Smoke rises from the trees and this is a scene which usually triggers fear and dire news reports. However, while it is true that fire can cause serious destruction, there are many places in which they are a necessary part of the ecosystem. This will be the first of two articles to look at wildfires, their role in the ecosystem, the factors that affect their severity, and what our response should be. This one will focus on the ecological role of wildfires as well as the effect of fire suppression. The second one will look at the factors that affect wildfires and how we should respond to them.
There are several ecosystems where fire plays a vital role. In these areas, plants have developed not only adaptations to survive fire, but in many cases, are also dependent on it. According to Faith Ann Heinsch, Greg Dillon, and Chuck McHugh, of the U. S. Forest Sevice’s Rocky Mountain Research Station, who responded in an email, all ecosystems are adapted to fire in some way. Some ecosystems require fire to function. In the western U. S. many vegetation types evolved with fire whether from natural or human causes, though they require different types and frequencies of fire. The open, dry ponderosa pine forestes of the western U. S. require frequent, low intensity fires that burn approximately every 10-15 years to keep the area open. Lodgepole pine forests, also of the western U. S., require less frequent high intensity fires. In many places, they are adapted to stand-replacing fires that occur every 100 years or so. The longleaf pine forests of the southeast are also adapted to fire as it clears out competing vegetation. In these ecosystems, plants have developed a number of specific adaptations. W. J. Bond of the University of Capetown and R. F. Keane of the Rocky Mountain Institute in “Ecological Effects of Fire” (2017) cite thick bark, open crowns, deep roots, and sprouting from insulated buds. In addition, several species of conifer have what is called serotinous cones, meaning they only open in intense heat. Bond and Keane also say that grasses are among the most fire resistant species and can survive frequent fires, though few species are dependent on burning.
There are a number of ecological benefits to fire. In addition to opening serotinous cones, Heinsch, Dillon, and McHugh say it can improve forest health and create better wildlife habitat. It also helps to return nutrients to the soil. Bond and Keane state that fire-stimulated flowering is common among grasses and herbs. In addition, they also say that dormant seeds in soil show heat stimulated germination. In grasslands, fire helps avoid encroaching trees and shrubs. Elk, deer, and bears eat vegetation in areas opened by fire. According to Richard L. Hutto, Robert E. Keane, Rosemary L. Sherriff, Christopher T. Rota, Lisa A. Eby, and Victoria A. Saab, “Toward a More Ecologically Informed View of Severe Forest Fires” (2015), black-backed woodpeckers (Picoides arcticus) eat the larvae of wood boring beetles that are attracted to trees killed by fire. While they are known to occur outside severely burned forests, studies show growing populations only in recently burned forests.
In spite of fire’s role in the ecosystem, the main policy of the Forest Service for several decades has been fire suppression. However, in ecosysems that are adapted to fire, this has had a negative effect on flora and fauna. It is only relatively recently that the true role of fire had been studied seriously. Heinsch, Dillon, and McHugh stated that fire suppresssion began with European settlement and started in earnest during the early to mid 1800’s. They also said that a major fire in 1910 set the stage for full fire suppression. According to Diane M. Smith, “Missoula Fire Lab: 50 Years Dedicated to Understanding Wildlands and Fire” (2012), in the early twentieth century most political leaders saw fire as too dangerous to be allowed to burn, though this resulted in harming the ecosysems the agencies sought to protect. Smith also refers to the 1910 fire and said estimates vary, but it burned approximately 3 million acres and killed over 80 people, most of them firefighters. Nevertheless, Gifford Pinchot, the first Chief of the U. S. Forest Service, and his contemporaries understood the beneficial role of fire. Fire suppression left forests more vulnerable to disease and insect infestations. In the early to mid twentieth century research began on the causes of fires and how they spread. In 1970, a study tested a new approach to fire management in the White Cap Creek Drainage in Idaho. Vegetation was sampled, evidence of fire history was collected, and the effects of fire exclusion. In 1972, a fire was allowed to burn and it put itself out after four days. In 1973, another fire was also allowed to burn and it was only put out when it moved beyond the test area.
While fire is important to a number of ecosystems, some recent wildfires have killed a number of people in addition to causing serious property damage. So, are wildfires getting worse, or is this the natural order and what should our response be? The next article will look into these questions.
The Nature Journal 