Lodgepole pine and bark beetles

Another new study published by the Ecological Society of America titled “Does wildfire likelihood increase following insect outbreaks in conifer forests?”  by Garrent Meigs and coauthors concludes that bark beetles outbreaks do not lead to greater likelihood of fires. This research joins a growing list of studies, all using different methods of evaluation that finds that bark beetles are not a driving force in wildfire. Rather climate, terrain, and other factors are more important.

Yet the Forest Service continues to promote the idea that logging beetle kill trees will reduce future fires in direct conflict to contradictory research.


Lodgepole pine is one of the most common trees in the Northern Rockies. For instance, 80% of the trees in Yellowstone National Park are lodgepole pine. However, it is also a common tree in the Cascades, Sierra Nevada, and into British Columbia.

One of the important drivers in lodgepole pine ecology is periodic beetle kill from the mountain pine beetle.  Bark beetles are like wolves that thin an elk herd down to its carrying capacity. Typically only the older trees are suitable for attack, so mortality in lodgepole forests is usually less than 50% of trees. The remaining trees, freed up from competition grow much faster and for a while are able to resist any future beetle attacks.

Bark beetles lay their eggs in the inner layer of tree bark where larvae develop. The larvae eat the living layer. A fungi that enters the tree with the bark beetles. The two factors often kill the tree. Leading to a common sight of red-needled trees covering hillsides.

Since beetle mortality usually occurs in a mosaic with patches of dead trees and patches of live tree, the overall ecosystem biodiversity increases. Species dependent on dead trees like cavity nesting birds benefit from beetle kill, while those that might need some live trees—say thermal cover for elk in winter—also benefit.  Thus beetles can be thought of a “keystone species” that creates habitat for many other species.  Some research suggests that beetles create greater biodiversity overall as a consequence.


Bark beetle numbers surge during drought periods. Trees stressed by drought are unable to cast off beetles.  One of the common assumptions behind logging/thinning projects being promoted around the West is that beetle kill will increase fire risk. So the solution to this perception is to log forests to preclude beetle kill by reducing densities and/or to remove existing dead trees to reduce fuels.

However a host of studies demonstrate that beetle killed forests are no more likely to burn than green forests. Indeed, some studies suggest that for a period of time after a bark beetle outbreak, forests are less likely to burn.

This is easily explained by fuels. One of the big misconceptions about wildfire is that fuels drive them and the more biomass, so the thinking goes, the more likely you are to have a major fire. But the “fuels” that carry wildfires are the small flashy fine fuels like pine needles, cones, small branches, not the boles of trees. That is why there are “snags” left after a fire. Most of the tree is not consumed or burned in a wildfire. So once a beetle kill tree loses its needles and the small branches break off in winter storms, they are actually less flammable than live green trees.

In fact, green trees, due to their abundance of resin-filled needles and branches will burn more intensely than dead wood under extreme weather conditions of low humidity, high temperatures and high winds. These are the kind of weather conditions that drive large wildfires.

There is a nuance here, however. As the young trees unaffected by bark beetles grow up in the understory of remaining trees, they do provide more “ladder” fuel that can sometimes increase fire spread for a few decades until the canopy closes and fire risk is again reduced—assuming that conditions for fire spread exist at all during those decades and there are ignitions.

Of course, the other factor in the beetle/fire story has to do with timing of fires in lodgepole pine forests. Lodgepole pine tends to burn at long intervals of hundreds of years. That is because the right combination of wind, humidity, and ignition simply do not exist every year and often for decades or centuries. So while beetles may kill trees, the likelihood that those particular trees will be in the path of a fire is a low probability.


As a consequence a number of studies have demonstrated that there is no greater increase in fires in beetle kill area on average than other sites. In some cases, at least until the younger trees start to fill in the forest, fire risk is actually reduced.

Despite this evidence the Forest Service continues to advocate logging/thinning on the flawed assumption that a reduction in beetle kill trees, will preclude large wildfires. Not only is this not the case but in reality we need large wildfires for the ecological work they do. Even if it were possible to reduce fires we would not to do this.


Some 98% of all beetle outbreaks are in remote areas and the likelihood that they will encounter or threaten homes is extremely small. Nevertheless, it is well established the best way to protect homes from wildfire is not by thinning the forest, but by keeping homes from being built in the “fire plain” in the first place, and for those homes already in the fire plain, reducing the flammability in the home ignition zone (200 feet is all that is need) surrounding a home is the only proven way to safeguard homes.


