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.