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Media Advisory, October 30, 2007

Contact: David Hogan, (619) 473-8217(office), or (760) 809-9244(cell)

Science vs. Myths on Southern California Fire and Chaparral

SAN DIEGO, Calif.– To support accurate media coverage, the Center for Biological Diversity is providing the following basic scientific information relating to fire and chaparral vegetation management in southern California.

Native chaparral was the dominant vegetation burned in the southern California wildfires over the past week. Chaparral is not one plant but rather a diverse community of plants that are unique to California’s Mediterranean climate and is the most widespread natural vegetation from the coast to the mountains. Contrary to common misperceptions, the best available science shows that old-growth chaparral is an ecologically rich natural resource, that frequent fire is not necessary to maintain the health of chaparral, and that fire suppression has not produced an unnatural accumulation of chaparral fuel or caused the catastrophic wildfires in southern California.

“It’s an all-too-common myth that past fire suppression has allowed uncontrolled plant growth and an increased risk of unnaturally severe fire,” said Dave Hogan with the Center. “While this is true of some forests, California's chaparral is actually experiencing more fire than is natural owing to human ignitions. Chaparral has evolved with fire and is very resilient under the right conditions. But too much fire, including prescribed fire, destroys habitat and allows exotic grasses to replace natural vegetation.”

According to the best available science:

  • Prescribed fire and other fuel treatments in chaparral are not effective for fire safety

Fires occurring under non-extreme weather conditions are fairly easily suppressed, so prescribed fire in chaparral is either likely to be unnecessary under non-extreme conditions, or ineffective under extreme conditions (Keeley et al. 2004)[1]. Prescribed fire is also risky because it can escape and become an even more hazardous wildfire (Keeley and Fotheringham 2003)[2].

According to Moritz et al. (2004)[3]: “Fire management policy based on eliminating older stands of shrubland vegetation through fuel treatments [e.g. prescribed fire] will not diminish the size of wildfires ignited under extreme weather.” According to Keeley et al. (2004): “Under extreme weather conditions, there is overwhelming evidence that young fuels, or even fuel breaks…will not act as a barrier to fire spread. This is quite evident for the recent [2003] fires. Crossing nearly the entire width from north to south of the east-west burning Cedar Fire were substantial swaths of vegetation that were less than 10 years of age, not just in one but two parts of that fire… The Otay Fire exhibited the same phenomenon…; the fire burned through thousands of acres that were only 7 years of age.”

Cohen and Saveland (1997)[4] reached a related important conclusion when they found that “Vegetation management beyond the immediate vicinity of a building has little effect on structure ignitions.”

  • Fire suppression has not resulted in an unnatural accumulation of chaparral fuel and catastrophic fire

According to Moritz et al. (2004): “Fire suppression is not an underlying cause of catastrophic wildfires in southern California.” Southern California chaparral is burning more frequently than a century ago, with a higher number of ignitions and a shorter fire return interval than occurred prior to organized fire suppression activities (Keeley et al. 2004; Keeley and Fotheringham 2003). Fire suppression has not effectively excluded fire in southern California chaparral (Keeley and Fotheringham 2003; Keeley and Fotheringham 2001;[5] Mensing et al. 1999[6]).

  • Overly frequent fire actually increases the risk of wildfire and is harmful to chaparral

Overly frequent fire, including prescribed fire, produces a negative cycle of invasion by highly flammable exotic grasses, which in turn results in an increased fire frequency and the related significant threat to public safety, firefighters, property, natural resources, and economic values like water storage and quality.

Chaparral will convert to highly flammable exotic grasslands if burnt too frequently. According to Keeley (2006)[7]: “In recent years ineffective fire prevention has allowed an unnaturally high number of wildfires on chaparral landscapes, which has resulted in conversion to alien dominated grasslands…”; A repeat fire within a decade is typically sufficient to provide an initial foothold for exotic grasses; “…[A]lien grasses increase the probability of burning…”, and; “As fire frequency increases there is a threshold beyond which [chaparral] cannot recover.” The conversion of native chaparral to exotic grasslands harms biodiversity and increases erosion, landslides, and other harmful landform changes (Keeley 2006, emphasis added).

