Climate and The Western Wildfire Problem

 

Dr. Thomas W. Swetnam

Laboratory of Tree-Ring Research

The University of Arizona

Tucson, AZ 85721

520-621-2112

tswetnam@ltrr.arizona.edu

 

            Forest fires are raging across the western United States and the only surprising thing about this event is that some people are surprised.  Scientists and managers have predicted “the big blow up” for many years.  “The Smokey the Bear effect” of eliminating natural fires is now widely recognized as only a delaying action that has ultimately made matters worse.  For more than a century we have excluded the frequent, low intensity burns that once maintained open pine forests, but now we know that wildfires will occur anyway, and probably as catastrophic crown fires during the driest and hottest years – such as the summer of 2000.  The accumulated fuels – live and dead trees – from a century of fire exclusion are a primary problem, but the other important factor receiving much less attention is climate. 

 

As we escalate tree cutting and prescribed burning in the west to deal with the fuels, it is all the more critical that we apply our new understanding of climatic patterns.  We will continue to make mistakes like Cerro Grande – the prescribed fire that almost destroyed Los Alamos -- unless we begin to heed the season-to-season, and year-to-year warning signs that climatologists have learned to read. 

 

The importance of the drought conditions this year is demonstrated by the fact that many of the big fires in Idaho and Montana are burning in high elevation forests where the Smokey the Bear effect is minimal.  Tree densities in these forests have not appreciably changed during the 20^th century relative to the pre-Smokey era.  These high elevation forests generally only burned in the past during rare, extreme drought years, such as this one.  The problem in these areas is not ecological -- it is climatological and sociological.  People have built homes within or near forests that are predestined to burn during years like this. Climate-related fires threaten their homes and lives, just as climate-related floods and hurricanes threaten homes and lives on flood plains and coastlines.

 

We are all accustomed to using daily weather forecasts – from planning to take an umbrella on a walk, to evacuating a coastline in advance of a hurricane landing.  Our thinking and planning for fire seasons, however, have yet to catch up to breakthroughs in our ability to forecast general weather conditions over regions and time periods of months and seasons (i.e., climate forecasts). The breakthrough in long-range climate forecasting that has relevance to this and future fire seasons has to do with the infamous El Niño pattern.  In particular, we have learned that during El Niño events the Southwestern and Southeastern U.S. generally receive much more winter and spring rainfall, and during La Niña events, such as this year, winter and spring rainfall is often reduced.  Furthermore, during some La Niña events drought persists through the spring and summer months in more northerly states, affecting the Great Basin and Northern Rockies, resulting in huge forest fires across the western U.S.  The La Niña-related droughts and fires of 1988-1989 and 1999-2000 are examples of this climate-fire pattern.

 

Like day-to-day weather forecasting, season-to-season climate forecasting is probabilistic, and therefore not always correct.  However, when it comes to disasters, the costs of being under-prepared due to ignorance are almost always greater than the costs of being over-prepared because of a false forecast.  Not all El Niño or La Niña events have the same strength or effects on climate, weather and fire, but these patterns have sufficient consistency to be of some use in fire management planning. 

 

Forecasts for extreme drought persisting into the spring and summer were available this past winter, and they were discussed at length in a workshop my colleagues and I held at the University of Arizona in February with fire managers from throughout the western U.S. and Florida.  We knew that a bad fire season was probably coming, but unfortunately these warnings did not materialize into management actions that might have averted the Cerro Grande disaster or lead to better preparedness for the massive fires now burning throughout the west. 

 

If managers had been fully aware of the high state of fire hazard at lower and middle elevations in the Los Alamos area, and in the rest of the Southwest, perhaps they would not have proceeded with the prescribed fire on Cerro Grande. Alternatively, in recognizing the high fire hazard at broader scales than the area and time period they were planning to burn, they might only have proceeded if more fire fighting forces were available to help catch the fire if (when) it escaped their control lines.

 

Inadequate awareness of climatic conditions and related risk is a general problem in fire management as indicated by the fact that Cerro Grande was not the only “escaped” prescribed fire this spring.  Another one burned a huge area on the north rim of the Grand Canyon at about the same time as the Cerro Grande fire.  More fire fighting forces are desperately needed right now to fight the enormous fires burning throughout the western United States. The La Niña-based forecasts for continued dry conditions through the spring and early summer months could have been used during the winter to justify the hiring and training of a much larger seasonal fire fighting force, but in general, this information was not used.  Planning procedures for prescribed burns and upcoming fire seasons do not explicitly incorporate these new long-term climate forecasts.  Thus, the root of our fire problem in the west is not just fuel accumulations, but also our failure to heed climatic warnings. 

 

What is needed is better interagency coordination by regional decision makers who are monitoring broad-scale climate and fuel conditions and fire fighting resources, and who have authority to suspend prescribed burning in any or all management areas during certain seasons when the risks are too high.  Extra contingency resources should be required if prescribed burning operations are to be carried out during drought conditions -- even if local conditions for the prescribed burn are suitable for the prescription.  Fire fighting forces should be built up and positioned in the critical regions following extreme winter droughts, especially when the long-range forecasts call for continued dry conditions during the spring and summer.  Scientists and government agencies responsible for monitoring and forecasting the weather and climate must communicate the forecasts in more effective and useful ways for fire managers.

 

Finally, what is needed is acceptance of responsibility by all of us for the problems that we have created.  Houses should not be built (or rebuilt after fires!) in the middle of flammable forests and scrublands.  People who are currently living in forests and scrublands should clear fuels around their houses. We must begin the work of clearing the millions of small diameter trees that have grown up in many (but not all!) of our forests.  We will need to tolerate some air polluting smoke from carefully conducted prescribed fires during planned times so that we might avoid even more smoke during unplanned, catastrophic wildfires.  Fire and forest managers have a huge job ahead of them, and to succeed they will need to make better use of our new understanding of long-term climatic patterns.