Crosscutting Fuels and Multiple Benefits Evaluation and Validation

Background

Photo Credit

USDA Forest Service Photo by Ryan Conway

A landscape image from the Eldorado National Forest.

Over much of the West, a history of fire exclusion and past management practices has led to large-scale changes in landscape patterns and processes. In response, forest growth in the region has progressed unchecked by wildfires leading to the accumulation of surface and canopy fuels, transitions to fire intolerant species, and forest encroachment into non-forest patches. Over large scales, these processes translate into a highly contagious landscape with few barriers to prevent fires from becoming large and severe. As a result, ecosystem resilience to wildfires –entrained in these systems through recurrent fires – has largely been diminished, and local communities and associated infrastructure embedded in these landscapes are imperiled by future wildfire.

Efforts to combat the rising tide of severe wildfires throughout the West stem from a need to strategically allocate treatments to maximize their benefits. This often leads to treatments located in and around vulnerable communities – a strategy proven to help protect life and property. However, given that the upper 2% of fires contribute the majority of burned area each year, the landscape context within which communities are situated is critically important to the delivery of fire to these communities. Furthermore, fuel reduction treatments are effective at not only protecting resources but can also improve other resource benefits including carbon uptake and storage, wildlife habitat, and hydrologic productivity. Taken together, managers must consider not only the proximal benefits to risk reduction but also their potential contribution to other key ecological and cultural resources and their impacts on the broader landscape resilience.

A Cross-Collaboration Among R&D Stations

Scientists from the Pacific Southwest Research Station (PSW), Southern Research Station (SRS), and Oak Ridge National Labs (ORNL) are collaborating on a computer simulation model for informing the strategic placement of fuel reduction treatments in fire-prone landscapes. The model provides a spatially explicit treatment design aimed at mitigating severe fire spread while maintaining multiple ecosystem services over time. The prioritization leverages a variety of established tools as well as a new agent-based model developed by SRS and ORNL – FIREPATH – that together assess wildfire contagion at regional scales in relation to their potential impacts on key resources and assets.

Modeling fuel contagion and wildfire spread

FIREPATH is a new agent-based model that identifies likely pathways of fire among key resources identified on the landscape and then assigns fuel treatments specifically to stem the flow of fire to these important patches. The model uses LANDFIRE fuels, topography, and windspeed data to delineate corridors of fire flow between the patches, where patches are delineated representing any number of valued resources such as old-growth forest, critical habitat, infrastructure, or rural communities. Walkers originate from each patch and their paths are recorded if they successfully reach another patch. Over thousands of model iterations, highways of fuel contagion emerge and indicate areas where treatments can potentially disrupt the flow of fire to prevent patch-to-patch spread.

In a parallel effort, PSW scientists are combining mechanistic wildfire spread models developed by the Rocky Mountain Research Station (RMRS) with a spatial connectivity model, Omniscape, borrowed from the field of animal movement ecology, which uses circuit theory to find high-conductance routes across a landscape (i.e., high fuel contagion). Combined, these models produce maps depicting cell-level fire behavior and heat maps used to identify potential “corridors” of severe fire spread. Targeting these wildfire highways with fuel reduction treatments may help to mitigate fire severity at local and landscape-levels via the strategic placement of fuel breaks.

Decision support modeling for prioritizing fuel treatments for multiple benefits

Given the scale and the scope of the wildfire crisis across the Western US, decision support tools are needed to prioritize fuel reduction and ecological restoration treatments to help maximize their utility. Understanding the amount, distribution, and connectivity of fuels across landscapes is a move in the right direction in terms of planning management responses to the crisis. However, given the many ecosystem services provided by forested landscapes, managers must consider how treatments may impact conditions locally as well as the potential downstream effects on other resources. Furthermore, ongoing climate change adds further uncertainty regarding the appropriate management responses to attain and maintain desired treatment outcomes.

The PROMOTE decision support model was designed to provide users with insight into the conditions across multiple resource benefits (e.g., forest resilience, carbon, biodiversity, fire dynamics, water security) while also considering their vulnerability to climate change. Across resources, PROMOTE provides a quantitative level of support for four management strategies: Monitor (good condition now and in the future), Protect (good now but vulnerable to climate change), Adapt (poor now but low vulnerability to climate), and Transform (poor now and in the future). Strong support for any one of these strategies may suggest either a hands-off management approach or indicate where active management may help attain and maintain desired conditions.

PROMOTE model outputs are also being used within spatial prioritization software, such as FORSYS, to develop a treatment schedule to maximize benefits across multiple ecosystem resources. For example, in the Upper Mokelumne River Watershed Authority landscape in the central Sierras we are integrating fuel connectivity modeling with PROMOTE outputs in Potential Operational Delineations (POD) boundaries, to determine areas with high fuel connectivity and the potential to improve conditions across resources under climate change constraints. These treatments included selecting POD boundaries to reduce fuel contagion, target areas with the Adapt PROMOTE strategy for biodiversity, carbon, and forest resilience, and avoid treating in Monitor areas. These treatments were then modeled to simulate prescribed fire and thinning treatments. Treatment impacts were evaluated as changes to fuel connectivity to the entire landscape and to “high value” patches (including late seral forests, and patches of resources in Monitor condition). We have found that simulated treatments placed in areas with high fuel connectivity can reduce wildfire contagion locally and to ancillary resources away from the treatment placements, and that outcomes of treatments are highly dependent on their spatial arrangement in the landscape.