by Gil Gale
From a safe vantage point above Johnson Creek in the Anaconda-Pintler Range, late on an afternoon in August 2000, “Dugger” Hughes looked across a half-mile of solid green timber to the leading edge of the Mussigbrod Fire that was relentlessly growling its way towards him. Dugger, who had twenty years of close-encounter experience with wildfires throughout the Rocky Mountain West, was working as an Operations Chief on this incident. As he watched, his assistant standing next to him, the fire fingered down into the bottom of the steep-sided drainage and seemed to relax its progress. Suddenly, it roared to life, spreading out and racing up the north slope at a speed that riveted Dugger in amazement. He had enough time to click the timer on his digital watch as the fire moved rapidly up through almost a mile of densely timbered mountainside. When it reached the top of the ridge, the fire slowed and resumed its earlier methodical pace. Dugger estimated the distance of the flashover he had just witnessed and then looked at the time it had taken for the flame front to reach the top of the ridge. He checked his calculation three times. He showed the number to his assistant and they both stared at it in disbelief. The fire had moved up the side of the mountain at a rate of over 60 miles an hour—a speed unheard of in the wildland firefighting world.
In recent years, fire behavior analysts have observed fire intensities and rates of spread that increasingly fall outside of the current model predictions—which is what they use to anticipate what a fire is going to do in the various fuel types on any particular day. Accurate predictions are critical for firefighter safety and wildfire management planning. Yet many fire analysts are beginning to question whether the assumptions built into their computer models are still valid and what they need to do to adapt to what appears to be a new trend in wildland fire behavior.
They aren’t the only ones asking the questions about what is happening with our Montana wildfires—and what is in store for us. There are a number of articles in various popular publications that are making a strong claim that wildfire occurrences, size and behavior are changing as a direct result of global warming. A 2009 article in Scientific American stated that we are witnessing an increasing number of these megafires. Thomas Swetnam, director of the Laboratory of Tree-Ring Research at the University of Arizona, cites a measureable increase in the magnitude and severity of wildfires across the globe, from Australia to the U.S. Southwest. In the past 20 years, the area scorched by fire in the western U.S. has increased 600% over the number of acres burned in the 1980s. Swetnam attributes this dramatic spike in wildland fire activity largely to the longer, drier summers emerging out of the global warming trend. Another summary paper out of Northern Arizona University cites the increase in average global temperatures over the last 100 years as already causing drastic ecosystem effects in the southwestern states—including increased wildfire hazard. Land managers have begun to use the term “hot” forest fires to distinguish the seemingly unique characteristic of recent fires from the dominant fire patterns of several decades ago. “Hot” forest fires have more long-lasting effects, such as altering the physical and chemical properties of soils.
There is no doubt that climate change can dramatically affect how wildfires operate on our landscapes. But was it a prime contributor, for example, to the event witnessed by Dugger on that hot August afternoon of the new millennium in western Montana, or was that just a freak incident? Just where are we, at this point in time, with the relationship between climate change and wildfire? Is climate change affecting wildfire behavior differently depending on latitude, location or habitat types across the country? And, lastly, does it matter how precisely we understand the various causes of fire behavior, or is that just an academic concern? Perhaps the most urgent question is how the interplay of all those factors should influence land management planning and actions. For example, will a more accurate understanding of the current interaction of climate change and wildfires influence the manner, location and degree of fire suppression and prescribed fires? And what difference would that knowledge make in designing management strategies for timber and forest fuels over the next couple of decades?
While there are varying opinions and interpretations circulating through the media and professional circles, no one involved in these discussions is debating the scientific fact and reality of climate change. Anyone who has read a sampling of the scientific literature on the topic knows that climate change is real. One persistent question, though, is whether or not we have reached some tipping point in the interaction between climate change and wildfire.
The ecological sciences have been described as the realm of extreme multi-tasking. Scientists are deep into the task of sorting out the cause-and-effect relationship between climate change and the wildfires that have moved over the landscape in recent years (see figure 1). Are the wildfires we’ve seen in the last decade, for example, really outside the range of natural variability? Jack Losensky, retired Historical Fire Ecologist with the U.S. Forest Service Rocky Mountain Research Station, says that the wildland fires in recent years are still consistent with those seen by the Rockies over the last 120 years. Present-day fire patterns, for example, can fit within the same range of natural variability that includes the ferocious fires of 1890 and 1910.
For Losensky, the key is in understanding the fuel accumulation picture on western forests over the last 100 years. Losensky says that the burn severity today is creating greater-than-average impacts because of the unnatural amounts of fuel that have built up, particularly in dry ponderosa pine stands. He believes that climate change is one more factor contributing to the perceived trends in wildfire severity—which is then layered on top of other factors, including the fuel buildup and changes in species composition and forest structure that have resulted from decades of fire suppression. Other researchers recognize the interplay of factors, but there appears to be a difference in opinion about the degree to which climate change is influencing wildfire intensity at this time.
So have we reached a tipping point where climate change has indeed overtaken forest composition and other factors as the primary cause of intensifying wildfires? Are we still in a transition phase where other ecological conditions play a dominant determining role in wildfires in the West? We’ll look deeper for the answers to these questions in the next installment (coming in the winter 2014-2015 issue. –Ed.).
—Starting as a wildland firefighter, Gil Gale served for thirty-five years with the U.S. Forest Service on many suppression and prescribed fire management operations in roles including strike team leader, prescribed fire burn boss and resource advisor. Currently, he works as an ecologist and program leader for several resource areas on the Bitterroot National Forest.
This article was originally published in the Fall 2014 issue of Montana Naturalist magazine, and may not be reproduced in part or in whole without the written consent of the Montana Natural History Center. ©2014 The Montana Natural History Center.
Click here to read more articles from Montana Naturalist magazine.
Want to learn more about our programs? Sign up for our e-newsletter! You can also become a member and get discounts on our programs as well as free reciprocal admission to 300+ science centers in North America!