Bitterroot Valley Wildfire Response Guide

Reducing Fuels in the Wildland Urban Interface (WUI) Area

Introduction – In the Bitterroot Valley over the past 2 decades, several large wildfires have burned either into the wildland urban interface (WUI) from surrounding public lands, or from private lands onto public lands. Some were human-caused and some were lightning-caused, but all fires had some level of impact to residents and visitors. It would be unrealistic to think we will not have more fires in the future considering the effects from climate change on the vegetation and that this area needs wildfire as part of its natural life cycle. Whether these major fires will be a disaster or just a well managed event is our choice depending on how well we are prepared. We need to prepare for wildfires in the WUI by reducing trees and brush (fuels) in and adjacent to the WUI.

Much of the lower elevation private and public lands in the Bitterroot Valley are either grasslands or forested areas containing ponderosa pine, western larch and Douglas-fir trees.  Researchers, counting tree rings from tree “cookies” cut from fire-scarred ponderosa pine tree stumps in this area estimate that wildfires historically moved across these lower elevation landscapes as often as every seven years. This means these are fire-dependent ecosystems – ecosystems that are maintained and sustained by wildfire- as a natural and necessary process. Typically, these fires were of low intensity, burning along the ground.

As European settlers moved into the valley and constructed homes, barns, fences and other structures in these fire-dependent systems, one can only imagine the challenges they had in trying to protect these structures from the frequent wildfires.  Very quickly, wildfires became an unwelcomed guest and were suppressed whenever possible.  As fire suppression technology became more effective, so did success in preventing wildfires.

This success in firefighting and fire prevention came with consequences. By interrupting this natural and frequent process, some unhealthy changes to these ecosystems occurred.

• Natural fuels removed by frequent low intensity wildfires in the past have now accumulated to hazardous levels in many areas creating the potential for large, intense wildfires to occur.
• The landscapes were once mostly open mature ponderosa pine stands with lots of grasses and herbs growing underneath are now dense stands of mixed ponderosa pine/Douglas-fir trees, adding to the potential for high severity fires that would damage important watersheds and reduce browse and forage for animals.
• Many more trees per acre equates with evapo-transporation and more “intercepted loss”. This means that the snow lands on tree limbs and evaporates instead of landing on the ground and melting. This results in less water in streams impacting fisheries and irrigation potentials.
• Conversely, when large, intense wildfires damage more trees, the opposite occurs. The risk of erosion greatly increases because of more water run-off with no evapo-transpiration or intercepted loss and much bare soil. This can lead to flooding and detrimental impacts to fisheries.

Ultimately, years of fire suppression and other human activities created a presently unsustainable landscape condition across much of the forested areas of the Bitterroot Valley. To see the vegetation changes, here are three pictures all taken from the same spot in Lick Creek west of Darby over a 70 year period.

The term “Condition Class” in the pictures above refers to how many times the area missed experiencing its natural fire frequency. Condition Class (CC) 1 implies low departure meaning the area has recently burned and vegetation and other conditions are close to natural conditions, CC 2 has moderate departure, and the area has missed one or more fire cycles and vegetation changes from the natural condition are becoming obvious, and CC 3 has high departure, meaning several fire cycles have been missed, vegetation changes are considerable, and the situation is no longer sustainable. Using satellite imagery, all of Ravalli County has been mapped by condition class and that map is displayed below.

While the map doesn’t clearly display the locations of the changes, it does indicate much of the moderate and high departure areas (CC 2 in yellow and CC 3 in orange) are found along the boundary between National Forest and private lands. These are the lower elevation lands in the Bitterroot Valley that are now at most risk from wildfires and where many homes and subdivisions now exist.

With this volatile condition class and increasing development, land managers and residents need to talk about mitigating the fire risk. Together, we need to address hazardous fuels reduction in the wildland urban interface (WUI) where structures or other human development meet with undeveloped forest and rangelands.

For the Bitterroot Valley, it is the area immediately adjacent to, and on both sides, of the boundary between the Bitterroot National Forest and other land ownerships.  The WUI has recently been mapped for Ravalli County and the following map shows the results. The darker green area is the WUI that includes National Forest lands and the light purple area is the WUI in other ownerships.

Treatment of hazardous fuels is an effective, proactive way to reduce the potential impacts from wildland fire. Reducing the density of trees and shrubs reduces the fire risk in an area and increases the chance that fire protection agencies can control a fire more quickly. Defensible space practices and forest fuel treatments are effective ways of protecting residential homes, neighborhoods, communities, and watersheds.

Tens of thousands of acres of fuel treatment have occurred on private, state, and federal lands over the past decade but there is much more to do. A Montana Department of Natural Resources and Conservation (DNRC) and Forest Service, estimated over 162,000 acres of high-risk forested areas within the Valley’s WUI need some kind of fuels reduction activity to adequately lower fire risk and protect area residents. Once the fuels are reduced, regular maintenance is necessary to maintain the conditions that contribute to lower fire risks.

The map below shows the completed hazardous fuel treatment areas in the past 10 years on Bitterroot National Forest and those treated on private lands through grant programs administered by the Bitter Root RC&D. From 2001-2009 the Bitter Root RC&D has obtained over 3.5 million dollars in grant funding through the Forest Service State & Private Forestry program and State of Montana DNRC under the Western States grant and Community Protection Fuel Mitigation (Stevens) grant. These grants cover Ravalli, Mineral, and Missoula Counties as well as four other RC&D’s in other parts of Montana. The U.S. Forest Service continues developing and implement fuel reduction projects on the Bitterroot National Forest using a combination of commercial thinning (selling the trees for timber or biomass) to open the spacing between the crowns of trees, pre-commercial thinning to reduce and remove ladder fuels which are dead lower limbs on trees, clumps of smaller trees, and down material that allow a fire to climb up into the crowns of trees, and a combination of piling and chipping. The Forest Service works with several adjacent private landowners who already treated and reduced the trees and brush on their properties or are planning to treat fuels to coordinate fuel and fire mitigation efforts.

In preparing the Stevensville West Wildfire Response Guide, crews will identify the high risk areas on both private and public lands in the WUI. With this information, fuel reduction work can be concentrated in areas of highest priority and potential effectiveness (highest values, greatest hazards, highest population density, and high fire occurrence frequency) and where the negative impacts of wildland fire would be greatest.