Very large fire break being constructed in Southwest France

About 1,000 feet wide

firebreak wildfires southwest France
Fire break under construction in Southwest France. July, 2022. France24.

The Bordeaux region in Southwest France has experienced many fires in the last few weeks that have burned a total of about 50,000 acres (20,000 Ha). Thinking that it will stop future fires, officials are building a large fire break three miles (5 K) long and about 1,000 feet (300 meters) wide.

map wildfires southwest france
Red areas on a map of Southwest France represent heat at wildfires detected by satellites during the seven-day period ending July 22, 2022. NASA FIRMS.

In parts of the Western United States back in the 1960s building fire breaks was a common practice. Some were only one or two dozer blades wide scraped down to mineral soil, while others were wider. But in later decades firefighters realized that no firebreak is likely to stop a rapidly spreading blaze.

Fires become large most often because they are burning in copious amounts of vegetation (fuel) during strong winds. Under unusually hot, dry, and windy conditions burning embers are lofted into the air. As they are blown downwind they can ignite new fires, “spot fires”, hundreds of feet or even up to a mile away from the main fire. Usually these embers are small, but can be as large as tree branches or even a four-by-eight-foot sheet of plywood, both of which have come close to or even hit air tankers working over the fire.

Under extreme conditions nothing will stop a large fire unless it completely runs out of fuel over a very large area, or the weather changes. A 1,000-foot fire break can stop a slow moving fire, but not a conflagration of the type that wipes out dozens of structures.

Something that cannot be ignored is that removal of all vegetation can result in severe environmental damage.

In the United States land managers are now more prone to build fuel breaks. They do not attempt to remove all vegetation, but only reduce it to the point where it will slow the spread of a fire enough that firefighters, sometimes aided by aircraft dropping water or fire retardant, can safely move in close to the flanks, make a direct attack, anchor the heel, and work their way along the edges and eventually stop the head of the fire. Fuel breaks helped firefighters last year on the Caldor Fire near South Lake Tahoe in California.

The first video below describes the firebreak in France. The next one is an update on the wildfires in the southwest part of the country.

Do fuel reduction treatments increase resistance to insects and drought?

Not always, according to researchers

Prescribed fire at Mount Rushmore National Memorial
Prescribed fire at Mount Rushmore National Memorial, April 29, 2020. Photo by Paul Horsted.

Intuitively we might think that fuel reduction treatments and prescribed fire would lead to more resistance to drought and attacks by beetles. While that is sometimes the case, it turns out that following the extreme 2012-2016 drought in California, prescribed burning increased beetle infestation rates and increased mortality of red fir and sugar pine in an area studied by scientists.

Researchers studied 10,000 mapped and tagged trees in a mixed‐conifer forest following mechanical thinning and/or prescribed burning treatments in 2001 through the extreme drought in California. The work was conducted in the Teakettle Experimental Forest (36°58′ N, 119°2′ W) located in the High Sierra Ranger District of Sierra National Forest, in California’s Sierra Nevada. Elevation of the forest ranges from 1,880 to 2,485 m.

While prescribed burning is an important tool for increasing resistance to wildfire their results suggest prescribed burning does not necessarily also instill drought resistance.

Below is an excerpt from a paper  titled, “Do forest fuel reduction treatments confer resistance to beetle infestation and drought mortality?” It was written by: Z. L. Steel, M. J. Goodwin, M. D. Meyer, G. A. Fricker, H. S. J. Zald, M. D. Hurteau, M. P. North, and published by the Ecological Society of America January 22, 2021.


Management challenges
Density reduction treatments that rely on mechanical thinning alone had neutral to positive effects on conifer survival during the 2012–2016 drought (Figs. 7, 8). The overstory treatment that removed medium to large trees (e.g., ≥25 cm) was most beneficial to residual individuals, suggesting such a strategy could be used broadly to increase drought resilience for some species (i.e., Jeffrey pine and white fir). While removal of smaller trees (e.g., ≤25 cm) may be less effective at mitigating drought mortality, treatments focused on ladder and surface fuels may still be preferred when considering non‐drought objectives such as reducing fire hazard or maintaining wildlife habitat (Stephens et al. 2012).

Prescribed burning appears less effective than mechanical thinning at reducing drought mortality and in some cases can lead to higher beetle infestation and mortality rates (Fig. 8). This is most striking in the case of large sugar pines which died at much higher rates in prescribed burn plots during the drought. The negative effect of burning on tree survival is somewhat surprising given that the fire regime under which these forests developed was characterized by frequent (i.e., 11–17 yr) low‐ to moderate‐severity fire (North et al. 2005, Safford and Stevens 2017), and that the prescribed burn occurred approximately a decade prior to the drought.

