wildfire

The Subtleties of California Wildfire

Infrequent, but catastrophic, fires are a natural part of chaparral habitat, as seen in this picture from the U.S.G.S.

Infrequent, but catastrophic, fires are a natural part of chaparral habitat, as seen in this picture from the U.S.G.S.

Wildfire is a natural, but destructive, component of many natural ecosystems. In California, wildfires are a complicated issue: On one hand, periodic wildfires are unavoidable and necessary for the perpetuation of some ecosystems. On the other hand, wildfires cause unthinkable damage and threaten lives. The complexity of the issue balloons even further once competing human interests enter the picture.

As is often the case in complicated matters, fire suppression strategies and the characteristics of various fire regimes have been over simplified.

Fire Suppression

Following several fires in the late 19th century, and the establishment of the U.S. Forest Service at the dawn of the 20th century, foresters began arguing that fires should be suppressed in order to protect the very forests they were charged with overseeing. By the early 1930s, a policy of total fire suppression had taken hold of the forest management community. The goal was to prevent as many fires as possible, and aggressively battle all those that did start. (FOREST HISTORY SOCIETY, 2014)

During the 1960s and 1970s, ecologists began refining their understanding of fire ecology. In some places, they found that — contrary to the fire suppression strategies of the time — fires were an important process for the ecosystem. This led forest managers to re-think their approaches to fire and fire suppression.

Not All Fires Are Created Equally

Though often treated as a single phenomenon, the periodic fires that occur in different locations exhibit different characteristics. Fire professionals and ecologists use the term “fire regime” to describe the characteristics of the periodic fires in different areas.

Broadly speaking, fires exhibit characteristics that vary along a spectrum. Some regimes feature frequent, low-intensity fires that primarily affect the surface vegetation, while infrequent, catastrophic fires that destroy the entire canopy represent the opposite end of the spectrum. Some areas experience regimes that are intermediate between these two types.

Forest Fires

The historic fire regime of many Californian coniferous forests featured relatively low-intensity fires that recurred every 4 to 30 years. (San Diego Wildfires Education Project, n.d.) Generally, the only plants affected by such fires were the low-lying herbs, grasses, shrubs and seedlings – large trees usually escaped with no significant damage. These types of fires did not often spread far and were relatively easy to suppress, so foresters did just that.

Unfortunately, in many places, these fire suppression strategies created a ticking-timber-time-bomb. Without regular fires to clear out the underbrush, leaf litter and dead trees, the forests became prone to incredibly intense fires, which were much more difficult to contain. These dangerous fires were more likely to threaten human-occupied areas and they were more difficult for fire professionals to control.

Accordingly, foresters began prescribing small, controlled burns in these habitats. In the case of these coniferous forests, the strategy is very successful and helps to maintain the habitat. However, this strategy is not appropriate for all habitats.

Fires in the Chaparral

Most of coastal California is covered in a habitat called the chaparral. Like coniferous forests, chaparral plant communities depend on fire, but the fire regimes of the two habitats are drastically different.

Unlike the surface fires that occur in many pine forests, chaparral fires are very intense events, in which the tree canopies burn. The landscape often looks completely barren after such fires, excluding the piles of ash and smoldering coals. Another difference between these fires and those of the forests is the rate at which they occur: Chaparral fires historically occurred at intervals of 30 years or more. Some were even less frequent, occurring more than 130 years apart. (California Chaparral Institute, n.d.)

Unfortunately, in the modern world, wildfires are much more common. (California Chaparral Institute, n.d.) The increase in the frequency of these habitats led some to suggest that foresters should burn some of the chaparral forest regularly. Besides clearing some of the fuel for future fires, some researchers thought that this would lead to a “mosaic” of different aged stands. This, the hypothesis asserted, would stop the spread of these fires, as the younger areas would not burn as readily as the older patches would. (Chou, 1997)

Unfortunately, this was not an effective strategy. According to research from the University of California and the U.S. Geological Survey demonstrates that chaparral habitat burns completely, regardless of the age of the stand. (Fotheringham, 2001) The problem was not that foresters were not burning the chaparral regularly enough, the problem was that too many fires were occurring. Chaparral vegetation has not evolved to survive amid frequent fires. Fires that occur less than 20 years apart from each other cause considerable stress on the local flora, and often lead to state-transition, in which invasive, non-native species replace native chaparral species.

Accordingly, while foresters are wise to allow and encourage periodic, low-intensity fires in some habitats, others require very aggressive fire suppression strategies if the habitats are to have any chance of surviving.

References

Allen, R. J. (2012). Impact of Recurrent Fire on Annual Plants: a Case Study from the Western Edge of the Colorado Desert. Madroño.

California Chaparral Institute. (n.d.). Fire & Science. Retrieved from CaliforniaChaparralInstitute.org: http://www.californiachaparral.org/fire/firescience.html

California Chaparral Institute. (n.d.). Fire and Nature. Retrieved from California Chaparral Institute: http://www.californiachaparral.org/fire/firenature.html

Chou, R. M. (1997). Wildland Fire Patch Dynamics in the Chaparral of Southern California and Northern Baja California . International Journal of Wildland Fire.

FOREST HISTORY SOCIETY. (2014). U.S. Forest Service Fire Suppression. Retrieved from FOREST HISTORY SOCIETY: http://www.foresthistory.org/ASPNET/Policy/Fire/Suppression/Suppression.aspx

Fotheringham, J. E. (2001). Historic Fire Regime in Southern California Shrublands. Conservation Biology.

San Diego Wildfires Education Project. (n.d.). Fire in Mixed Conifer Forest. Retrieved from San Diego Wildfires Education Project: http://interwork.sdsu.edu/fire/resources/conifer-forest.htm