Fire is a powerful,
natural phenomenon. Fire has great impact on the people and environment
of North America as one saw when in 1988 wildfires broke out all over Yellowstone
National Park burning 793,880 acres. For hundreds of years man has
suppressed wildfires. The federal government controls fires on federal
forestland, and state government controls state forestland. It was
believed that by suppressing the fires man ensured a healthy future for
the forest. But, as scientists have gathered more information on
the effects of fire on forest ecosystems, they have learned that fire exclusion
might not have been the best practice for land management. A new
technique known as prescribed fire has been used in the last twenty years
to reintroduce the natural process of fire back into the forests.
While not all the effects of prescribed fire are seen right now, we do
know the effects of fire exclusion, and we do know some of the benefits
of prescribed fire.
Over the past couple of decades, forest management teams have noticed that fire suppression has caused many problems in the forest ecosystem. Today it is known that fire exclusion causes thick vegetation and large amounts of dead fallen materials. The heavy vegetation and dead material increase the fuel quantity on the forest floor and may cause fires to ignite more easily. When a fire does begin on the thickly covered floor, the blaze burns at a much higher intensity causing more damage to the forest ecosystem.
Not only does fire exclusion cause an accumulation of thick vegetation on the forest floor, but also causes and increased density of smaller trees. When fire does occur, these small trees guide the raging fire from the forest floor to the crown of the older trees causing a crown fire.
Another observed result from fire suppression is vegetation modification. Forests that have not had a fire in decades may become the home to a plant species that is not adapted or dependent on fire. Plants that are adapted for wildfire usually have a thick layer of bark to protect its living tissue from the heat. Also, many trees are dependent on the heat of fire in order to open up their seed cones for regeneration. Vegetation modification also effects the ecosystemís insects and diseases, wildlife populations, soil structure, and nutrient recycling.
Thick vegetation, excessive dead material, and vegetation modification all caused by fire suppression, have caused forest managers to turn to a technique known as prescribed fire. A prescribed fire is a fire that is started by man or by nature and is monitored very carefully. Such items that forest managers consider when starting a prescribed fire are wind conditions, seasons, weather, humidity, the amount of moisture in dead vegetation, and the fullness of the forest floor vegetation. If all of these conditions prove favorable for a fire then the forest manager will plot an area for the burn. Boundaries are usually set using natural firebreaks such as roads, ditches, and water. The firebreak must be devoid of natural fuels so that the fire cannot spread past its boundaries.
Forest managers clearing the firebreak.
On the actual day of the fire, the fire planners will again check such conditions as wind and moisture content in the vegetation. The wind direction will determine where the fire is started. Fire crews start the burn with a device called a drip torch. A drip torch is a can of fuel with a flame-carrying wick at the end. When the crewmember tilts the wick toward the ground, a flame streams out and ignites the vegetation. Most of the effort that goes into a prescribed fire is making sure that it is contained in the boundaries set for the fire. Firefighters and fire suppression equipment are near the site if the fire grows out of control.
Firefighters wearing protective gear while setting a prescribed burn with a drip torch.
While not all
the effects of prescribed burns are known some are very evident.
The first of these common effects is that vegetation and fallen dead material
are burned creating an open forest floor. This eliminates any fuel
that could contribute to a high intensity fire in the future. When
the fire burns the organic material in the forest, nutrient rich ash is
left behind. When the first rain comes, the nutrients in the ash
dissolve into the soil for the new plants to use. This process is
called nutrient recycling. These nutrients left in the soil are a
good source of food for the young plants that will begin to grow back.
Another outcome of prescribed fire is that new growth begins immediately after the fires have been extinguished. Within a few weeks green will emerge from the layer of ash. Many of the seeds that sprout were protected under the soil before the fire occurred, but some were released during the fire. Some trees, like the lodgepole pine, release cones, and those cones release their seeds when heated. The new vegetation that begins to grow thrives in the nutrient rich soil. Also, the new plants have little competition for sunlight and food which enables them to mature at a faster rate.
Regrowth after a burn
have concerns that prescribed fires effect animals in a negative way.
The fire itself does not harm the animals for several reasons. Most
prescribed burns travel at a slow rate of 0.1 to 1.6 miles per hour giving
most insects and animals time to leave the area or burrow deep into the
ground. Only 290 animals were found dead as a result of the Yellowstone
fires in 1988, and this fire was uncontrollable and burned at very high
intensities. Also, most prescribed fires occur in February, March,
April, September, October, early November when animals are not nesting
or caring for their young. The real threat that animals face is when
the fire has been extinguished. Finding food and shelter are the
main problems animals encounter after the fires. But most creatures
migrate to other unburned areas of forest and return to their old home
when food and cover grow back.
There are also concerns with the air pollution that prescribed fires cause when the fires release smoke into the atmosphere. One major argument against this is that although prescribed fires release smoke, they do not release as much smoke as uncontrolled fires do. Many steps such as monitoring wind and fuel moisture are taken to ensure that the smallest amount of smoke will be released. Forest managers do all they can to meet the guidelines on air quality set by government agencies.
Should forest management teams continue to reintroduce fire into forest ecosystems? Gathered from most research, the answer is yes. More and more government agencies such as the National Parks Service and the USDA Forest Service are adopting prescribed fire plans. Although not all of the long term effects of prescribed fires are known, most evidence shows that a prescribed fire planís benefits outweigh a fire exclusion planís benefits. Several things need to be done in order to keep fire prescription a useful technique. More studies need to be conducted on the long term effects of a prescribed burn. Also, the publicís awareness of prescribed fire needs to be raised. Until man realizes that fire shaped most of the forests that we see today, we will let our forest ecosystems slowly dwindle away.
Other Related Sites
National Interagency Fire Center
Wildfire News and Notes
Fire in Yellowstone
Forest fires broke out in the Chattahoochee National Forest on November 14, 1999. The fires were started by human activity. The fires have been burning for a week now and have been contained in the fire lines. Dry weather is to blame for some of the spread of the fires. Some rain has fallen aiding firefighters who are extinguishing the blaze. No information could be found to see if there had been any major fires in the past years. We do not know if prescribed burning could have prevented these fires from occurring. Also, no information could be found on prescribed fire practices.