Prescribed fire does not benefit chaparral and in fact can be very harmful when prescribed fire becomes a part of an overly frequent cycle of fire (Keeley and Fotheringham 2003) that causes conversion of chaparral to more flammable and less ecologically and economically valuable exotic invasive grasslands (Keeley 2006). Prescribed fire is regularly applied outside the normal fire season and this can produce extreme resource damage (Keeley 2006).

  • Old-growth chaparral is not unhealthy and doesn’t need to burn

Chaparral is not threatened by a lack of fire (Keeley and Fotheringham 2003). According to Keeley et al. (2005)[8]: Chaparral more than a century old is just as resilient to fire as younger chaparral; A long fire-free period “…had little impact on the ability of these shrublands to recover following fire…” and; A fire-free period of even as much as 150 years may not be outside the norm.

  • Southern California wildfires have not become not unnaturally large or intense

According to Keeley and Fotheringham (2003), “Historically fire intensity was variable, and there is no credible evidence that it has increased during the era of fire suppression…” “ The firestorm during the last week of Oct. 2003 was a natural event that has been repeated on these landscapes for eons… While the recent 273,230 [acre] Cedar Fire … was the largest in California since official fire records have been kept, there are historical accounts of even larger fire events. For example, during the last week of Sept. 1889, a Santa Ana wind-driven fire east of Santa Ana in Orange County, California reportedly burned 100 miles north and south and 10-18 miles in width … This event would have been three times larger than the recent Cedar Fire. Collectively, Sept. 1889 would have exceeded all of the Oct. 2003 burning because there was another fire that ignited that week near Escondido in San Diego County and in 2 days the same Santa Ana winds blew it all the way to downtown San Diego…” (Keeley et al. 2004).

Cited information is available upon request.

For more information please contact:
Dr. Jon Keeley, (559) 565-3170,
Dr. Max Moritz, (510) 642-7329,

The Center for Biological Diversity is a nonprofit conservation organization with more than 35,000 members dedicated to the protection of endangered species and wild places.


[1] Keeley, J.E., C.J. Fotheringham, and M.A. Moritz. 2004. Lessons from the 2003 wildfires in southern California. Journal of Forestry 102(7):26-31.

[2] Keeley, J.E. and C.J. Fotheringham. 2003. Impact of past, present, and future fire regimes on North American Mediterranean shrublands, pp. 218-262. In T.T. Veblen, W.L. Baker, G. Montenegro, and T.W. Swetnam (eds), Fire and Climatic Change in Temperate Ecosystems of the Western Americas. Springer, New York.

[3] Moritz, M.A., J.E. Keeley, E.A. Johnson, and A.A. Schaffner. 2004. Testing a basic assumption of shrubland fire management: How important is fuel age? Frontiers in Ecology and the Environment 2:67-72.

[4] Cohen, J. D, and J. Saveland. 1997. Structure ignition assessment can help reduce fire damages in the W-UI. Fire Management Notes 57(4): 19-23.

[5] Keeley, J.E. and C.J. Fotheringham. 2001. The historical role of fire in California shrublands. Conservation Biology 15: 1536-1548.

[6] Mensing, S.A., J. Michaelsen, and R. Byrne. 1999. A 560-year record of Santa Ana fires reconstructed from charcoal deposited in the Santa Barbara Basin, California. Quaternary Research 51:295–305.

[7] Keeley, J.E. 2006. Fire management impacts on invasive plant species in the western United States. Conservation Biology 20:375-384.

[8] Keeley, J.E., A.H. Pfaff, and H.D. Safford. 2005. Fire suppression impacts on postfire recovery of Sierra Nevada chaparral shrublands. International Journal of Wildland Fire 14: 255-265.

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