Fire Mosaics in Southern California and Northern Baja California

In spite of suppression efforts, severe wildfires burn large areas of southern California grassland, coastal sage scrub, and chaparral. Such large burns may not have been characteristic prior to the initiation of fire suppression more than 70 years ago. To compare controlled with uncontrolled areas, wildfires of southern California and adjacent northern Baja California were evaluated for the period 1972 to 1980 from Landsat imagery. Fire size and location, vegetation, year, and season were recorded. It was found that suppression has divergent effects on different plant communities depending on successional processes, growth rates, fuel accumulation, decomposition rates, and length of flammability cycles. These variables establish feedback between the course of active fires, fire history, spatial configuration of flammable vegetation, and fire size. Suppression has minimal impact in coastal sage scrub and grassland. Fire control in chaparral reduces the number of fires, not burned hectarage; fires consequently increase in size, spread rate, and intensity and become uncontrollable in severe weather conditions. The Baja California chaparral fire regime may serve as a model for prescribed burning in southern California.