Forest Fires

Every Forest is Different

Four Points to consider when thinking about forest fires
1. Every Forest is Different
Some forests, like the lodgepole forests in the Rocky Mountains and Yellowstone National Park (as shown in the photo at the top of this page) have long fire return intervals, are naturally dense, and are filled with a significant amount of woody material. In contrast, dry ponderosa forests in the Southwest and mixed-conifer forests in the western Sierra Nevada have frequent, mixed-severity wildfires that burn with a mixture of high-severity (most trees are killed) and low-severity (most trees are only scorched). Past fire suppression has caused many of these forest to miss several fire cycles, leading to the build up of vegetation in some locations (see #4 below). Forests above 7,000 feet are sparse, having fire return intervals on the order of centuries. Other forests, like those in the Pacific Northwest, are so moist that huge trees and dense understories of ferns and shrubs are the norm (prior to industrial logging). A few forest types are shown below. Click on the photo to see the larger version.
Natural fires are infrequent on most western landscapes. Contrary to the view that fires are supposed to burn frequently, everywhere, the reality is that most ecosystems in the West have long natural fire return intervals. Chart lists ecosystems with naturally long fire return intervals. Click to enlarge.
Sparse forests of high elevation High Sierra Nevada. The natural time between fires is on the order of centuries.
Jeffery pine grove of about 5 acres in the Sierra Nevada. This is the "open park-like" forest some promote as the natural condition of all forests. It only occurs naturally in small areas.
A wall of wood in the Pacific Northwest, that would eventually become Olympic National Park. Unfortunately, the trees pictured did not survive the logging industry and mismanagement by the US Forest Service.
A post fire snag forest in the low elevation, western Sierra Nevada. This habitat provides an incredibly rich, biodiverse environment. It was scheduled by the US Forest Service to be salvaged logged until it was stopped by a lawsuit.
Dense, lodgepole pines in Yellowstone National Park. High-intensity, large fires are the natural pattern.
Artificial tree plantation. This is what fire officials and foresters often describe as the preferred forest. No shrub understory, trees spaced 10-20 feet apart, and little biodiversity.
2. Logging and Over-grazing
Historically, many Western forests have been severely damaged by industrial logging. Timber companies would first search out and cut the largest trees. Later, huge areas were clear cut. Livestock were often brought in afterwards and used to clear whatever habitat remained. Sheep herders and cattle ranchers also overgrazed forested landscapes, causing significant soil damage and removing the grasses that would have carried low-intensity surface fires. Consequently, large areas were opened up. With the rich soil and ample rain, forests regenerated with massive numbers of trees. This was the origin of the so-called "dog-haired" thickets and overly dense forests often mentioned in the media. Ironically, this damage is usually ignored in the forest fire discussion. Instead, the blame for what some claim as over-stocked forests and the large number of dead trees is directed at government efforts to suppress wildfire. Even fire officials, the ones who do the suppression, blame themselves. While fire suppression has indeed added to the ecological imbalance, it was, and remains, the greed of extraction industries like logging and ranching that is the actual source of the problem.
3. Climate Change
Global climate change is raising temperatures in many forested areas in North America. Higher temperatures contribute to increased tree mortality, lengthening of fire seasons, and increasing the number of large, high-intensity fires.
4. Fire Suppression Fallacy
Some low elevation (below 7,000 feet) mixed-conifer forests (like those in the western Sierra Nevada) and dry ponderosa forests in the Southwest have missed natural fire cycles due to fire suppression. However, most forests have not since most natural fire return intervals are a century or more, long before significant fire suppression efforts got underway (see chart above). The actual problem faced by forests that have missed natural fire cycles is not so much about an "artificial" build-up of vegetation, but rather the legacy of past land abuse - clearcut logging, soil disturbance, overgrazing, and the establishment of dense tree plantations (by private as well as USFS managers). Such disturbance continues today with the addition of chemical herbicides and salvage logging. The notion that recent forest fires are a result of past fire suppression via "fuel" build up is a fallacy. Wildfires are driven by drought, high temperatures, low humidity, and wind, all being exaggerated now by human-caused climate change. Hence, the call to log and clear forests of habitat is more about satisfying timber industry interests than reducing wildfire risk. Please see the letter of opposition signed by dozens of national and local science and environmental organizations to US Senate Bill 4431 by Daines/Feinstein, a bill that mistakenly calls for increased logging as a solution. Also, an excellent op-ed in the Los Angeles Times provides additional information on this subject: Don't believe self-serving messengers. Logging will not prevent destructive wildfires.
Intensively Managed (logged) Forests Burn Hotter Than Native Forests
“Areas intensively managed burned in the highest intensities. Areas protected in national parks and wilderness areas burned in lower intensities. Plantations burn hotter in a fire than native forests do. We know this from numerous studies based on peer-reviewed science.”*- Dominick DellaSalaFrom: Exploring Solutions to Reduce Risks of Catastrophic Wildfire and Improve Resilience of National Forests. Congressional testimony by Dr. Dominick DellaSala, Sept. 27, 2017.
* The research cited above analyzed 1,500 fires in 11 Western states over four decades - an overwhelming convergence of evidence. Some of those studies include the following: 1. Odion et al. 2004. Fire severity patterns and forest management in the Klamath National Forest, northwest California, USA. Cons. Biol. 18:927-936.
2. Zald, H., and C. Dunn. 2018. Severe fire weather and intensive forest management increase fire severity in a multi-ownership landscape. Ecol. Applic. 4:1068-1080.
3. Bradley, C.M., et al. 2016. Does increased forest protection correspond to higher fire severity in frequent-fire forests of the western United States? Ecosphere 7:1-13. 217 scientists sign letter opposing logging as a response to wildfires (we are signatories).

