San Diego Natural History Museum--Your Nature Connection[San Diego County Bird Atlas Project]

Viejas Fire—What's the Aftermath?

Santa Ana winds and a carelessly tossed cigarette combined to usher in the new year with a huge inferno—the Viejas Fire. The extremely dry vegetation and winds up to 90 miles per hour fueled a raging fire that traveled more than 10 miles and consumed 10,000 acres in 24 hours. Now that the fire is out, what will happen to the burned area?

Wildfires are natural events in southern California, and the native vegetation will grow back quickly. For many plant species, fire is required to break their seeds' dormancy and allow germination. Most annual plants respond vigorously to fire, and the increased minerals and nutrients in the ash often allow them to grow to extra-large sizes. There are dozens of wildflowers that are "fire-followers," especially in the poppy and waterleaf families. Shrubs and trees may grow back from seed after fire. Many woody species also have the ability to resprout from stems or burls. In most cases, vegetative cover is fully re-established after 3 to 5 years (no additional erosion expected). Within 10 to 15 years the vegetation structure is similar to, though usually less dense than, the structure before the fire. Chaparral vegetation usually will not burn again until it is 25 to 30 years old. Coastal sage scrub, however, may re-burn after only a few years, before shrubs have become large enough to survive another fire. This is a major concern, as too-frequent fire can rapidly convert coastal sage scrub to non-native grassland, particularly at drier inland sites. Such a conversion can be seen over large areas of the San Jacinto basin in western Riverside County. Next to development, fire is likely to emerge as the greatest threat to coastal sage scrub.

Adaptations for recovery after fire are not limited to chaparral species. Even species that may burn less often, such as trees in riparian areas, are able to recover from fires. Coast live oak trees have very thick bark and are extremely resilient. Even trees that have been severely burned are usually able to resprout from their crowns. Most other oak species that grow as trees (black oak, canyon live oak, Engelmann oak) are usually "top-killed" by fire but will resprout from the base. Sycamore, willow, and cottonwood trees resprout vigorously from their roots.

Costa's Hummingbird

Costa's Hummingbird

What about the animals? Hawks, ravens, and vultures congregate to feed on animals that were burned in the fire. In a fast-moving fire, rabbits, woodrats, and other animals may become confused and run into the flames. At the Viejas fire, we noted several birds that were killed or injured, including a Golden-crowned Sparrow and a Wrentit. Fires may reduce animal populations substantially for one to several years depending on the species' reproductive rate. In the first few years after the fire, the abundant flowers, new growth, and resprouts are highly nutritious and very attractive to Costa's Hummingbirds, deer, and quail. The effect on Costa's Hummingbird is especially dramatic because some of the plants that proliferate after fires, like the sticky nama or poodle-dog bush (Turricula parryi), Penstemon spectabilis, and woolly blue-curls (Trichostema lanatum) attract feeding and nesting Costa's Hummingbirds in numbers far higher than in mature chaparral. Recently burned areas may be favored by birds that prefer less dense vegetation, such as the Sage Sparrow and Rufous-crowned Sparrow. The seeds of fire-following fiddleneck and popcornflower plants are a major food for Lawrence's Goldfinch. Often Lazuli Buntings colonize recovering chaparral in large numbers. Although bird densities in burned areas are typically higher than those in older chaparral, nesting success may be lower, as nests are more easily detected by predators.

So, what are the land-management agencies doing to prepare for future fires? The Forest Service and other agencies have several tools:

  1. Prescribed burning is used to develop a mosaic of age classes in vegetation, to help limit future fires to smaller sizes. For the Cleveland National Forest, the current emphasis in forested areas is on underburns, which are used to thin trees and understory shrubs. This type of burning reduces the "ladder fuels" that allow fires to climb into the top of the trees. Thinned forest stands will be much less prone to crown fires in which the top of the tree is consumed, killing the tree. The timing of prescribed burns is constrained by the vegetation type, fuel moisture, air-quality issues, and firefighters' availability. Some shrub species, such as chamise and ceanothus, may be killed if they burn in spring, so fires are planned to avoid negative effects on these species. Fire managers also plan prescribed burns to avoid the breeding or nesting season for mammals and birds. The Cleveland National Forest usually burns forested areas in the fall or winter, chaparral in winter or early spring. It is best to burn during times when natural fires might occur. In San Diego County, this is nearly all year! When we are officially in the "emergency fire season," usually July to October or November, prescribed burning is usually avoided.
  2. Fuelbreaks are constructed to prevent the spread of fire from natural lands to residential areas (and vice versa). Fuelbreaks are areas where shrubs are cleared so that there is defensible space to use for backfiring or firefighting. The fuelbreaks are maintained by burning them every few years to keep them free of woody vegetation. They are usually burned in June. One recent example of how fuelbreaks help to manage wildfire was the Warner Fire (1995), near Warner Springs, where the fire advanced to existing fuelbreaks, then went out after covering a relatively modest 3000 acres.
  3. Education about fire safety is one of our most important tools. Fire-prevention officers work with homeowners to ensure that buffer zones around homes are maintained. They also do interviews with the media, prepare news releases, and distribute educational material at public events.
  4. Research. The local research office of the Forest Service, the Pacific Southwest Research station in Riverside, is dedicated to the study of fire ecology. In addition, the National Interagency Fire Center in Boise, Idaho, has compiled extensive information on how different plant and animal species respond to fire. This is available on the Internet at www.fs.fed.us/database/feis

For any fire over 300 acres, the national forests prepare detailed reports analyzing the effect of the fire and expected recovery of plants and wildlife. These are summarized in "Burned Area Emergency Rehabilitation reports." Examples of recent reports are posted on the Cleveland National Forest website.

The website currently features a fire-history map for San Diego County. If you would like to see some recent fires and their recovery, the Warner Fire (1995) may be seen from Hwy. 79/Palomar Divide Road near Warner Springs. The La Jolla Fire (1999) may be viewed from Hwy 76 or East Grade Road near Lake Henshaw. The Viejas Fire (2000) is visible from I-8 near Viejas Casino and along most of Japatul and Dehesa roads near Alpine.

Because fires are a fundamental feature of our region's ecology, please don't neglect burned areas when you're in the field for the San Diego County Bird Atlas. With the habitat more open and fire-following plants and birds flourishing, you are likely to find recovering burned chaparral more interesting and productive birding than mature chaparral!

Map of Viejas Fire

Shaded area burned in the Viejas Fire, January 2001. Mapping by Corey Ferguson.

-- Kirsten Winter

birdatlas@sdnhm.org

Spring 2001 Wrenderings | Wrenderings Archive | Bird Atlas Introduction