Alaska’s Arctic parks: a fire record corrected, with 72 new perimeters discovered

A fire ecologist measures how deep the soil burned in tussocks one year after a fire in Noatak National Preserve. NPS/Jennifer Barnes

Old fire maps for Alaska’s Arctic parks turned out to be wrong in places. In the 1987 fire in Cape Krusenstern, the first perimeter was probably digitized from a hand-drawn map; a satellite image from later that year showed the fire had burned 3,082 acres more than reported. The National Park Service has now checked fire reports from 1956 to 2020 against archived satellite imagery and corrected the record for the five parks of the Arctic Network (ARCN).

The Arctic Network is Bering Land Bridge National Preserve, Cape Krusenstern National Monument, Noatak National Preserve, Kobuk Valley National Park, and Gates of the Arctic National Park and Preserve.

What the record says

Fire touches all five parks. Official records start in 1956, but charcoal records show fire in these parks at least 6,000 years ago. Since 1956 the parks have had fires burning nearly 1.1 million acres, an area almost twice the size of Cape Krusenstern National Monument. Lightning started 97% of the fires.

Figure 1. Acres burned and number of fires per year within the Arctic Network, 1955–2020. The ten-year moving average shows two periods of more fire: the 1970s and the mid-2000s.

The average is 8 fires and roughly 16,000 acres a year, but years differ widely. Some have few or no fires; others have 20 to 30, and 2010 had up to 50.

Figure 2. Acres burned and number of fires by park (left) and over time (right).

Fixing the history

Staff checked each reported fire against imagery to find its most accurate point of origin, acres burned, and mapped perimeter. These checks improved the official NPS fire records and the statewide Alaska Fire History – Perimeters database, which holds mapped perimeters back to 1940.

• 253 NPS historical fire records improved
• 137 perimeters updated
• 72 of those were perimeters that had never been mapped
• A change of over 208,000 acres of area burned

Figure 3. Four historic fires newly mapped: the 1985 BTT W 62 Fire in Gates of the Arctic (408 acres), the 1991 BTT N39 Fire in Gates of the Arctic (331 acres), the 1977 Bilge Fire in Bering Land Bridge (1412 acres), and the 2012 Agashashok River 3 Fire in Noatak (216 acres).

For the 1987 Cape Krusenstern fire, the left image below shows the original perimeter as a black and white dashed line. The right image shows the perimeter redrawn in blue from a LANDSAT 5 satellite image taken after the fire was declared out.

The 2019 Kaluktavik River Fire burned over 6,300 acres and was 1 of 5 fires in Noatak that season. The Kaluktavik River Valley is one of several areas in the preserve where fire is more common because of topography, weather and lightning patterns. NPS/Dan Stevenson

Why keep watching

Alaska is seeing warmer temperatures, earlier snow melt, tundra “greening” and longer growing seasons. All of these influence fire patterns and their ecological effects. Fire regimes in northern regions, including the Arctic Network, may therefore change quickly, with more fires and more area burned. The overall trend has stayed relatively flat because fire varies so much from year to year, but the 10-year averages have risen (Figure 1).

An accurate history is the base for judging three things: long-term trends in how often fires occur and how much burns, departures from the natural fire regime, and how parks may respond to climate, vegetation change, fuel moisture, ignition sources and other factors.

How the parks track fire

When a fire starts in a park, Alaska’s fire protection agencies record where and when it began, its size, and the fuel type it is burning in. The perimeter is often mapped. Park Service staff help monitor and map active fires from aircraft or with remotely sensed imagery. The data feed two layers: all reported fires (points) and all mapped fire perimeters. Extent comes from the perimeter, or from the acreage in the national fire reporting system when there is no perimeter. Each year the data is summarized to show trends.

The aims are to learn the variability and decadal trends in fire frequency (fires per year), average fire size, maximum fire size, and total area affected. That information supports fire management planning, decisions, risk evaluation, and judging ecological impacts.

Historic fire perimeters (purple), 1956–2020, within or crossing into Arctic Network park units.

More on fire in the network’s parks is on the Arctic Network fire page.

Sources

• National Park Service, Fire Extent and Frequency Resource Brief for the Arctic Network; rewritten in hubnx's own words.