1. The natural fire return interval for chaparral is 30 to 150 years or more. Today, there are more fires than the chaparral ecosystem can tolerate - see #2 below).
2. Fires more than once every 20 years, or during the cool season by prescribed fire, can eliminate chaparral by first reducing its biodiversity through the loss of fire-sensitive species, then by converting it to non-native weedlands (called type-conversion).
3. Being dense, impenetrable, and prone to infrequent, large, high-intensity wildfires is the natural condition of chaparral. It's not the fault of past fire suppression, poor land management, "unnatural" amounts of vegetation, or environmental laws as some claim.
4. The age and density of chaparral has little to do with the occurrence of such large fires. Large fires in California shrublands are driven primarily by weather, such as Santa Ana winds, sundowner winds, and multi-year droughts.
5. Chaparral has a high-intensity, crown fire regime, meaning when a fire burns, it burns everything, frequently leaving behind an ashen landscape. This is in contrast to a "surface fire regime" found in dry Ponderosa pine forests in the American Southwest where fires mostly burn the understory and only char the tree trunks rather than getting into the tree tops (crowns).
6.Native Americans did burn the landscape for various purposes in the past. In fact, some of their burning practices likely eliminated native shrublands in some areas (like the Central Coast) through type-conversion (see #2 above). However, their burning activity did not prevent the occurrence of large, infrequent, high-intensity chaparral fires. Such fires have always been a natural and inevitable part of the landscape.
Knowledge is Power: Learn the Science about Fire
Many of us who love the chaparral often find ourselves involved in conversations where we hear the tired, old paradigm that chaparral "needs" to burn, that large chaparral fires are "unnatural," and that large fires can be prevented if we could just burn off large patches of chaparral on a regular basis (known as the Baja/Southern California fire mosaic hypothesis).
Below is an example cited by the WildlandFireLessonsLearnedCenter, a consortium of fire agencies in the United States, that adds to the growing list of scientists and firefighters who challenge this hypothesis. This is a powerful reference to cite in our continuing efforts to help spread the truth about the chaparral:
"For decades, land-management policy in the region has been based on the idea that landscape-level fuel management can ultimately limit the size of these massive fires. A growing body of research has called that paradigm into question, and the results have big implications for land and fire management." Download the full article here.
Mean and max percent fire return interval departure (FRID). Hot colors indicate areas with fire frequencies in excess of natural levels. Cool colors represent areas that may have missed one or more natural fire return intervals.
Chaparral is being threatened by too much fire
"The ecological subsections surrounding the San Diego, Los Angeles, and Santa Barbara metropolitan areas are among the most negatively departed in the state... In these areas, extensive landscapes characterized originally by dense native shrublands have been converted to degraded, open stands of native shrubs and exotic annual grasses and forbs, which are easily reignited. These fire-mediated changes in vegetation lead to higher rates of erosion, increased exotic species invasion, and higher fire hazard as grass fuels replace shrubs."
has little to do with the occurrence of large wildfires
The map below shows how the 2007 fires in San Diego County overlapped the 2003 fire scars (bright purple), burning nearly 70,000 acres of four-year-old, recovering vegetation. According to conventional wisdom this was not supposed to happen. It did. The ecological health of these re-burned landscapes has now been seriously compromised.
Left photo shows the four-year-old vegetation recovering from the 2003 Cedar Fire. According to the Minnich hypothesis and many of those who promote landscape-leve prescribed burns and other vegetation "treatments," this type of landscape will not burn in a wildfire. Right photo shows the same location after the 2007 firestorm burned through the area. Location: Boulder Creek region, San Diego County. Photos by Wayne Spencer.
