Repeat Fires Are Thawing Permafrost in Wrangell-St. Elias

Fire ecology crew from the Eastern and Western Alaska Fire Management teams: Sarah Brey, Fleur Nicklen, Sarah Martin and Olivia Lawrence. NPS.

Fire ecologists study the effects of wildfire to learn how often prescribed fire should be used. In interior Alaska, prescribed fire is so rare that little is known about fire effects.

An unusual double burn

In July 2024, with funding from the Bipartisan Infrastructure Law, ecologists studied an area of Wrangell-St. Elias National Park and Preserve that burned twice in seven years: in the 2009 Chakina Fire and again in the 2016 Steamboat Creek Fire. That is far from typical. Most of interior Alaska burns only every 60–150 years, and this area even less often, every 150–200 years.

The area also holds some of the southernmost permafrost, ground that stays frozen all year, beneath a layer that thaws and refreezes each year. This permafrost is typically within a few degrees of thawing, and thawing permafrost is a serious environmental concern.

What the crew measured

Soils were sampled in plots that:

1. had not burned in more than 100 years;
2. burned once, in 2009;
3. burned in both 2009 and 2016.

Mean surface temperature in July 2024 in unburned, once-burned and twice-burned plots. NPS.

Warmer ground, less permafrost. Surface temperature rose from unburned to once-burned to twice-burned plots. Frozen ground within 1 m of the surface was found in:

Thinner insulation. The organic mat that insulates the soil averaged:

Duff plugs showing organic mat depth in an unburned plot (left), a plot burned in 2009 (center) and one burned in 2009 and 2016 (right). NPS.

In winter a thick mat can have the opposite effect, helping keep the soil warmer, though that depends on how much snow, another insulator, lies on top.

A black spruce forest burned by the Chakina Fire in 2009 and the Steamboat Creek Fire in 2016, one year after the first fire (2010), one year after the second (2017) and eight years after it (2024). A clear shift toward deciduous trees is likely. NPS.

Why it matters

Current models already predict that near-surface permafrost in this region will decline in coming decades. This study shows that fire, and especially repeated fire, can speed that loss in vulnerable areas.

Sources

• National Park Service, "Repeat fires tip the scale on near-surface permafrost in Wrangell-St. Elias National Park and Preserve": https://www.nps.gov/articles/000/wrst-fire-studies.htm
• The NPS article calls the 2016 fire both the "Steamboat Fire" and the "Steamboat Creek Fire"; this page uses the latter.