According to the study, published in the journal Biogeosciences, fires in the Alaskan tundra have become more frequent in the past century than in any other period over the previous three thousand years.
A new study finds that fires on Alaska's North Slope have reached levels not seen in the past 3,000 years. According to the study, published in the journal Biogeosciences, fires on the Alaskan tundra have become more frequent in the past century than at any other time in the previous 3,000 years.
The research was conducted in Arctic Alaska by an international team of scientists from institutions in Germany, Poland, the United Kingdom, and Romania, along with the Toolik Field Station of the University of Alaska Fairbanks.
Angelica Feurdean, the paper’s lead author and a senior researcher at Goethe University in Germany, explained that the team combined several scientific methods to compile a “long-term diary” of fires. The findings suggest that the recent increase in fires is linked to the spread of dense vegetation and drying soils, both processes that are linked to rising temperatures.
“The combined changes over thousands of years mean that the fires of recent years are a sign of a system in the midst of rapid change,” said Feirdian.
Digging towards the Arctic
To find evidence of ancient fires, the researchers collected peat samples by drilling about half a meter deep into tundra soils at nine sites north of the Brooks Range. The sites are located along the Dalton Highway, between Toolik Lake and Franklin Bluffs.
Each layer of peat contained evidence of past environmental conditions, including charcoal, pollen, and fragments of dead plants and microbes. The team analyzed the concentrations of these materials, and used carbon-14 and lead dating to determine the age of the layers. Combining the data allowed the researchers to reconstruct patterns of fire activity, vegetation changes, and soil moisture over thousands of years.
The material taken from the peat cores dates back 3,000 years, to about 1000 BC. The charcoal records show that fire activity was low for the first 2,000 years. Activity increased slightly between about 1000 and 1200 AD, when the tundra soils began to dry out. It then declined again to low levels for the next 700 years.
A sharp leap in the modern era
Around 1900, fire activity began to increase again. By 1950, it had reached unprecedented levels, with the peat reaching record dryness and dense shrub vegetation flourishing. Fire activity continued to increase and the soils continued to dry out until 2015, the year the cores were taken.
The scientists then compared the “ancient history” of fires to modern activity by matching charcoal remains with satellite data. The satellite data confirmed what the charcoal records had indicated: fire activity has been increasing since the second half of the 20th century. The late 60s, the 90s, and the 2000s and 2010s were particularly notable, when fires were frequent.
Randy Fulweber, research associate and manager of geographic information systems (GIS) and remote sensing at the Tolik station, said the combination of coal and satellite data has also provided new insights into the severity of current fires. He said evidence from large fires in recent years “may indicate that they are burning at higher temperatures, consuming more fuel and leaving less coal behind.”
“This may indicate a changing fire regime, one where the fires are really burning at high intensity,” he said.
Pulweber attributes the ability to reach these conclusions to the collaborative nature of the Tolik field station, which allows the team to combine expertise in paleoecology, GIS and remote sensing. “There’s something unique that a field station like Tolik provides, in terms of breadth and depth of expertise,” he said, “and that’s what allows these kinds of studies to happen, and ultimately opens up more scientific questions.”
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