  1. Area burned in the western United States is unaffected

by recent mountain pine beetle outbreaks

SarahJ. Harta,1, Tania Schoennagela,b, Thomas T. Veblena, and Teresa B. Chapmana



  1. The European spruce bark beetle Ips typographus

in a national park: from pest to keystone species

Jo¨rg Mu¨ ller Æ Heinz Bußler Æ Martin Goßner Æ

Thomas Rettelbach Æ Peter Duelli

Biodivers Conserv (2008) 17:2979–3001


DOI 10.1007/s10531-008-9409-01

  1. Does wildfire likelihood increase following

insect outbreaks in conifer forests?





www.esajournals.org 2 July 2015 v Volume 6(7) v Article 118


  1. Don’t Blame the Beetles

By Cally Carswell


10 OCTOBER 2014 • VOL 346 ISSUE 6206

  1. Fire severity and tree regeneration following bark beetle outbreaks: the role

of outbreak stage and burning conditions


Brian J. Harvey 1a, Daniel C. Donato1, William H. Romme2, Monica G. Turner1

Ecological Society of America

  1. The influence of mountain pine beetle outbreaks and drought on severe wildfires

in northwestern Colorado and southern Wyoming: A look at the past century

Dominik Kulakowski ⇑, Daniel Jarvis

Forest Ecology and Management 262 (2011) 1686–1696


  1. Management for Mountain Pine Beetle Outbreak Suppression:

Does Relevant Science Support Current Policy?

Diana L. Six 1,*, Eric Biber 2 and Elisabeth Long 2

Forests 2014, 5, 103-133; doi:10.3390/f5010103

  1. Are density reduction treatments effective at managing for resistance

or resilience to spruce beetle disturbance in the southern Rocky


Christian Temperli a,⇑, Sarah J. Hart a, Thomas T. Veblen a, Dominik Kulakowski b, Julia J. Hicks a,

Robert Andrus a

Forest Ecology and Management 334 (2014) 53–63

  1. Bark Beetles and Fire;: Two Forces of Nature Transforming Western Forests


  1. Bark beetle outbreaks, wildfires and defensible space:

how much area do we need to treat to protect homes

and communities? Glen AronsonA and Dominik Kulakowski  International Journal of Wildland Fire 2013, 22, 256–265 http://dx.doi.org/10.1071/WF1107

11. FIRE SEVERITY UNAFFECTED BY SPRUCE BEETLE OUTBREAK IN SPRUCE-FIR 4 FORESTS IN SOUTHWESTERN COLORADO Robert A. Andrus1a, Thomas T. Veblen1, Brian J. Harvey2, Sarah J. Hart1file:///C:/Users/office/Downloads/Andrus%20beetle%20x%20fire%20severity%20San%20Juan%20mtns%20EA%20pre-print%202015.pdf







  1. Ida Lupines Avatar
    Ida Lupines

    All of the keystone species are fascinating.

  2. Pat Finnegan Avatar
    Pat Finnegan

    You’re correct George. And going a step further, my experience has been that fire behavior intensifies when it reaches commercial harvest units. Commercially driven silviculture tends to leave units overstocked (usually w/Doug. fir). A 20 year old cut is something any wildland firefighter learns to stay away from when fire behavior becomes extreme (like, every year in the Rockies any more…). As you mentioned, it is the green branches that carry a crown fire, not standing snags or down wood.

    1. Nancy Avatar

      + 1 Pat.

      Had a forest fire burning just a few miles from where I live, last summer. A lighting strike. Heard more than a few times from “local experts” that it was a damn shame though, that this area couldn’t of been logged out before it burned…

      No thought at all to the fact that it was probably contained and burned out by forces (other than firefighters, swarming over the area) because of where it was burning and had no doubt, burned before. Aerial views.

  3. Ida Lupines Avatar
    Ida Lupines

    Nevertheless, it is well established the best way to protect homes from wildfire is not by thinning the forest, but by keeping homes from being built in the “fire plain” in the first place.

    Totally agree!

    1. rork Avatar

      aka, the “stupid zone”. We have ’em in MI too, but haven’t had catastrophic fires much lately, and folks may have forgotten (historically we have, e.g. “The Metz fire” and “the great MI fires”, and MN and WI had giants too). Some of the fires that made news in CA this year made me look at satellite views of the neighborhoods, and wonder in disbelief – who would insure a place up there, much less want to build one, and why are they letting the conifer forest surround the houses in a famously fire-dangerous place? (It’s charming living right in the woods, I know.)

  4. Shari Avatar

    So how do you explain the 1 plus million acres burned int he last 2 yrs in WA? Are all of you who hate logging living in houses built with wood or some other material? Just curious.

    1. rork Avatar

      It was kinda dry this year. Cheatgrass isn’t helping. Fire suppression may get some blame. Have you been around some of that country? It’s not a perfectly Darwinian way to say it, but “it wants to burn”.

      Just cause there’s some wood in my house, doesn’t mean I want to subsidize logging everywhere. False dichotomy.

  5. eugene beckes Avatar

    George, Just wanted to thank you for your response to the piece in The Flathead Beacon, by the head of The Boone & Crockett Club. I knew when I read it that it was 99% bs, but I don’t have the fine writing skills (or background eduction)you have. I appreciate your efforts.


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George Wuerthner