We Have a Fire Deficit – Watts Up With That?

Guest Essay by Kip Hansen — 12 February 2025  — 750 words

A new study published in Nature Communications on 10 February 2025,  “A fire deficit persists across diverse North American forests despite recent increases in area burned”, Parks et al. (2025), states:

“…despite increasing area burned in recent decades,… a widespread fire deficit persists across a range of forest types and recent years with exceptionally high area burned are not unprecedented when considering the multi-century perspective offered by fire-scarred trees.”

Let’s review that one more time:

“Wildland fire was common and widespread across many forests and woodlands in North America prior to the late 19th and early 20th centuries. In subsequent decades, fire exclusion—the practice of preventing and suppressing nearly all wildland fires—occurred as the result of the disruption of traditional burning, livestock grazing, and active suppression of human- and lightning-ignited fires. As a consequence, average annual area burned since the late 19th and early- to mid-20th centuries is generally less than that experienced under historical fire regimes across many North American forests, resulting in a widespread 20th century ‘fire deficit’ relative to earlier time periods.”

Note:  The authors use “the term ‘traditional burning’ to encompass both Indigenous fire stewardship and post-colonization traditions of burning that were widely adopted in the eastern United States.”  

Here’s their findings in one simple table:

[ click here for full sized image in new tab/window ]

The ecoregions are shown in this map:

The table shows that only one single region, the Taiga & Hudson Plain, in Northern Canada, had had more fires in the 1984-2022 study interval than would be predicted based on the burn scar data prior to 1880.

The study gives a conceptual explanation of the causes and effects as:

[ This figure has a rather long explanation.  See it by viewing the image in its full size here. ]

The study summarizes its results as:

“Overall, contemporary fires (1984–2022) burned NAFSN [North American tree-ring fire-scar network]  sites less frequently than fires  during the historical reference period (pre-1880), indicating that a substantial fire deficit persists and is still accumulating across many forests and woodlands across the United States and Canada (Table 1). Based on the historical fire-scar record, NAFSN sites collectively would be expected to have burned 4346 times from 1984– 2022, yet they burned 989 times, or only 23% of what would be expected under the historical fire regime.”

The mass media would rather focus on studies such as “U.S. fires became larger, more frequent, and more widespread in the 2000s” ,  Iglesias et al. (2022), found in Science Advances.  Iglesias et al.  only studied fires since 1984.   Looking at Parks et al. (2025) Figure 4 above, we see that time period as the raging fires fed by 100 years of fire deficit.

Bottom Lines:

1.  Claims made repeatedly in the mainstream media that wildfires are getting more common and more severe are not supported by the findings of this study. 

2.  When looked at over the last 200 years, we have a severe fire deficit, not an excess.   In the ecoregions studied (U.S. and Canada), fires have been far less frequent and the result is a fire deficit.   This is true of all the ecoregions except the most northern parts of Canada.

3.   The long-term fire deficit, unburned wildlands,  sets up wildlands for more fiercely burning fires that consume all the extra fuel left by the lack of fire.

4.  Parks et al. (2025) has a very interesting discussion section that covers possible long-term effects and regime shifts that might result from the century of fire suppression.

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Author’s Comment:

Fire is always a news worthy topic.  Humans seem, even in our technologically advanced era, to be fascinated by fire while at the same time, depressingly ignorant of its causes and effects.   This is seen all over the United States in the building of highly flammable homes in our forests and, as in Los Angeles, on indefensible hillsides covered with incendiary  brush and grasses. 

With that in mind, the Washington Post ran a very interesting story on “What the homes that survived the L.A. fires reveal”. 

It is no mystery why some recent fires have been particular hot.  The basics of fire have not changed:  fuel + oxygen + heat = fire.   More fuel with adequate oxygen makes hotter fires. 

Studying short-term data sets for long-term phenomena is not good science. 

After uploading the above essay, I found that Roger Pielke Jr. has picked up on the same study. His piece is The North American Fire Deficit.

Thanks for reading.

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