The Rim Fire one year later: a natural experiment in fire ecology and management

The enormous conflagration known as the Rim Fire was in full fury, raging swiftly from crown to crown among mature trees, when it entered the backcountry of Yosemite National Park in California’s Sierra Nevada in late August 2013. But inside the park, the battle began to turn, enacting a case study in the way management decisions and drought can combine to fuel large, severe fires.

“When the Rim Fire hit the park, it eventually encountered lands where fire had been used as a management tool, rather than immediately suppressed,” said Hugh Safford, a regional ecologist for the U.S. Forest Service based out of Vallejo, Cal. “When the Rim Fire hit these areas, the amount and continuity of forest fuel became a limiting factor,” he said. “There just wasn’t enough fuel in the system to keep it going.”

Safford will lead a group of visiting ecologists on a two-day excursion into the Rim Fire’s path this August during the Ecological Society of America’s 99th Annual Meeting to view the effects of the fire on adjacent landscapes that have been managed very differently over the last century.

Fire ecology is a hot topic at this year’s meeting, which will bring 3,500 environmental scientists to Sacramento on August 10-15 to discuss the most recent advances in ecological research, education, and policy.

Day one of the field trip will take visitors to sites in the Stanislaus National Forest, and day two to the National Park.

“The minute you leave the park, you’re on lands that get used by a lot of people for a lot of things,” Safford said. “The Forest Service is dealing with places that have had a lot of human impact and occupants.”

The Rim Fire: a natural experiment


The progression of the Rim Fire from  August 19 and September 2, 2013, as reported by fire managers. <i>Credit, Robert Simmon/ <a href="">NASA Earth Observatory</a></i>.

The progression of the Rim Fire from August 19 and September 2, 2013, as reported by fire managers. Credit, Robert Simmon/ NASA Earth Observatory.

The Rim Fire is in a sense a natural experiment. Yosemite, set aside in 1864, is mostly old growth forest, in which lightning-ignited fires have often been allowed to burn since the 1970s. The National Forest is a working landscape that includes private lands, major highways, dams, power lines, and communities, which the Forest Service protects by suppressing wildfire.

“I’m not suggesting one’s right and one’s wrong, but it presents an interesting contrast,” Safford said, “It’s a good case study to look at the effects of large, severe fires on watersheds subject to different management regimes.”

The fir, cedar, and pine forests of the high Sierra are adapted to frequent fires ignited by lightning. Fire scars on older trees, including the 2000-year-old giant sequoias record a history of low intensity fires recurring every 10 to 20 years. Fires that burned at low intensity through the understory tended to kill few of the mature trees, on the order of 5 to 10 percent. Recent studies have found that wildfires in the mixed conifer forests of the Sierra often run out of fuel and go out when they encounter sections of forest that have already burned within the last decade.

Though it smoldered on into October, by September 3rd, 2013, the Forest Service was reporting that the Rim Fire was 70 percent contained. Most of the acreage burned in the first week. The blaze that began as an alarming, out-of-control monster became just another big fire that managers were using to do ecological work.

Ignited by a hunter’s illegal campfire near the Rim of the World Vista in Stanislaus National Forest on August 17th, the fire ultimately burned for three months, consuming 257,314 acres of trees and $127 million taxpayer dollars. Smoke from the fire prompted air quality warnings from the Bay Area to Reno, Nev. It was the largest recorded fire in the Sierra Nevada.

A trend toward mega-fires

Rim Fire, California 2013. Mike McMillan, USFS.

Fire Line. The Rim Fire blazes in tree crowns of the Stanislaus National Forest, California, in late August, 2013. Credit, Mike McMillan/ U.S. Forest Service.

In the past few decades, ecologists have noted a trend toward intense “mega-fires” in the mountain forests of the western states. Recent record-breaking fires in Arizona and New Mexico join the 2013 Rim Fire, the 250,000-acre Carlton Complex fire currently burning in eastern Washington State, and the even larger Buzzard Complex fire in Oregon.

