September 25, 2011
California Wildfires
Soil biodiversity and conservation ecology has become a hot issue, specifically in Southern California, due to numerous factors. Due to anthropogenic factors such as human caused wildfires, and use of fertilizers on grasslands, Southern California’s soil is losing nutrient richness, and a decline in productivity is occurring. Other naturally occurring factors that contribute to the decline in suitable soil in Southern California are sediment deposits and high winds.
In the case of California wildfires, as explained in the article “Ecological Effects of Southern California Fires Could Be Devastating,” human induced wildfires are much more harmful to flora and fauna than naturally occurring fires, according to Dr. James Danoff-Burg. “There are a lot of species that have adapted to a fire-dependent ecosystem,” Danoff-Burg says. “But there will be more mortality across the board, including in fire-adapted species, because these fires are more intense than normal wildfires.” Due to these intense fires, species are not only dying, but the microbes and soil productivity is decreasing.
The second anthropogenic problem in Southern California deals with fertilization. According to the abstract of “Effects of Soil Resources on Plant Invasion and Community Structure in Californian Serpentine Grassland” by the Ecological Society of America, fertilization with chemicals such as nitrogen and phosphorus have led to an increase in biomass of native vegetation initially, however by the second season the non-native grasses began to invade, and dominate areas originally inhabited by native grasses. In this instance species richness declined with fertilization due to the increase in biomass production by non-native organisms, and changes in community structure demonstrated that the invisibility of plant communities may be influenced directly by nutrient availability.
The Los Angeles Basin is where the majority of Los Angeles County inhabitants reside, and is an area high in sediment and low in stability. Due to the high deposits in sediment the area is more susceptible to ecological impacts from urbanization and urban sprawl of the Los Angeles Basin, as well as natural hazards such as earthquakes or winds. This means that one of the most densely populated regions in the United States is living directly on top of land that is very unstable, and very susceptible to earthquakes at a high frequency and high magnitude. Another effect of the instability is water supply. According to the U.S. Geological Survey, More than 10 million people live in the Los Angeles metropolitan area, and the majority depends on water pumped from beneath the surface of the Los Angeles Basin. In the central and west coast basins a third of the water consumed by the four million residents come from ground water. More than 30 monitoring wells have been drilled in an effort to better understand just how the instability of the basin could affect the future water supply.
Lastly, winds in Southern California are particularly dangerous because of the desert. Hot, dry winds blowing from the inland are very commonly called Santa Ana winds. These winds are responsible for the high frequency of wildfires in Southern California. This ecological impact is what causes the dry desert region to be so nutrient depleted. The drastically different terrains within southern California make it hard for conservation ecology to improve the soil biodiversity.
About the authors: Liam Sharkey and Katie Graves are undergraduate students in the USC Dornsife College of Letters, Arts and Sciences.
Although we see that California wildfires will cause “mortality across the board”, it is important to emphasize the benefits of fire brings to ecosystems. Fire-dependent species often need fire for germination purposes. Fire-dependent species “have evolved barriers to seed germination that are overcome only by fire-related cues”(Shebits, D. et al, 2003). The extreme heat is needed for the survival of the species, fire will break open the seeds to be fertilized or the chemicals involved in combustion can induce germination (Shebits, D. et al, 2003). Many species of pine trees in California need fire for regeneration. In fact, many ecosystems have lost the ability for natural fires, and humans will induce them to regenerate the ecosystem. The high mineral content of ash and charcoal make the soil more nutrient-rich after fires.
One of the potential solutions to these “artificially” large fires is having controlled burns. Controlled burns simulate natural burns, in which the undergrowth does not have as much time to build up, and therefore are less intense but occur in greater frequency.
However, controlled burns are not always as controlled as they seem. They have previously resulted in burns that become out-of-control, damaging even more of the precious soils that they have set out to save.
Another issue is that controlled burns cannot function in areas with human settlement. However, these areas also contain valuable soil microbes.
The question, then, becomes one of risk management and balancing the highest benefits with the potential risk of burns becoming out-of-control.