Spatiotemporal analysis of wildfires in California from 2000 to 2019

The environmental pollution, property losses and casualties caused by
wildfires in California are getting worse by the year. To minimize the
interference of wildfires on economic and social development, and
formulate targeted mitigation strategies, it is imperative to understand
the scale and extent of previous wildfire occurrences. In this study, we
first investigated the temporal distributions of past wildfires in
California divided by size and causes and analyzed the changes observed in
the past two decades against the last century. The trend of wildfires in
different time scales (yearly and monthly), as well as the distribution of
wildfires across different spatial scales (administrative units, climate
divisions in California from 2000 to 2019) were also studied. Furthermore,
to extract the significant variables on the risk of wildfire occurrence,
multivariate analyses of environmental and human-related variables with
wildfire densities were carried out. The results show that the wildfire
density distribution of the burned area in California conforms to the
characteristics of the Pareto distribution. Over the past two decades, the
frequency of small (< 500 acres), human-caused wildfires has
increased most rapidly, and they are widely distributed in central and
western California. The wildfire season has lengthened and the peak months
have been advanced from August to July. In terms of the variables related
to the risk of wildfire occurrence, the temperature, vapor pressure
deficit, grass cover, and the distance to roads are crucial. This study
reveals the relationship between environmental and social background
conditions and the spatial-temporal distribution of wildfires, which can
provide a reference for wildfire management, the formulation of future
targeted wildfire emergency plans, and the planning of future land use in
California.