January 23, 2012
Fires of the South Coast Bioregion and Our Efforts to Suppress Them
The South Coast bioregion is comprised of a complex system of natural landscapes, climatic patterns, and ecological zones. This area includes the interior lands that line the Southern California bight. More specifically it is bordered by the Transverse Mountains, the US and Mexican border, the Peninsular Ranges and the Pacific Ocean. The Los Angeles Basin is located within these borders. The Transverse Ranges progress in an east to west trend, while the Peninsular Ranges progress north to south. This area, although making up only 8% of the land area of California, accounts for 56% of the state’s population (Keely et al.). In terms of the climate, the bioregion has a relatively mild climate, lacking in severe seasonality. The summers are hot and dry, while the winters are cooler and receive moderate amounts of precipitation. During the transition between summer and autumn, the area is hit with the strong Santa Ana winds. These winds can blow at extremely high speeds and account for much of the wildfire that spread is Southern California. The flora of the South Coast bioregion has been described as a mosaic. The aspects of this mosaic include grasslands, shrub land, woodland, and forests. These areas coexist within each other and fire regimes have very unclear boundaries. Because of this, the area can be divided into two larger ecological zones: the montane zone and the coastal valley/foothill zone.
Fires have been an aspect of the region as early back as 5-15 million years ago within the chaparral. Fossil charcoal records have been found within this area and support the claim that fires have been a key player since this time. How these fires have come about has changed drastically over time. Lightning strikes were the dominant ignition source in most parts of the region throughout the first half of the Holocene. The lightning strikes would not have created fire large enough to burn areas of the entire region, but if these localized fires were timed at a similar point in the year as the Santa Ana winds, the fires would be pushed by the winds and spread rapidly in the same way as we see in wildfires today. Fires started by lightning strikes were pretty rare during this time. It wasn’t until Native Americans and Spanish settlers reached this area of the United States that we saw a different ignition source pop up. As people began to settle the area they brought with them practices for agriculture, like burning shrublands for type conversion. This practice was common among many different kinds of people all over the region. These practices continued on into more recent times, but with more settlers came another change in vegetation. Spanish settlers spread nonnative grasses and forbs that competed with the natural fauna, and grazing became a threat to the land as well. Burning of the shrubland, especially in the areas where Los Angeles now sits, helped clear land for settlement and grazing of farm animals. It also paved the way for the extreme urbanization that is happening today and altering fire regimes even more than these beginning practices.
The Southern California area is home to an extremely dense population that requires further expansion into and development of untouched areas. With this population comes a higher risk for ignition of fires. A debate has risen over whether or not our fire suppression efforts in this area have helped or harmed the natural landscape. In a report done by the California Chaparral Institute, it noted that fire return intervals for chaparral was originally 30 to 150 years, but once humans settled in this area, the intervals have decreased dramatically, placing a great amount of stress on the chaparral. In his article “Reexamining Fire Suppression Impacts on Brushland Fire Regimes, Jon E. Keely examines the efforts of individuals to suppress fires by maintaining a young stand-age of fuels in the chaparral. It is believed that younger fuels will not burn as readily and limit the impact of fire. However, Keely goes on to show that fires are not stand-age dependent and will spread even with the younger fuels and the suppression efforts in their current form have not been successful.
Other individuals have believed that our suppression efforts have left an overabundance of vegetation that will help in the spreading of fires, but the California Chaparral Institute disputes this in their argument that while some forests have an overabundance of vegetation, the chaparral of California do not. They point out that instead of criticizing fire suppression efforts, we should value them for maintaining the damage fires could cause. It has been said many times that fire frequency and intensity in this area has increased, and the amount of potential damages is much higher than what it actually is (i.e. chaparral forests could have been completely converted to invasive weeds). This difference is due to the current fire suppression efforts. But as Keely brings up at the end of his article, more good could be done if we fine tune our efforts and focus not so much on the age of fuels, but more on creating a buffer zone between natural landscape and urban areas.
This post was written by Amelia Bahr, a senior Environmental Studies major (BA) with a minor in East Asian Languages and Cultures; and by Alex Anthony, a senior Environmental Studies major (BS).
Keely, Jon E. “South Coast Bioregion.” Fire in California’s Bioregions. 350-90. Print.
Controlled fires by Native Americans then European settlers have vastly extended the amount of grasslands in the region. During the first half of the nineteenth century, these grasslands became invaded and overtaken by non-native species brought by Europeans. There are three dominant factors believed to have exacerbated the fire regimes: first, warming in the Holocene period favored annual plants over perennials; second, a long co-evolution of the invasive European species and human settlement, which selected for aggressive colonizing plants; third, the high frequency of burning by Native Americans changed the native landscape, and favored rapid invasive species.
When originally conceived, fire suppression was never intended to be anything other than a means of protecting human lives and human property. In the many years since it’s become general practice, however, the public has begun to regard fire suppression as something akin to a service we’re providing to the natural environment. There’s minimal understanding that wildfires are a natural and necessary part of the South Coast bioregion. To that end, I find the statement that Southern California “is home to an extremely dense population that requires further expansion into and development of untouched areas” to be particularly troubling. I feel that the sentiments underlying this statement and statements like it can be used to justify continued, ecologically detrimental fire suppression practices. Rather than continuing to expand ad infinitum, there must be more efforts made to consolidate population centers into areas of greater density, if only to minimize the extent to which we encroach on the natural environment.
Fire suppression is a very hot topic among the Forestry Service and I believe practices depend entirely on the area that is in question. For instance, in Mammoth Lakes, CA, the FS in that region routinely clears the fire brush that accumulates in the forests as vegetation dies off to reduce the risk of fire in somewhat populated region and protect the Inyo National Forest. However, in the LA region, fire suppression makes the severity of the fires much worse when they do happen. I would much rather smaller frequent fires than, big substantial ones. This is because the larger the fire is, the deeper its heat penetrates the soil below. A big fire can create a deep impermeable clay layer in the soil which stops water percolation into the groundwater and dehydrated the roots of the surviving plants only to live out their death sentence. This was demonstrated to us on a field trip to the San Dimas experimental forest in my GEOL 470 class. Rather, smaller and frequent fires, contrary to what you might think, does not cause this deep penetrating layer, but instead a shallow one that is close enough to the surface to be washed away in run-off that is accompanied by rain.