Farming has changed climate almost as much as deforestation

http://www.cbc.ca/news/technology/agriculture-climate-change-1.4257023

Harvesting, tilling remove large amounts of carbon from soil
Thomson Reuters Posted: Aug 22, 2017

Agriculture has contributed nearly as much to climate change as deforestation by intensifying global warming, according to U.S. research that has quantified the amount of carbon taken from the soil by farming.

Some 121 billion tonnes (133 billion tons) of carbon have been removed from the top two metres of the earth's soil over the last two centuries by agriculture at a rate that is increasing, said the study in PNAS, a journal published by the National Academy of Sciences.

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While soil absorbs carbon in organic matter from plants and trees as they decompose, agriculture has helped deplete that carbon accumulation in the ground, he said.

Widespread harvesting removes carbon from the soil as do tilling methods that can accelerate erosion and decomposition.

"It's alarming how much carbon has been lost from the soil," he told the Thomson Reuters Foundation. "Small changes to the amount of carbon in the soil can have really big consequences for how much carbon is accumulating in the atmosphere."

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But the findings show potential for the earth's soil to mitigate global warming by absorbing more carbon through such practices as better land stewardship, more extensive ground cover to minimize erosion, better diversity of crop rotation and no-till farming, he said.

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