Senator calls for forest thinning to prevent exploding trees

U.S. Senators John McCain and Jeff Flake, both representing Arizona, spoke to residents in Show Low and Pinetop-Lakeside March 24. According to an article in the Arizona Journal, Senator McCan discussed the importance of thinning forests in the state, in part to prevent trees from exploding. Here is an excerpt from the article:

“In the State of Arizona, and in Navajo County, the future rests on two issues to a large degree, and that’s fire and water,” said Sen. McCain, relating the statistic that 20 percent of U.S. national forests have been consumed by fire in the past 15 years.

McCain noted that the issue of forest thinning has been given top priority by officials at the nation’s capitol. “Unless we thin these forests, we are going to see the kinds of things that we saw with the Chedeski fire and the Walleye fire, and that is trees literally exploding as the fuels that have accumulated around the bases of the trees burns up,” he predicted.

“Without forest thinning, fires will just sweep right through,” he said, also pointing out the ‘snowball’ effect that forested areas decimated by fire also become susceptible to chronic ground surface water runoff, which worsens drought conditions.

Having been a wildland firefighter for 33 years, as far as I know trees exploding in wildland fires is a myth. I’ve never seen it, heard it, or talked to anyone who has witnessed such an event. This has been perpetuated in a number of books and articles, but I have never seen the evidence.

When lightning strikes a tree it can explode when the moisture inside is converted to steam in a millisecond. And maple trees can explode in below freezing temperatures when the sap freezes. There are unconfirmed reports that eucalyptus trees in Australia can explode in a fire but I’m not convinced this is true. I understand that heated gasses or sap can shoot out of a crack in a eucalyptus tree and can be ignited during a fire. Maybe some of our Australian friends can provide more accurate information.

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Author: Bill Gabbert

After working full time in wildland fire for 33 years, he continues to learn, and strives to be a Student of Fire. Google+

11 thoughts on “Senator calls for forest thinning to prevent exploding trees”

  1. He states “Walleye Fire”….This is a perfect example of the disconnect between politicians and what goes on in the fireground. Talk of exploding trees and other misinformation. It was the “Wallow Fire” I believe, the biggest in Arizona state history. Does McCain think he is a Senator of Minnesota?

    1. While I pretty much agree, I also never underestimate the ability of any reporter to misquote anybody.

  2. Reading the description in the article, I believe that he is taking a little creative license. His audience isn’t firefighters, it’s the soundbite loving media/public. Explosions are COOL! Let’s watch! His description of the litter underneath the trees causing rapid fire growth isn’t that far off. I suspect thinning and prescribed fire wouldn’t be bad for the land, so maybe we accept the overall message?

  3. here in Auburn California,were east of Sacramento in the foothills,we used to do prescribed burns,we just called it lot burning,to prevent fire coming up out of the North Fork of the American river,steep rugged country, and into town,we literally sit on top of the canyon rim.It was very effective,but things changed in the mid 1980s with the EPA ect,and a little old lady with asthma who would fire a lawsuit every year.the first year we were not allowed to burn,she paid (thats rumor,but no ones ever denied it) to have a half mile long area cleaned of all under brush.i dont know how deep it is?..mean half mile by ???…but it worked in that area,so in years after other areas were cleaned and now all it takes is maintanice each year to protect the canyon rim.there are those who claim the cleaning is detramental to wildlife and future growth,but after a destructive fire near lake tahoe some years back,where there was a policy where locals could not clean up the pine needles ect in an effort to stop erosion into the lake,but what happened was that just fueled the fire into a frenzy and distroyed many homes that would have been ok if it had all been cleaned.

  4. Thanks for this article and particularly your skepticism about the myth that eucalyptus trees “explode.” Here in the San Francisco Bay Area, the native plant movement has a death grip on our public lands. They have demanded the eradication of all non-native trees and tens of thousands have been destroyed. Now they have sued to demand the destruction of over 400,000 more trees that are predominantly eucalyptus. The public hasn’t been sympathetic to the argument that they “don’t belong here,” so they have discovered that if they claim they are more flammable than native trees, the public will accept their agenda. Here is an article that responds to their claim that eucalyptus trees are called “gasoline trees” in Australia: http://milliontrees.me/2016/02/19/will-the-real-gasoline-tree-please-stand-up/. This claim fails the smell test because gasoline is not a word that is used by Australians to describe what they call petrol.

    1. While eucalyptus trees may not explode, the leaves produce a volatile highly combustible oil, and the ground beneath the trees is covered with large amounts of litter which is high in phenolics, preventing its breakdown by fungi. Wildfires burn rapidly under them and through the tree crowns. It has been estimated that other than the 3,000+ homes that burned in the 1991 Oakland Hills Fire in California, about 70 percent of the energy released was through the combustion of eucalyptus. In addition, the thin stringy bark can be lofted into the convection column while burning, and can ignite spot fires miles away.

      We wrote about this in 2014.

      1. But it was those 3000+ homes that provide most of the fuel for that fire–a tremendous release of energy. According to the firefighter anecdotes I’ve heard about that fire, the many wood shake roofs that ignited also released firebrands which in turn ignited other combustible homes. Stronger building and planning codes would have done a lot to mitigate that disaster.

  5. i know this has nothing to do with the current post,but during the Oakland hills fire,or when it started,my folks were on a bus headed to Candlestick park for a 49er game,this was a game day “party bus” out of Sacramento,they rode it with other booster club members.Mom looked out a window and commented to my dad,a volunteer fireman since 1962,that she saw a small smoke,and commented she hoped they picked it up fast.Then during the game,the sky slowly darkened and they began to have ash and soot fall on them.mom still complains that her brand new white pants were ruined that day.It was announced over the PA system there was a major fire in Oakland and people driving home should be carefull.took em hours to get across the bridge and past the area due to heavy traffic,idiots rubber neckin.

  6. Exploding trees, seems like a misquote to me or a congressional member attempting to gain attention with a spectacular, misleading and false quote about something they know nothing about, nothing unusual for a politician.
    Over the years I have seen some trees or bush that seem to explode but is more of a flare due to ignition of volatile vapors but never a exploding one. Many years ago I was near a tree that was struck by lighting and did explode due to the heating of the internal moisture and ended up being peppered with splinters in my back, I was lucky that my knapsack absorbing most of them.

  7. In my experience trees, of any species, do not explode, although they sometimes “flare off” spectacularly. I have witness lightning struct trees explode violently- without fire observed or later confirmed.

    Beyond dangerous to draw conclusions from the event (as reported above) I didn’t attend and witness. Without being an apologist for anybody here is my quick take based on decades of critical observation:

    1. Exploding stuff sells- just ask Hollywierd.
    2. For effect, and to get attention, politicians often speak in hyper-terms.
    3. Rank and file news reporters typically don’t know their butt from a stump in the ground.

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