June 16, 2024

Strange burn: new research identifies unique patterns in Utah wildfires
Utah’s variable topography produces a tremendous range of wildfire behavior, according to new research from the Quinney College of Natural Resources at Utah State University. Credit: Bureau of Land Management

For a century fire ecologists have worked to decipher a complex question—what does a “normal” wildfire year look like in the West? That’s a hard question to answer for many reasons, but new research from a team in the Quinney College of Natural Resources shows that thanks to the state’s unique landscapes, Utah’s wildfire patterns may never fit into what is considered “normal” for other Western states. The research is published in the journal Fire.

Utah landscapes are diverse—from dense forests of pinyon-juniper to scattered patches of sagebrush and grasslands, Utah’s variable topography produces a tremendous range of wildfire behavior, said Jim Lutz, professor and author on the research. In some ways, it defies easy characterization. Utah’s basin and range geography limits areas of connected vegetation and wildfire fuel, a big factor for minimizing the chance of megafires (so far) compared to other Western states, he said.

How a acts and the level of impact it has on a landscape depends in large part on the type of vegetation it moves through, how the vegetation and trees are connected across space, and the amount of built-up on-the-ground fuel left from the U.S.’s long policy of suppression. Although the state’s topography tends to produce comparatively smaller fires, that doesn’t mean Utah is out of the woods for impacts from future wildfires. Just because a fire isn’t big, doesn’t mean that it doesn’t have big impacts.

Lutz and Joseph Birch, from the Department of Wildland Resources, compiled and compared from the complete set of the hundreds of medium-sized (100–1,000 acres) and large (over 1,000 acres) wildfires in Utah between 1984 and 2022. They assessed each incident for burn severity in different types of vegetation. Typically the size of a fire is considered tied to its impact on the land—but this research found that medium-sized fires in Utah sometimes had a comparatively large impact.

Strange burn: new research identifies unique patterns in Utah wildfires
The distribution of satellite-derived fire severity for medium-sized (40 ≤ area < 400 ha) and large (≥400 ha) fires across primarily forested vegetation types in Utah, USA from 1984 to 2021. Colors indicate fire severities (red—high severity, yellow—moderate severity, cyan—low severity, and dark green—no change detected by satellite). Credit: Jim Lutz

On average, Utah wildfires tend to be heavily influenced by sagebrush and shrubland vegetation types—a category that covers a considerable area in the state. The medium-sized fires that the team analyzed in this type of non-forested vegetation had more severe impacts than large fires. In forests though, large fires burned at higher severity—sometimes much higher.

“Fires of any size can have considerable ecosystem benefits, including reducing the fuel loads that might later lead to extreme fire behavior, and reducing forest density. Both of these may become even more important in ,” said Lutz. “Prescribed fires that are as large as practically manageable can also provide these benefits.”

The authors suggest that deciding on a tractable size for prescribed burns, and predicting the characteristic results, could be aided by looking at the data on medium-sized fires in each vegetation type. Overall averages for burn severity of a given fire type, whether considered at the statewide level or for individual vegetation types, tend to be weighted to large fires, the researchers said.

“Fire activity from the recent past could help us understand what is going to happen in coming years, and serve as an informative baseline,” Lutz said, “but the long period of we’ve had and increasing drought suggest that future fire may be more active than what we’ve seen in the past.”

More information:
Joseph D. Birch et al, Fire Regimes of Utah: The Past as Prologue, Fire (2023). DOI: 10.3390/fire6110423

Strange burn: New research identifies unique patterns in Utah wildfires (2023, December 4)
retrieved 4 December 2023
from https://phys.org/news/2023-12-strange-unique-patterns-utah-wildfires.html

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