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Most forest fires have beneficial effects on a wide variety of animals and plants, and are necessary for the long-term health of the forest.

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In August 1910, hot dry winds caused fires burning in Montana, Idaho, and Washington to blow up into the worst wildfire event in this country’s history: 3 million acres were burned in 2 days, and 87 people were killed. That event caused people throughout the country to view wildfire as a monstrous evil, to be fought with every resource available. To the full extent possible, every wildfire was extinguished – the official policy called for fires to be suppressed by 10 a.m. on the day after the fire was first reported.

During the 1960s, however, research began to show that fire played a positive role in forest ecology. How could such a destructive force play a positive role? This post will look into some of the answers to that question.

Figure 1, repeated from the previous post, shows the understory of a mature stand of lodgepole pines along the Avalanche Lake Trail in Glacier National Park. Even a casual glance shows how densely the trees are packed together. You can notice that there is very little growing on the forest floor – no grasses, flowers, bushes, and no baby pine trees. Instead, downed wood litters the forest floor. This is unhealthy. No plants on the forest floor means that there is little for animals to eat. No baby pine trees means the forest can’t renew itself. And the build-up of dead wood makes the forest ripe for an extreme and destructive fire.

(Click on graphic for larger view.)

Figure 2 shows Lower Two Medicine Lake in Glacier National Park, but I want you to look at the pine trees on the slope to the left of the lake. These are also lodgepole pines. You can get a sense of how thousands of acres are covered with these densely packed trees. In fact, 80% of Glacier Park is forest, and 80% of that is lodgepole pine. Lodgepole pines are also the dominant trees in Yellowstone and Grand Teton National Park.

 

 

 

 

 

 

 

 

 

 

You can also see that all the lodgepole pines are roughly the same height. That’s because they are all the same age. “How can that be?” you may ask.

Like all pine trees, lodgepole pines bear their seeds in cones. Figure 3 shows the cone of a lodgepole pine in Grand Teton National Park. Figure 4 shows some cones in the top of a white pine in St. Louis. Contrast the two: the white pine cones have opened while still on the tree. The seeds have been discharged to germinate and make little white pines. On the other hand, the lodgepole cone has not opened. It is sealed shut with a resinous substance. To release its seeds, something has to melt that resinous substance. Only fire is hot enough. These kinds of cones are called “serotinous cones.” Not all lodgepole pines have serotinous cones, but the ones in the Rocky Mountains mostly do.

 

 

 

 

 

 

 

 

 

 

 

 

Serotinous cones mean that lodgepole pines can’t disperse their seeds unless there is a fire. When there is a fire, the cones open and disperse their seeds. The seeds fall on ground that has been cleared by the fire, and which has been fertilized by chemicals from the ashes of the burned trees. They sprout and grow in thick stands, which mature into the dense forests shown in Figures 1 and 2. Thus, fire is not only beneficial for healthy forests of lodgepole pine, it is required.

Aspen trees also benefit from fire. If you look at stands of aspen trees, often they too are all roughly the same age. Aspens don’t sprout from seeds, however. They send runners underground, and then suckers sprout up from the runners. In a grove of aspens, every tree may be genetically identical, having suckered from one parent tree. Aspens are not as long-lived. Though originally dense, after several decades they tend to decay and rot, and other species can invade and take over. Without fire, the entire stand may vanish. With fire, however, the land is cleared, but the runners underneath the ground survive. They sprout again, and the stand, still genetically identical, renews itself. The genetic material in some aspen stands is thought to have derived from a single parent aspen thousands of years ago.

Many animals also benefit from fire. In the first year after a fire, animal populations may crash, due to lack of food. But the first colonizers of a burn area are flowers and berry-producing bushes that are much better food sources than are mature stands of lodgepole pine. They grow luxuriantly in the sun and fertilized soil, without competition from taller trees. Feeding on this rich forage, animal populations quickly recover.

Which animals benefit from fire? Elk, deer, and bear all do. Rodents experience the highest fire-related mortality of any animals, but because they reproduce so abundantly, their populations quickly rebound. Most bird species are not directly harmed, and a few benefit, such as species that live in holes in dead trees. Moose is one species that does seem to have declined in Yellowstone as a result of the 1988 fires.

