More and more of Alaska’s boreal forests are burning each year, according to a study released last week. Researchers found that the acreage of forest burned in interior Alaska has climbed almost five-fold since 1943. That increase is likely influenced by a regional shift to a warmer, drier climate, as well as by human disturbances like encroaching development and fire suppression. Researchers found that that increase was most pronounced in the region’s most populated area, where firefighting efforts are most intense.
Thanks to its size and the remoteness of much of the state, Alaska has had to take a highly targeted approach to fighting wildfires. In the 1980s, the state established four zones of fire response, depending on whether the events happen near human settlement, whether there are valuable natural resources in the area and how likely the fire is to spread. The state’s population hubs, like Anchorage and Fairbanks, are designated as “critical” zones and receive the most protection — which often means fire suppression.
In a concerning twist, the study’s authors found the steepest increase in area burned has been in the highest tiers of protection. Fairbanks, the most populated area they looked at, was the most glaring example: on average, 12.4 percent more acreage burns there each year than the previous one.
The reasons for that increase are likely complicated and include the region’s logging history. In Fairbanks, in particular, the landscape was basically denuded in the 1900s, thanks to the gold rush. Miners cut down the region’s forests to build homes and mining infrastructure and to burn to heat the frozen soil for digging. In the 100 years since, the forests have grown back and slowly gone through their natural succession, from the relatively fireproof willows and birches to the flammable black spruce.Monika Calef, the study’s lead author, used to live in the Fairbanks area, but moved away after one too many close calls with wildfire. “It's all old trees,” she said in an interview with HCN. “There are lots of dead trees and litter on the ground.”
In the paper, which will be published in the peer-reviewed scientific journal Earth Interactions, Calef theorized that the forest “is probably now approaching its peak flammability,” after being completely logged.
In addition to the logging history, the new study also noted three other factors that are likely causing more fires in Alaska. First is the role of fire suppression. Whether suppression increases fire risk remains a source of controversy, but Fairbanks’ fire troubles may indicate that the state’s firefighting strategy has left heavier fuel loads in areas where fires are fought aggressively. Second, as Alaska’s population has increased, human-started fires may be contributing to the growing burned area near places like Fairbanks.
Third, and perhaps the biggest driver, is the changing climate. Alaska has been warming more quickly in response to global climate change than in the rest of the country and the past several decades have been marked by warmer, drier conditions. Those changes were driven in part by shifts in large-scale atmospheric forces that prevented the delivery of the usual summer rains. Previous studies found that these forces were driving an increase in fires throughout the boreal region, which also includes Canada and the northern reaches of Europe and Asia.
But the increase may not spell failure for Alaska’s wildfire strategy. Although inhabited areas have seen the most rapid increase in area burned, fires still burn a relatively small portion of the populated zone. For example, the zone that receives the least fire response has nearly seven times more of its area burned each year. That's in part because fires in the critical zone are typically put out in the early stages, when attack is most effective. The state’s fire managers have also been working on other fire prevention strategies whose effects may not yet be shown in Calef’s data, including clearing brush.
Calef’s research clearly has implications for Alaskans, but it is also relevant on a more global scale. In the past, Alaska’s forests have acted as a carbon sink, pulling greenhouse gas out of the atmosphere and slowing the planet’s warming. If that pattern is reversed (and there’s some evidence it may be starting to), then the forests could instead begin to release the carbon they’ve stored into the atmosphere and contribute instead to more warming. And that warming could feed more burning, which could feed more warming and so on.
While that cycle would eventually stall out for lack of spruce forests to burn, Calef says that by then, the fires would already have released huge amounts of carbon into the atmosphere: “That would be catastrophic.”
Kate Schimel is an editorial intern at High Country News. Follow her @kateschimel