How Much Did Ancient Land-Clearing Fires in New Zealand Affect the Climate?

 

I suggest reading the whole article.

 

 https://insideclimatenews.org/news/20102021/ancient-lndigenous-fires-newzealand-climate/

 

vBy Bob Berwyn
October 20, 2021

 

There’s new evidence, this time from the Southern Hemisphere, that human activities altered Earth’s atmosphere long before the start of the fossil-fueled industrial age that kicked global warming into high gear.

Research published Oct. 6 in Nature suggests that soot from the land-burning practices of the seafaring Polynesians that settled New Zealand spread widely around the Southern Hemisphere. The detailed analysis of six ice cores from Antarctica found a sharp spike in depositions of climate-altering black carbon starting in about 1300.

Using models of winds in the Southern Hemisphere, along with other records showing possible sources of black carbon, the scientists found that the most likely source was fires started by the Māori to clear forests for agriculture and to ease their hunts as they settled the islands. 

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Several recent studies reinforce the importance of understanding pre-industrial aerosols in the context of modeling modern climate change, he added, singling out research by aerosol expert Ken Carslaw, with University of Leeds.

Until recently, such emissions were believed to be so low that researchers weren’t interested in studying their impacts on the climate, he said, so the idea that pre-industrial human activity caused such a big change in atmospheric black carbon was surprising. The findings show that, even in remote and sparsely populated regions, the environment wasn’t pristine, said McConnell, who has also traced lead pollution in ice cores from Greenland to the Roman empire.

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And it’s not just fires. Deforestation before 1850—a date often used to demarcate the start of the industrial era—resulted in 300 million tons of carbon going into the atmosphere, Ruddiman said, but only about half as much since then.

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“You could easily make a claim that the anthropocene began thousands of years ago, causing a slow warming that stopped a natural cycle of cooling,” he said. “It kept the climate warmer than it would have been.” The emerging science suggests that warming driven by human activity started earlier, and makes up more of the measured heating of the atmosphere than acknowledged up to now, he added.

For instance, the once widely held assumption that most deforestation happened in the last 150 years or so is starting to crumble under the weight of new data, he said. The evidence includes “hundreds of pollen records from lakes showing forests at the maximum extent about 6,000 to 7,000 years ago,” when mass forest clearing and slow warming started, he added.

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Understanding those past changes won’t lead to a “magic solution” to climate change, he added, but “knowing can help us, because it shows that, if we can regrow a large percentage of the forests that have been cleared, we could do something to reduce our CO2 impacts on the atmosphere.” 

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