The process of recovery takes many years. Mature stands of lodgepole pine may be 90-300 years old. What follows is a series of photos showing some early stages in the forest’s recovery after a fire. They were all taken in August-September 2016.

Figure 5 shows a burn area from the Berry Fire (2016) near the northern boundary of Grand Teton National Park. This area burned about 2-3 weeks before this photo was taken. Everything is dead, nothing is growing.

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Figure 6 shows the burn area of the Reynolds Creek Fire (2015) in Glacier National Park. The regrowth is about 1 year old. Notice the growth of grasses and flowering plants, many of which provide good forage for animals. The pink flower is fireweed, a common colonizer of burned areas.

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Figure 7 shows regrowth from the West Thumb Fire (2009) in Yellowstone National Park. September is late in the season for Yellowstone, so the flower- and berry-producing plants have all finished. Though it has turned brown, you can see that there is grass among the burned trees, while there was no grass under the trees of the mature lodgepole forest. You can see the 7-year old lodgepole pine sprouts.

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Figure 8 shows regrowth following the Red Eagle Fire (2006) in Glacier National Park. Notice how a whole new forest of lodgepole pines has sprouted and is growing healthily. They are interspersed with grasses and other plants. You can see how densely they have sprouted – in time, they will form a dense forest. These trees are 10 years old; you can see that full recovery takes a bit of time.

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Figure 9 shows regrowth following the Moose Fire (2001) in Glacier National Park. At bottom are willows along a riverbed. In the middle are 15-year-old lodgepole pines in the burn area. On the ridge at left are mature lodgepole pines that were left unburned by the fire. This is a common story. Wildfire is very fickle about what it burns and doesn’t burn. This photo gives some idea of how, when left to its own devices, fire creates a patchwork landscape consisting of various types of trees in various stages of development. This sort of patchwork is very healthy for the forest. You wouldn’t want a city where everybody was 65-years-old, you would want a city composed of people of every age. Similarly, the healthiest kind of forest is one consisting of a variety of habitats in all stages of development.

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Figure 10, the final photo for this post, shows the Upper Geyser Basin in Yellowstone, home to Old Faithful. While the photo is intended to be about the steamy geysers, it also shows the forested hills behind the basin. This is the same part of the park shown in the dramatic photo of a wall of flame bearing down on the Old Faithful Photo Shop that was included in previous posts (North Fork Fire, 1988). You can see that the forest is still in a process of regrowth, especially along the top of the ridge. But the predictions that Yellowstone had been devastated were wrong: Yellowstone is well along the process of recovery, even from the terrible fires of 1988. Trees are abundant, forests are healthy, and, at least during my visit, wildlife was everywhere.

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A raging crown fire can be a destructive force that achieves none of these beneficial effects. But most forest fires have beneficial effects on a wide variety of animals and plants, and are necessary for the long-term health of the forest.

In the next post, I’ll look at some data to address the question of whether wildfire behavior is changing over time.

Sources:

Forest History Society. 2016. U.S. Forest Service Fire Suppression. Downloaded 9/30/2016 from http://www.foresthistory.org/ASPNET/Policy/Fire/Suppression/Suppression.aspx.

Johnsgard, Paul. 2013. Yellowstone Wildlife: Ecology and Natural History of the Greater Yellowstone Ecosystem. Boulder, CO: University Press of Colorado.

Reinhart, Karen. 2008. Yellowstone’s Rebirth by Fire: Rising from the Ashes of the 1988 Wildfires. Helena, MT: Farcountry Press.

Rockwell, David. 2007. Glacier: A Natural History Guide. Second Edition. Guilford, CT: Falcon Guides.

Yellowstone National Park. 2016. Fire. Downloaded 10/1/16 from https://www.nps.gov/hell/learn/nature/fire.htm.

Yellowstone National Park. 2016. Yellowstone Resources and Issues Handbook. National Park Service. Downloaded 9/28/2016 from https://www.nps.gov/yell/learn/resources-and-issues.htm.