Forests under (mega)fire in the Pacific Northwest

Accompaniment to the Third Pod from the Sun Episode

Featured Image: “Forests under fire” original artwork by Jace Steiner. Used with permission.

Paper: Cascadia Burning: The historic, but not historically unprecedented, 2020 wildfires in the Pacific Northwest, USA

Authors: Matthew Reilly, Aaron Zuspan, Joshua Halofsky, Crystal Raymond, Andy McEvoy, Alex Dye, Daniel Donato, John Kim, Brian Potter, Nathan Walker, Raymond Davis, Christopher Dunn, David Bell, Matthew Gregory, James Johnston, Brian Harvey, Jessica Halofsky, Becky Kerns

The natural legacy of fire in the Pacific Northwest (PNW) is complex.  The variable geography of the wet, westside temperate rain forests, to the dry, high elevation forests beyond the Cascade crest make it difficult to find a “catch-all” description of PNW forest fires.  For instance, drier forests of ponderosa pines in eastern Washington experience more frequent, low-severity fires while the temperate rain forests of western Oregon rarely see fires.  However, scientists can reconstruct historical fire regimes and identify centuries-long patterns of burning related to precipitation, temperature, and ignition frequency to define what are historical patterns and what is modern climate change.  In 2020, multiple megafires (a wildfire that burnt more than 100,000 acres of land) broke out in the typically wet parts of Oregon and Washington, burning more than 700,000 acres combined.  This event is called the 2020 Labor Day Fires, and Matthew Reilly and colleagues have revealed these fires were likely part of historical regimes and not a product of accelerated climate change.

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How does smoke from wildfires in the western U.S. change the regional climate?

Feature image from Pixabay

Article: Biomass Burning Smoke and Its Influence on Clouds Over the Western U. S.

Authors: C. H. Twohy, D. W. Toohey, E. J. T. Levin, P. J. DeMott, B. Rainwater, … & E. V. Fischer

The area burned by wildfires has been increasing in the western U.S. in recent years and is expected to continue to increase due to climate change. In fact, a large wildfire is currently burning in Sequoia National Park in California, threatening to impact some of the largest and oldest living trees in the world. While wildfires directly impact people, wildlife, and the environment in many ways, a lesser-known impact, involving clouds, can influence the regional weather and climate.

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Wildfires are making our rivers longer

Featured image: Wildfire in Portugal by Michael Held on Unsplash

Paper: Ball, G., Regier, P., González-Pinzón, R. et al. Wildfires increasingly impact western US fluvial networks. Nat Commun 12, 2484 (2021). https://doi.org/10.1038/s41467-021-22747-3

The wildfire season is getting longer and more severe, and current models suggest that this trend will only continue as anthropogenic climate change gets worse. Wildfires dramatically alter the landscape they inundate, leaving vegetation charred and the atmosphere ashy. While jarring, there is one consequence of these natural disasters that isn’t fully understood: their effect on rivers and streams. While it may seem intuitive to think that wildfires disrupt the hydrologic cycle and cause rivers to dry up or shrink, Grady Ball and colleagues found the opposite: wildfires are making our rivers longer.

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