Preindustrial Earth wasn’t as squeaky-clean as once thought

(CN) — The Māori people of New Zealand torched large swaths of virgin forest beginning in the year 1300 to make way for human settlements, especially during the 16th and 17th centuries, depositing black carbon across the Southern Hemisphere, according to a new study.

New Zealand was among the last land masses on earth to be settled by humans. The Māori people arrived from Polynesia during the 13th century and almost immediately began clearing the heavily forested island to open up land for settlement and farming. Within a century they had begun to make a noticeable impact — not only on New Zealand — but the surrounding regions as well, as recorded in the ice record.

An international team of scientists from North and South America and Europe studied six ice core samples pulled from Antarctica and found traces of black carbon, or soot, where it was not expected. After narrowing down the list of possible preindustrial culprits based on predicted wind patterns, the team determined the Māori’s land clearing operations were likely responsible. They describe their results in a new study published Wednesday in the journal Nature.

“We were very surprised that black carbon emissions from Māori burning soon after settlement in the late 13th century overwhelmed background variations from natural, climate modulated burning emissions in other higher latitude regions such as Patagonia and Tasmania,” said Dr. Joe McConnell, research professor of hydrology at the Desert Research Institute, or DRI, and lead author of the study, in an email.

“We know this because for the first 1300 years of the Common Era, the north-south pattern of black carbon (a.k.a., soot) deposition was surprisingly constant,” McConnell continued. “Everything changed once the Māori colonized New Zealand and started using fire for land clearing and management. When I say overwhelmed, black carbon deposition in the northern Antarctic Peninsula increased to three times what it was prior to Māori burning — that is an enormous impact especially considering that the ice core site is more than 7000 [kilometers] from New Zealand so increases were probably as large or larger over most of the South Pacific sector of the Southern Ocean.”

Many scientists previously believed that human societies only began emitting significant amounts of carbon in relatively recent years since the dawn of the industrial age, but new evidence is swiftly refuting that idea. The authors found that the Māori’s land-clearing activities had a noticeable impact on the atmosphere across the Southern Hemisphere for centuries, surpassing that of other preindustrial peoples in the region.

The team employed a continuous ice-core analytical system developed by McConnell’s lab in 2007 to analyze the six ice core samples pulled from James Ross Island and continental Antarctica. The samples displayed increased levels of black carbon beginning around the time of the Māori’s arrival in New Zealand in the 1300s and tripling over the course of 700 years. The Māori’s carbon emissions ultimately peaked around the same time Europeans began settling America in droves during the 16th and 17th centuries — long before the first piece of industrial machinery whizzed or whirled.

The authors began with a list of three potential culprits based on atmospheric modeling, which they used to determine where a carbon source likely originated based on historical weather pattern predictions and where the carbon was ultimately deposited.

“From our models and the deposition pattern over Antarctica seen in the ice, it is clear that Patagonia, Tasmania, and New Zealand were the most likely points of origin of the increased black carbon emissions starting about 1300,” said Dr. Andreas Stohl with the Norwegian Institute for Air Research and co-author of the study, in a related statement.

Researchers scoured paleofire records from all three candidates and determined New Zealand was the only viable location from which the black carbon could have originated. The records demonstrate increased fire activity on the island beginning around the year 1300, coinciding with the arrival of the Māori people. The results surprised researchers given New Zealand’s relatively small size and the roughly 4,500-mile distance from James Ross Island.

Despite long-held assumptions that preindustrial Earth was a sort of virgin paradise, environmentally speaking, the study shows that humans have been affecting the planet far longer than once believed. Researchers also noted that fallout from biomass burning in New Zealand led to an explosion of phytoplankton growth across much of the Southern Ocean, likely resulting in a centuries-long aquatic boom in the region.

“From this study and other previous work our team has done such as on 2,000-year old lead pollution in the Arctic from ancient Rome, it is clear that ice core records are very valuable for learning about past human impacts on the environment,” McConnell said in a related statement. “Even the most remote parts of Earth were not necessarily pristine in preindustrial times.”

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