Forest Fire Hyperbole

Look at the photo of the high-severity burn patch from the 2013 Rim Fire. What you will hear from the US Forest Service is that this forest burned at unnaturally high-severity because past fire suppression had created an overly dense forest. The situation is much more complicated than that. This area shows the ghost of devastation past. All the large, magnificent, fire-resistant trees were logged long ago. Clear cutting likely came next, in several waves. Once the land was barren, a new forest exploded with growth (notice the trees are all about the same size). The only natural portion of this scene is the native shrubland in the lower left corner - now becoming a new, biodiverse pyrogenic habitat, soon to transform into montane chaparral, if allowed. The US Forest Service's response? Salvage log, tear up the soil, and "reforest" with planation trees. What's the ecologically sound thing to do? Leave Nature alone and stop repeating the same mistakes over and over again. The forest will return in time. We just need to stop pretending it's supposed to happen tomorrow.
A large, high-fire severity patch burned during the 2013 Rim Fire. Notice the size of the trees - all young, all approximately the same age. This is the classic symptom of industrial logging, not fire suppression. Click image to enlarge.
For additional insight into how wildfires in forests are misunderstood by the media, please see our document, The Mischaracterization of Wildfires In California.

The Folly of "Salvage" Logging

Ecologist Chad Hanson stands in a Rim Fire snag forest regenerating on its own with ferns, wildflowers and young trees (7/2018 Los Angeles Times).
Salvage Logging Causes Significant Environmental Harm An article in the Los Angeles Times (7/18/18) discussed the folly of pretending that we know better than Nature when the US Forest Service and timber companies promote the practice of post fire "salvage" logging, in this case the fragile post fire, pyrogenic habitat created by the 2013 Rim Fire on the Stanislaus National Forest. Contrary to what logging advocates claim, nature does not need our help in “restoring” the fragile post-fire forest habitat created by the Rim Fire in the Stanislaus National Forest. Post-fire forests in the Sierra Nevada need to be left alone so they can carry on as they always have by creating rich opportunities for a wild diversity of plants and animals to thrive.
Despite overwhelming science showing that post-fire logging causes significant ecological damage, advocates for the timber industry ignore the fact and use Orwellian double speak ("restore" actually means to log or clear cut) to confuse the public. At times, the disregard for Nature is blatantly exposed. Such occurred during a USFS sponsored field trip through the Rim Fire on May 30, 2019. When confronted with the fact that thousands of nesting birds would likely be killed in in an upcoming salvage/grinding operation, a board member with the Sierra Nevada Conservancy said that such a thing didn't matter because, after all, birds will be killed in the next fire anyway. See Figures 1 and 2. When confronting cognitive dissonance, individuals and institutions will reject, rationalize, or ignore the truth. This is why we filed a lawsuit to stop the forest from being destroyed by salvage logging.
Figure 1. A remarkable pyrogenic habitat created after the 2013 Rim Fire. The US Forest Service designated this place as "unhealthy" and scheduled it to be logged, then planted with plantation trees. Click image to enlarge.
Figure 2. Multiple species of pine and fir emerging in the biodiverse pyrogenic habitat developing after the 2013 Rim Fire, scheduled to be clear cut and crushed by logging equipment.
A rich, pyrogenic, post fire habitat, unlogged, unsalvaged, left alone. Post 2013 Rim Fire, Stanislaus National Forest.
This cheat grass-invaded tree farm was planted after the area was salvaged logged and sprayed with herbicides to eliminate shrubs and natural biodiversity. Post 2013 Rim Fire, Stanislaus National Forest.

