Tuesday, October 14, 2008


George Wuerthner

I attended the 88 fires: Yellowstone and Beyond fire conference in Jackson, Wyoming. The conference went on for five days and had many simultaneous presentations, featuring some of the latest insights into wildfire ecology and fire behavior. The following are some of the highlights.

Weather and climate figured into many presentations for a variety of reasons. Speakers like Tony Westerling of the University of California and Tom Swetnam of University of Arizona spoke about long term global climate change which will likely increase the severity and number of large wildfires in the future.

Many speakers from agency managers to wildfire ecologists emphasized over and over again the influence of drought, low humidity and wind on fire spread and behavior. The conclusion of speakers is that under severe weather conditions, some fires are unstoppable and we are already seeing such a trend in fires today.

For instance, Yellowstone researcher Roy Renkin emphasized that fuel moisture is the primary determinant of fire severity. His research suggests that wind and drought must exceed the 97th percentile before one gets a stand replacement fire, and if it exceeds the 99th percentile nothing will stop a fire and it will burn through all fuel types, including thinned forest stands. In other words there are very predictable thresholds in fuel moisture and wind speed that creates the ideal conditions for fire spread. When these conditions are met, wildfires are large and unstoppable.

Other speakers talked about the effect of wind on fire spread. Even in a dry year like 1988, the majority of fires are small without wind to drive them. For instance, Bob Mutch retired from the Missoula Fire Lab, found that out of 249 fires that started in the Greater Yellowstone Ecosystem in 1988, the majority or 81% burned ten acres or less. Huge acreages of the forest were consumed during the few days when high winds prevailed.

For instance, the 1988 Canyon Fire that burned through the Bob Marshall Wilderness was propelled by high winds of the Jet Stream which dipped down to the surface above the fire. With the Jet Stream pushing it, the fire raced across 190,000 acres in a single day. Researchers emphasized that wind was a major factor in all large fires including historic blazes like the 1910 Burn that charred more than 3 million acres of the Northern Rockies.

During a field trip, I talked to Penny Morgan of the U of Idaho who recently published a couple of papers on the fire history of the Northern Rockies. She found that a strong connection between climatic conditions and fire years. Of 11 years with significant acreage burned by wildfire between 1900 and 2003, six occurred prior to the 1940s and five have occurred since 1988. All were correlated with dry springs and hot summers. The years between 1940 and the 1980s were wetter and cooler than the years before and since those years, calling into question whether fire suppression has been as effective as previously assumed. Yet it is these post war years that forms the basis for our views about what is “normal” behavior for wildfires.

This is where other speakers’ research fit into the mix. Cathy Whitlock of Montana State University has looked at long term fire histories throughout the West, including a 17,000 year fire history for Yellowstone. Her conclusions are that the recent past climatic conditions no longer exist. In other words, trying to “manage” for past vegetation patterns is not going to work because we now have a new climatic regime that is has warmer temperatures, a longer drying season, and generally higher winds than the recent past. Thus thinning forests to “restore” a “historic” appearance to the landscape may be pointless. We are now into a new climate model that will change fire behavior as well as vegetation response.

Proposed treatments like thinning, logging and other prescriptions are ineffective for many forest types under the new climatic conditions. For instance, Ronald Wakimoto of the U of Montana Forestry School suggested that thinning of lodgepole pine forests as is now occurring on Forest Service lands in the Northern Rockies is “fool management” not fuel management. Thinning, as Wakimoto noted, simply makes the forest floor hotter, drier and windier—all ingredients that increase fire spread and severity.

Megan Walsh of the U of Oregon looked at charcoal remains for the past 1000 years to determine the fire history in the Willamette Valley of Oregon. For decades it was presumed that Native American fires maintained the valley grasslands and open oak woodlands. Her research suggests that valley fire activity responded primarily to climatic changes.

The influence of Native Americans on wildfire frequency appears to be localized, primarily in and near places where permanent occupation occurred. The idea that Native American significantly affected fire frequency across the larger landscape is called into question.

Another presentation by Dick Hutto of the U of Montana emphasized the ecological importance of dead trees, in particular, burnt trees. Hutto, like many ecologists, is opposed to salvage logging of burnt trees, especially on the assumption that dead trees are a “wasted” resource. Hutto’s research focuses on birds, and there are many species that live and forage primarily in burnt forests. Such an evolutionary response suggests to Hutto that stand replacement fires have occurred in all forest types, not just high elevation forests like those found in Yellowstone. Despite assertions by the ill informed to the contrary, we may be experiencing a deficit of wildfires. In other words, even if it were possible to suppress large fires—which clearly it is not--we need more large wildfires, not fewer.

Like Hutto other researchers are finding that large blazes have profound positive effects upon forest ecosystems and associated species. For instance, Wayne Minshall of Idaho State University has studied fire effects on streams for decades. His research found that stream drainages that experienced high severity fires rather than being “destroyed” had the highest biomass of aquatic insects, which in turn supported higher densities of cutthroat trout. But the fire also had an effect on terrestrial species as well. Minshall found that severely burned watersheds also supported higher density of fly catching birds, bats, and riparian spiders, among other animals.

On a field trip through Jackson and up into Yellowstone with researchers Monica Turnker, Dan Tinker and Bill Romme, participants observed a forest that had been heavily infected by pine beetles in the 1970s. If Romme had not mentioned it to us, none of the field trip participants would have guessed that the forest had ever experienced a major beetle outbreak. As Romme explained, beetles, even under the most severe infestations, seldom kill all trees. With the death of some trees, the remaining trees grow very quickly to fill in the gaps in the forest canopy.

Furthermore, Romme and other researchers have found that beetle killed trees do not necessarily increase fire hazard. Once a year or two has passed, and dry needles and small branches fall off, the forest is actually less likely to burn than a green forest under severe fire conditions. The green forest needles and branches are loaded with resins that burn extremely well if the internal moisture of the trees dips as occurs during severe droughts. In other words, fire hazard does not increase significantly as a result of beetle kill.

Additionally there are many ecological benefits associated with pine beetle infestations, including the creation of dead trees for wildlife use, increased nutrient flows into soils, and other affects. If communities and politicians panicking about current beetle outbreaks could visit the Tetons they would realize there is nothing to be feared.

The overall conclusions I took away from the conference was that climate change was going to create climate/weather conditions more conducive to large blazes. Management prescriptions like logging won’t change fire behavior under severe conditions, and in fact, may improve conditions for fire spread by opening up the forest to greater drying and wind penetration. Fortunately, large fires are ecologically beneficial and necessary for many ecosystem functions, including nutrient cycling, wildlife habitat creation, and other ecological processes. Therefore, an increase in large burns rather than being something to be feared or suppressed should be embraced. To do this, we need to change our approach to wildfires from suppression to co-existence.

The best way to achieve such a relationship is not to fight fires or log the landscape in the mistaken believe that we can affect fire severity or spread, rather we need to reduce sprawl into the wildlands urban interface through zoning and planning combined with greater attention to making existing structure fire safe. Even something as a requirement that all buildings in fire prone ecosystems have metal roofs would go a long ways towards reducing losses to wildfire.

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