Protecting Forests and Property with Smart Fuels Reduction Strategies

By Jennifer Hunt (Content Writer), Nicole Porter (District Manager), and Brian Vrablick (Intermountain Region Manager)

In fire-prone forests, the difference between a manageable wildfire and a catastrophic blaze often comes down to one factor—fuel. While land managers can’t control elements of nature like heat and oxygen, they can control fuel buildup, and proactive management can mitigate wildfire risk and influence fire behavior. There are several strategies land managers can use in fuels reduction, from thinning to prescribed burning and creating firebreaks. Here, we will explore fuels and fire behavior, common fuels reduction strategies, and the myriad benefits of fuels reduction.

Understanding fuels and fire behavior is best illustrated through the “fire triangle” and “fire behavior triangle.” First, the fire triangle notes the three elements needed to sustain a fire—heat, fuel, and oxygen. When one of these elements is removed, the fire doesn’t start or simply goes out. Next, the fire behavior triangle demonstrates the rate at which the fire spreads (in feet/hour) and its intensity (how long the flame is and how hot it burns). This triangle notes land topography, weather, and fuel. During particularly hot and dry seasons with low humidity, fuel moisture content is reduced, and wildfire risks increase. Strong winds push fires in a particular direction, increasing their spread and intensity. Topographical features like slope, aspect, and elevation contribute to fire behavior as well. For instance, fires spread more rapidly uphill because heat rises, and fuels are preheated and drying ahead of the flames. As such, the steeper the slope, the faster the fire moves. South and west-facing slopes receive more sunlight, drying out fuels more quickly and making them more prone to burning. Lower elevations dry out earlier in the fire season, while higher elevations tend to retain moisture longer. However, higher elevations are more inclined to lightning strikes, which are a primary ignition source in many mountainous areas.

It's important to point out that while each leg of the triangle contributes to fires and fire behavior, the common denominator is fuel. Several fuel types contribute to wildfire risk, including:

• Surface fuels: This includes dead leaves, pine needles, grass, shrubs, small branches, and other organic material on the forest floor. These fuels ignite easily and help fires spread quickly.

• Ladder fuels: Live or dead vegetation, like snags (standing dead trees) and large branches, allow a fire to climb up from the forest floor to the tree canopy. They can burn for long durations and increase fire intensity.

• Crown fuels: The tops of trees, including leaves and needles, can sustain intense and rapidly spreading crown fires.

• Man-made fuels: Structures, wooden fences, and other human-made materials can contribute to fire spread, especially in wildland-urban areas.

The combination of fuels, coupled with weather and topography, can make a fire extremely challenging to manage, so landowners and their land managers must employ fuel reduction strategies.

After assessing a landowner’s site, your AFM forester or land manager can determine the appropriate course of action. It can include a combination of several strategies, including any of the following:

• Thinning: This method decreases ladder fuels and crown fuels by thinning trees in a stand. Foresters will consider tree spacing, which trees should be thinned, etc. “Thinning from below” (a common approach in even-aged stands) removes smaller, suppressed trees, preventing them from providing the “ladder” to dominant trees. Another benefit is that it increases the space between tree crowns, and larger trees have a thicker, more fire-resistant bark. Timing is an important consideration here, especially when thinning in pine and Douglas-fir stands, as certain management activities can provide breeding materials for Ips bark beetles. These pests can attack healthy trees after they emerge.

• Prescribed burning: While this method mimics natural fire cycles and promotes ecosystem balance, it is not without risks. There are generally two categories of prescribed burns, including slash burning and prescribed burning. Slash burning reduces fuels after many silvicultural treatments and is often done in tandem with other forest treatments such as thinning, harvesting, etc. Land managers and foresters will constantly monitor weather conditions, as sudden weather changes can impact fire behavior. Since prescribed burning comes with considerable risks, this method isn’t as commonly selected for fuels reduction on private forestlands as on state or federal lands.

• Creating fuelbreaks and firebreaks: Both methods have established pros and cons that land managers will take into consideration. Shaded fuel breaks are often attractive both aesthetically and financially, as they are less expensive to construct, and the sale of merchantable trees can help offset the cost of construction. However, fires can still burn through a fuelbreak (albeit at reduced speed and intensity), and they need to be retreated every decade. Firebreaks (aka fire lines) are usually only constructed during a current wildfire threat. Agencies use them as an anchor point to prevent the spread of fire. Preventative firebreaks can be created around homes and structures and are usually considered part of “defensible space.”

• Pruning and canopy management: Pruning is often done in concert with thinning in young stands, and it decreases ladder fuels. By pruning low tree limbs, it increases the tree crown’s height. The pruning slash must be dealt with as well, and land managers may consider several ways of disposal, including chipping or piling and burning.

The use of these methods is part of an ongoing process to reduce fuels on private property. While the initial costs of activities like those listed above can be pricey, their subsequent maintenance treatments are generally less expensive. These treatments are all essential facets landowners should consider as an opportunity to protect and maintain their investment, as effective fuels reduction have clear and tangible benefits to landowners and ecosystems.

In the past, fire suppression policies in the U.S. were aimed at preventing wildfires, but after many decades, these efforts actually contributed to dense, fire-prone forests with an overabundance of smaller, shade-tolerant trees and excessive woody debris. The result is a continuous fuel source that links surface fuels to the canopy, aka ladder fuels. However, thinning and safe prescribed burns can change the forest structure and composition by reducing surface fuels. Wildlife habitats are protected from severe fire activity; forests build resilience to the effects of climate change; native vegetation and pollinator habitats can emerge, and carbon stability will increase in the soil and overstory trees. Forests become healthier overall as the reduced density promotes better growth, resilience against drought, and resistance to pests.

Landowners in fire-prone areas have an incredible opportunity to be proactive and reduce the risks of the disastrous consequences that wildfires can have on their property. Professional foresters like those at AFM can create a comprehensive forest management plan that not only takes into account your wildfire prevention goals but also other land management goals like habitat preservation, recreation, and more. Ongoing land and forest management activities have significant advantages, many of which translate into economic benefits. Reach out to the professionals at AFM to help you protect one of your most treasured assets for generations to come.