Did Smokey Bear Get It Wrong?

19 Jul Did Smokey Bear Get It Wrong?

Reading Time: 5 minutes

Forest fires are in the news. Again. Currently, several fires are burning out west. Climate change is blamed for the widespread droughts and, subsequently, for the increase in the frequency of forest fires. It seems, however, that the cause of forest fires is often misunderstood. This article attempts to clarify the types and causes of forest fires, and what role forest management plays in the dynamic.

Forest Fire Categories

There are three types of forest fires: surface fires, crown fires, and ground fires. Surface fires are confined to the surface of the ground and are the least harmful type of forest fire. In fact, surface fires are often intentionally ignited as a management tool used to remove thick understory vegetation. For example, foresters will set a surface fire to burn thick undergrowth to better promote tree growth, a practice common in forests of the southeastern United States. And, occasionally, surface fires are used as an essential forest management tool to prevent a fire from transforming into a more serious crown fire, or to get a larger fire under control. This technique, called back-burning, is used to eliminate fuel in the path of a fire in the hopes that, when the forest fire reaches the back-burned area, the fire’s progress is at least slowed if not fully prevented.

Crown fires are the most devastating type of forest fire. When a fire grows out of control, it begins to burn with an ultra-intense heat. The fire becomes so hot that it ignites tree trunks which, in turn, incinerate the tree crowns. During the most intense crown fires, fires can become so hot that tree sap boils, causing trunks to explode. In thick forests, especially coniferous forests out west, crown fires can reduce an entire forest to cinders. Crown fires seem to be occurring more and more frequently out west (more on this later).

Ground fires occur in areas where there is abundant organic matter below the surface (such as humus, peat, dead tree roots, coal, etc.). A surface or crown fire can ignite this underground organic matter, which then begins to burn very slowly. Ground fires are difficult to extinguish, normally requiring excavation. They sometimes overwinter, reigniting a fire in the spring. Some of the worst ground fires occur in old coal mines where they have been burning for decades.

How Do Forest Fires Start?

Lightning is the most serious culprit in causing devastating forest fires. According to the US Forest Service, approximately 44% of wildfires in the Western United States are caused by lightning, and they are responsible for about 71% of the area burned. In Canada, lightning also causes slightly less than 50% of all wildfires, but accounts for 67% of the land area burned.

Human-caused forest fires still occur, either by accident or arson. But these fires are almost always less devasting than lightning-induced fires because they normally occur near population centers, meaning they are often extinguished more quickly and are therefore normally smaller in magnitude.

Enter Smokey Bear

Smokey Bear (“Only YOU can prevent forest fires.”) was created by the U.S. Forest Service in the 1940s to enlist the help of the public in curbing human-caused forest fires. At that time, more than 30 million acres of American forest burned annually. By 1988, the annual figure hovered around 7.5 million acres per year until rising to 10.1 million acres in 2020 (40% of which burned in California). It turns out that Smokey Bear may have done too good a job. Ironically, the U.S. Forest Service and their forest management practices have become the primary reason for the increase in devastating forest fires. Why? Because frequent fires burn the undergrowth. In the absence of frequent surface fires, undergrowth proliferates, increasing the accumulation of kindling, and thus promoting an environment conducive to more devastating fires.

What else causes dense undergrowth — and, therefore, forest fires — to proliferate? There are three common reasons:

1. Selective logging normally leaves behind unwanted branches and other debris known as “slash.” When slash dries, it becomes kindling.
2. Plant succession can result in an abundance of understory fuel. Plant succession is the normal sequence of plant growth that occurs in each habitat. The nature of plant succession is a function of the geography and habitat type present. For example, in many western coniferous forests, the lodgepole pine is a common tree that proliferates, often in a crowded fashion, after forest fires. Lodgepole pines are shade intolerant and are not long-lived. As succession proceeds, they are eventually overtopped by other tree species. When this happens, the lodgepole pines die and eventually dry, at which point they, too, become fuel for fires. Thus, when a forest fire begins in such a forest, the lodgepole pine becomes the fuel that can lead to a crown fire and possible conflagration.
3. There are also certain biomes that evolve in the presence of recurring fires. In the Western United States, especially California, there is a biome known as chaparral. It is characterized by low, dense, scrubby vegetation. Rainfall tends to be abundant in winter and scant in summer. Some of California’s most lavish homes and neighborhoods were built amid the chaparral biome. Consequently, homeowners do all they can to prevent fires. In the absence of fire, the dead plant material accumulates. When lightning strikes or an electrical wire arcs and causes a fire, there is little that can be done to stop it, and homes are often reduced to ashes.

When Are Crown Fires a Good Thing?

Yellowstone National Park, arguably the most famous of all the national parks in this country, caught fire on June 14, 1988. Ignited by lightning, nearly a million acres burned. The forest understory was replete with fuel, creating a crown fire and conflagration of epic proportions. Despite the involvement of thousands of fire fighters, the fire was mostly uncontainable. It burned throughout the summer and was only extinguished when November rain and snow smothered the relentless blaze.

Hand wringing continued throughout the summer and fall; people were aghast and fretting about the ecological disaster because fire wiped out untold acres of old forests, formerly choked with dead trees and devoid of any herbaceous understory. But what happened as a result? The following spring, secondary succession (the natural ecological growth process that occurs in the wake of such fires) unfolded. From the devastation sprouted long-dormant seeds of every kind of native vegetation. Rejuvenated, gray landscapes turned green, and, in a few short years, wildlife populations exploded due to the advent of new foliage. In short, Yellowstone underwent an ecological renaissance that has been studied and published in scientific journals for the past 30 years.

Conclusion

It is undeniable that the pacific northwest is experiencing record temperatures. But temperature alone, while it may exacerbate the situation by drought, does not cause forest fires. The data is clear: forest management practices over the past 70 years have created forests conducive to crown fires. Most destructive forest fires are started by lightning. Many of these fires do what they have done for millennia; they burn themselves out, and the forests regenerate. Does heat and dry weather increase the risk of fire? Yes. But better forest management practices moving forward will reduce the risk of conflagrations. Then, better planning on the local level will reduce risk even further by not building homes in areas that are intensely fire prone, such as chaparral.

References

The United States of Fire – American Forests

Was Smokey Bear wrong? How a beloved character may have helped fuel catastrophic fires. – The Washington Post

Controlled burn – Wikipedia

In the West, Lightning Grows as a Cause of Damaging Fires – The New York Times (nytimes.com)

Fire behaviour (nrcan.gc.ca)