When it comes to the records of human history, don’t overlook Earth’s only uninhabited continent.
Researchers recently discovered soot preserved in Antarctic ice which they linked to fires started in New Zealand by Maori settlers, the islands’ first human inhabitants. Finding evidence of fires thousands of miles away is a dramatic example of the environmental impact of early humanity, the team suggests.
These results were published Wednesday in Nature.
An international team of researchers led by @DRIScience analyzed ice core samples from James Ross Island in Antarctica and found that early human activity caused significant changes in Earth’s atmosphere. The results were published in a new @Nature article. https://t.co/evRkzNB2ca pic.twitter.com/iZOOIUS0b3
– Desert Research Institute (@DRIScience) October 6, 2021
Since the 1960s, researchers have been extracting long cores of ice from Antarctica, Greenland and other snow-covered locations. Ice cores, which are made up of layers of snow that build up every year and have compressed over time, are not just ice. They can also contain particles such as soot and volcanic ash that were once suspended in the air.
“Ice cores actually tell you what fell from the sky,” said Joseph McConnell, an environmental scientist at the Desert Research Institute in Reno, Nevada.
By studying particles in ice cores, scientists can identify past events such as major fires, volcanic eruptions, and even industrial smelters.
In 2008, McConnell and his colleagues began analyzing six ice cores drilled in Antarctica. Working with sections of ice about 3 feet long at a time, the team melted each one and poured the resulting liquid into an instrument that turned it into aerosols. The researchers then passed these aerosol particles through a laser, which heated and glowed the soot present.
“We are measuring that incandescence,” McConnell said.
Using this technique, the researchers calculated the speed at which soot particles had fallen on Antarctica over the past two millennia. They found that four of the ice cores, all collected from mainland Antarctica, exhibited roughly constant rates over time. But two other ice cores, both taken from James Ross Island in the northern Antarctic Peninsula, showed about a triple increase in soot from the late 13th century.
This discrepancy was disconcerting. “How was the northern Antarctic Peninsula different? McConnell said.
The team turned to atmospheric modeling to investigate the mystery. The soot that eventually settled on James Ross Island could only have come from a few places, the researchers found. “Due to atmospheric circulation New Zealand, Tasmania and southern Patagonia do the trick,” McConnell said.
To focus on the most likely source, the researchers analyzed published records of charcoal found in each of the three locations. The charcoal reveals that woody material was burned nearby, and changes in its abundance over time can be traced, as can soot recordings in the ice.
Only New Zealand showed a marked increase in charcoal abundance in the late 13th century, which matches data from ice cores from the northern Antarctic Peninsula.
“We see this big spike, which we call the initial burn period, about 700 years ago,” said Dave McWethy, an ecologist at Montana State University who studies charcoal in New Zealand and co-author of study.
But finding the signatures of these fires thousands of miles away in Antarctica was a big surprise, McWethy said. “No one knew he could travel this far and be saved in ice cores.”
The increase in fire activity in New Zealand in the late 13th century is most likely linked to the arrival of the Maori, researchers have suggested. Like other Indigenous groups, the Maori have used fire to make their surroundings more habitable, McWethy said. “Fire is an extraordinary tool for people all over the world. “
More than 90% of New Zealand was forested when Maori settlers arrived, and burning parts of the landscape would have made it easier to travel through the dense forest, McWethy said. “It’s pretty impenetrable.
The fire would also have been important in clearing land to cultivate crops such as taro, yam and kumara, said Kelly Tikao, a researcher in Maori traditions at the University of Canterbury in New Zealand, of Ngai ancestry. Tahu, Ngati Mamoe and Waitaha, who did not participate in the research. In addition to allowing agriculture, burning parts of the landscape would have promoted the growth of wild but edible plants such as the fern which thrives after the fires, Tikao said.
The Maori used fire on purpose, but they never intended to destroy their landscape, Tikao added.
“Our very philosophy of who we are is based on the elements of Earth, fire being one of them,” she said. “When you believe the earth is yourself, the last thing you want to do is kill it.”
This article originally appeared in The New York Times.
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