Beetle-kill wildfire threat? Color me skeptical

By Jeff Mitton

Snow was falling lightly on a winter evening, but I was comfortable sitting by a fire of lodgepole pine. I had cut logs and split the wood, dried it for a year.

This evening I had started with dry kindling, then piled on the lodgepole; the fire was warm and bright. But my brother called and that distracted me for 30 minutes. When I returned, the fire had gone out.

The mountain pine beetle has been at epidemic levels for more than a decade, and this epidemic is 10 times greater in magnitude than any previous epidemic. The geographic extent of the epidemic is difficult to grasp; it reaches from New Mexico to the Yukon Territory and from the Front Range of Colorado to the Pacific Ocean. But it has also been more intense than previous epidemics, with very high mortality of mature lodgepole pines.

This is the second mountain pine beetle epidemic since 1979. The first epidemic was in ponderosa pine, and it raged from the Front Range to the Laramie Mountains and in forests in California and Oregon.

During and immediately after each mountain pine beetle epidemic, the warnings are sounded. Beetle-killed forests are ready to burst into flame, and they pose a threat to life and property. The dead wood is dangerously flammable and abundant, with grey forests stretching to the horizon. Something must be done, immediately, to avoid a conflagration. Strident inculcations of warnings about dead trees bursting into flames come from forest managers, elected officials and news broadcasters.

Looking back through the years, fires have run through immense expanses of forest. In 1876, the Bighorn Fire took 500,000 acres in Wyoming. In 1910, a drought permitted hundreds of fires to start and wind caused them to coalesce into the Big Burn, which took 1 million acres, several towns and 87 lives in Washington, Idaho and Montana. In 1988, the Yellowstone fire took 793,880 acres and caught the attention of the entire nation. In 2002, the Hayman fire consumed 137,270 acres, 600 houses, barns and other structures. More recently, still fresh in our minds, the Fourmile, High Park, Waldo Canyon and Black Forest fires came in quick succession.

All of those big fires were in green forests.

Grey stands of lodgepole pine stretch from Colorado through British Columbia. Forests of lodgepole pine have turned grey in the Williams Fork Mountains, Gore Mountains and the mountains surrounding Dillon, Vail and Steamboat Springs. By far the largest tracts of grey are in stands of lodgepole in British Columbia -- expanses of dead trees stretch for hundreds of miles. So let's recall all the devastating fires that have consumed those vast expanses of grey, or have followed the mountain pine beetles' previous epidemics.

None come to mind -- I am not aware of any. Since the beginning of the epidemic on the Western Slope in Colorado, there have not been any large fires in beetle-decimated forests.

In the 1940s, spruce beetles erupted in an intense epidemic in Engelmann spruce forests on Grand Mesa and further north in the White River National Forest, killing 50 percent of mature spruces on Grand Mesa and a higher proportion in the White River National Forest. That was arguably the largest and most intense epidemic in Colorado history. Did forest fires follow the beetles through the forests?

A study by University of Colorado professor Tom Veblen and his colleagues concluded that the incidence of forest fires in the White River National Forest did not increase in the 50 years following the epidemic.

The most flammable trees in the forest are dry green trees; their resins explode into flames as fire approaches.

The red needles of recently killed trees have lost much of the resins and have also lost moisture. Green needles are easier to ignite, though. Red needles may burn hotter, but red needles do not stay on the trees for long. A beetle-decimated forest is grey, not red.

When I burn split and seasoned lodgepole pine in my fireplace, I have to tend the fire or it goes out. And I have never heard of a big fire in a grey forest. So when it comes to warnings about devastating fires in grey forests, color me skeptical.

Jeff Mitton mitton@colorado.edu is a professor in the Department of Ecology and Evolutionary Biology at the University of Colorado Boulder. This column originally appeared in the Boulder Camera.