Forests Regrow After High-Severity Fires

The Forest Service often claims that without clearcut logging, artificial replanting, and spraying of toxic herbicides (glyphosate), the forest will not grow back. However, growing evidence indicates that such activities destroy the forest.
A new study found that natural regeneration of conifer trees after the 2013 Rim Fire fire was abundant, including in the interior of the largest high-intensity fire patches. This is good news because it means we do not need to subject forests to the well-documented harms caused by post-fire logging.
In the process of making this determination, the researchers also discovered why the Forest Service has failed to accurately assess forest regrowth in big western US fires like the Rim Fire area. First, when the USFS establishes their field plots (the specific areas where they actually look for tree seedlings) they make them much too small to accurately assess the amount of regrowth across the landscape, leading to false reporting of large areas without natural regrowth. The new study established plots that were dozens of times larger and found that the size of the plot was highly significant in relation to detecting the level existing conifer regeneration. While some previous studies reported findings which suggested the possibility that plot size was important, the new study is the first one ever to specifically explore that question and prove the importance of plot size.
Second, the Forest Service fails to exclude areas that did not have conifers before the fire (such as rock outcroppings, streams, and bare ground damaged by past logging). The new study made sure that plots that did not support conifers before the fire were not included when looking for conifers growing after the fire. With these two important corrections, the researchers found on average hundreds of conifers per acre naturally regenerating in large high-intensity fire patches where the Forest Service assumed there were few or none. In fact, there is abundant natural forest regrowth even in areas more than 1000 feet from the nearest live, surviving conifer.
In the era of climate change, when many are understandably concerned about the ability of our forests to regenerate after big fires, these are hopeful findings, and not just for the Rim Fire burn area. The methodological issues that the new study identified which resulted in an underreporting of tree regrowth after wildfires are not just limited to surveys by the Forest Service in this burn area. In fact, many of the studies that have been covered in the media claiming a failure of forests to regenerate after high-intensity fire suffer from the same errors. The new findings indicate that forest ecosystems are much more resilient to wildfire than we humans give them credit for. Download: Hanson, C.T., and T.Y. Chi. 2021. Impacts of postfire management are unjustified in spotted owl habitat. Frontiers in Ecology and Evolution 9: Article 596282.
A severely burned forest is not a “destroyed” forest, but rather a habitat restored.
That is not something you are likely to hear during or after the next large forest fire in the Sierra Nevada. It certainly wasn’t during the 2013 Rim Fire in Yosemite and the Stanislaus National Forest. It should have been, however, because the science is clear – severely burned forests provide some of rarest and most biodiverse habitats on earth.
Tahoe National Forest, after the 2008 American River Complex Fire.

Research questioning the notion that high severity fires in the Sierra Nevada are “unnatural”


“Our results suggest that wildfire burning under extreme weather conditions, as is often the case with fires that escape initial attack, can produce large areas of high-severity fire even in fuels-reduced forests with restored fire regimes.”– Lydersen, J.M., M.P. North, B.M. Collins. 2014. Severity of an uncharacteristically large wildfire, the Rim Fire, in forests with relatively restored frequent fire regimes. Forest Ecology and Management 328: 326-334.
“Proposals to reduce fuels and fire severity would actually reduce, not restore, historical forest heterogeneity important to wildlife and resiliency. Sierran mixed-conifer forests are inherently dangerous places to live, which cannot be changed without creating artificial forests over large land areas. However, people can adapt to fires by channeling development to safer areas and modifying ignition zones near houses and communities to survive fire.”– Baker, W.L. 2014. Historical forest structure and fire in Sierran mixed-conifer forests reconstructed from General Land Office survey data. Ecosphere 5: 1-70
“The rate of high-severity fire has been lower since 1984 than the estimated historical rate. Responses of fire behaviour to climate change and fire suppression may be more complex than assumed …Management could shift from a focus on reducing extent or severity of fire in wildlands to protecting human communities from fire.”– Hanson C.T. and D.C. Odion. 2014. Is fire severity increasing in the Sierra Nevada, California, USA? International Journal of Wildland Fire 23: 1-8.
In relation to thinning forests in an attempt to reduce high severity fire in Northern Spotted Owl habitat, "We found that the long-term benefits of commercial thinning would not clearly outweigh adverse impacts, even if much more fire occurs in the future. This conclusion applies even if adverse impacts of treatments are quite modest because of the vastly larger area that would need to be treated compared to area of high-severity fire that might be reduced by thinning."Odion, D.C., C.T. Hanson, D.A. DellaSala, W.L. Baker, M.L. Bond. 2014. Effects of fire and commercial thinning on future habitat of the northern spotted owl. The Open Ecology Journal 7: 37-51.
Please listen to this special podcast with Roy Ben-Tzvi This interview provides an excellent overview of all things chaparral including what we do, what chaparral is, the best way to deal with wildfire risk, and the role Nature can play to create better lives and a more positive society.
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