The costs of fighting wildfires have dramatically increased in the past decade, as have the size and severity of wildfires. Much of the millions of dollars spent fighting fires is spent in the wildland-urban interface (WUI), where expanding development into the forest creates more and more homes that are threatened when wildfires inevitably occur.
The Forest Service has sought to reduce the rapidly rising costs of fighting wildfires by thinning forests and removing fuel in the WUI before a wildfire occurs. These fuel treatments have amounted to an investment of millions of acres treated at a cost of millions of dollars, largely funded since 2000 by the National Fire Plan (NFP). But is this pro-active strategy working?
The year 2007 was an exceptionally active fire year in the northern Rockies, and the most active in Idaho since the historic Big Burn of 1910. In central Idaho alone, several massive wildfires combined to create the East Zone and Cascade megafires, which burned more than 240,000 hectares and cost over $70 million to try to suppress. However, weather conditions were so extreme and the wildfires so dangerous that little could be done beyond evacuating people and protecting property.
Two local communities - Secesh Meadows and Warm Lake - were located directly in the path of these advancing wildfires. Fortunately, no lives or homes were lost. Firefighters credit NFP-funded fuel treatments located immediately adjacent to the structures for slowing the momentum of the advancing crown fires.
The fact that extreme crown fires tested these fuel treatments provided Rocky Mountain Research Station scientists and collaborators at the University of Idaho an opportunity to assess whether fuel treatments also mitigate severe fire effects on vegetation and soils. So, the question arises: Can fuel treatments mitigate wildfire effects?
Researchers found the answer to be a qualified 'yes.' The severe wildfire killed most trees, but fewer trees died on treated sites than on untreated sites. Furthermore, most trees on untreated sites were completely charred, while trees on treated sites dropped their scorched needles in the weeks following the wildfire, helping to protect the soil from erosion.
There were exceptions; some treated sites in which the piled fuel from forest thinning had not yet been removed experienced more severe wildfire effects than adjacent untreated sites. Nonetheless, this case study provides solid evidence that fuel treatments generally do mitigate severe fire effects.
The researchers also reviewed dozens of retrospective (but often anecdotal) studies that support the widely held consensus among forest managers that forest thinning followed by some form of fuels removal, such as prescribed burning, is the most effective fuel treatment strategy. The benefits of fuel treatments as documented in this comprehensive report (Hudak et al. 2011) will help incident commanders, fuel specialists, forest planners, and national policymakers make wise decisions about allocating resources to fuel treatments.