Mortality and probability change
Indirect effect of forest treatment on drought mortality. Treatment abbreviations are UU for Unburned/Understory Thin; UO for Unburned/Overstory Thin; BN for Burned/No Thin; BU for Burned/Understory Thin; and BO for Burned/Overstory Thin. Value distributions represent change in probability of mortality relative to controls for two tree sizes. The scale of the x‐axis varies among species. (From the research)

Further, van Mantgem et al. (2016) observed decreased tree mortality associated with prescribed fire elsewhere in the Sierra Nevada following the initial two years of California’s drought, and Meyer et al. (2019) found no difference in mortality between paired burned and unburned plots in red fir forests during the middle and late periods of the drought. The forests Meyer et al. (2019) sampled were at higher elevations than Teakettle where soil moisture is substantially higher and temperatures lower.

The results presented here could be unique to the Teakettle Experimental Forest, but we suspect they are more likely attributable to the historic severity of the 2012–2016 drought. When beetle populations are less than epidemic such as at higher elevations, during moderate droughts, or early in severe droughts, previous fire and its associated reduced density may be neutral or ameliorating for conifer mortality.

Our sugar pine results may indicate a tipping point beyond which the combination of extreme water stress from drought, bark beetle outbreaks, and fire result in increasingly high rates of tree mortality (Nesmith et al. 2015), and subsequent forest structural changes outside the natural range of variation (Young et al. 2020).

These results suggest cautious low‐intensity and small (i.e., stand) scale prescribed burning, as it is often applied by managers, may only benefit forests under short duration drought stress while contributing to higher mortality in red fir and sugar pine during prolonged and exceptional droughts.

High mortality rates of large sugar pines may be related to prescribed fires consumption of deep litter and duff layers that have accumulated around the base of pine species under fire suppression, suggesting removal of litter and duff through raking could protect individual trees. Nesmith et al. (2010) found raking increased survival and reduced bark beetle activity when fire intensity was moderate (<80% crown scorch) and when fuel depth was ≥30 cm. Thus, protecting individual trees of high ecological value may be possible prior to prescribed burns. However, such targeted measures are infeasible at broad scales in fire‐prone landscapes of the Sierra Nevada. In the long run, retaining sugar pine in these pyrogenic landscapes may hinge on fostering sunny, bare mineral soil conditions favorable for sugar pine regeneration and in the future reducing surface fuels on a regular basis.

Infestation probability
Marginal effects on beetle infestation. (C) host species basal area within a 10‐m radius, and (D) whether a tree experienced a prescribed burn treatment. Beetle and tree species abbreviations are jpb for Jeffrey pine beetle; rtb for red turpentine beetle; mpb for mountain pine beetle; eng for fir engraver; pije for Pinus jeffreyi (Jeffrey pine); pila for Pinus lambertiana (sugar pine); abco for Abies concolor (white fir); and abma for Abies magnifica (red fir). For C, thick lines show mean effect estimates with labeled solid lines represent relationships where the 90% credible interval does not include zero. To illustrate the spread of credible effects, 30 model posterior draws are also drawn as faint lines. Note the y‐axis scale differs for (D). (From the research)

Treatment effects on large diameter trees are often the focus of management restoration efforts since these structures have been reduced from past logging, take a long time to develop, and are associated with important ecosystem services (e.g., sensitive species habitat and carbon storage). Treatments using only thinning consistently reduced mortality of large (>75 cm DBH) trees across species, albeit with different effect sizes. For incense‐cedar and especially white fir, there was a greater reduction in mortality for small versus large trees, which are often the target of fuel reduction treatments. Prescribed fire has mixed effects, reducing mortality of large Jeffrey pine and slightly reducing small white fir mortality when combined with thinning, but increasing mortality of large red fir, incense‐cedar, and significantly increasing large sugar pine mortality.

While prescribed burning is an important tool for increasing resistance to wildfire (Stephens and Moghaddas 2005, Prichard et al. 2010), our results suggest such fuel treatments do not necessarily also instill drought resistance. There is general benefit to all species in reducing density, but the means (i.e., mechanical vs. prescribed fire) of treatment matters, suggesting caution in widespread use of fire in drought‐prone areas where managers want to retain large sugar pines and red fir.

Environmental groups sue BLM over plans to construct 11,000 miles of fuel breaks

The projects would be in California, Oregon, Washington, Idaho, Nevada, and Utah

BLM Fuelbreak Map

Environmentalists have filed a notice of intent to sue the U.S government to block plans to build up to 11,000 miles of fuel breaks they contend would violate the Endangered Species Act in a misguided effort to slow the advance of wildfires in six Western states, the Associated Press reported.

On February 14, 2020 the Bureau of Land Management (BLM) released the Final Programmatic Environmental Impact Statement (PEIS) for Fuel Breaks in the Great Basin. It outlines the construction and maintenance of a system of up to 11,000 miles of fuel breaks within a 223 million acre area to aid in the control of wildfires in portions of Idaho, Oregon, Washington, California, Nevada, and Utah.

The Preferred Alternative outlined in the PEIS analyzes manual, chemical and mechanical treatments, including prescribed fire, seeding, and targeted grazing to construct and maintain a system of fuel breaks. These treatments would be implemented along roads and rights-of-way on BLM-administered lands to minimize new disturbance and wildlife habitat fragmentation and to maximize accessibility for wildland firefighters.

Thanks and a tip of the hat go out to Kelly.

