Despite Rhetoric, Study Finds Severe Wildfires NOT Increasing in Western Dry Forests

A new study from Dr. William Baker of the University of Wyoming titled “Are high-severity fires burning at much higher rates recently than historically in dry-forest landscapes of the western USA?“, was published today in the international scientific journal PLOS ONE, and is freely available here.

Below is a portion of the press release:

LARAMIE, Wyo., Sept. 9, 2015 /PRNewswire/ — Severe wildfires are often thought to be increasing, but new research published today in the international science journal PLOS ONE shows that severe fires from 1984-2012 burned at rates that were less frequent than historical rates in dry forests (low-elevation pine and dry mixed-conifer forests) of the western USA overall, and fire severity did not increase during this period.

The study by Dr. William Baker of the University of Wyoming compared records of recent severe fires across 63 million acres of dry forests, about 20% of total conifer forest area in the western USA, with data on severe fires before A.D. 1900 from multiple sources.

“Infrequent severe fires are major ecosystem renewal events that maintain biological diversity, provide essential habitat for wildlife, and diversify forest landscapes so they are more resilient to future disturbances,” said Dr. Baker. “Recent severe fires have not increased because of mis-management of dry forests or unusual fuel buildup, since these fires overall are occurring at lower rates than they did before 1900. These data suggest that federal forest restoration and wildfire programs can be redirected to restore and manage severe fires at historical rates, rather than suppress them.”

Key findings from the new study:

• Rates of severe fires in dry forests from 1984-2012 were within the pre-1900 range, or were less frequent, overall across the western USA and in 42 of 43 smaller analysis regions.

• It would take more than 875 years, at 1984-2012 rates, for severe fires to burn across all dry forests, which is longer than the range of 217-849 years across pre-1900 forests. These forests have ample time to regenerate after severe fires and reach old age before the next severe fire.

• Severe fires are not becoming more frequent in most areas, as a significant upward trend in area burned severely was found in only 3 of 23 dry pine analysis regions and 1 of 20 dry mixed-conifer regions in parts of the Southwest and Rocky Mountains from 1984-2012. Also, the fraction of total fire area that burned severely did not increase overall or in any region.

• Although not yet occurring in most areas, increases in severe fire projected by 2046-2065 could be absorbed in most regions without exceeding pre-1900 rates, but it would be wise to redirect housing and infrastructure into safer settings and reduce fuels near them.

Pre-1900 rates of severe fires were calculated from land-survey records across 4 million acres of dry forests in Arizona, California, Colorado, and Oregon, and analysis of government Forest Inventory and Analysis records and early aerial photography. These reconstructions are corroborated by paleo-charcoal records at seven sites in Arizona, Idaho, New Mexico, and Oregon.

Dr. William L. Baker is an Emeritus Professor in the Program in Ecology/Department of Geography at the University of Wyoming, Laramie, Wyoming. He is the author of over 120 peer-reviewed scientific publications, and also contributed to the new book, The Ecological Importance of Mixed-Severity Fires: Nature’s Phoenix, which features the work of 27 scientists from around the world.

12 Comments

  1. Who are these “some people” who see wildfire as the “sole solution?” I’ve never met any of them. Most people I know support prescribed fire, less, aggressive fire suppression, storm-proofing the road system, reduced livestock grazing, weed removal, low-impact recreation, cutting small encroaching trees, etc.

    • I see them all the time, admonishing people that we should “let nature take its course” and “fires are natural and beneficial”, as well as “Let those fires burn”. You really don’t have to look very hard to find those types of comments. It just shows how many people just aren’t “progressive” enough to accept science-based forest management, in favor of having an imaginary being manage it for them.

      • Yeah Matt…the six paragraphs of “limitations” that didn’t make the “key points”.

        “These trend analyses and fire rotations have some inherent limitations. The Landfire Biophysical Settings maps aim to predict historical vegetation predating the trend analyses, but could still exclude non-forested area that was burned in dry forests at high-severity early in the 1984–2012 period, leading to false upward trends [17]. Fully reliable trend analysis across large land areas requires a nationally consistent and detailed vegetation map based on imagery that predates MTBS data coverage in 1984. Because I cannot definitely exclude a possible false upward trend, the four significant upward trends, and other trends close to significant, are particularly clouded by this uncertainty.

