The Production of Large and Small Wildfires

N aturallarge (catastrophic) disturbances are important because of their potential long-lasting impact on their surroundings, but underlying differences between frequent small and less common large disturbances are not well understood (Turner and Dale 1997, Romme et al. 1998, Turner and Dale 1998, chapter 4 of this book). Smaller disturbances may be better understood given their relative abundance, which lends itself more readily for study, but it is, perhaps, more useful to understand the forces driving damaging, catastrophic events. Wildland fires represent a perfect example. Nationwide, over 130,000 wildfires burn more than 4 million acres annually (1960-2002), these fires costing Federal agencies in excess of $768 million a year (1994-2002) in suppression alone (National Interagency Fire Center, http://www.nifc.gov/stats/index.html). Average wildfire size was 31 acres, with a suppression cost of $4800 per fire. The average wildfire does not appear a catastrophic threat, however this ignores the spatial distribution of these fires in relation to values at risk (an averaged size fire in a heavily populated area poses a different risk than a similarly size fire far removed from people and items of value). Catastrophic fire events, while relatively infrequent, do occur with some regularity-the 2000 Cerro Grande fire in New Mexico devastated 47,650 acres, two fire complexes in California in fall of 1999 each burned for three months and consumed a total of 227,647 acres, and during the 1998 Florida summer wildfire season, two fire complexes accounted for 205,786 acres or 9 percent of all wildfire acres, nationwide, in that year (National Interagency Fire Center, http;lIwww.nifc.gov/stats/index.html). Do the largest fires account for a disproportional amount of the area burned and damage? Is it possible that the largest 1 percent of fires account for 99 percent of the area, as Strauss et al. (1989) explored? For the state of Florida, the largest 1 percent accounted for 67 percent of total area burned with an average fire size of 2,641 acres versus 13 acres for the smallest 99 percent (1981-2001). Understanding the differences between small and large wildfires, including the exogenous factors influencing each, may provide decision-makers with better tools to mitigate future large-scale fire events. It is not necessarily true that large