Prescribed burns are capable of reducing fuel hazard and fire risk, achieving wildlife habitat maintenance and improvement. Prescribed burns can also have possible negative effects on plants and animals, and may have an adverse effect on the soil in medium to high intensity fires. As well, tree damage resulting from wildfire occurrence is one of the most used descriptors of the prescribed fire effect (Fernandes and Botelho 2003). Prescribed fires have yielded mostly positive results in mixed-conifer forests, places like the Sierra Nevada, but practices have become implemented more frequently at lower elevations as well. Although prescribed burnings are usually beneficial when conducted in mixed-conifer forests such as those in the montane and alpine elevations of the Sierra Nevada, prescribed burns can devastate the lower-elevation shrublands and chaparral. This article will explore how the benefits of prescribed burns that have originally been attributed to mixed-conifer forests have been applied to ecosystems at lower elevations. This paper will examine the implementation of prescribed burns at different elevations from a system perspective and issues of sustainability of this practice. It will offer other options to the system to establish if a more sustainable system can be constructed and what the implications of those alternatives might be.
History of Fire Management
Fire management in National Parks as a whole is a practice that has changed dramatically over the past few decades. While traditionally viewed as a negative force, fire has more recently been acknowledged to be tremendously beneficial and an integral part of a forest’s ecological balance. For years, forest fires were feared and suppressed and as a result, the natural occurrence of fire was eliminated, causing overgrown and unhealthy forests.
In higher elevations of the Sierra Nevada, many plants are fire resistant and many benefit from the smoke and heat of fires. Pyriscence is an adaptation that many plants in the Sierra Nevada have in which the maturation and release of seeds are triggered by fire or smoke. As well as providing an opportunity for seeds to be released and germinate, fires also clear forests in a way that allows shade-intolerant trees to establish themselves. Animals too, may benefit from natural fires. Birds, who can evacuate relatively easily during a fire, are at an advantage over their prey once they return to a newly cleared forest. Microbial organisms may benefit from fires from an increase in available nutrients after the fire has passed.
Between 1930 and 2010, a total of 3,199 lightning fires ignited, and they burned 197,027 acres within Yosemite National Park. The result was an average fire size of 61.6 acres. However, before 1972, 1,340 fires burned 7,689 acres. This represents 42% of all ignitions, but only 4% of the total acres burned. The average fire size during this 42-year period decreases to 5.7 acres. All fires were suppressed per the management policies of the time (Wagtendonk 2011). These statistics make it abundantly clear that fire suppression has caused fires to burn larger and in turn become more detrimental. Beginning in 1972, Yosemite established a prescribed natural fire program that afforded the opportunity to manage lightning ignited fires, allowing them to burn under prescribed conditions (Wagtendonk 2011).
Table 1 Large Fires are Becoming More Common in the West
While fires are natural occurrences that are necessary for a healthy forest, there are many variables in fire management and there are negative and detrimental effects that have occurred from prescribed fires. It is apparent that the suppression of naturally occurring fire is responsible for creating fires that become more expansive and possibly more detrimental in the future. Without the clearing of brush and the aid that fire provides many plant species to be able to reproduce and thrive, ecosystems become more delicate and susceptible to hotter fires. While many plants and animals rely on fires, at a higher intensity they can destroy rather than create and sustain habitats. This realization of the unhealthiness of total suppression that has led to prescribed fires has sometimes had its own unhealthy effects on the ecosystem in Sierra Nevada.
Although the benefits of prescribed burns are clear, the potential for things to go wrong always exists and it has in the past. Even though prescribed fires are potentially positive, management actions to mitigate its negative consequences are limited and restricted to fuels. Current fire fighting technology fails when faced with multiple-fire events, and is not able to cope with wildfires burning under severe weather conditions (Fernandes and Botelho 2003). Fire intensity is not regulated when prescribed burns take place and this can mean that fires that are too intense for an area can actually damage the local flora and fauna.
Along with the risks that prescribed fires pose in alpine elevations, more devastating is the result of prescribed burns at lower elevations in California. According to recent studies, California chaparral is extraordinarily resilient to very long periods without fire and continues to maintain productive growth throughout pre-fire conditions (Hubbard 1986). Seeds of many chaparral plants actually require 30 years or more worth of accumulated leaf litter before they will successfully germinate. When intervals between fires drop below 10 to 15 years, many chaparral species are eliminated and the system is typically replaced by non-native, invasive, weedy grassland.
