AgricultureÂ has contributed nearly as much to climate change asÂ deforestation by intensifying global warming, according to U.S.Â research that has quantified the amount of carbon taken from theÂ soil by farming.
Some 121 billion tonnes (133Â billion tons)Â of carbon have been removed from theÂ top two metres of the earth’s soil over the last two centuriesÂ by agriculture at a rate that is increasing, said the study inÂ PNAS, a journal published by the National Academy of Sciences.
‘It’s alarming how much carbon has been lost from the soil.’
– Jonathan Sanderman, soil scientist
Global warming is largely due to the accumulation of carbonÂ dioxide in the atmosphere from such activities as burning fossilÂ fuels and cutting down trees that otherwise would absorbÂ greenhouse gases such as carbon dioxide.
But this research showed the significance of agriculture asÂ a contributing factor as well, said Jonathan Sanderman, a soilÂ scientist at the Woods Hole Research Center in Falmouth,Â Massachusetts and one of the authors of the research.
- Farmer suicides rise in India as climate warms, study shows
While soil absorbs carbon in organic matter from plants andÂ trees as they decompose, agriculture has helped deplete thatÂ carbon accumulation in the ground, he said.
Widespread harvesting removes carbon from the soil as doÂ tilling methods that can accelerate erosion and decomposition.
“It’s alarming how much carbon has been lost from the soil,”Â he told the Thomson Reuters Foundation. “Small changes to theÂ amount of carbon in the soil can have really big consequencesÂ for how much carbon is accumulating in the atmosphere.”
Sanderman said the research marked the first time the amountÂ of carbon pulled out of the soil has been spatially quantified.
The 121Â billion tonnesÂ of carbon lost from soil compares toÂ about 127 billion tonnesÂ (140 billion) tons lost due to deforestation, he said,Â mostly since the mid-1800s and the Industrial Revolution.
Crop rotation, no-till farming could help
But the findings show potential for the earth’s soil toÂ mitigate global warming by absorbing more carbon through suchÂ practices as better land stewardship, more extensive groundÂ cover to minimize erosion, better diversity of crop rotation andÂ no-till farming, he said.
The world’s nations agreed in Paris in 2015 to reduceÂ emissions of greenhouse gases generated by burning fossil fuelsÂ
that are blamed by scientists for warming the planet.
President Donald Trump pulled the United States out of theÂ landmark Paris accord in May, saying it would undermine the U.S.Â economy and weaken national sovereignty.
Supporters of the accord, including some leading U.S.Â business figures, said Trump’s move was a blow to internationalÂ
efforts to tackle global warming that would isolate the UnitedÂ States.Â