The Ecological Effects of Forest Fires
"I have often wondered how it is possible there is any timber left in the western mountains when one thinks of the thousands of years since the last glacial epoch, when lightning and Indian-set fires ran unchecked, with no protective organization." -- Elers Koch, Forty Years a Forester, 1998
Like Elers Koch, many residents of the northern Rockies have likely wondered how populations of plants and animals could ever persist in the face of repeated forest fires. It is hard to imagine how an apparently destructive force like fire could be "integral to the life of western forests."
"Ecological science makes it clear that fire is just as integral to the life of western forests as wind, rain, and sunshine." -- Arno and Allison-Bunnell, Flames in our Forest: Disaster or Renewal? 2002
But fire has long been a fact of life in northern Rocky Mountain forests, changing the nature of these communities, repeatedly, over millennia. These changes are neither inherently good nor bad from an ecological standpoint. Instead, fire is simply a type of "disturbance."
A disturbance is defined as an event that abruptly kills, displaces, or damages one or more individual plants or animals, thereby creating an opportunity for new individuals to establish (Sousa 1984). Floods, hurricanes, and microbursts are a few other types of disturbance. Fire is by far the most important agent of disturbance in northern Rocky Mountain forests and has been so for thousands of years.
Fires affect forest communities in many ways. In the short-term, fire consumes vegetation, downed woody debris, and soil organic matter. It heats soil and stream water. It kills animals unable to escape or avoid excessive heat and smoke. These and other immediate effects of fire continue to shape forests long after any flames have passed. Fire-caused changes in soil productivity and forest structure direct future vegetation development, which, in turn, influences soil loss to erosion. Fire-caused changes in water temperature and sedimentation rates affect populations of aquatic organisms. And fire-caused changes in forest development affect the abundances and distributions of other creatures, from microbes to megafauna, within the region.
Many of these ecological effects can be gleaned from simple observations of burned and unburned forests. The most convincing cause-and-effect relationships, however, are usually demonstrated with fire experiments, like those conducted in conjunction with prescribed burns. Over the past few decades, a great deal of fire-effects information has been amassed from observations and experiments in northern Rocky Mountain forests. Ongoing research is supported by a number of agencies and institutions including the USDA Forest Service, the National Park Service, the U.S. Geological Survey, The University of Montana, Montana State University, and The University of Idaho.
In the following sections, we synthesize the fire-effects information gleaned from studies of various forest components in the Northern Rockies - research conducted in our own backyards. Select a topic to learn more.
Arno, F. A, and S. Allison-Bunnell. 2002. Flames in our Forest: Disaster or Renewal? Island Press, Washington, DC. USA.
Koch, E. 1998. Forty Years a Forester: 1903-1943. Mountain Press, Missoula, Montana, USA.
Sousa, W. P. 1984. The role of disturbance in natural communities. Annual Review of Ecology and Systematics 15:353-391.