        The MTBS program has provided a remarkable dataset, but 29 years is still a limitation. Estimated fire rotations are hundreds of years, and nearly a full fire rotation of data is needed to accurately estimate the rotation [72]. Trends over the 29-year period hinge on the timing and magnitude of only a few major fire peaks (Fig 4). Thus, estimated rotations are valid for the 29-year period, but subject to change as more data accrue. Data from 25.7 million ha temper this concern, but fire can be synchronized over large land areas by teleconnections with periods > 29 years [74], thus 29 years are also insufficient from the standpoint of potential climate cycles. Also, high-severity fire rotations may not be homogeneous across landscapes; high-severity fire could be favored in certain biophysical settings and dis-favored in others (e.g., 5, 39). Thus, recent fire-rotation estimates in this study represent averages for analysis regions that warrant use with caution in smaller subareas of these regions.

        MTBS data, which are for fires generally > 400 ha in area, may or may not contain 95% of total burned area, as estimated by the MTBS program. One estimate for part of the Sierra Nevada was 92.8% [17]. If the actual percentage was not 95%, then fire rotations could be somewhat too low or too high. Some caution is thus warranted from this standpoint in the use of estimates, although this concern is buffered by the use of a large historical range for comparison.

        The GLO-based reconstructions may be one of the few available ways to reconstruct historical severe fires in the spatially extensive manner that is needed to provide data about fire rotation, patch size, and other attributes. These reconstructions are calibrated, validated, and corroborated [27–29, 40, 56, 65], but would benefit from additional calibration and validation to improve the linkage of forest structure with fire severity and to help estimate the precision of estimates of fire rotation. Precision is not known very well, except that there is calibration and validation with tree-ring reconstructions, there is corroboration by early historical records and maps, and there is congruence between the findings of GLO-based, aerial-photo-based, and paleo-fire based methods (Table 1). GLO-based methods are typically based on 100–140 year periods before the surveys, thus less than a full historical fire rotation. These methods also cannot provide fine detail about high-severity fire patterns, since they are based on data pooled across 259–1,036-ha areas. It would be beneficial to combine GLO-based methods with tree-ring reconstructions and compare paleo-fire and GLO-based reconstructions in the same areas. More landscape-scale fire history is needed and may lead to further refinements in understanding of rates and patterns of historical high-severity fire.

        The projections are first approximations. The Yue et al. [42] projections are not specific to dry forests or high-severity fires, are not based on dynamic vegetation models, and use only a moderate emissions scenario. Potential vegetation changes may be large [73], particularly for P. ponderosa in the Rocky Mountains and Southwest [75]. Although the projections here may appear simplistic, the Yue et al. projections are sophisticated. It is just that their direct transfer here to dry forests provides only first approximations and context for thinking about future fire in dry forests until projections specific to dry forests appear. The projections also assume similar continuing fire management and no non-linear responses. For example, a landscape trap [76] could arise if high-severity fire created more fire-prone landscapes that then burn increasingly at high severity, possibly increasing area burned at high severity beyond projections.”

            • Sorry you hide your identify only to rip people down. What science on this topic do you find to be credible (i.e. non low brow?) Come out of the shadows and we’ll host a debate between you and Dr. William Baker, if you like.

            • Matt and I may disagree about how policy becomes politics but PLOS has a unblemished record except for anecdotal evidence of confirmation bias in one paper.

              There regional exceptions were fuels have been accumulating but 2015 really is a nearly average wildfire year compared to mid-20th century seasons.

      • I just kinda wonder how much such a study is really worth. Is it supposed to make us think that what we are seeing now is really “normal”, and therefore, should be embraced? Does it talk about fuels buildups? Does it talk about species compositions? Does it talk about the current reality of today’s overstocked forests. Finally, the big one is, are suffering humans going to care that this is “normal” for an ancient America?

  2. Matt, you jumped to pump this Baker guy several years ago. That paper didn’t go over real well with Thomas Swetnam, if I remember right.
    The yawning mistake that jumps at me right now is the cutoff at 1900 for fire patterns. Firefighting wasn’t even a factor, there was no fire policy at the time, no significant suppression.
    This is like having Tim Ingalsbee PhD. Sorry.

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