A century of fire suppression, compounded by global warming and drought, has led to more destructive wildfires in the Western United States. Conventional wildfire management strategies, including prescribed burns, thinning, mastication, and piling and burning, aim to reduce excess fuel loads such as dead trees, needles, leaves, and fallen branches. These efforts help decrease fire intensity, protect fire-resistant trees, and promote forest resilience.
Despite these efforts, the buildup of surface fuel continues to outpace prescribed burning, creating a "fire deficit"-the gap between accumulated fuel and the level of fire management required to mitigate it. This increases the likelihood of severe wildfires.
While prescribed fires are an essential tool, they also present challenges. Escaped burns can become wildfires, and smoke emissions negatively impact air quality, visibility, and public health, particularly by exacerbating respiratory conditions. In the Pacific Northwest, emissions from prescribed burns have been linked to numerous respiratory illnesses and workday losses due to poor air conditions.
Additionally, the capacity of forests to absorb and store carbon is diminishing due to deforestation, logging, pests, drought, and high-severity wildfires. Effective forest management is critical not only for wildfire risk reduction but also for lowering carbon emissions and increasing carbon storage to combat climate change.
For millennia, Indigenous communities in the Western U.S. have managed forests through controlled burns and the collection of dead wood for firewood, shelter, and cultural practices. Modern management has drawn from these traditional techniques, but researchers are now examining the direct removal of dead wood as a way to mitigate wildfire risks while reducing carbon emissions.
Florida Atlantic University researchers focused on the impact of physically harvesting dead wood in the Sierra Nevada to assess its effectiveness in reducing fire hazards and carbon output. Their study analyzed various management techniques, including selective removal of dead trees and fallen branches, and their effects on wildfire behavior and carbon emissions.
The study tested eight different forest management strategies through simulations, including thinning, prescribed burning, and physical fuel removal, individually and in combination. Compared to a control scenario with no intervention, the researchers found that combining dead wood harvesting with thinning significantly decreased tree mortality and the occurrence of crown fires. This approach also reduced overall carbon emissions while facilitating long-term carbon storage.
Published in the Journal of Environmental Management, the study highlights biochar-a form of charcoal produced by heating organic material in a low-oxygen environment-as a viable method for locking carbon into the soil instead of releasing it into the atmosphere through combustion.
"In an era of increasing fire weather, rising smoke-related health risks, and the urgent need for enhanced carbon sequestration, exploring alternative forest management strategies is imperative," said Scott H. Markwith, Ph.D., co-author and professor in the Department of Geosciences at FAU's Charles E. Schmidt College of Science. "By integrating physical harvesting with thinning-targeting small and fire-vulnerable trees-we can promote forest health and resilience. Using harvested wood to create carbon-storing products instead of burning it could reduce wildfire severity, smoke, and carbon emissions while generating carbon credits."
The findings offer valuable insights for future wildfire management and carbon sequestration efforts.
"Over time, repeated fuel reduction treatments such as prescribed burns can emit more carbon than a single wildfire in an untreated forest," said Rabindra Parajuli, Ph.D., lead author and doctoral graduate from FAU's Department of Geosciences, now a postdoctoral researcher at the University of Georgia. "However, by harvesting dead wood and converting it into biochar-a stable carbon form-emissions can be minimized. This approach not only reduces health risks but also increases carbon sequestration, helping to mitigate climate change while improving forest ecosystems."
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