Climate Driving Force in Large Wildfires

There is very little evidence that fuel reductions are a good strategy or really work as fire prevention

By George Wuerthner

Both the timber industry and Forest Service have implied that with fuel reductions (read logging) there would be few fires or blazes would be easily contained. One needs to question such assertions and assumptions. There is very little evidence that fuel reductions are a good strategy or really work.

Next time someone suggests that fuel reductions stopped a fire or significantly affected fire behavior, one must ask for more information. What was the weather doing when the fuel reduction supposedly halted the fire? Did the wind speed drop? Did the humidity go up? Did the fire run into a rock wall? Did the temperature drop? Was it night when humidity and temperatures are lower? Was the fire burning downhill which reduces preheating of fuels?

In almost all the instances that I have reviewed of fuel reduction “successes,” these other factors that are critical to fire spread occurred.

While there will always be exceptions, and no doubt occasional fuel reductions do work, most thinning projects fail in part because their effectiveness – to the degree there is any – is short lived.

Furthermore, under extreme fire weather conditions, almost all fuel reductions fail. Why is this an important qualifier? Because all large fires burn under extreme fire weather. So the very fires we most wish to control are those that are burning under conditions when fuel reductions repeatedly fail.

On the other hand, under less than extreme fire weather, most wildfires will self-extinguish whether we do anything or not. We just take credit for putting them out when a change in weather or other factors actually put out the flames.

The idea that fuel reductions could significantly alter fire behavior and spread is a myth perpetuated by the timber industry and Forest Service.

Even though we have thinned millions of acres of the West, the acreage burned by wildfire continues to climb. Many scientific review studies have documented that when you have extreme climate/weather — like a thousand-year drought — thinning and other fuel reduction projects don’t work for two reasons.

First, the probability that a fire will encounter a fuel reduction during the very limited time it may be effective is extremely small.

More importantly, extreme weather overcomes most fuel reductions.

For example, one review found: “Extreme environmental conditions … overwhelmed most fuel treatment effects … This included almost all treatment methods including prescribed burning and thinning … Suppression efforts had little benefit from fuel modifications.”

Another study concluded: “Area treated (by fuel reductions) has little relationship to trends in the area burned, which is influenced primarily by patterns of drought and warming.”

A third study states: “Fuel treatments … cannot realistically be expected to eliminate large area burned in severe fire weather years.”

The non-partisan Congressional Research Service determined “From a quantitative perspective, the CRS study indicates a very weak relationship between acres logged and the extent and severity of forest fires.”

Thinning/logging will not alter this outcome. In fact, it could make things worse.

The CRS went on to note that logged areas appeared to increase wildfire: “The data indicate that fewer acres burned in areas where logging activity was limited.”

This agrees with another review study published this past year that “found forests with higher levels of protection had lower severity values even though they are generally identified as having the highest overall levels of biomass and fuel.”

In other words, “active management” advocated by the timber industry appears to increase fire severity and extent.

These studies suggest that thinning/logging is a poor strategy in part because it fails to acknowledge that climate/weather is the driving force in large wildfires.

George Wuerthner is an ecologist who has published two books on fire ecology and numerous articles. He divides his time between Livingston and Bend, Oregon.

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