PDF _ R40811 - Wildfire Fuels and Fuel Reduction
16-Sep-2009; Ross W. Gorte; 18 p.

Abstract: Severe wildfires have been burning more area and more houses in recent years. Some assert that climate change is at least partly to blame; others claim that the increasing number of homes in and near the forest (the wildland-urban interface) is a major cause. However, most observers agree that wildfire suppression and historic land management practices have led to unnaturally high accumulations of biomass in many forests, primarily in the intermountain West. While highintensity conflagrations (wildfires that burn the forest canopy) occur naturally in some ecosystems (called crown-fire or stand-replacement fire ecosystems), abnormally high biomass levels can lead to conflagrations in ecosystems when such crown fires were rare (called frequentsurface- fire ecosystems). Thus, many propose activities to reduce forest biomass fuels.

Biomass fuel reduction activities are designed to affect various fuel characteristics. Fuel moisture content is critical, but is generally a function of weather patterns over hours, days, and weeks. Fuel size is also important—fine and small fuels (e.g., needles, grasses, leaves, small twigs) are key to fire spread, while larger fuels (e.g., twigs larger than pencil-diameter, branches, and logs) contribute primarily to fire intensity; both are important to minimizing fire damages. Fuel distribution can also affect damages. Relatively continuous fuels improve burning, and vertically continuous fuels—fuel ladders—can lead a surface fire into the canopy, causing a conflagration. Lastly, total fuel accumulations (fuel loads) also contribute to fire intensity and damage. Thus, activities that alter biomass fuels—reducing total loads, reducing small fuels, reducing large fuels, and eliminating fuel ladders—can help reduce wildfire severity and damages.

Several tools can be used to reduce forest biomass fuels. Prescribed burning is the deliberate use of fire in specific areas under specified conditions. It is the only tool that can eliminate fine fuels, but is risky because it burns any fuel available. Wildland fire use is the term used for allowing a wildfire to be used like a prescribed burn (i.e., within specified areas and conditions). Thinning is a broader forestry tool useful for eliminating fuel ladders and total fuels in the crown, but it does not eliminate fine fuels, and it concentrates fuels in a more continuous array on the surface. The combination of thinning with prescribed burning is often proposed to combine the benefits, but it also combines the cost of both. Logging does little to reduce fuel loads.

The federal land management agencies undertake all of these activities under general authorities for wildfire protection and land and resource management. Fuel reduction, primarily via prescribed burning, is funded with direct annual appropriations for wildfire management. Other activities, particularly thinning, are funded through other annual appropriations accounts, such as vegetation management. Also, several mandatory spending accounts provide funds for related activities, such as treating logging and thinning debris. In addition, wildfire assistance funding allows the Forest Service to provide technical and financial aid for reducing forest biomass fuel loads on nonfederal lands, among other things.

The issues for Congress include the appropriate level of funding for prescribed burning and thinning for fuel reduction and the appropriate reporting of accomplishments. Current reporting does not identify ecosystems being treated and the effectiveness of the treatments. Similarly, current appropriations and reporting do not distinguish thinning for fuel reduction from thinning for other purposes, such as enhancing timber productivity. More complete reporting could allow Congress to better target its appropriations for fuel reduction to enhance wildfire protection. [read report]

Topics: Forests, Natural Resources

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