‘Let burn’ narrative put to the test on USFS lands

Fires not fully suppressed but herded around and allowed to burn have allegedly been an unofficial USFS practice since the 1970s. A new study challenges whether that practice is as common as many believe.

The naming convention for the practice has reportedly changed repeatedly. They were originally called “let burn” fires, but forest managers soon dropped the term because a pervasive misunderstanding quickly arose that wildland firefighters were ignoring fires and letting them run amok. Even though other terms like “Natural Wildland Fires” and “Managed Fire” took the “let burn” term’s place, the incorrect view of the practice has persisted, being referenced as recently as in 2021’s Tamarack Fire.

That lightning-caused fire forced the evacuation of nearly 2,000 residents, destroyed 25 structures, and burned 67,000 acres in California and Nevada. Many members of the public blamed the fire’s negative outcomes on the supposed “let burn” practice, despite the policy’s not formally existing.

Tamarack Fire lifts evacuation orders for nearly 2,000 residents

Researchers from the USFS Rocky Mountain Research Station wanted to put the “let burn” narrative to the test — by quantifying the damage from consequential lightning-caused fires such as the Tamarack Fire.

The study, published in SpringerOpen Fire Ecology scientific journal, used multiple sources of fire-reporting data to identify numerous USFS fires from 2009 to 2020 using management strategies similar to those used during the Tamarack Fire. Of the 940 wildfires that burned within that time, the researchers found only 32 fires with characteristics similar to the Tamarack, nearly half of which ignited within wilderness areas.

Woodbury Fire Phoenix Roosevelt
The Superstition Wilderness inside the perimeter of the Woodbury Fire, June 22, 2019. InciWeb.

The researchers found that firefighter hazard mitigation was the primary driver on 26 of the 32 wildfires, with only six of the fires managed for “resource objectives” like the reported “let burn” fires. Risks posed to firefighters from terrain, snags, or inaccessibility were by and large what fire managers are concerned about during a wildfire — not how they can let the fire burn for potential ecological gains, or for the oft-alleged “treatment acreage quota.”

ICS-209“Our results suggest that a ‘let burn’ strategy is not a predominant USFS management approach,” the researchers concluded. “A limited palette of strategic reporting categories may be partially responsible for the falsely premised ‘let burn’ narrative.”

Researchers theorized that a large reason for the pervasiveness of the “let burn” misconception is how fire managers fill out ICS-209 forms post-fire. Managers select one of four categories to classify the intent behind their decisions, including “monitoring,” “confine,” “point or zone protection,” or “full suppression.” The subtlety that’s lost on which option is chosen —  any option other than full suppression — may be responsible for the spread of misinformation on the fire’s management.

“These categories may not capture enough of the nuance and complexity of the decision environments in which they are made,” said the Rocky Mountain Research Station. “In turn, this information gap may permit inaccurate explanations to dominate the conversation.”