What is a fuel break?
What is a Fuel Break?
A fuel break is a strip of land where vegetation has been removed down to bare earth so that a fire moving into the area can be more readily controlled. For a fuel break to be effective, the width and length must be sufficient to reduce fire spread and intensity. The theory of a fuel break is that when the fire hits the break, there is no fuel for it to continue spreading, therefore stopping the fire from progressing. In addition, by creating breaks ahead of time, there are established zones that firefighters can use to make a stand.
The recommended dimensions of a fuel break in forested areas is approximately 300 feet wide (variation in width is largely determined by vegetation type, slope, access, and other site specific needs and objectives). The length of a fuel break will vary from site to site. Typically fuel breaks will span from existing manmade breaks such as roads or highways. Common strategic locations for fuel breaks include ridgetops, access roads, and the outer boundary of subdivisions within the wildland-urban interface. These strategic locations are chosen to break up large, continuous tracts of dense vegetation with the intention of controlling fire spread.
Shaded Fuel Breaks
One variation of the traditional fuel break is a shaded fuel break. In a shaded fuel break, the trees within the break zone are thinned and pruned to reduce the fire potential yet retain enough crown canopy to make a less favorable microclimate for surface fires. In theory, a shaded fuel break does not remove all vegetation in the treatment area and instead favors the growth of large native species by removing the understory ladder fuels to prevent a wildfire from moving to the overstory tree canopy. The intent of a shaded fuel break is to favorably modify wildfire behavior while providing the foundation for a healthy and resilient forest.
Do Fuel Breaks Work?
The short answer is it depends. MTS wrote extensively on this subject in our February 7th 2023 newsletter (available on our website). There are many variables in play with wildfires. Overall studies have shown that fuel breaks are effective at stopping fires approximately 50% of the time.
Fires can roughly be separated into two categories: those that are wind-driven versus those that are fuel-driven. In the event of a wind-driven fire, fuel breaks have been found to be widely ineffective. Fuel breaks tend to have the greatest success with fuel driven fires. Studies have also shown that fuel breaks are the most effective when strategically placed to provide access for firefighting activities.
Here on the North Coast, weather patterns during the summer make wind-driven fires less likely compared to other areas of the western US. However, during late fall and winter we can experience local strong winds, and if these occur during periods of drought, it can present dangerous wind-driven fire conditions. Outside of that, we can mostly expect fuel-driven fires here making this area a good candidate for implementing fuel breaks as part of a broader fire hardening strategy.
Shaded fuel breaks can be effective in reducing the likelihood and severity of wildfires. By removing or thinning vegetation in the understory leaving the overstory canopy intact, shaded fuel breaks can create barriers that can help slow or stop the spread of fires. The effectiveness of shaded fuel breaks depends on a number of factors, including the location, size, and design of the fuel break, as well as the intensity and behavior of the fire.
Research has shown that shaded fuel breaks can be particularly effective when they are combined with other strategies for managing wildfires, such as prescribed burns, and forest thinning within the understory leaving large diameter trees in place. In addition, shaded fuel breaks can help protect communities and infrastructure located near wildland areas, which are particularly vulnerable to wildfire.
However, it's important to note that shaded fuel breaks are not a silver bullet solution to the problem of wildfire. Other factors, such as climate change, land use change, and human behavior, can also increase the risk and severity of wildfires. Therefore, a comprehensive approach that includes a range of strategies, including forest management, fire prevention, and community outreach, is needed to effectively reduce the impact of wildfires.
The Broader Picture
The elephant in the room when it comes to fire resiliency is that commercial timber harvest greatly increases surface fuel loads and therefore significantly increases the risk and intensity of wildfires (see our 2/7/2023 newsletter). The history of past commercial forest management has left our forests and adjacent communities more susceptible to wildfire. With warmer, drier seasons forecast for our future, fire danger will steadily increase along the North Coast, threatening both our forests and our communities.
Logging can increase fuel loads and fire risk in several ways:
Residual woody debris: Logging operations often leave behind large amounts of residual woody debris such as tree branches, tree tops, and small trees that were not commercially valuable. This debris can create a significant amount of surface fuels for fires, particularly when it is left in large piles or scattered across the forest floor.
Slash and logging debris: Logging operations can also generate significant amounts of slash and logging debris, such as logs, branches, and sawdust. If left on the forest floor, this material can create a dense layer of fuel that can increase the intensity and spread of wildfires.
Soil compaction: Logging equipment can cause soil compaction, which can reduce soil moisture and make it harder for plants to regenerate. This can lead to an increase in fine fuels such as native and non-native grasses and invasive shrubs, which can contribute to a higher risk of wildfires.
Fragmentation of forest landscapes: Logging can fragment forests, creating smaller and more isolated patches of forest. This can lead to changes in microclimate, such as increased wind and temperature fluctuations, which can increase the risk of fires.
Decreased canopy and increased sun exposure to the forest floor: Decreasing the canopy by removing larger trees accelerates surface fuel drying, lowers near surface humidity levels, and fosters the growth of grasses and brushes all which facilitate and exacerbate wildfire behavior.
In addition, logging can also alter forest structure and composition, which can change the way that fires behave in the forest. For example, logging can create more uniform stands of trees that are of similar age and size, which can increase the likelihood of crown fires that can spread rapidly through the tops of the trees.
These factors can create conditions that are more conducive to the spread and intensity of wildfires.
Conclusions
Fuel breaks can and should be part of a comprehensive fire management plan but with some major conditions. The fuel breaks must be combined with other strategies such as prescribed burns, and surface fuel removal. The shaded fuel breaks must be accompanied by a comprehensive, clearly articulated strategy for forest-wide fire and climate resilience.
Fuel breaks must follow a ground-up strategy focusing first on treating surface fuels, second on ladder fuels removal, and not the removal of large, mature fire resistant trees. One concern is using fuel breaks and fire hardening as a reason for removing larger, commercially viable trees. This practice is unacceptable in that it creates a worse fire scenario by removing fire-resistant trees and opens up the canopy allowing greater sun exposure and subsequent ladder fuel growth.
Perhaps most importantly, for long lasting fire management in JDSF to be successful, we must address one of the major underlying causes of the large fuel loads and phase out commercial timber extraction within the state forest.