USC Dana and David Dornsife College of Letters, Arts & Sciences > Blog

January 23, 2012

Fires of the South Coast Bioregion and Our Efforts to Suppress Them

Filed under: Fire — admin @ 6:24 pm

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.

January 20, 2012

Fire in the South Coast Bioregion

Filed under: Fire — admin @ 12:04 am

Although wildfires are normally associated with the immediate destruction they also have necessary function and a place in many ecosystems. Some benefits from periodic wildfires include the removal of accumulated dead wood, which may have been building; this then gives plants requiring higher levels of sunlight the opportunity to flourish. This excess of land also gives animals a chance to forage or nest. In addition to its land clearing capabilities, fires can be the stimulant enabling some plants to distribute their seeds and provide conditions allowing seeds to germinate. For these reasons it is clear the misconception that fires are bad is false. When viewed on a larger scale of multiple years or decades it is obvious that fires are a natural component of an effectively functioning bioregion.

Wildfire occurrence in the south coast bioregion is endemic. The dry climate of the natural desert of Southern California is a perfect catalyst for naturally induced fires. The boundaries to this area are the Transverse mountain ranges, the US border with Mexico, the peninsular mountain ranges, and the Pacific Ocean (this area does include the channel islands) – North, south, east and west respectively.

Lightning is often a frequent source of ignition for wild fires. This is not, however, the case in the winter and early spring, when ocean winds delay the onset of fire season in the coastal regions. Additionally the colder and wetter climate of the region at this time of year moistens the organic life making it harder to ignite.

An important contributory factor affecting fire occurrence in the south coast bioregion is the Santa Ana winds. These winds force hot dry air toward the coast. Firstly, they are preferred conditions for a fire to start and secondly, they occur at a time in early autumn when the plant life is at its driest and most susceptible to fire. Fire will also spread more rapidly due to the dry climate and the dry Santa Ana winds if a fire outbreak should occur.

Both lightning storms and foehn winds such as the Santa Anas overlap briefly, accounting for naturally occurring fires. However, in modern times, wildfire ignition is predominantly associated with human activity, and as such the surrounding bioregion has been exposed to a disproportionate number of fires what is deemed natural.

Although fires can serve a biological function, excessive fire to the organics of southern California is damaging to the previously mentioned organics and thus puts unnecessary strain on the local bioregion. This raises a moral question as to how human involvement is putting a strain on the south coast bioregion due to accidental fire ignition.

In the Sidebar 15.1 section, Keeley compares the fire regimes of Southern California to Northern Baja California. In 1975 United States’ scientist Dodge believed the burning patters would be different between the chaparral and coniferous forests depending on the side US/Mexico border. They believed Mexico did not practice fire suppression outside of towns and that fires were actually encouraged. Dodge found the “lack of fire suppression, frequent burning of the shrublands, and over-gazing Baja California” (Keeley 361) suggested land use patterns were the same above and below the border (361).

In 1983, Minnich compared burning on both sides of the border between 1972 and 1980 and found that fires were larger on the US side of the border (361). Critics, however, dispel these findings because they are based on two reports of large fires north of the border, but written records of fires south of the border were not available. The historical aerial photographs Minnich used in their place did not suffice, according to Keeley (361). The conclusion is the smaller fires south of the border represent the natural fire regime, and that the larger fires in southern California are a result of human induced fire avoidance. The fuel for the fire thus accumulates immensely for years, and the resulting fires are huge (361). This conclusion too is criticized because with fire suppression, large fires in southern California have not increased. In terms of comparing conifer forests, scientists attribute differences in forest structure as the reason for the differences in fire frequency.

Fulé et. al, studied fire occurrences in Chihuahua, Mexico. They found the prevalence of fire control regimes led to more severe wildfires, thus surface fire should be used as a management too, thus contradicting Keeley’s argument against Minnich’s conclusion that fires increase in strength with the accumulation of fuel with human-induced fire prevention.

Keeley also asserts some scientists believe climate could play a more prominent role than fire management policies. However, Keeley demonstrates the three-degree difference in latitude shows only few differences in forest structure and species.

Forrest and Harding state:

“People and their activities are as much a part of the post-fire environment as are native plants and animals, and any approach that does not incorporate human resources and values as part of a mitigation strategy fails to appreciate the practical interface between humans and their environment.”

While Forrest and Harding’s statement may be anthropogenic and optimistic, there is an important point to apply to Keeley’s study. Forrest and Harding affirm Keeley’s statement that humans drastically affect their environment. Human stewardship of land will determine its ability to function in its natural state.

This post was written by Elise Fabbro, a double major in Political Science (BA) and Environmental Studies (BA) who is currently pursuing her MA in Environmental studies, and by Richard Charlesworth a senior in Environmental Studies (BA) with a minor in Architecture.

Works Cited

Forrest, Carol L, and Harding, Michael V. ”Erosion an sediment control: Preventing additional disasters after the Southern California fires. ” Journal of Soil and Water Conservation  49.6 (1994): 535.

Keeley, Jon E. “South Coast Bioregion.” Fire In California’s Bioregions. 350-91. Print. Peter Z Fulé, José Villanueva-Díaz, and Mauro Ramos-Gómez. ”Fire regime in a conservation reserve in Chihuahua, Mexico. ” Canadian Journal of Forest Research  35.2 (2005): 320-330.