As the Florida Forest Service provides updates on multiple wildfires affecting Bay, Calhoun and Gulf counties, people may encounter unfamiliar fire science terminology.
To provide some explanation, we asked David Godwin, a fire ecologist with the UF/IFAS School of Forest, Fisheries, and Geomatics Sciences and director of the Southern Fire Exchange. He’s based at the Tall Timbers Research Station & Land Conservancy, a partnership with several agencies that is located in Tallahassee.
Q. What does “percent contained” mean in reference to the wildfires?
A. Percent contained refers to (approximately) how much of the perimeter of the fire has been surrounded by natural or human-made containment lines that can prevent further spread of the fire. Containment doesn’t mean that the fire is “out,” but it’s a helpful metric to communicate progress toward stopping the advance of the fire into new areas.
Once a fire is 100% contained, it is likely still burning, smoldering and producing hazardous smoke. It may take weeks before a fire is officially declared “out,” and all residual hotspots and smoke are extinguished through the work of firefighters and Mother Nature.
Q. Is there a certain percentage we want to see, to indicate the situation is under control?
A. 100% contained is the goal. But even then, depending on weather and fuel conditions, there are times when fires can escape across containment lines. High winds and low relative humidity can blow embers across containment lines creating new “spot fires.” Sometimes you’ll hear that fire crews will widen existing containment lines, essentially making wider patches of bare soil in efforts to reduce the likelihood of embers establishing spot fires across lines.
Q. What are “firelines”?
A. Firelines are linear patches of bare soil created by fire managers and wildland firefighters to stop the forward advancement of surface fires. We call this creating a “fire break.” Firelines can be created by hand using hand tools or, more often in the Southeast, by using heavy equipment such as bulldozers equipped with a fireline plow. A plow turns over the soil, exposing bare earth that doesn’t burn.
Q. What suppression methods are used to contain wildland fires?
A. Water from fire engines, portable pumps and aircraft can be used to extinguish small spot fires and to help protect structures. Unfortunately, once wildfires become large, there’s rarely enough water to stop the fire from spreading. For that reason, firelines are created to help stop the spread of surface fires by creating fuel breaks.
Where firelines have been created or when existing fuel breaks exist, wildland firefighters will sometimes use burnout operations, essentially fighting fire with fire. Burnouts are fires intentionally ignited ahead of or adjacent to a wildfire to remove fuels to stop the advance of the wildfire. When possible, burnouts are often ignited at night or during cooler and wetter periods to reduce their intensity and increase firefighter safety.
Finally, smothering the fire with soil from shovels or bulldozers will often be used to extinguish the flaming or smoldering remnants of fires. This can be a long and tedious process, but it is important to help reduce the likelihood that a fire will reignite and spread across containment lines.
Q. Can you explain the term “fuel load?”
A. Fuel load is a measure of the amount of burnable material present at a particular location. Typically in the case of wildfires and prescribed fires, fuels are composed of vegetative material, such as pine needles, palmettos, leaves, twigs, branches, grasses, and plants growing near or at ground level.
The intense winds of Hurricane Michael in 2018 deposited literal tons of vegetative material that had been in the tree canopy onto the forest floor. According to the Southern Group of State Foresters, following the storm, it was estimated that fuel loads in the most severely impacted areas went from an average of 4.8 tons per acre to over 100 tons per acre.
Even in 2022, much of that material is still on the ground. In the months and years since, new shrubs and brush have grown up amongst the hurricane debris providing additional fuel for wildfires. The fuel loads on many of these sites are very high and this is contributing to intense fire behavior, beyond what we might see in other parts of the state. In addition, post-hurricane debris may prevent firefighters from accessing some areas. The jumble of twisted and snapped trees can make cutting firelines much more challenging, requiring that forestry agencies use their larger classes of bulldozers.
MORE FROM DAVID GODWIN: “How a hurricane fueled wildfires in the Florida Panhandle” in The Conversation.
Q. What else should people know about wildfires, fire science and natural resource management?
A. Fire is a natural part of life in Florida, and people have been living with and using fire in our state for thousands of years. Florida has a year-round fire season, and wildfires can occur at any time.
Learning more about wildland fire can help you be more informed about ways to reduce wildfire risks for your home and community. Learning how our native plants and animals have adapted to fire can help you understand how and why responsible land managers use prescribed fire to foster healthy ecosystems and reduce the risk of future catastrophic wildfires.
UF/IFAS supports the Southern Fire Exchange, which is a southeastern leader in connecting the public, land managers, and wildland firefighters with cutting-edge fire science information and tools. You can subscribe to the organization’s newsletter and learn more at southernfireexchange.org.