According to Safford, increased fuel on National Forest lands resulting from the long-term lack of fire is one of the principal drivers of recent increases in the size and severity of wildfires, trends which appear to be absent in the National Parks.

“The Rim Fire is not random occurrence. It’s part of a trend in big fires, and a real wake up call,” Scott Stephens agreed. Stephens, a professor at the University of California, Berkeley, authored a recent review on the characteristics and challenges of mega-fires with fellow fire specialists from Australia, Canada, Spain, and China, as well as the western U.S. in the March 2014 issue of Frontiers in Ecology and the Environment.

Large fires are a problem facing many of the world’s temperate and boreal forests. As was the case with the Rim Fire, mega-fires are often driven by a combination of drought, heat, wind, fuel from fire suppression, budget cuts, and encroaching development, Stephens said.

These big fires are more expensive to contain and to recover from than the more frequent but less destructive fires that used to characterize the Sierra’s mixed conifer forests, and they are dangerous for firefighters. They char enormous swaths of land, leaving large areas of up to 30,000 acres with no mature trees to seed a new generation.

“Most of the trees died in the Rim Fire. Not just the little guys. We’re looking at multiple patches of high severity fire that are of thousands of acres in size,” said Safford. “Where are the seeds going to come from? The landscape will be dominated by brush for a long time.”

Prelude to a habitat regime change

Very large, intense fires can take out entire habitat ranges, and, in combination with the pressures of land use change and development, leave nowhere for animals to retreat and await regrowth (while at the same time benefitting species that thrive in snag fields). Forest is slow to return, topsoil erodes, and quick-spreading opportunistic exotics capitalize on the disturbance.

In concert with warming climate, which is increasing water stress on forest species, there is potential for a permanent change in habitat type, from forest to brush or to grassland.

“After severe fire, mixed conifer forests in the Sierra Nevada are replaced by chaparral stands. When chaparral burns, it burns hot, and with the increasing frequencies of severe fire that are predicted, we expect to see progressively more forest converting to brush and not returning. With continued high fire frequencies, brush can convert to grassland as well,” said Safford. “We’re seeing that type of thing happening in southern California already, mostly in chaparral lands that are turning to fields of exotic grass.”

Questions of forest management are really questions about our priorities for the function and appearance of our landscapes—juggling priorities to protect property and respiratory health, esthetics, habitat, carbon sequestration, and water availability.

Given the difficulty of managing fire in proximity to homes and businesses, the Forest Service is considering mechanically thinning forests where it can, but these initiatives remain small in proportion to the huge fuel reduction backlog, and are currently expensive compared to controlled burning. Safford thinks it is an effort that all stakeholders should prioritize.

“We need to think about our grandkids,” said Stephens. “When I think about climate change, I look at the opportunities to do more to change the structure of the forest before big fires hit, and create the conditions so that when it does burn, we can have a party.” In 50 years, he said, opportunities are going to get squashed between the management history of the forests and an increasingly warm, dry climate. “If we begin the transformation now, we give future managers options.”

Ecological Society of America’s 99th Annual Meeting, August 10-15, 2014, in Sacramento, Cal.

Main * Program * Press Information * App


FT 18: The 2013 Rim Fire – Forest Management Influencing Fire Ecology
Friday, August 15, 2014: 7:00 AM-7:00 PM
Organizer: Hugh Safford, U.S. Forest Service, Region 5
Co-organizers: Eric Winford , Gus Smith , Jan van Wagtendonk , Kent van Wagtendonk, Becky L. Estes and Susan L. Ustin

More fire ecology at the upcoming meeting


Additional Resources:

  • Safford, Hugh D.; Van de Water, Kip M. (2014). Using Fire Return Interval Departure (FRID) Analysis to Map Spatial and Temporal Changes in Fire Frequency on National Forest Lands in California. Res. Pap. PSW-RP-266. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 59 p.
  • Scott L Stephens, Neil Burrows, Alexander Buyantuyev, Robert W Gray, Robert E Keane, Rick Kubian, Shirong Liu, Francisco Seijo, Lifu Shu, Kevin G Tolhurst, and Jan W van Wagtendonk (2014). Temperate and boreal forest mega-fires: characteristics and challenges. Frontiers in Ecology and the Environment 12: 115–122.
  • Online Special Issue: Prescribed burning in fire-prone landscapes. (2014). Frontiers in Ecology and the Environment 11 (August).



