Wildfires: Find out how and why they’re getting bigger and more frequent

Mike Archer included this link in his Wildfire News of the Day newsletter today:

Wildfires: Find out how and why they’re getting bigger and more frequent


It’s also in The Missoulian.

The first thing that jumped out at me is heat their nice looking charts are for “Continental U.S. wildfires over 1,000 acres, 1984-2019.” Why 1984? NIFC has data back to 1960, and other sources go back much farther.

6 thoughts on “Wildfires: Find out how and why they’re getting bigger and more frequent”

  1. I was thinking about the history of New Perspectives and found this piece by Doug MacCleery, which had this graph. Of course, this is acres burned and not wildfire by size.

  2. First, the temporal scale is suspect. Fire varies on long scales. Looking only at wildfire data since 1984 does not allow one to draw conclusions about the larger-scale patterns.

    Second, the conclusion is not supported by a number of different attempts to decipher this noisy wildfire data set. Most studies are unable to conclude that fires are getting worse.

    Brendan P. Murphy, Larissa L. Yocom, Patrick Belmont. 2018. Beyond the 1984 perspective: narrow focus on modern wildfire trends underestimates future risks to water security. Earth’s Future, 2018; DOI: 10.1029/ 2018EF001006 https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2018EF001006 (“Compiling several datasets, we illustrate a comprehensive history of western wildfire, demonstrate that the majority of western settlement occurred during an artificially and anomalously low period of wildfire in the 20th century, … A crucial first step toward realigning public perspectives will require scientists and journalists to present recent increases in wildfire area within the context and scale of longerterm trends. … A review of Science, Nature, and PNAS reveals that 77% of wildfire-related articles published about the western U.S. since 2000 (n=52) only address fire trends from the past few decades. In many of these studies, as well as in principal wildfire databases (Eidenshink et al., 2007; NIFC, 2017), ca. 1984 is frequently the first year presented, because this marks the beginning of consistent, satellite-derived records (Short, 2015). Wildfire area has rapidly increased since 1984, as ecosystems realize their potential to burn in an era of lengthening fire seasons and warming temperatures (Abatzoglou & Williams, 2016). However, this “1984 perspective” of wildfire is problematic. First and foremost, the 1980s represent the end of an anomalously low period for wildfire during the mid-20th century, and western U.S. landscapes remain well below historical wildfire activity (Barrett, et al., 1997; Leenhouts, 1998; Stephens et al., 2007; Littell et al., 2009; Swetnam et al., 2016). … Historical reconstructions of annual area burned demonstrate that wildfire area in the pre-settlement western U.S. was many times greater than the supposed ‘record highs’ of today (Barrett, et al., 1997; Leenhouts, 1998; Stephens et al., 2007) (Fig. 1A&C). Borne out by hundreds of fire-history studies, research consistently shows that dry western forests frequently burned by wildfire over the past few centuries (Falk et al., 2010). Although wildfire activity naturally oscillates over millennial timescales (Marlon et al., 2012), area burned across the West began to rapidly decline in the late 19th century with the introduction of railroads and livestock (Swetnam et al., 2016). This was especially true in dry forest ecosystems, where livestock ate the fine fuel necessary to carry widespread surface fires. By the mid-20th century (ca. 1950s to mid-1980s), the area burning annually across all western ecosystems had plummeted from 7-18 Mha to less than 0.5 Mha due to fire suppression activities (Leenhouts, 1998; Littell et al., 2009) (Figure 1A). This West-wide decline in area burned is corroborated by subregional records (Figure 1C) and is consistent with the 20th century “fire deficit” observed in fire scar and charcoal influx records Marlon et al., 2012). … The annual area burned, as well as burn severity, are projected to continue increasing across the western U.S. through the 21st century due to climate change and, in some ecosystems, excess fuel loading from fire suppression (Brown et al., 2004; Westerling et al., 2011; Hawbaker & Zhu, 2012; Abatzoglou & Williams, 2016; Abatzoglou et al., 2017).”)

    Schwind, B. (compiler). 2008. MTBS: Monitoring Trends in Burn Severity: Report on the PNW & PSW Fires — 1984 to 2005. https://web.archive.org/web/20130214220819/http://www.mtbs.gov/reports/MTBS_pnw-psw_final.pdf (“MTBS data does not support the assumption that wildfires [in the PNW] are burning more severely in recent years. … The majority of area burned falls within the unburned to low severity range, with relatively low annual variation in these severity classes. The high and moderate severity classes show higher relative variation between years, suggesting that these classes may be most influenced by variation in climate, weather, and seasonal fuel conditions.”)

    Ray Davis et al 2015. RMP Revisions for Western Oregon BLM DEIS. Appendix D – Modeling Wildfires and Fire Severity. http://www.blm.gov/or/plans/rmpswesternoregon/files/draft/RMP_EIS_Volume3_appd.pdf. (“… examined the MTBS data for any obvious temporal trends in wildfire severity [within the range of the spotted owl], but did not detect a strong signal (Figure D-6). Over the course of 25 years, there appears to be a slight increase in the percentage of area burned by low and moderate severity wildfire, and a slight decrease in the percent of area burned in high severity wildfire, although these trends are not statistically significant. …”)

    Alisa Keyser and Anthony Westerling, 2017. Climate drives inter-annual variability in probability of high severity fire occurrence in the western United States, Environmental Research Letters. Accepted Manuscript online 4 April 2017 https://doi.org/10.1088/1748-9326/aa6b10. (“We tested trends for WUS [western United States], each state, and each month. We found no significant trend in WUS high severity fire occurrence over 1984-2014, except for Colorado (table S1). While some studies have shown increasing fire season length, we saw no significant increase in high severity fire occurrence by month, May through October (figure S1). We found no correlation between fraction of high severity fire and total fire size, meaning increasing large fires does not necessarily increase fractional high severity fire area.”)

  3. Someone should put up a graph of the money spent during the same period.

    You cannot compare the amount of acreage burned historically to try to justify the fires taking place in our forests today. Our forests, forest ownership, and urban interface are very different now.
    People should not try to justify spending hundreds of millions of dollars burning up the last of our stands of “ancient forests”.


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