Wildfire Hazard Mitigation Protects Forest Values
Wildfire mitigation projects are designed and implemented with the intent to reduce the potential intensity and burn severity of a wildfire. Note that the term “fireproof” is not used. The objective of wildfire mitigation in the forest is not to “fireproof” the forest. Reducing fire intensity near homes and designated roadside evacuation routes during a wildfire gives firefighters a better chance at putting the fire out in a prompt and safe manner. It also provides citizens and firefighters with safe escape routes. These are critical issues in locations where lives and property may be at risk.
In more remote “backcountry” settings wildfire mitigation priorities often include municipal watersheds and areas with significant natural resource values. Mitigating potential wildfire damage in these forest environments is primarily accomplished by reducing the potential for a high severity burn. High severity burns expose soils to high temperatures for an extended duration of time and consume all or most of the organic matter present on the forest floor. Forests with excessive accumulations of woody fuels are targeted for wildfire hazard mitigation projects because they have the greatest potential for a high severity wildfire.
The combustion of organic material during a fire with long duration and high intensity creates gasses that penetrate the soil and condense to form a water repellent coating. During intensive rainfalls water which is not easily absorbed into the soil flows downhill over exposed soil that is no longer protected by a layer of organic material. The erosive force of the water expands exponentially as the depth of flowing water increases. This is why erosion and mudflows are a particular concern in high severity burn areas. It is also a reason that municipalities who depend on forested watersheds for clean water are highly concerned about reducing potential burn severity in order to protect water quality. Water flowing from a high severity burn area is likely to be heavily laden with sediment and debris and may overwhelm the capacity of municipal water treatment facilities to treat the water.
In contrast, a fire which burns through an area where wildfire hazard mitigation work has been completed will burn less intensively and with shorter duration. In fact, it is likely that many trees will survive the fire. Remnants of down logs, needles, limbs and decayed organic matter will remain present on the forest floor after the fire. This material helps to protect the soil from runoff and erosion and helps the soil to absorb water. Forest vegetation recovers quickly in low intensity burns from surviving plant roots and unburned seed. Weed infestations are less likely because less mineral soil is exposed to act as a seed bed.
Wildfire hazard mitigation work is typically accomplished by decreasing forest density. The primary goal is to reduce the amount of woody fuel that is available to burn at high intensity and at a long duration. Typically, smaller less commercially valuable trees are targeted for removal. If cut trees are of sufficient size and quality, they may be harvested and sold to local wood products manufacturers. In ponderosa pine, Douglas-fir, and western larch forests the largest, healthiest and most fire resistant tree are typically retained on-site. The mature trees are resistant to low intensity fire damage due to their thick protective bark. Small, stagnated, and unhealthy trees are removed to create open space between larger trees. The openings created in the forest canopy allow heat to escape during a fire and reduce the potential for a crown fire.
Wildfire mitigation projects protect a safer environment for firefighters and citizens, improve forest health and help to protect water quality. They result in a forest condition that provides sustainable ecological and economic value to Montana citizens. Environmental safeguards incorporated into the design of projects ensure that numerous natural resource values are protected for generations to come.