Figure 1 Fires Occurring More Frequently
Prescribed fires have also led to the contribution of invasive species, particularly cheatgrass. Although current efforts are in place to increase ecological functions, with the passage of the Healthy Forests Restoration Act of 2003 it is expected that in the coming decades western forests will have more thinning and fire restoration, which could enhance cheatgrass in some of these forests (Keeley and McGinnis 2007). The HFRA decreased public involvement, reduced environmental protection, and gave more free reign to the timber industry.
As well, improper burning techniques have caused thousands of trees to die due to uncontrolled severity. Fire return intervals under 20 years can seriously compromise the ecological health of chaparral either by eliminating keystone plant species (and their associated animal partners) such as non-resprouting ceanothus and manzanita.
Examples of detrimental effects of prescribed burns can be found in conclusions drawn from a prescribed burn on May 23, 2013, in San Diego County. This fire escaped and progressed to burn more than 2,700 acres of fragile habitat within the protected area. Since a large portion of this area had burned in the 2002 Pines Fire, the ecology was especially fragile and the fire caused serious damage to the soil and flora.
Other prescribed burns that have gotten out of control include the 2000 Cerro Grande Fire in Los Alamos, New Mexico, where 48,000 acres were burned and 280 homes were lost; The 2006 Sierra Fire in Cleveland National Forest, CA where 10,854 acres burned; The 2012 Creek Fire in Montana de Oro State Park, Ca where 103 acres were burned; and 2013 San Felipe Valley Wildlife Area, CA where 2,781 acres were burned.
Prescribed or Not: Fires Get Out of Control
Photo by sippakorn yamkasikorn on Unsplash
Many factors contribute to the dangerous impacts of shrubland fires, particular the season. Unseasonable fire can eliminate a chaparral plant community. When this is done incorrectly, it has clear consequences for the human population as well as the biodiversity of the chaparral community. As a response to the era of total suppression, for the last forty years or so, fire managers have encouraged the idea that prescribed burns are always necessary in order to protect ecosystems and communities. The idea has been promoted that this will restore fire’s natural role in the environment and thinning forest stands will reduce hazardous fuels. While this is true in areas where the natural fire regime was common, this is not true for the shrubland dominated ecosystems of southern California.
There is a community of fear in California surrounding fires. When fires burn communities, people are afraid of the impacts of prescribed burns. This fear is what created the initial suppression tactics that actually made fires worse and instilled more fear of fire. However, as more information has been discovered and management departments have begun using prescribed burns as a way of managing fires, some of these prescribed fires have gotten out of control and continued to have negative effects on surrounding communities. In response, an overabundance of prescribed burns has begun to take place in some areas, causing severe damage to local ecosystems.
Invasive species like cheat-grass that thrive in regions that have been exposed to too many fires, contribute to more fires and are create a vicious cycle. In these cases, not only are ecological zones severely damaged, but government resources are wasted. For example, in the Eldorado National Forest, cheatgrass and other annual bromes invaded the Celevent Fire of 1992 and altered the surface, fuel structure, and contributed to the 2001 St Pauli Fire. This latter fire re-burned a portion of the replanted Cleveland Fire area, killing about 70,000 trees over an area of about 100 ha for an estimated loss of US$250 000 in silvicultural treatments (Keeley and McGinnis 2007).
Wilderness Management Resources in California have taken steps to combat the perceived negative impact of fire suppression by creating and implementing prescribed burns.
US Forest Service Departments do not always take factors such as weather and seasons into consideration when planning a controlled burn. Presently, rotational prescription burning to maintain a landscape mosaic of different age classes is thought to inhibit large fire development; however, studies have been done that suggest that this strategy will be ineffective. Evidence suggests that prescription burning in some crown-fire ecosystems also has limitations not experienced in forest ecosystems. It can be ecologically harmful to native species to employ prescription burning in relatively young shrublands before a sufficient seed bank has accumulated to ensure successful regeneration (Odion and Tyler 2002).