Author: Liza Lester

ESA's Communications Officer came on board in the fall of 2011 after a Mass Media Science and Engineering fellowship with AAAS and a doctorate in Molecular and Cellular Biology at the University of Washington.

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  1. Drs. Safford and Stephens are concerned about large, severe fires, which is understandable, but now that the evidence has been analyzed from spatially extensive data from the land surveys and a review of complex early-seral forests in the Sierra, the perspectives they are espousing need updating. Below are links to the latest studies that establish that Sierran mixed-conifer forests and native montane chaparral, which they denigrate as “brush,” not only thrive with large, severe fires like the Rim fire, but depend upon mixed-severity fires for sustaining the rich biological diversity of the Sierra Nevada Mountains. The land-survey data show that the sizes of patches of forest burned at high-severity in Sierran mixed-conifer forests have not increased relative to sizes of historical high-severity patches, and forests successfully regenerated in montane chaparral fields after past fires. These high-severity patches are extremely biologically rich, and include diverse native montane chaparral shrubs whose seed germination is favored by smoke and heat, as well as an abundance of fire-adapted animals, including the fisher, the California spotted owl, and the black-backed woodpecker. Yes, at some point perhaps too much fire could occur if temperatures continue to rise, droughts persist, and we cannot control ignitions by people. However, we need to evaluate trends relative to a sound historical baseline across large land areas, and with data about the ecological value of complex early-seral forests, both of which have been lacking but are now available. The story presented in this news release does not cover this new scientific information, some of which is presented in an ESA publication.

    Here is the link to the new study on complex early-seral forests in the Sierra:

    Here is the link to the new study, published in an ESA journal, on historical fire and forest structure in the Sierra from land surveys:

    William L. Baker, Univ. of Wyoming

  2. I am disappointed in the ESA press release and related blog about Drs. Safford and Stephens perspectives of large fires. While their views are important in the overall debate, why was only one view of fire-dependent ecosystems in the region presented here? There are other evidence-based studies that conflict with their findings and this is still an area of hot topical debate, respectfully. In particular, other studies show that the myriad of ecosystem benefits from large fires is significant and important to ecosystems, which mirrors other large disturbance events as documented for Mt. St. Helens, coral reefs and intense storms, etc. To take a catastrophic view of large fires or any large natural disturbance event is not something I would expect from ecologists but its what I often here from land managers concerned about timber losses and “restoration” salvage logging. The trend toward larger fires also has been challenged by Drs. Odion, Hanson, and Baker. Why wasn’t this mentioned?

    Here’s the link to a different perspective based on all of this:

  3. There’s a DISTURBANCE ECOLOGY side to the Rim Fire story, which Safford and Stevens have not acknowledged. As someone who has published on this for 25 years now, I hope that participants in the Ecological Society of America’s meeting might also want to learn about the naturalness and ecological necessity of severe fire in our mixed-conifer forest systems. Here’s a link to one relevant paper:

    And here is a link to a PBS video that I did on this issue 15 years ago

  4. I am hopeful that during the session there will be acknowledgement that in many large, forested areas that have burned severely in the Sierra Nevada, the post-fire, successional process is unfolding beautifully. The key appears to be leaving the system alone. For example, after the Forest Service was stopped from “salvage” logging a large portion of the 2008 American River Fire Complex on the Tahoe National Forest, a beautiful array of native chaparral shrubs and conifers have been allowed to thrive under the shadow of large numbers of standing snags. During our observations of the Rim Fire area, we have seen many of the areas classified as “moonscapes” and severely burned by the Forest Service, show significant conifer regeneration.

