Resilient landscapes are the key to surviving wildfires

Recent, widespread and destructive forest fires in Oregon and throughout the West have rekindled debates about what really causes them. Scientists, forest managers and most all of us, want and need to understand causal factors in terms of individual events and the cumulative risk they represent over the years. Our knowledge has improved significantly over the last few decades.  

It is clear that recent increases in the number of large fires, their size and their impact on the land and human communities are tied to both increasingly hot and dry climate patterns and fuel increases across these landscapes. Efforts to blame one or the other are simplistic, site specific and/or politically motivated. In these times, we need to pull together and address this most pressing land management challenge because the solution to preventing tragedies and coexisting with wildfire will require it. 

Weather and fuels are fundamental to understanding and predicting fire behavior, as well as topography. Fortunately, our topography remains relatively constant, but weather and climate have been warming; in the absence of increased precipitation, this drives longer fire seasons and drier fuels in general. Fire seasons are already longer and all climate projections suggest that trend will continue. Against that climate and weather backdrop, many of our forested acres have more fuel within them than ever historically present, and those acres are more connected to each other than they likely ever have been. This is the result of Euro-American settlement and our management decisions for the last century.

Oregon and much of the Pacific Northwest historically experienced frequent, landscape-scale fire that mostly burned at low-to-moderate intensity, distributing relatively minor fire effects across a complex matrix of vegetation types. Ecosystems and ecotones (transitions among systems) were arranged and maintained somewhat predictably based on topography, climate and fuels:

• Grasslands that burned most frequently, sometimes annually, created and maintained ecosystems with little to no woody vegetation other than that found in protected sites due to topography and moisture availability.  

• Savannas burned nearly as frequently as the grasslands, but with sufficient safe sites distributed predictably over time and space to allow for the regeneration and persistence of a low density of trees. 

• Woodlands and sparse forests were developed and maintained on favorable microsites within these grassland and savanna landscapes that led to small-scale forest conditions. 

The combination of these first three dominated the landscape across lower elevations. Historic landscape photos document these conditions throughout much of the Pacific Northwest, supported directly by fire scars and charcoal in lake sediments and indirectly by tree growth reconstructions. With increasing moisture availability due to elevation and aspect, interacting with soil conditions and/or subsurface water, more dense forest conditions developed and were maintained on favorable sites, like pure ponderosa pine forests (with multiple fires per decade), mixed-conifer forests (multiple fires per century) and moist forests with multiple centuries between fires. 

These fire regimes, burning and reburning, dictated forest stand dynamics — frequent low-intensity fire maintained relatively low stem densities and basal areas, uneven-aged stand structures and low fuel loading dominated by grasses and other flashy fuels; complex spatial patterns often emerged in areas with micro-topography or other variability in moisture and associated fuels. Such interplay of composition, structure and dynamics ensured the low-to-moderate severity of subsequent fires, bringing this process full-circle. The gradual transition to less frequent fire with elevation and moisture created and maintained fire behavior variability in time and space, leading variability in composition, structure and dynamics that self-perpetuated. Our ancestors managed these fire regimes for millennia.

However, European settlement beginning in the late 1800s largely suspended landscape-scale fire with: one, the introduction of abundant domestic grazing that disrupted fuel continuity; two, concentrated human settlements and associated selective logging of larger trees for the construction of infrastructure; and three, the creation of organized fire suppression. Early fire suppression technology was limited but often still effective given the low quantities of fuel following grazing and with low, scattered densities of trees; however, following the 1910 fires and certainly by the 1940s, fire suppression technology was advancing rapidly and was highly effective at keeping most fires small during a relatively cool and moist climatic cycle, even with fuels accumulating rapidly on the landscape. In this way, fire was largely excluded from much of the landscape for more than a century. 

This long period of fire exclusion in dry ponderosa pine and mixed-conifer forests resulted in: more trees and more interconnected acres with more trees, expansion of less fire-adapted vegetation, increased surface fuel loading in the absence of regular underburning, decreased tree and forest vigor, and alterations to soils, nutrient cycles, watersheds, streamflow and a long list of other ecosystem services.

This is the backdrop for the modern large wildfire narrative, in which fire-adapted ecosystems ironically become the victim of wildfires. In which a resistant and resilient mix of ecosystems developed and sustained for millennia across broad, complex fire-adapted landscapes burn uncharacteristically. In which the inter-dependent processes of regeneration, growth and mortality processes once activated by fire to form a “memory” on the land is subsequently erased by modern large wildfires. And our mistakes and mismanagement at the stand scale, compounded over generations and careers, now explode to the landscape scale and across ownerships.

So, our current wildfire crisis is fundamentally rooted in climate change and our shortcomings around land management, including fire management and suppression, coupled with sociocultural change and an increasingly large human footprint downwind of the fuel. That is our situation, that is our understanding and that is our restoration challenge moving forward. We need to come together across ownerships and political interests to recreate resistant and resilient landscapes in this new reality.

John Bailey is a professor in College of Forestry at Oregon State University, where he teaches silviculture and fire management. He and his students/research team explore the specifics of various fuels and forest restoration options, their effect on the ecosystem and subsequent fire behavior, wildfire risk analyses and reduction strategies, and post-fire ecosystem recovery and management.