One of the misconceptions is that wildfires in California’s shrublands are a direct result of fire suppression, which is contradicted by the results in Moritz's study. As such, efforts should be made to take this into consideration when implementing prescribed burns in such areas. Moritz found that “before modern suppression methods were introduced, extreme weather conditions could have infrequently generated large conflagrations that spread through all age classes of vegetation, just as they do now” (Moritz 2003). This is important to note considering that current fire management uses fuel manipulations as a method to combat devastating wildfires.
In order to create a more sustainable system for chaparral and shrublands, more conditions should be taken into consideration than how often fires have occurred when creating a prescribed burn plan. Seasonal weather patterns in California have a drastic effect on the outcome of such prescribed fires and should be analyzed and used in a planning process.
Unseasonal fires can cause much more damage than fires managed during more conducive times of the year and when different climate influences are involved. A report from the USDA suggests that a variable fire regime including prescribed burns at different times of the year may alleviate the potential for undesired changes and maximize biodiversity (Kapp, Estes and Skinner 2009). In late seasons, it has been found that burns are more damaging possibly due to drier soil which in turn is affected more deeply and underground structures are more likely to be killed.
Soil is subject to damage from high intensity fires and at high temperatures soil can be damaged by killing biological diversity and root mortality as well as increased water repellency. A major factor in how much damage is caused is related to the soil moisture at the time. This suggests that burns should be implemented during times of the season when moisture levels are highest in order to avoid soil damage. In lower elevations, however, this has been implemented and prescribed burns frequently occur in the winter or spring, outside of the normal fire season. During these seasons, the soil has higher moisture levels and results in less intensity. Evidence from multiple studies has suggested that vegetation response is generally different in this case with, “reduced germination of certain herbs and potentially altered species composition” (Le Fer and Parker 2005),
Knapp suggests that the, …potential for shifts in the plant community exists when the heat generated by prescribed burning is dissimilar to what would have been experienced with the fire regime that species evolved with. Seeds of species requiring heat to germinate are dependent on receiving enough to break dormancy, but not so much that they are killed.
Wildlife should be taken into consideration when considering most appropriate ways to mitigate negative effects of prescribed burns as well. Avoidance of managed fires in some these sensitive areas should be observed in order to preserve a healthy habitat for wildlife in shrublands. While many species benefit from the result of healthy fires, total destruction of ecosystems drastically alters the potential for survival and can be devastating.
Pictograph of the System Element
Practices should be adapted in order to create prescribed fires that are more attuned to the natural systems in fire ecology. A connection between fires and sustained ecosystems is apparent but the realization of this after decades of complete suppression has led to an approach that has become in some cases too eager to create and manage unnatural fires. Furthermore, with the unseasonal approach that fire management plans have employed in many areas of California, chaparral biomes are suffering the impact of low-intensity fires as well as too frequent fires. This is a problem that can be managed and adapted to create healthier ecosystems with a focus on ensuring prescribed burns are carefully planned and viewed as a fully integrated natural response.
Fernandes, Paulo M., and Hermínio S Botelho. “A review of prescribed burning effectiveness in fire hazard reduction.” International Journal of Wildland Fire, 2003: 117–128.
Hubbard, R.F. Sant age and growth dynamics in chamise chaparral. Master’s Thesis, San Diego: San Diego State University, 1986.
Kapp, Erik E., Becky L. Estes, and Carl N. Skinner. Ecological effects of prescribed fire season: a literature review and synthesis for managers. General Techinical Report, USDA, 2009.
Keeley, Jon E., and Thomas W. McGinnis. “Impact of prescribed fire and other factors on cheatgrass.” International Journal of Wildland Fire, 2007: 96–106.
National Park Service. Fire Management. January 2014. http://www.nps.gov/yose/parkmgmt/firemanagement.htm.
Wagtendonk, Kent van. “Lightning Fire Ignition Patterns in Yosemite National Park.” eorge Wright Society Conference on Parks, Protected Areas, and Cultural Sites. 2011. 364–371.
Vincent Triola. Mon, Mar 01, 2021. Fire Management in California: A Systems Approach to Mitigating Risk Retrieved from https://vincenttriola.com/blogs/ten-years-of-academic-writing/fire-management-in-california-a-systems-approach-to-mitigating-risk