    Based on our study of the literature and what we have seen in the field, we are finding it increasingly difficult to believe that severe fire in Sierra Nevada forests were historically limited to small, 40 acre patches as described by some fire scientists after the Rim Fire.

    We have a few photos of what we have seen on the Tahoe and Stanislaus National Forests at our blog here:

  5. I really don’t know what Dellasalla, and especially Baker, are talking about frankly. Safford and Stevens are primarily pointing that if you add very large amounts of fuel to a fire prone landscape, you’re going to get larger and more intense fires, relative to the time when the frequency of surface fires was much higher (and it was MUCH higher before 1850-1870 as has been demonstrated by many fire history studies).

    More fundamentally, nobody has ever seriously proposed–nor do these authors here–that the mixed elevation forests of the Sierra were a monoculture of low density forests, so the issue is in fact basically a red herring. Basic reasoning demonstrates this fact; if a fire rotation period is x years, some fraction of the landscape will have had enough time to generate a dense vegetation of either large shrubs or high density saplings, and these will indeed burn at high intensity, if the next fire comes through soon enough. This is especially so when one considers that fire rotations are defined based on *equivalent* area burned over some defined time, not on the *actual* area burned, with some areas burning more than once and others not burning at all. Except for the river canyons and rock outcrops, all the mid-elevation Sierra Nevada is productive and will readily produce enough continuous fuel to burn severely after a decade or two.

    There are a number of problems with Baker’s cited paper. I am very familiar with the GLO survey data in Yosemite, and other early data in the Sierra Nevada, having used it in my research over the last 20 years. There is no way that one can reconstruct detailed vegetation structure with GLO survey data. Other than the recording of bearing trees, all other data, such as the entry and exit from different vegetation types and the recording of vegetation condition more generally, was haphazard and at the whim of the individual surveyor. There is no way to know how accurate these decisions were, nor how they varied from one surveyor to another. Furthermore, large groups of townships in California, including some of the data Baker used, were surveyed by the notorious Benson syndicate and the data therefrom range from unreliable to completely fabricated. Baker makes no mention of this at all, seeming to be completely unaware of the issue.

    Also, as I attempted several times to communicate to Williams and Baker without success, the tree-aging based techniques that they used in ponderosa pine forests to conclude that surveyors selected the closest tree over 95% of the time (hence making the bearing trees an unbiased survey of the trees on the landscape), are not correct. These give over-estimates of tree density because they fail to account for tree mortality since the time of original survey, which in Yosemite for example, was about 130 years ago in most places. As for the extensive quotes by Leiberg, Sudworth etc, many of us are well familiar with these. They are comments from 30 to 50 years after fire frequencies had dropped precipitously, and many of Leiberg’s for example actually refer to higher elevation fir forests that cannot be considered “mixed conifer” forests, while others are difficult to locate precisely.

    This is likely why he gets such high estimates of tree density over the landscape. About 10 years ago I resampled 20 large belt transects in Yosemite mixed conifer forests at 4 to 6 thousand feet elevation, originally sampled in 1911. These covered all of the forest types discussed in Baker’s paper. The mean density of trees > 6 in. dbh over all plots, was about 70 trees/hectare. Conversely, Baker reports a mean density, 30 years *earlier* and hence closer to the date of the end of the natural fire regime, of over 4X this value (293 trees/ha), and that at least 2/3 to 3/4 of the landscape had a minimum of 150 trees/ha. These values are at great odds with each other and would clearly have a great impact on the fuel loads and type of fire that could be expected.

    Finally, the idea that “people can adapt to fires by channeling development to safer areas and modifying ignition zones near houses and communities to survive fire” is highly unrealistic and demonstrates an ignorance of the current human settlement patterns in the Sierra Nevada and the likely future climate. In virtually all areas below the western Nation Forest boundaries, dwellings of all kinds–individual houses/cabins, groups thereof, ranches of varying size, small towns, you name it, ramify the entire low to mid-elevation areas. While these owners can and absolutely must create fire breaks around their properties, this practice is no guarantee of safety given the nature of fires like the Stanislaus Complex and Rim Fires, which are terrifying, uncontrolled fire storms of the highest magnitude, completely blocking roads, sending embers in all directions, and creating absolute chaos with heat and smoke. Does Baker propose to relocate all these people? If he is convinced of his strategy, I invite him to buy a house in this area, put a fire break around it, and then give us his views after one of these fire storms passes through.

