Industrial Timber Production Increases Fire Risk (And Other Things the Gov’t Doesn’t Want You to Know) Tom Wheeler, EPIC Fire severity—how impactful a fire is to the natural environment—escapes easy explanation. There is no one thing that determines fire severity, rather a variety of factors influence it. But looking across millions of acres of burned land in the West, one thing bears true: fires burned with less intensity on lands that had the highest protections from logging. Why is this? Wildland fire behavior is sometimes explained using the fire behavior triangle, with fuels, weather/ climate and topography all interacting with each other to influence how fast and how hot a fire will burn. Logging affects two sides of this triangle: fuels and weather/climate.
Logging obviously removes some “fuels” as trees and brush are combustible. But this simple truth masks some of the important complexity. How fuels are distributed within an area, both vertically and horizontally, together with their type (fast burning “fine” fuels, like leaves or twigs vs. longburning “heavy fuels, like logs, which may smolder longer but don’t typically flare up) and moisture all impact fire behavior. While logging removes some
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fuels, it typically removes the heavy fuels while redistributing finer fuels—the logging “slash” of limbs, tops, branches and needles—from standing trees to the ground. This can leave “jackpots” of fuels that can cause sudden and aggressive flare ups. Clearcut logging introduces yet another issue: uniform crown structure. As clearcutting produces even-aged forests, the tops or “crowns” of these trees will be approximately the same height. And given the high density of trees typically replanted after a clearcut, these are going to produce an interlocking, dense crown. If fire jumps to the crown, the fuel continuity provided by this uniform crown structure can quickly cause fast-moving and highly impactful fires. Logging also impacts the likelihood of tree survival. Large, old trees generally are more resilient to fire. Their thick bark helps insulate the trunk from damage and tall branches make fires jumping from the forest floor to the crown more difficult. Of course, logging can both remove big resilient trees and make their future development more difficult, as they are logged before they can reach a nice, ripe age. Weather and climate are Slash piles can leave “jackpots” of fuels that can cause sudden and aggressive flare-ups. Photo credit: Art Mielke, Mendocino Trail Stewards. also extremely important to understanding fire behavior. in forest products, like paper or lumber, the majority Logging affects both weather of carbon in a tree becomes susceptible to release as and climate. Cutting shade-producing trees can both greenhouse gases soon after that tree is logged. Only increase in-forest temperatures and reduce moisture a small percentage of a tree ever becomes a stable in the forest, producing a parched microclimate. forest product; the majority of the rest is typically Thinning trees increases in-forest wind speed, which burned or decomposes along the way, either in can both create a drier forest through enhanced slash piles in the forest or as “mill waste” burned to evaporation rates as well as fanning the flames produce heat or energy. By taking carbon that was during a fire to produce a greater intensity. safely sequestered for many decades and releasing While it is clear that logging can impact siteit suddenly in a quick pulse, logging significantly specific conditions that intensify fire behavior, contributes to greenhouse gas emissions—so much logging also is a major source of greenhouse gas so that researchers now report it is the largest emissions. Climate change serves to exacerbate source of greenhouse gas emissions in Oregon (and wildfires by broadly changing weather and climate presumably is the largest in the timber-producing conditions. Logging releases carbon that was once areas of California as well). locked up in a forest. While some carbon is stored www.yournec.org
SEPTEMBER 2021 ECONEWS
