Reduce the Area Burned

Perhaps the most obvious method to reduce wildland fire emissions is to reduce the area burned. Area burned can be reduced by not burning at all or by burning a subset of the area within a designated perimeter. Caution must be applied though, and programs to reduce the area burned must not ultimately result in just a delay in the release of emissions either through prescribed burning at a later date or as the result of a wildland fire. Reducing the area burned should be accomplished by methods that truly result in reduced emissions over time rather than a deferral of emissions to some future date.

This technique can have detrimental effects on ecosystem function in fire-adapted vegetation community types and is least applicable when fire is needed for ecosystem or habitat management, or forest health enhancement. In some areas and some vegetation types, when fire is used to eliminate an undesirable species or dispose of biomass waste, alternative methods can be used to accomplish effects similar to what burning would accomplish. Examples of specific techniques include:

• Burn Concentrations. Sometimes concentrations of fuels can be burned rather than using fire on 100 percent of an area requiring treatment. The fuel loading of the areas burned using this technique tend to be high. The total area burned under these circumstances can be very difficult to quantify.
• Isolate fuels. Large logs, snags, deep pockets of duff, sawdust piles, squirrel middens, or other fuel concentrations that have the potential to smolder for long periods of time can be isolated from burning. This can be accomplished by several techniques including: 1) constructing a fireline around the fuels of concern; 2) not lighting individual or concentrated fuels; 3) using natural barriers or snow; 4) scattering the fuels; and 5) spraying with foam or other fire retardant material. Eliminating these fuels from burning is often faster, safer, and less costly than mop-up, and allows targeted fuels to remain following the prescribed burn.
• Mosaic burning. Landscapes often contain a variety of fuel types that are noncontinuous and vary in fuel moisture content. Prescribed fire prescriptions and lighting patterns can be assigned to use this fuel and fuel moisture non-homogeneity to mimic a natural wildfire and create patches of burned and non-burned areas or burn only selected fuels. Areas or fuels that do not burn do not contribute to emissions. For example, an area may be continuously ignited during a prescribed fire but because the fuels are not continuous, patches within the unit perimeter may not ignite and burn (figure 8.1). Depressional wetlands, swamps, and hardwood stringers can be excluded by burning when soil moisture is abundant. Furthermore, if the burn prescription calls for low humidity and high live fuel moisture, continuous burning in the dead fuels may occur while the live fuels exceed the moisture of extinction. In both cases, the unburned live fuels may be available for future burning in a prescribed or wildland fire during droughts or dormant seasons.