Kelly, NET News
Lou Schnapp holds her sling psychrometer to measure relative humidity for the fire team.
As the two thermometers spun, water on the wet bulb evaporated from the wick, cooling the thermometer to the lowest temperature possible in minutes. The drier the air becomes the more the thermometer cools, providing a measurement of moisture in the atmosphere. It’s what commonly is called the relative humidity.
On a crackling two-way radio Schnapp called in her readings. "Dry bulb 47, wet bulb 46, which puts at an RH of 43. Lou out." RH stands for relative humidity. An RH below 20 is considered too dry to burn.
The burn boss, Bob Bale, also assessed the wind speed (it was a steady 6 miles per hour with some gusts up to 13 mph), using short-term forecasts from the National Weather Service and additional observations made at the site. Compiling the data gives him the information needed to determine whether conditions would meet the objectives of this specific burn.
More and more, field operations for controlled burns are dictated by knowledge gleaned from scientific research. It's long been known fire behavior is influenced by weather, the amount and type of available fuel and the lay of the land.
Since so much knowledge has been passed from one generation to the next, there's an unusual tension between new science and the traditional, often effective, methods of harnessing the benefits of fire.
"I think that prescribed burning is more of an art than a science, but you do have to understand fire behavior and use that," said Doug Wisenhunt of the USDA's Natural Resource Conservation Service. He admitted to mixed feelings about crews in the field relying too much on computer models and mathematical formulas.
"You can calculate some of that, but in general, it's just kind of knowing how the fire is going to react when you are burning at that time."
Wisenhunt has conducted dozens of burns in Nebraska and has helped form and train coalitions of ranchers and land owners to conduct prescribed burns in their regions. His advice, which he shared with the Nature Conservancy clinic, frequently mixes the intuition that comes from experience with the latest research.
One study he cites as especially useful for fire safety originated at Oklahoma State University. Data showed when the humidity drops below 20 percent on the Great Plains "you increase your chance of spot fires, of stuff carrying across the fire line and starting another fire on the downwind side," Wisenhunt said. It's had a major influence on when to safely conduct burns.
For Whisenhunt an ideal burn day has temperatures below 80 degrees, winds less than 20 miles per hour and humidity above that crucial 20 percent mark. Recent research on fire behavior focuses on the influence of temperature and humidity.
In 1998, the Forest Service began providing fire safety forecasts based on theories developed by meteorologist Donald Haines from the University of Wisconsin. The Haines Index is a mathematical formula calculating the potential for large wildfires to experience extreme fire behavior. It does not predict the possibility for a fire, like a tornado warning, but it can, according to the 2012 Iowa Fire Weather Operating Plan, "identify weather conditions that may allow an existing fire to spread rapidly or exhibit extreme fire behavior."
The Index, developed in the study of wildfire, became useful for land management experts planning prescribed burns.
Other research by academic institutions and the U.S. Forest Service hoped to improve the effectiveness and safety of burns. Studies concentrated on how smoke is dispersed and whether it has negative effects on the environment.
On the day of the burn near Gothenburg, the Nature Conservancy's Bailey decided the weather data met the parameters set out in the burn plan they had fine-tuned the day before.
As the teams prepared to ignite the first test plot, shifting winds prompted caution. "Be heads up on the slope in these winds. The fire may not be running uphill, it may be running downhill,” Baily advised the assembled burn team.
With that, it was time to break out the kerosene and start burning. There were more than two thousand acres on this ranch scheduled for burning during the exercise. They could only get a fraction of that done on the first day.
Those experienced in conducting prescribed burns say it's important to recognize that not all fires are created equal. Different prescriptions and different types of fire solve different problems.
"The objective (of this burn) is to decrease the amount of eastern red cedar in the area, so we want to make sure we get a decent kill on all the cedar five-foot or below," said Michael Henn of the Wyoming State Land Office. He was one of the students, but also has worked on the fire lines at many controlled burns and wildfires on his home turf.
Had the goal been to target the largest trees for destruction, a day with lower humidity levels might have dried them more completely and turned them into volatile fuel to the benefit of the burn.
"In other cases you might not want to burn certain trees," Henn said. "If you are in a different fuel type and you are in a timber stand, than the objective is to not burn the mature trees but take out the stuff underneath."
Meeting that goal would have required an entirely different burn plan.
Henn watched as Bailey moved across a ridge carrying a large, bright red canister resembling an oilcan. The torch dripped flaming kerosene into the dry grass, igniting immediately.
Crews with torches left a trail of fire behind them along the cattle trail and a county road a couple of miles to the east. The next day, the crew planned to burn off any remaining grass in the valleys in-between. By sunset, about 400 acres were blackened. This was a training burn, and the organizers with the Nature Conservancy said in that regard, it was successful. The second goal, killing off the cedars, fell short of expectations.
The relative humidity continued to creep up as the sun went down.
"We're not having the flame lengths that we ordinarily would have if the sun was out and everything was a little bit drier," Pawlik said. "The fire is having to do all the work by drying out the fuel."
Jeremy Bailey, covered in soot and exhausted, pulled off his helmet.
"Right now, we're at a threshold where our fire is no longer carrying. We're no longer creating black, so there is no more work to be done this evening other than patrol, get the firefighters back in bed and well-rested so they can come out in the morning and start all over."
For those brought in for the training, it was a good example of how small changes in a single factor, like the humidity, can help or hinder the goals set out for a prescribed burn.
Videographer Emily Kreutz spends the day with the controlled burn crew.
Editor's note: This Signature Story is part of our "Best of 2012" series of reports, airing Dec. 24 to Dec. 28, 2012 on NET Radio, looking back at some of the most memorable Signature Stories from NET News throughout the year. It originally aired March 29.