Auburn professor comments on potential for wildfires during extremely dry conditions

Dr. Will Gulsby, assistant professor of wildlife ecology and management in Auburn University’s School of Forestry and Wildlife Sciences, comments on the potential for wildfires during extremely dry conditions. Earlier this week, the Alabama Forestry Commission issued a statewide fire alert.

How much quicker can a fire spread during dry conditions?

Although dry conditions certainly play a role, wind is the most important factor that determines how quickly a fire spreads. The major concern is that during dry conditions, the probability of ignition and intensity of fires increases. This means it is easier for a wildfire to start, and when it does the embers from the fire are more likely to start additional fires, which is referred to as spotting. Additionally, fires will burn with greater intensity during dry conditions and they are more difficult to control or extinguish. Currently, the Keetch-Byram Drought Index, which we use to estimate the dryness of the soil and duff layers, is greater than 600 across Alabama, with some areas as high as 700-800. For reference, 800 is considered oven dry, and prescribed burning is not recommended during this time of year when it exceeds 450. Under these conditions, fires will consume all fine fuels (grasses, leaves, small sticks, etc.) to bare mineral soil; larger fuels like dead branches and logs will actively burn and increase fire intensity; and stumps will be consumed to below ground level.

What would be the economic loss if a fire occurred in a pine plantation?

That depends on a number of factors. As already mentioned, wildfires during such dry conditions can get very intense. If a wildfire occurred in a pine stand that has accumulated a significant fuel load due to an absence of low-intensity prescribed fire, under extremely windy and dry conditions, the majority of the stand could be lost. If the trees in the stand were at or near maturity, the economic loss would be significant.

How does humidity, or lack thereof, affect the spread of wildfires?

Temperature and relative humidity are two of the most important factors affecting fire behavior. Generally, as humidity decreases, flame lengths and rate of spread increase because a greater proportion of the fuels in a stand are dry enough to burn and contribute to fire intensity. Lower relative humidity also increases the likelihood that fires will spot, starting additional fires in other areas. Over the next several days, relative humidity is forecast to be around 35 percent during midday. For reference, the suggested range in relative humidity for conducting prescribed burns is around 30-55 percent. So we’re toward the lower end of the “safe” range for prescribed burning, but when you couple that with the dry conditions and high temperatures we are experiencing, wildfire risk becomes much greater.

How do wildfires affect the wildlife population?

The simple answer is “it depends.” Many species of plants and animals in Alabama and throughout the Southeast are adapted to, and even benefit from some fire. This is why prescribed fire is a frequently used tool in wildlife management. We implement prescribed fire periodically with the goal of enhancing or maintaining coverage of beneficial wildlife plants in an area. Without periodic fire, populations of some animals (including some species of conservation concern) will decline or go locally extinct. Very intense wildfires, on the other hand, can cause direct mortality of less mobile species, particularly small mammals, reptiles and amphibians. They can also damage or destroy den trees used by a variety of birds and mammals. On the other hand, some wildlife species can only excavate nesting cavities in dead trees, so tree mortality resulting from wildfire can actually benefit those species.

How does prescribed fire minimize the potential of wildfire?

Prescribed fire minimizes the potential risk of wildfire by reducing fuel loading. Basically, low-intensity prescribed fire is a safe way to consume most of the vegetative material in an area that would contribute to a wildfire. Thus, if a wildfire subsequently comes through that area, the amount of fuel available to contribute to the intensity of that fire is reduced. Combined with the wildlife benefits, this is why periodic prescribed fire is an important tool for resource managers.

Are there other management tools that land owners might employ to reduce the risks of wildfire?

In addition to periodic prescribed fire, landowners in wildfire-prone areas can install firebreaks or roads around any sensitive areas, and make sure that any potential fuel sources like shrubs or tall grass are kept a safe distance away from homes, barns, vehicles and other valuable structures or objects.