    The idea that the Rim Fire was anything like a “natural” fire for this area is completely preposterous and the claimed evidence for such is based on a very weak set of logical connections and inferences between various existing data. This fire completely incinerated a large part of the landscape, likely altering soil structure and hence inherent productive potential, and it is only by fortune of location, wind patterns, large fire retardant drops, and previous controlled burns, especially in Yosemite, that it did not cause loss of life or greater damage. Hopefully, it will serve as a real impetus for serious fuel reductions, and Baker’s entirely dangerous view of how the landscape should be managed, which is exactly how it *has* been managed to date, will be avoided.

  6. Hi Jim,

    Some short answers to your questions and responses to your points:
    1. DellaSala et al. lays out the evidence for high native biological diversity in Sierran forest areas burned at high severity.
    2. Many authors have assumed that fuel has built up as a result of suppression of low-severity fires. The effects of fire suppression, however, are much more complex than you imply, as fuels were also extensively reduced by livestock grazing in the late-1800s, as documented in Vankat and Major.
    3. Regarding the monoculture of low-density forests, yes many authors have proposed that low-density forests dominated Sierran mixed-conifer forests–see the citations in the introduction. Your logic about fire rotation is something I could not follow, perhaps just because of wording.
    4. Regarding the surveys, I excluded fraudulent surveys and surveyors who did not record the information they were required to enter, and focused on the best surveys. The paper explains this and shows the sample sizes for reliable surveys for each question.
    5. I do not recall hearing from you about your questions regarding surveyor bias, but your argument is also unclear.
    6. The Leiberg quotes were selected from areas that are in Sierran mixed-conifer forests as they were defined in the paper, not from higher-elevation areas.
    7. If you think that the Leiberg evidence should be ignored, then why do you use your own evidence from 1911 inventories, since that 1911 evidence is from one to several decades after Leiberg’s? Also, regarding your Yosemite study area, the 293 trees/ha is the mean across the whole Sierra study area, not the specific estimate for your study area in Yosemite, which was much lower. I hypothesize that a fire, after the surveys, reduced tree density in that area, something that Collins et al. also mention as a possibility, although they argue against it. This is, to me, an unresolved specific case that requires more research, since the estimates are from different times.
    8. Jim, you may be right that I was being optimistic that individuals and communities can adapt to severe fires in this area. It would have been better if people had not moved into these areas, but now perhaps the best remaining option is to adapt. Your reading of my language, however, is that I am implying that people can live safely in these areas, but that was not my intention, but instead I was suggesting that current efforts to reduce fire severity in the forest are unlikely to succeed, therefore people need to adapt. I will make this clearer in the next opportunity I have to publish something about this paper. It is important to note that I make the case that current programs to reduce fuels likely cannot produce a fire-safe landscape either.
    9. I did not make the case that the Rim fire is natural–it is human set, and my article says that.
    10. Tone it down, Jim. Your comment is welcome, but you use hyperbole and strong language (e.g., “preposterous”) when the scientific debate about the Rim fire requires careful science.
    11. This is why several of us have commented on this press release, since it also quotes Drs. Safford and Stephens, who also appear to use some strong language and hyperbole, not careful scientific evidence. For example, it reports that Dr. Safford says that all the trees are dead in the Rim fire area. The initial USFS map of fire severity inside the Rim fire perimeter showed that only about 30ish percent of the burn area burned at high severity, thus by definition about 70ish percent of the burn area contained many surviving trees. No source of evidence is given by Dr. Safford for his suggestion that all the trees are dead. Also, why is it science to talk about our grand kids as support for using logging to lower fuel loads and reduce fire severity? That is not science, it is rhetoric.

