The Impact of humans and climate on wildfires in California

Background/Question/Methods

Number of wildfires and area burned were studied in California on landscapes protected by the California Division of Forestry and Fire Protection (Cal Fire, formerly CDF) over the 49 year period from 1960 – 2008.  These areas include forests, woodlands, shrublands and grasslands outside the national parks and forests in the state. 
Results/Conclusions

During the period of study the number of fires peaked in the early 1980s and have declined since then, however the amount of area burned has increased, particularly in the last 10 years. There was a significant negative relationship between area burned and latitude, distance from the coast and elevation. Causes of fires varied greatly across the state. There was a negative relationship between number of human caused wildfires and latitude and distance from the coast, whereas there was a positive relationship between number of lightning caused wildfires and latitude and distance from the coast. Statewide, the only significant correlation with climate was the severity of drought during autumn, which suggests the length of the annual drought is an important factor determining fire activity in the state.