Why Comparisons Between Southern California and Baja Fires are Not Valid
For a complete analysis of why this comparison has been rejected by the scientific community (known as the fire mosaic hypothesis), please download:
It is a common misconception that wildlands are unnaturally "overgrown" with a half-century's worth of highly combustible shrubs and small trees because of successful firefighting efforts since the 1950s. In addition, environmental groups and government regulations are often blamed for preventing thinning and prescribed burns to help alleviate this hypothesized buildup. Such oversimplifications of a very complex problem are not helpful in finding solutions. They also have nothing to do with California's most characteristic wildland, the chaparral.
Forests are Different from Chaparral
It does appear that some, but certainly not all, of our nation's forests have "unnatural fuel loads," a consequence of past logging and grazing practices as well as fire suppression efforts. However, without understanding the dramatic differences between forests and the chaparral-covered hillsides in California, some are promoting a single solution to deal with the threat of wildfire everywhere. This will not only lead to a waste of tax-payer money and damage valuable natural resources, but will do little to prevent the kind of firestorms southern California continually experiences.
The notion of performing prescribed burns to create different-aged patches of backcountry chaparral as a way to prevent wildfires is the basic tenet of the southern/Baja California fire mosaic hypothesis first elaborated by Richard Minnich of UC Riverside in 1983. The hypothesis suggests that the size of wildfires north of the Mexican-Californian border are larger than those in Baja because of dramatically different fire management strategies.
According to the hypothesis, a century of fire suppression in Southern California has caused an "unnatural" accumulation of "fuel" that has consequently led to large, destructive chaparral fires. A map showing small fire perimeters south of the border and large ones to the north is often used as supporting evidence.
At first, the map is convincing and the logic appears reasonable. However, after being tested by a diversified group of scientists over the past ten years, the fire mosaic hypothesis fails for a simple reason. It ignores a significant number of important variables. For additional details, please download "Why Large Wildfires in Southern California? Refuting the Fire Suppression Paradigm" mentioned above. Large, Infrequent Fires are Normal
One of the more indefensible assumptions of the fire mosaic hypothesis is that large fires never existed in southen California prior to the influence of fire suppression activitives (usually identified as starting after 1910) - presumably because "mixed-aged mosaics" would naturally prevent the spread of fire. A 2009 paper by Keeley and Zedler has put to rest the false claim that large fires did not occur prior to 1910. And while fires will sometimes stop in younger vegetation, firefighter experience refutes the notion that mosaics can be depended upon to naturally constrain a fire, especially during extreme weather conditions (see Halsey, et al. 2009). What is the Solution Then?
The first task is to objectively examine the research. Unfortunately, fire management has become increasingly politicized. Instead of scientifically analyzing the data, some have the tendency to personalize the discussion and assign names or labels to particular positions. This is not only counterproductive, but confuses the public about how science is supposed to work. There are no positions. There are only collections of observations and facts with conclusions being derived from such data. By looking at the methods, the scientific design, and underlying assumptions, it becomes relatively easy to determine whether or not ignored variables or biases have influenced the results. The best way to reduce the risk of wildfire is to allocate scarce fire management resources at the wildland-urban interface (called the WUI - where homes meet wildland areas) and enforce fire-safe building/planning codes. This includes new regulations encouraging retrofitting older, flammable homes with such things as ember-resistent vents and non-combustible roofing, emphasizing strategic (and rational) fuel management directly around communities, and restricting development in extremely high fire hazard areas.
Leave the rest of the landscape alone.
Samples of research refuting the Fire Mosaic Hypothesis:
"Early studies characterizing differences in fire size north and south of the United States border invoked fire suppression as the primary explanation for these patterns (Minnich 1983, Minnich and Chou 1997). However, recent analyses show no evidence that 20th-century fire suppression has diminished fire activity on these landscapes.
"The fire regime in this region is dominated by human-caused ignitions, and fire suppression has played a critical role in preventing the ever increasing anthropogenic ignitions from driving the system wildly outside the historical fire return interval. Because the net result has been relatively little change in overall fire regimes, there has not been fuel accumulation in excess of the historical range of variability, and as a result, fuel accumulation or changes in fuel continuity do not explain wildfire patterns."
