January 23, 2012
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.