Wildfires in the tundra, the cold, treeless biome of the Arctic, have been more active this past century than at any time in the past 3,000 years, according to a study conducted in Arctic Alaska.
The research was conducted by an international team of researchers from Germany, Poland, the United Kingdom, Romania and the University of Alaska Fairbanks’ Toolik Field Station.
The team, according to a statement by the university, took a multidisciplinary approach to reconstructing fire history. “Their findings point to record-high activity caused by increasing woody plants and drying soils, two consequences of warming temperatures,” the statement noted.
To reconstruct wildfire activity, the team cored half a metre into tundra peat soils at nine sites north of the Brooks Range, along the Dalton Highway between Toolik Lake and the Franklin Bluffs.
They found charcoal, pollen and pieces of dead plants and microbes buried within each layer of the core were.
The team then measured the amounts of these materials within cores and used radiocarbon and lead dating to determine the ages of these layers. These measurements painted a picture of past fire activity, dominant vegetation and moisture conditions.
The material from the peat cores dated back 3,000 years to around 1000 B.C. “Charcoal records indicated fire activity was low for the first 2,000 years. Activity rose slightly between roughly A.D. 1000 and 1200 when tundra soils started to dry. But it dropped back to lower levels for the next seven centuries.”
In 1900, fire activity began to heat up again. By 1950, fire activity spiked to unprecedented levels as peat reached record dryness and woody shrubs increased. Fire activity rose and soils continued to dry through 2015, when the cores were taken, according to the statement.
The researchers then compared ancient fire history with that of modern activity by pairing charcoal remnants with satellite records.
“Satellite records confirmed the evidence from charcoal records that fire activity has been rising since the latter half of the 20th century. Specifically, the late 1960s, 1990 and 2000s-2010s saw frequent fires,” the note stated.
According to the experts, they were also able to gauge how severe the modern-day fires were by combining the charcoal and satellite records.
They added that evidence from recent large fires “may be indicative of these fires burning hotter, consuming more fuel and leaving behind less charcoal.”
The tundra biome is characterised by frigid temperatures, low precipitation (like a cold desert), permafrost (permanently frozen ground), and short growing seasons.
The study was published in the journal Biogeosciences.