  7. Well, with Baker now accusing Safford, Stephens, and I of using “strong language and hyperbole, not careful scientific evidence” we can pretty well see where he stands. In fact, careful attention to the evidence is the main point of my comment above, and the lack thereof is the reason that Baker’s conclusions regarding the historical vegetation conditions and rate of severe fires in Sierran mid-elevations are **not to be trusted**. If the issue were entirely limited to an academic disagreement with little practical significance that would be one thing. But since Baker bases statements/arguments regarding best policies for fire and fuels management (arguing against the importance of fuel treatments), that moves the debate into another realm ltogether, because these decisions by land managers directly affect public safety and ecological stability, in a very major way.

    When time permits I will provide a more detailed, point-by-point response to several of his statements above which range from incorrect to unsupportable.

  8. Jim,

    Your perspective is certainly welcome Jim, although a calmer published, evidence-based response will be most valuable to the scientific community as scientists sort through the evidence.

    As to where I stand, I am pretty sure I am the expert on that, and you have it wrong. What is troubling in the news story is that the statements by Safford and by Stephens are not clearly based on evidence from new scientific studies, and appear contradicted by USFS fire-severity evidence that many trees survived. And, of course, the argument that logging is needed for our grand kids, which is not science.

    Another correction, Jim, if you look at what is said in the discussion of the article, I certainly say the findings imply that fuel-reduction treatments are needed where they are most effective, which is very near houses and infrastructure, if the goal is to increase the possibility of survival of those features in a fire.

    But, much more important than what is said here is the scientific evidence is in the article itself, which is here:

    News stories, too, warrant scrutiny, particularly when they come from scientific societies. We have to have sound news stories or the credibility of ESA as a trusted source of scientific information may be diminished.

  9. William, the scientific evidence as presented in your cited paper, and certain papers of Williams and Baker, and their logical relationship to each other, is in fact at the core of my objections. There are analytical problems here, particularly but not exclusively with respect to the estimation of tree density and vegetation structure from GLO data, an objective fraught with complex problems. A couple of us have been trying hard the last several years to make people aware of the nature and mathematical roots of these problems, but apparently to little effect. It takes a LOT of time and effort to address and communicate these issues, as they are subtle and not well understood.

    I am very intimately familiar with all of the data sources used in the paper, and others that you are not aware of and did not use, and also the fire history literature and the more general history of Sierra Nevada vegetation since the 19th century. Your estimates for pre-settlement tree densities are not correct; they are in fact not even close. For example it is relatively easy to show, in ponderosa pine and true mixed conifer forests, for which you cite forest densities of around 260 to 280 trees/hectare in the Southern Sierra study area, that a mean corner -to-tree distance of around 25 to 30 links (5 to 6 m) is required over all section and quarter corners combined, even if the prescribed number of trees per corner type (i.e. 2 or 4) were in fact recorded, which they often were not. The mean distance to bearing trees, in at least the Yosemite area (and likely over the entire area), is twice or more this value, depending on exactly which townships/corners are included in the analysis (which is not clear in your study, since the underlying data are not available for examination). This in turn translates directly into a density that is at best, 25% of what is claimed. (Note also that your Table 4 data show no major differences in density between the northern and southern study areas, as you state above.) This figure agrees well with independent data from timber cruises in the early 20th century, only a small fraction of which did I refer to above. If you in fact correctly computed densities in the Yosemite area, then the only way to get such high densities over your southern Sierra sub-region as a whole would be to have enormously high compensating densities in the Sequoia-Kings area, which is contrary to what we know about the climatic and fire gradients in the range–it gets thinner as you move south (and west). The more likely explanation is that all of the GLO-based computations are incorrect, over the entire study area. There is no information given as to exactly how you computed these density (and basal area) values.

    Also, as mentioned above, several of the surveyors listed in your table C1 are known to have been involved with the Benson Syndicate, including having had surveys rejected as fraudulent, and subsequent prosecution by the federal government. I recognized their names from your Table C1 immediately and they surveyed a significant fraction of the total survey miles.

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