Viewpoint: The myth of open forests
George Wuerthner
One of the frustrations I face as an advocate for forest protection is the continuous stream of wildfire and forest ecology misinformation from government agencies such as the Forest Service and state forestry.
For example, I received an article from the Forest Service titled "Multiple treatments are key to resilient Western Forests. In the opening paragraph, the article asserts: "Forests in the West used to be a lot more open, so wildfires were much less severe."
The problem with this characterization is that, at best, only about 10% of western conifer forests were historically "park-like", dominated by frequent low-severity blazes.
The primary tree that fits this model is ponderosa pine. However, even in these pine forests, high-severity blazes occurred, leaving many trees dead.
Most western forest types (and most non-forested areas like chaparral) tend to have much longer fire intervals, often many decades to hundreds of years between significant ignitions.
These trees include fir and spruce, hemlock, cedar, Douglas fir, western larch, some pines like lodgepole pine, whitebark, Bishop pine, knobcone pine, Monterey pine, and white pine, as well as aspen. None of these trees fit the high-frequency-low-severity model. When these forests burn, they exhibit significant high-severity mortality.
In between these major fires, down logs, snags, and ground litter accumulate. However, this is all within the natural historical condition, not some aberration as often suggested by the Forest Service.
And many national forests had few, if any, ponderosa pine. In the Northern Region of the Forest Service, which includes northern Idaho and all of Montana, only 4% of the forest type is ponderosa pine and other "dry conifer" forests.
A further problem right up front in the opening paragraph goes on to say, "We can actually see scars from old wildfires in cross-sections like this one. By cross-dating fire scars from multiple trees, scientists can reconstruct what past forests looked like, including how dense forests were."
The problem ignored by pro-deforestation agencies to justify thinning and logging the forest is that there are serious methodological issues with such fire-scar studies that tend to exaggerate fire frequency.
For instance, the main way scientists obtain fire scars is by wandering through the forest in search of scarred trees. But this is not a random selection, which biases the studies from the very beginning.
It is analogous to going into a bar on a Saturday night, asking the crowd how many people like to drink alcohol, and getting nearly 100% agreement from the patrons that alcohol is good—then extrapolating that percentage to the community's overall population.
By contrast, the use of other methods to determine past forest stand composition and fire frequency, including photo interpretation, sediment flow studies, pollen studies, charcoal studies, government land office reports, and evolutionary evidence, typically reports longer fire intervals and high-severity blazes as natural events rather than aberrations.
A study of "Spatially extensive reconstructions show variable-severity fire and heterogeneous structure in historical western United States dry forests" concluded that: "Park-like stands of large trees maintained by low-severity fire predominated only in parts of the study landscapes." The main conclusions were: "forests were structurally variable, including areas of dense forests and understory trees and shrubs, and fires varied in severity, including 15–65% high severity fire."
In short, the idea that most western ecosystems burned frequently were characterized by open, park-like stands, and were "healthy" ignores both evolutionary and ecological realities. It is a narrative promoted to support more logging of our forests.
The way to protect homes and communities is to reduce the flammability of structures through home hardening. Home hardening is by far the most cost-effective means of reducing wildfire risk and has the fewest ecological and environmental impacts.
George Wuerthner is an ecologist who has written numerous articles on wildfire ecology and several books on the topic.