More prescribed burning not likely to influence smoke

Recently the Oregon Environmental Quality Commission approved new smoke rules that relax air quality standards to permit more prescribed burning. The assumption behind the new standards is that greater prescribed burning in spring and fall will reduce smoke from wildfires in the summer.

Prior to the new regulations, agencies doing prescribed burning had minimal windows of time available for burning when there was good air dispersal. The new rules will allow more smoke if it remains below a level deemed harmful to sensitive groups.

It is understandable that people would grasp at anything that promises a reduction in summertime smoke given the conditions that trapped residents in the Rogue Valley and elsewhere in Oregon last summer. However, there are reasons to believe this proposal will do little to improve summer-time air quality.

First, the majority of smoke that occurred in Oregon last summer was coming from fires burning in other parts of the West from British Columbia to California. Treating Oregon forests will have little impact on these smoke sources.

Second, on a per acre basis, burning when fuels are wet produces far more smoke than fires burning during the dry conditions of summer.

Third, even if prescribed burning reduces the number of fires, it may not have much effect on smoke conditions. The reason is that most fires never amount to much.

An important concept that evades most “active forest management” proponents is that the vast majority of all wildfires burn less than 5 acres.  These fires are burning under less than extreme fire weather conditions, and most of these fires are destined to go out naturally with or without suppression.  On a relative basis, they produce very little smoke.

So, the very fires that prescribed burning can influence—those burning under low to moderate fire weather conditions–do not produce a significant amount of smoke.

Most of the smoke in the atmosphere is the result of a very few large blazes that are burning under what is called “extreme fire weather” conditions.  When you have drought, coupled with low humidity, high temperatures and, high winds, you have fires that cannot be stopped. Furthermore, these fires regularly burn through, over, and around any prescribed burn or even thinned forest.

An excellent example of such a fire is the Eagle Fire which charred portions of the Columbia Gorge. It jumped the mile and half wide Columbia River due to high winds. Does anyone believe that a prescribed burn or even a thinned forest can stop such blazes when the complete absence of any fuel does not influence wildfire behavior?  The same thing occurred with several recent fires in California where the only “fuel break” that halted the Thomas Fire by Santa Barbara and the Woolsey Fire by Malibu was the Pacific Ocean.

More than 200 scientists, including some of the top fire ecologists in the country, sent a letter to Congress last fall that questioned prescribed burning as well as thinning as a panacea for wildfire management. They asserted: “Thinning is most often proposed to reduce fire risk and lower fire intensity. When fire weather is not extreme, thinning-from-below of small diameter trees followed by prescribed fire, and in some cases prescribed fire alone, can reduce fire severity in certain forest types for a limited period of time. However, as the climate changes, most of our fires will occur during extreme fire-weather (high winds and temperatures, low humidity, low vegetation moisture). These fires, like the ones burning in the West this summer, will affect large landscapes, regardless of thinning, and, in some cases, burn hundreds or thousands of acres in just a few days.”

The critical phrase in their letter is that “when fire weather is not extreme.”  The very fires that produce the bulk of all smoke are blazes that prescribed burning and thinning are mostly ineffective in influencing.

That is not to suggest that prescribed burning doesn’t have a place as a management tool. Burning in the immediate area around homes and community boundaries if done on a regular basis (and routine maintenance is critical) can give firefighters an edge in protection homes. However, most research suggests that reducing the flammability of homes is far more effective at protecting communities from wildfire.

I suspect that proponents of “active management” will continue to mislead the public into believing the solution to smoke and wildfires is more logging and burning. That is easier to promote than “active management” to reduce human sources of GHG emissions. In Oregon, logging is the greatest single source of GHG emissions, but few are demanding less logging. Instead, we are wasting valuable resources on “halfway” solutions that ignore science.






  1. Bruce Bowen Avatar
    Bruce Bowen

    It seems like the various federal agencies are doing their best to rid the forest of organic matter in opposition to the many forest experimental stations that recommend leaving a lot more organic matter in the forest.

    The business/capitalistic oriented minds out there simply cannot grasp ecology. They are destroying the forests productivity for what they think will appease industry and the common populous.

    I think concerned people should demand a moratorium on all logging and burning in all federal forests.

    1. rork Avatar

      We have some burns on federal forest that have more goals than fire suppression, but I’m in Michigan. They help our native plants beat the invasives. They make nutrients available to grow trees. Some wildlife likes it like turkeys, and it keeps some patches of prairie intact, or black oak barrens. We have endangered butterflies and birds (like Kirtland’s warbler) that depend on us burning – that’s a relatively unusual case where you are actually trying to burn jack pines to death. We just don’t have enough acres burning by themselves. I’m not saying it is always good, just that somethings it might be.
      Oh, it can make very nice mushroom flushes too, and blueberries. Near me, on State or other public land, we burn and it’s never about smoke or fire suppression, but only for ecological reasons, mostly in oaks. 20 years ago I was skeptical. Now I want more fire, because of what I’ve seen it do. I’m not saying that is true other places.
      I also thank George, and agree that diminishing severe fire this way seems unlikely.

  2. Jack Avatar

    It’s untrue that the bulk of 2018 smoke, at least in sw Oregon, was coming from distant fires. The Rogue Valley was surrounded by large fire events on nearby lands that contributed the vast majority of smoke over a long period of time. The real issue that’s being ignored here is that climate change is shifting some western forests toward larger / more intense fire events, which has adverse effects on ecosystems as well as people. To declare that all “natural” fires are good is not ecologically accurate and oversimplifies a complex set of issues.

  3. Jimmy James Avatar
    Jimmy James

    Wow… The author here really needs to come up to speed on what the real issue is. Your claim of the fire jumping the Columbia shows that you do not understand how the lack of fires (and preventative fires) has actually caused the fire front to travel higher, and hotter and carry embers MILES compared to forests that have had frequent fires or been allowed to burn. WE created the condition of the Megafires now. Drought conditions have always existed and have come and gone each year, and yet even during those times the number and size of Megafires was never what they are now.

    If you need some help, brush up on this easily digestible TedTalk “Living (Dangerously) in an Era of Megafires” ->


George Wuerthner is an ecologist and writer who has published 38 books on various topics related to environmental and natural history. He has visited over 400 designated wilderness areas and over 200 national park units.

Subscribe to get new posts right in your Inbox

George Wuerthner