On Nov. 27, 2018, the IR published a piece where Michael Garrity states “sagebrush only burns every 100 to 200 years, while juniper burns on average every 200 to 400 years. This is not true for the forests in our area. Pure logic can be used to help understand this. Prior to 1900, there was fuel (grass, shrubs, trees); there was lightning and Native Americans to start fires; there was nothing to put them out. Unless you believe that lightning, Native Americans and fuel only combined to start a fire every 100 years, simple logic says Mr. Garrity’s claim cannot be true.
Most of us are familiar with different forest types — think about how forests change by elevation and aspect. Fire was a frequent visitor to these forests before 1900. It is difficult to realize how much the forests and how wildfire behavior has changed — it has been drastic.
The Helena Forest commissioned a study in the Elkhorns by a fire history expert (Barrett, 2005) to research current and pre-European fire frequency. Numerous scientific studies support his findings; this study is of interest because it is specifically from our area.
This study shows the following fire frequency:
- grasslands and shrublands 10-20 years
- savannas (sparsely forested grassland/shrublands) 10-25 years
- low elevation conifers (Douglas fir, ponderosa pine, limber pine) 20-40 years
Frequent fires generally result in low tree mortality with small patches of burned trees and grassland. Individual trees can survive these fires; they become large and old with fire scars that record fire history. Infrequent fires burn larger areas of land with high tree mortality. Generally fire doesn’t reburn areas that it has visited for at least 5-20 years.
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Since 1900 wildland fire policies and land uses have resulted in stopping small fires. Many fire cycles have been missed, resulting in major changes in the vegetation and fire behavior.
Our grasslands, shrublands and savannas are being invaded by many more junipers and other trees than would have been there with frequent fires. These trees are now so thick that the canopies are touching, leaving sagebrush skeletons and sprigs of native grasses underneath. These plants cannot thrive without sufficient sunlight and water, which is limited by the trees. There are few plants adapted to these conditions and these areas can become biological deserts. Ever notice forests that have little but moss in the understory? That is all that can live in these conditions on these sites. These areas would have many different native plants in an open tree canopy.
Our dry forest sites are also filling in with many trees that are able to survive without fire. These forests are now much thicker and the trees are smaller than were on these sites 100-plus years ago when fires thinned the trees and juniper in the understory. There isn’t enough moisture or nutrients for this kind of forest. The trees are susceptible to native insects — mountain pine beetle and spruce budworm. In healthy forests these insects kill a few weak trees, but don’t cause the massive mortality that we have seen since 2000. Where mountain pine beetle has killed the ponderosa and lodgepole pine on these sites, or spruce budworm has killed the Douglas fir, the fuel from standing and fallen dead trees is tremendous. The many grass and dry shrub species that would have lived in a more open tree canopy situation are not able to survive here.
Another effect of all the excess trees is a decrease in available surface and ground water. Woody plants use far more water than grasses and shrubs. In our dry vegetation types this has been a major change.
The bottom line is that our forests and grasslands are “out of whack” compared to pre-1900. The junipers and conifers that we see in the lower elevations are far more numerous. The number of trees in all forest types is much greater than before. Most of these trees will not make a harvestable product except chips, will allow insect epidemics and will cause very different fire behavior. Vegetation that doesn’t belong where it is or how thick it is creates very different ecosystems than those that our native plants are adapted to. False stories about fire and other natural processes are harmful to the health and resiliency of our forests. We have factual information and it must be used to correct these myths. The forests, grasslands and our very lives depend on it.
Lois Olsen of Helena, who retired in 2012, spent 34 years with the U.S. Forest Service and worked as a vegetation ecologist for Helena National Forest from 1980-2012. She holds a master's degree from Montana State University in land, resources and environmental sciences and is currently on the board of TriCounty FireSafe Working Group.