Modern fires are most often started by humans, either accidentally or on purpose, but fires have been occuring periodically since the end of the last Ice Age. For example, it is estimated that the Santa Monica Mountains (Malibu area) have burned 500 times in the past 11,500 years. [1] That is one fire every 20 to 25 years. Natural fires would have been started by lightning in the high mountains, been pushed west by strong, dry Santa Ana winds, and progressed unobstructed to the Pacific Ocean. Also there is evidence suggesting that some Native Americans may have started fires to promote the growth of certain food plants and in all likelihood they would have accidentally started fires also.

The climate and some features of the plants themselves make conditions right for fire virtually every year. Winter and spring rains averaging from 15 to 25 inches produce abundant growth. By May or June, the rainy season is over. Summer brings days of relentless sunshine and temperatures in the 90s and higher. Annuals dry up and perennials go dormant. Flammable oils on the foliage of some shrubs keeps them functioning, but under enough drought stress, they will shed some leaves. Then Santa Ana winds start in the fall. This is a weather system that lasts for a few days at a time and where dry air from the desert blows to the west. Wind gusts can reach hurricane force, the humidity drops to single digits, and the temperature is usually hot. The weather along with all of the dead plant matter make a fire nearly inevitable.

ImageImageWe usually see fire as a destructive force, but it can be a life-giving force. It serves an important purpose. Mature plant communities are full of dead leaves and branches that are tying up nutrients. In many climates, nutrients and minerals are recycled though decay. However, decay progresses very slowly in the dry California climate. Fire quickly returns essential nutrients to the soil. Fire also cleans out diseased and insect-infested plant matter.

The mature chapparal community is dominated by a relatively small number of species. Fire opens up the canopy and allows the sunlight to reach the soil. Competition for water is greatly reduced. Plants that had not been seen in years or decades suddenly appear. The number of species explodes. Plants with telltale names like fire hearts (Dicentra ochroleuca) and fire poppy (Papaver californicum) are only seen within a few years of a fire. Those in the know seek out burned areas to view infrequent species like these.

Fire is a very severe force. How can anything survive it? In fire-prone ecosystems, species have several strategies for survival.

ImageRoot-crown sprouting: Some species will resprout from the base after a fire. This is usually the first kind of recovery seen. The California walnut (Juglans californica) in this picture shows two years' growth since the last fire.

ImageSurviving as seed: Some plants will be completely killed in a fire but the species comes back due to the seeds in the ground. Most annuals have already finished their life cycle by the time fire season starts, but their seeds survive the fire. Some species will only sprout after a fire or they germinate more efficiently after a fire. The fire weakens the seed coat so that water can penetrate and the seed can germinate. These kinds of plants are sometimes called fire-followers. Stinging lupine (Lupinus hirsutissimus) at the right is a fire-follower.

ImageGoing underground: The geophytes are dormant during fire season. The soil above protects the bulb or tuber from excess heat. The photo shows an abundance of Catalina mariposa lilies (Calochortus catalinae) the spring following a fire.

ImageSucculence: The high moisture content in some plants protects them. The leaves of this yucca (Hesperoyucca whipplei) have been burned off, but the succulent core remained alive and is sprouting new leaves and even a flower stalk. Though not a true succulent, the coast live oak (Quercus agrifolia) can be protected by the moisture in its bark.

ImageAvoidance: If you can't take the heat, stay out of the chaparral. Chaparral and forest fires can be very hot. Grass fires are less hot. Plants with less fire resistance are relegated to grasslands and other areas where fires are less hot. This valley oak (Quercus lobata) has survived for hundreds of years in a grassland.

The next time you see a wildfire on television, you may be concerned for the firefighters and residents, but you don't need to worry about the plants. They'll survive and thrive. They've been doing it for thousands of years. Beauty will rise out of the ashes.


[1] McAuley, Milt, Wildflowers of the Santa Monica Mountains, Canyon Publishing Company, 1996.