What is a prescribed fire?
A prescribed fire is a fire ignited under pre-determined weather conditions for specific resource management objectives including fuel reduction and brush control, and to reintroduce a natural disturbance to a fire-dependent forested landscape.
How are prescribed fires conducted?
The first step is creating firebreaks, or pathways that surround the burn site. To create firebreaks, trees, shrubs and grass are cleared using a chainsaw, mower or other equipment. The firebreaks may also be raked or disked using a tractor to remove nearly all flammable wildland fuels. An example of an already existing natural fire break would be a river or lake.
The burn unit is then ignited using drip torches—portable canisters used to drop small amounts of flammable material (usually a mixture of diesel fuel and gasoline) along a fire line. A carefully planned ignition pattern utilizes wind direction, topography and other factors to help control the spread of fire until it extinguishes itself at the firebreaks, where it runs out of fuel.
Special wildland firefighting equipment also helps control the fire and protect the fire crew – such as mobile water sources (e.g., an ATV or pick-up truck with a water tank and pump), flame-resistant clothing, specialized fire control tools (e.g., backpack pumps and a wide range of hand tools), portable pumps and hoses.
How is the fire kept under control?
Four strategies are employed in every burn to keep the fire under control:
- Setting prescriptions—or required conditions—for elements such as wind speed and direction, relative humidity and other factors ensures that the fire will only be ignited under safe, manageable conditions. Prescriptions also include estimates of fire behavior, identifying the crew and equipment needed to manage the fire, making back-up contingency plans and setting other specific guidelines for the burn.
- Trained burn crew members continuously patrol the burn unit and its firebreaks watching for potential hazards. They use wildland fire fighting equipment when needed to ensure that the fire remains within the burn unit boundaries.
- Establishing firebreaks and a specific fire ignition pattern restricts the fire to the targeted area.
- Emergency fire suppression equipment—including fire pump trucks—stationed at each burn can be used to quickly extinguish the fire should weather conditions change or the fire threaten to escape control.
How will this affect the ecosystem, including plants and wildlife?
Extensive research in hardwood forests shows that fire helps cycle nutrients and reduces the invasion of less desirable fire-sensitive species such as non-native buckthorn, native hazel and ironwood. Fire can also improve the vigor of the fire-dependent plants more characteristic of these fire-dependent systems.
Because prescribed fires are relatively small and slow-moving, most wildlife can easily escape the flames by moving to adjacent areas or by hiding in underground burrows. Some birds fly away, while others, such as hawks, may soar overhead, hunting for small prey flushed out by the fire. Some mortality of small animals may occur during fires; for this reason, land managers conscientiously burn small fragments at a time. Patchwork burning (i.e., burning one-quarter of a preserve in a given year) enables small animals to find refuge from fires and enables recolonization of burned areas from these refuges after the fire. It is important to realize that not burning will, in the long term, lead to loss of habitat for some wildlife species. While burning may entail short-term loss, fire managers look at habitat and wildlife management over the long term.
Fire is beneficial because it helps preserve biodiversity by maintaining habitat for species that need sunny, drier conditions to germinate and thrive, such as most oaks and many herbaceous wildflowers. Once the canopy is opened up by fire, it may provide an opportunity for these species by increasing the light on the forest floor.
Changes brought on by the fire can create habitat that draws an influx of new species, while other species may decline in response to the changed environment. Burned trees can provide shelter for small animals and an abundant food source for wood-boring insects such as ants, beetles and wasps. While the post-burn conditions may be less hospitable to some nesting birds, they may help others to thrive by meeting their specific habitat, food source and nesting requirements. For example, a 1995 study in California showed that nests located within a burn zone had a success rate 15% higher than in the unburned habitat. In this way, prescribed burns can help increase biodiversity by providing food and shelter for a changing variety of wildlife.
FAQs used with permission from Gabe Chapin, Nature Conservancy Land Steward, New York (firstname.lastname@example.org) and the Shawangunk Ridge Fire Management web site.