Success story — fire prevention along Interstate 84 in Idaho

Average fire size decreased by 95 percent

I-84 Fire prevention wildfire Idaho

In order to deal with an increasing number of wildfires that were starting along Interstate 84 southeast of Boise, Idaho the Bureau of Land Management worked with local cooperators to establish a fuel modification program along the highway.

Their first action, from 2007 to 2012, was to reduce the existing vegetation by mowing, constructing fuel breaks, and establishing perennial grasses to reduce invasive annuals in the right of way adjacent to the interstate. It is a small sample size but during this period there was little significant change in the annual acres burned, average fire size, or the number of fires.

During the next seven years, from 2013 to 2019, the treatment strategy also included reestablishment of the gravel apron along the edge of the pavement surface to a minimum of 12 feet. The implementation required years of adaptive management and hard work, but the effort is producing results: average fire size for the last seven years has been reduced 95 percent even though traffic flow increased by more than 30 percent.

I-84 Fire prevention wildfire Idaho

I-84 Fire prevention wildfire Idaho

Images and graphics: BLM

Some prescribed fires are more challenging than others

Prescribed fire fuel break Angeles National Forest
Prescribed fire on the Clear Creek fuel break in the Angeles National Forest. ANF photo.

Firefighters on the Angeles National Forest are using prescribed fire on the Clear Creek fuel break north of Los Angeles that separates the Arroyo Seco from the Big Tujunga drainages.

“It helps to protect some of the largest communication sites anywhere, some of LA’s drinking water storage, and major communities,” said Robert Garcia, Fire Chief on the Angeles National Forest. “It is also on some of the toughest ground we have on the ANF making initial attack very difficult. The adjacent slopes are unfortunately known from such incidents as Woodwardia, Bryant and more recently the origins of the 2009 Station Fire.”

When I worked on the Laguna and El Cariso Hotshots nearby on the Cleveland NF, to us the ANF was infamous for its extremely steep slopes, which are evident in these photos.

Prescribed fire fuel break Angeles National Forest
Prescribed fire on the Clear Creek fuel break in the Angeles National Forest. ANF photo.
Prescribed fire fuel break Angeles National Forest
Prescribed fire on the Clear Creek fuel break in the Angeles National Forest. ANF photo.
Prescribed fire fuel break Angeles National Forest
Prescribed fire on the Clear Creek fuel break in the Angeles National Forest. ANF photo.
map Prescribed fire fuel break Angeles National Forest
Clear Creek fuel break in the Angeles National Forest. ANF.

In most other locations super-steep slopes are not a serious obstacle while conducting prescribed fires, as in the example below.

Prescribed fire at Chickasaw National Recreation Area
Prescribed fire at Chickasaw National Recreation Area in Oklahoma by M. Fidler, February, 2013.

BLM plans to build 11,000 miles of fuel breaks

BLM Fuelbreak EIS

On Friday, February 14 the Bureau of Land Management (BLM) released the Final Programmatic Environmental Impact Statement (PEIS) for Fuel Breaks in the Great Basin. This Final PEIS provides for the construction and maintenance of a system of up to 11,000 miles of fuel breaks within a 223 million acre area to aid in the control of wildfires in portions of Idaho, Oregon, Washington, California, Nevada, and Utah.

The Preferred Alternative outlined in the PEIS analyzes manual, chemical and mechanical treatments, including prescribed fire, seeding, and targeted grazing to construct and maintain a system of fuel breaks. These treatments would be implemented along roads and rights-of-way on BLM-administered lands to minimize new disturbance and wildlife habitat fragmentation and to maximize accessibility for wildland firefighters.

BLM Fuelbreak Map

The estimated total cost of developing and producing the PEIS was $2.3 million.

“Wildfires pose an enormous threat to rangelands in the Great Basin – rangelands that people depend on for both recreational opportunities and their livelihoods, and that wildlife rely on for habitat,” said BLM Deputy Director for Policy and Programs William Perry Pendley. “Fuel breaks are one of the most important tools we have to give wildland firefighters a chance to safely and effectively contain rapidly moving wildfires and potentially reduce wildfire size.”

cost constructing fuel breaks BLM
From the BLM PEIS

Wildfires in sagebrush communities in the Great Basin states are becoming more frequent and larger, fueled by large, unbroken swaths of grasses, brush and other vegetation. Over 13.5 million acres of historically sagebrush communities on BLM land burned within the project area between 2009 and 2018. Wildfires that consume sagebrush provide the opportunity for invasive annual grasses to increase, making future large and severe wildfires more likely.

BLM Fuelbreak
Example of a mowed fuel break. BLM photo.

The concept behind fuel breaks is to break up or fragment continuous fuels by reducing vegetation in key locations. When a wildfire burns into a fuel break, the flame lengths decrease and its progress slows, making it safer and easier for firefighters to control.

An electronic copy of the Final PEIS and associated documents is available for public review for 30 days on the BLM Land Use Planning and NEPA register at https://go.usa.gov/xnQcG. Other documents related to the EIS are at the BLM’s ePlanning website.  The BLM will issue a Record of Decision after the end of the public review period.