Large California wildfires: 2020 fires in historical context

Jon E Keeley,Alexandra D Syphard

doi:10.1186/s42408-021-00110-7

Jon E Keeley, Alexandra D Syphard

Open Access

https://doi.org/10.1186/s42408-021-00110-7

Copy DOI

Abstract

BackgroundCalifornia in the year 2020 experienced a record breaking number of large fires. Here, we place this and other recent years in a historical context by examining records of large fire events in the state back to 1860. Since drought is commonly associated with large fire events, we investigated the relationship of large fire events to droughts over this 160 years period.ResultsThis study shows that extreme fire events such as seen in 2020 are not unknown historically, and what stands out as distinctly new is the increased number of large fires (defined here as > 10,000 ha) in the last couple years, most prominently in 2020. Nevertheless, there have been other periods with even greater numbers of large fires, e.g., 1929 had the second greatest number of large fires. In fact, the 1920’s decade stands out as one with many large fires.ConclusionsIn the last decade, there have been several years with exceptionally large fires. Earlier records show fires of similar size in the nineteenth and early twentieth century. Lengthy droughts, as measured by the Palmer Drought Severity Index (PDSI), were associated with the peaks in large fires in both the 1920s and the early twenty-first century.

Highlights

The western US has a long history of large wildfires, and there is evidence that these were not uncommon on preEuroAmerican landscapes (Keane et al 2008; Baker 2014; Lombardo et al 2009)
Since some of the fires came from data reported in newspapers, not a typical scientific data base, we did an initial investigation comparing Fire and Resource Assessment Program (FRAP) reported fire size with size reported in newspaper reports
This was not an exhaustive study since FRAP data before 1950 presents relatively few fires by date or fire name making it difficult to match up fires with newspaper reports; we found half a dozen potential comparisons (Table 1)

Summary

Introduction

The western US has a long history of large wildfires, and there is evidence that these were not uncommon on preEuroAmerican landscapes (Keane et al 2008; Baker 2014; Lombardo et al 2009). While large fires are known in the historical record, in the first few decades of the twenty-first century, the pace of these events has greatly accelerated (Keeley and Syphard 2019). California in the year 2020 experienced a record breaking number of large fires. We place this and other recent years in a historical context by examining records of large fire events in the state back to 1860. Results: This study shows that extreme fire events such as seen in 2020 are not unknown historically, and what stands out as distinctly new is the increased number of large fires (defined here as > 10,000 ha) in the last couple years, most prominently in 2020. As measured by the Palmer Drought Severity Index (PDSI), were associated with the peaks in large fires in both the 1920s and the early twentyfirst century

Methods

Results

Discussion

Conclusion