The 2023 Rainbow Fire on Grand Canyon's North Rim

The Rainbow Fire burning the understory of the ponderosa pine forest on Grand Canyon's North Rim. Photo by Brannfors, National Park Service.

On July 24, 2023, lightning started the Rainbow Fire on the Rainbow Plateau, on the North Rim of Grand Canyon National Park. The North Rim has a long history of prescribed fires and wildfires that help keep the ecosystem healthy, and the Rainbow Fire burned inside the perimeters of two earlier fires: the 3,400-acre Saffron Fire of 2019 and the Swamp Fire of 2001. "The Rainbow Fire is a great example of a fire occurring in an area that is both adapted to and regularly exposed to fire," said the park's fire management officer, Ed Waldron.

Watching instead of fighting

Park and fire managers set management action points — lines that, if the fire reached them, would trigger a different response — aimed at protecting resources and keeping firefighters safe. Because the fire kept moving slowly through ground vegetation, it was managed as a low-complexity incident: one to five staff periodically patrolled, mapped and monitored it, with little need to do more. That approach kept firefighters safe; aggressive suppression would have put their lives at risk while doing nothing for natural resources.

What the fire did

Over 39 days, the Rainbow Fire crept and smoldered across 115 acres of ponderosa pine understory, thinning the ground vegetation that had regrown since the Saffron Fire and could otherwise carry flames. It burned light fuels at low intensity but was hot enough to smolder through heavier fuels such as fallen trees.

The fire burned at low intensity but with enough heat to consume heavier dead and downed fuels. Photo by Brannfors, National Park Service.

Returning fire to this area brings several benefits:

• less hazardous fuel;
• forest regeneration;
• better wildlife habitat;
• a more open forest understory, closer to its natural state.

Sources

• National Park Service, Grand Canyon National Park: "Rainbow Fire proves excellent example of monitoring tactics reaching management objectives for Grand Canyon's north rim." The source dates the Saffron Fire to 2019 but also says vegetation had 13 years to regrow after it; the length of time is not given here.