Around mid-summer each year, stories about wildfires, especially in the Western United States begin to dominate the news. Since 2000, there have been between 40,000 to 100,000 wildfires in the U.S. each year that are responsible for an average of 19 fatalities and 7 million burned acres (about the size of Massachusetts).
When humans live in regions that experience natural burns, there are bound to be problems. Even worse, modern fires are becoming larger and hotter than historic fires. Following some severe wildfires in the early 1930s the US Forest Service was given the task of suppressing fires in order to protect forests. Recall the Forest Service’s mascot Smokey Bear’s familiar mantra, “Remember, only YOU can prevent forest fires”. Although the Forests Service’s suppression efforts were effective, there was a consequence of suppressing all these fires. Without any forest fire, all the leaves, grasses, branches, and trees that fell to the ground began to accumulate fueling much more severe forest fires! On top of that, climate change is resulting in dryer and longer summers, which is the perfect recipe for more severe wildfires.
Of course, destructive fires cause huge problems for people living in those areas, but that leads to the question: are all fires bad? The answer is – NO! In many parts of the country, fires are really important for a healthy ecosystem. Historically, in the southeastern US, frequent ground fires removed much of the natural forest litter, but were cool enough to allow for large trees and much of the below ground stuff (like tree roots) to survive. These ground fires help maintain a diverse variety of grasses and herbs that are adapted to fire.
In the western U.S., wildfires aren’t always so tame. In 1988, Yellowstone National Park experienced severe wildfires that killed trees over a large area. Despite the destruction, such severe stand-replacing fires are part of a natural fire cycle in the Park. In fact, the common species of pine in this region, known as Lodgepole Pine, has a unique adaptation known as “serotinous cones” where seeds are tightly trapped inside cones that can only be cracked opened in the high temperatures that occur during fire. Although the Yellowstone fires killed adult trees, a new generation of pine seedlings were released after the fire from the serotinous cones. Far from being destroyed by fire, the burned forests were actually renewed by it.
Fire also has an interesting role in the evolution of both plants and humans. The origin of fire occurred early in the history of life when plants first evolved the ability to live on land. Think about it: To combust, fires require oxygen (which was being produced by plants) and dry fuel (which came from the plants themselves!). Charred plant remains have been found that are dated back to 440 million years ago.
But fire wasn’t just important in the evolution of plants, it also played a role in the evolution of humans. The rise of Homo erectus is linked to fire which played an integral part in cooking, safety, and development of social abilities (like sharing of labor for hunting and cooking). After the extinction of large herbivores (such as mammoths, and ancient species of horse, deer, and bison), scientists believe fire was used to clear land for human habitats, to attract game for hunting, and to stimulate the growth plants used for foraging.
Many scientists and governmental agencies now recognize that fire has long played a role in shaping ecosystems and understand the dangers of completely suppressing fire. In fact, many agencies and land owners are now literally fighting fire with fire by using controlled burns to reduce fuel build-up to prevent more severe fires in the future. Prescribed fire is also used to restore natural fire regimes and habitats, or to enhance the vegetation for game animals. The Forest Service has even changed Smokey Bear’s mantra to recognize the importance of some fires. Have you noticed that the new slogan has been updated to, “Only you can prevent wildfires”?
Far from being all bad, fires have a renewing effect on many ecosystems and many ecologists and land managers are working to strike a balance between the destructive potential and the ecologically renewing effects of fire.
- Forest History Society, U.S. Forest Service Fire Suppression. U.S. Forest Service History. URL: http://www.foresthistory.org/ASPNET/Policy/Fire/Suppression/Suppression.aspx.
- Pausas, JG and Keeley, JE, 2009. A burning story: The role of fire in the history of life. BioScience 59: 593–601.
- National Wetlands Research Center, 2000. Fire Ecology in the Southeastern United States. Factsheet URL: http://www.nwrc.usgs.gov/factshts/018-00.pdf.
- National Interagency Fire Center, 2014. Fire statistics. http://www.nifc.gov/fireInfo/fireInfo_main.html
- Turner, 2004. Surprises and lessons from the 1988 Yellowstone fires. Frontiers in Ecology and the Environment 1: 351–358.