Behavior Modification: Tempering Fire at the Landscape Level

With a history of management choices that have suppressed fire in the West, ecosystems in which fire would play a vital role have developed tremendous fuel loads. As a result, conditions are prime for fires to grow large, escape attack measures, and become catastrophic conflagrations that damage watersheds, forest resources, and homes. With a quiver of treatment options, land managers have successfully used prescribed burning and thinning to modify landscapes at the stand level. But planning treatments to modify fuel build up on a patch of forest is vastly different than planning treatments that could modify fire’s spread over larger landscapes.Using information specific to a site, such as fuels, topography, and weather, simulations are run to identify the pathways fire would likely follow, the elements that would cause a fire to grow from moderate to severe, and the treatment options that would best modify the fuel load present. The simulations identify the best placement of treatment units and number of units on a landscape. Little is known about how long treatments will last, but studies suggest the benefits are limited to 10 to 15 years. To achieve desired effects in tempering fire’s behavior, land managers must apply optimally placed treatments at a rate of 1% to 2% per year.Key Findings

• The pattern of fuel treatment units on a landscape is critical. Fuel treatment patterns placed optimally on a landscape (along a fire corridor) are roughly twice as efficient at changing large fire growth as random arrangements.
• When arranged in an optimal pattern, fuel treatment must occur at a rate of 1% to 2% per year to achieve reductions in large fire sizes or growth rates. The rate of treatment must produce treated area faster than the rate of plant regrowth and new fuel accumulation.
• Using sufficient treatment rates, the benefits of a fuel treatment program take about 1 to 2 decades to achieve.
• Long-term programs of fuel treatment involve maintenance of previously treated areas as well as implementation of new treatment units. The location of the treatment areas as they relate to the major corridors for fire spread are the most important factor in determining whether to maintain them.
• Variation in treatment unit sizes has the least impact on modifying large fires compared to treatment pattern and rate of treatment.