1. The natural fire return interval for chaparral is 30 to 150 years plus (today, there are more fires than the chaparral ecosystem can tolerate - see #2 below).
2. Fires more than once every 20 years, or during the cool season by prescribed fire, can eliminate chaparral by first reducing its biodiversity through the loss of fire-sensitive species, then by converting it to non-native weedlands (called type-conversion).
3. Being dense, impenetrable, and prone to infrequent, huge wildfires is the natural condition of chaparral (it's not the fault of past fire suppression, "unnatural" amounts of vegetation, or environmental laws).
4. The age and density of chaparral has little to do with the occurrence of such large fires (large fires in southern California shrublands are driven primarily by weather, such as Santa Ana winds and drought).
5. Chaparral has a high-intensity, crown fire regime, meaning when a fire burns it burns everything, frequently leaving behind an ashen landscape. This is in contrast to a "surface fire regime" found in dry Ponderosa pine forests in the American Southwest. Although there can be high-intensity patches where all the trees burn (high-severity), these fires typically burn at low-intensity, consuming mostly just the understory and leaving the larger trees unharmed except for occasssional fire scars.
Fire and Chaparral - it's probably not what you think
Contrary to what you may have heard, fire is causing severe damage to the chaparral ecosystem today. This is because there are too many fires due to human activity. This increase in fire frequency is threatenting the chaparral with type-conversion, whereby native species are replaced by highly flammable, non-native weeds.