"Despite overwhelming evidence that fire frequency is continuing to increase in coastal southern California (Keeley et al. 1999, Moritz et al. 2004, NPS 2004), the current fire-management program subscribes to the paradigm that fire suppression has led to fewer, larger fires, and that landscape-scale prescribed fire should be used to create a fine-scaled age mosaic. Considering the results of our simulations, we believe that adding more fire to the landscape through broad-scale prescribed burning may have negative ecological effects. Instead, our results are consistent with recent recommendations from the U.S. National Park Service to change the fire management program to focus fuel-reduction efforts and prescribed fire on strategic locations such as the wildland–urban interface (NPS 2004)."
Mosaics and Biodiversity? In terms of creating mosaics to increase biodiversity, researchers from another Mediterranean-type climate, Australia have concluded (Parr and Andersen 2006),
"We identified serious shortcomings of PMB (patch mosaic burning): the ecological significance of different burning patterns remains unknown and details of desired fire mosaics remain unspecified. This has led to fire-management plans based on pyrodiversity rhetoric that lacks substance in terms of operational guidelines and capacity for meaningful evaluation. We also suggest that not all fire patterns are ecologically meaningful: this seems particularly true for the highly fire-prone savannas of Australia and South Africa. We argue that biodiversity-needs-pyrodiversity advocacy needs to be replaced with a more critical consideration of the levels of pyrodiversity needed for biodiversity and greater attention to operational guidelines for its implementation."
Considering the potential for significant ecological damage and the lack of efficacy in preventing fire spread, the creation of mixed-aged mosaics in native shrublands needs to be seriously re-evaluated.
Fire Suppression, Science, and Personal Opinion
When discussing an idea, it is usually best to ignore personalities and stick to the data. This is how science is supposed to work.
Well, there comes a time when a viewpoint becomes so disconnected from the accepted body of scientific knowledge that it distracts from constructive dialogue. At times it can even delay or alter important policy decisions. Such delays create negative consequences for future generations by creating unproductive, "my expert" vs. "your expert" politicized debates in the press. Although each of the experts are assumed to have equally valid viewpoints supported by objective data, one or more are often only interested in promoting their own individual cause or agenda regardless of the facts. Sometimes these causes are pushed by narrow, special interests in a consciously dishonest manner. Or alternatively, the promoter honestly believes his or her own view of the world so strongly that he or she is unable to objectively evaluate contrary data. Instead, everything is seen in light of a favored theory and seemingly obvious contradictions are dismissed (often unconsciously). Consequently, when the cause is continually taken to the popular media instead of being objectively discussed within the framework of science, it becomes impossible to ignore the messenger. This is why a number of well-know fire scientists spoke out in 2006 about Thomas Bonnicksen who was disregarding scientific fact to promote politically motivated policies dealing with wildland fire.
The June 16, 2007, San Bernardino County Sun news article "Forests Need to Burn" was a signal to many of us in the wildland fire and fire science communities that the time had come to directly address individuals who continually promote incorrect and potentially damaging notions about wildland fire management. In summary:
In their insistence on focusing on only one variable (chaparral age), promoters of the Baja/Southern California fire moasic hypothesis do not appear to have a clear understanding of wildland fire. Wildland fire risk in California is not the fault of the fire service, or the result of old stands of chaparral, it is an inherent part of the landscape.
Laying more fire on the ground on a landscape level or allowing fires to run is unacceptable in Southern California for both safety and ecological reasons. The fire mosaic hypothesis described in 1983 and elaborated further in 1997 is not applicable to the region. The best and most efficient way to reduce wildland fire risk is through proper community design, fire-safe building construction, adequate vegetation management around structures and strategically placed fuel treatment projects. Download the full document, "Fire Suppression, Science, and Personal Opinion," here.
Lastly, here are two classic papers discussing the importance of examining all variables and not ignoring contrary data: