Month: September 2020

By Jack Cohen and Dave Strohmaier

We must abandon our expectation that we can suppress 100% of wildfires and reject the false narrative that community protection requires wildfire control. Community wildfire disasters have only occurred during extreme conditions when high wind speed, low relative humidity, and flammable vegetation result in high fire intensities, rapid fire growth rates, and showers of burning embers (firebrands) starting new fires. Fire agencies primarily use wildfire suppression tactics for protecting communities from wildfires. But as we see from current extreme wildfire conditions in California, Oregon, and Washington, fire suppression can quickly become overwhelmed and ineffective.

Wildfires, and thus extreme wildfires, are inevitable. Does that mean wildland-urban (WU) fire disasters are inevitable as well? Absolutely not! WU fire research has shown that homeowners can create ignition resistant homes to prevent community wildfire disasters. How can that be possible?

Recall the destruction in Paradise, CA, during the extreme 2018 Camp Fire. Most of the totally destroyed homes in Paradise were surrounded by unconsumed tree canopies. Although many journalists and public officials believe this outcome was unusual, the pattern of unconsumed vegetation adjacent to and surrounding total home destruction is typical of WU fire disasters. In 2020 we see the same patterns of home destruction and adjacent unconsumed vegetation in photos from Malden, WA, and Phoenix, Talent, Blue River, and Mill City OR. Home destruction with adjacent unconsumed shrub and tree vegetation indicates the following:

• High intensity wildfire does not continuously spread through a residential area as a tsunami or flood of flame.
• Unconsumed shrub and tree canopies adjacent to homes do not produce high intensity flames that ignite the homes; ignitions can be only from burning embers and low intensity surface fires.
• The “big flames” of high intensity wildfires are not causing total home destruction.

Surprisingly, research has shown that home ignitions during extreme wildfires result from conditions local to a home. A home’s ignition vulnerabilities in relation to nearby burning materials within 100 feet principally determine home ignitions. This area of a home and its immediate surroundings is called the home ignition zone (HIZ). Typically, lofted burning embers initiate ignitions within the HIZ – to homes directly and nearby flammables leading to homes. Although an intense wildfire can loft firebrands more than one-half mile to start fires, the minuscule local conditions where the burning embers land and accumulate determine ignitions. Importantly, most home destruction during extreme wildfires occurs hours after the wildfire has ceased intense burning near the community; the residential fuels – homes, other structures, and vegetation – continue fire spread within the community.

Uncontrollable extreme wildfires are inevitable; however, by reducing home ignition potential within the HIZ we can create ignition resistant homes and communities. Thus, community wildfire risk should be defined as a home ignition problem, not a wildfire control problem. Unfortunately, protecting communities from wildfire by reducing home ignition potential runs counter to established orthodoxy.

There are good reasons to do “fuel treatments” for ecological and commercial objectives. But the greatest fuel treatment effect on wildfire behavior is within the fuel treatment area; fuel treatments do not stop extreme wildfires. So let’s call a spade a spade and not pretend that many, or even most fuel treatment projects actually reduce home ignition potential during extreme wildfires. Because local conditions determine home ignitions, the most effective “fuel treatment” addressing community wildfire risk reduces home ignition potential within HIZs and the community. Wildfires, exacerbated by climate change, will occur. Community destruction during extreme wildfires will continue as long as wildfire suppression remains the primary approach for community protection. Conducting the same ineffective strategy and tactics expecting different results will continue to be a recipe for disaster when it comes to protecting homes from extreme wildfire.

To make this shift, land managers, elected officials, and members of the public must question some of our most deeply ingrained assumptions regarding fire. For the sake of fiscal responsibility, scientific integrity, and effective outcomes, it’s high time we abandon the tired and disingenuous policies of our century-old all-out war on wildfire and fuel treatments conducted under the guise of protecting communities. Instead, let’s focus on mitigating WU fire risk where ignitions are determined – within the home ignition zone.

For further information:

• “Your Home Can Survive a Wildfire” video
• Preparing your home ignition zone for wildfire

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Jack Cohen, PhD, retired US Forest Service Research fire scientist determined how structures ignite during extreme wildfires, created the home ignition zone concept, and co-developed NFPA Firewise USA.

Dave Strohmaier is Missoula County Commissioner. He previously worked for both the Bureau of Land Management and US Forest Service in fire management, and has published two books on the subject of wildfire in the West.