Wednesday, September 17, 2008

Wildfire myths


With most science, it takes a while for the latest research and observations to be published, and then be assimilated into the public consciousness. Typically new science does not entirely invalidate the old ideas, but provides new insights and nuances. I see that happening now with fire ecology and how fire issues are reported in the media.

One of the frequently repeated “truths” is that fires are more “destructive” than in the past due to fire suppression. By putting out fires, we are told, we have contributed to higher fuel loads in our woodlands that is the cause of the large blazes we seem to be experiencing around the West.

But like any scientific fact, the more we know, the more we understand how little we really understand. While fuels are important to any blaze, the latest research is suggesting that weather/climatic conditions, rather than fuels, drive large blazes. In other words, you can have all the fuel in the world, but if it’s not dry enough, you won’t get a large blaze.

On the other hand if you have severe drought, combined with low humidity and high winds, almost any fuel loading will burn and burn well. Despite all the rhetoric about “historic” fire seasons, including several years where more than 7-8 million acres burned, the total acreage burned today is actually quite low by historic standards. As recently as the 1930s Dust Bowl drought years, more than 39 million acres burned annually in the US. And long term research going back thousands of years suggests that the past 50-70 years may be real anomalies in terms of acreage burned as well as fire severity. It may be that the limited fire activity between the 1930s and 1990s was more a reflection of moister climate conditions than due to any effective fire suppression.

Indeed, most fires just go out on their own with or without fire suppression if the conditions for fire spread are not conducive. Nevertheless, we take credit for putting out the blazes that may well have gone out without any intervention at all. At a recent fire forum I attended, a forest supervisor admitted as much when he quipped that his agency was “very good at putting out fires in wet years, but not very good at putting out fires in dry ones.” He was acknowledging how weather/climate controls fire activity and the success or failure of agency fire suppression efforts.

There undoubtedly has been some fuel build up in a few ecosystems due to fire suppression, particularly low elevation forests such as those dominated by ponderosa pine that burned at frequent intervals. However, most of the acreage burned in recent years has been either range fires influenced largely by the presence of the exotic and highly flammable cheat grass and/or higher elevation plant communities, which typically did not burn frequently. Stand replacement fires characterize these higher elevation forest communities. These forests types have suffered no fuel build up due to fire suppression because successful fire control hasn’t exist long enough to have affected the interval between blazes that typically dominates these forests.

What is missed in the “fire suppression” has created fuel build ups assertion is the fact that mixed to high severity stand replacement blazes are the “norm” for most western ecosystems including chaparral, aspen, spruce-fir, western larch, boreal forests in Alaska, lodgepole pine, and many other forest types. For instance, the lodgepole pine forest of Yellowstone NP typically burns every 300-400 years. Fire suppression has had no impact on fuel loading in these forests.

New research is even beginning to question the common assertion that low elevation forests dominated by ponderosa pine have all been affected by fire suppression. Researchers are finding more and more evidence for the occurrence of stand replacement blazes even in these forests—long before fire suppression could have had any influence on fuel buildup. In fact, it may be that all forest and plant communities will burn and burn well if we have the right conditions of wind, hot temperatures, and drought. The fact that recent fires are burning through clear cuts, thinned stands, and other forests that are supposed to be fire proofed, suggests that big blazes are, at least in some situations, the norm.

This has huge policy implications, especially in light of global warming. We are now entering a period of warmer, dryer conditions that creates conditions favorable to large uncontrollable fires. Public agencies like the Forest Service will increasingly find that like the forest supervisor admitted, they are not good at putting out fires in dry years. Furthermore, presumed “solutions” put forth by logging advocates such as thinning programs are unlikely to work effectively in drought years. And since nearly all big blazes occur in drought years, these are the only fires that are worth worrying about.

Beyond the fact that we probably cannot control large blazes, it is likely a bad idea to try. In terms of ecosystem processes, big blazes are needed—for the majority of ecosystem work done by fire annually is the result of less than one percent of all blazes. Despite tens of thousands of fire starts in a typical summer, the majority of all acreage burned is the result of no more than a few dozen fires.

We need to embrace large blazes and learn to live with them. Fire in the forest is not bad. Fire in our communities is. The real solution to the West’s fire woes is to reduce the fire risk of our communities through mandatory building codes designed to reduce the flammability of individual homes, and zoning that restricts sprawl in fire prone landscapes so that the inevitable large blazes can sweep across the land with a minimum of harm to humans.


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