"Severe wildfires have been burning more acres and more structures 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, particularly in the intermountain West. While high-intensity 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. The characteristics of forest biomass fuels affect the nature, spread, and intensity of the fire. 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. 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."
CRS Report for Congress, R40811
The National Agricultural Law Center: http://nationalaglawcenter.org/