Advances in high-yield agriculture over the latter part of the 20th century have prevented massive amounts of greenhouse gases from entering the atmosphere – the equivalent of 590 billion metric tons of carbon dioxide – according to a new study led by two Stanford Earth scientists
The yield improvements reduced the need to convert forests to farmland, a process that typically involves burning of trees and other plants, which generates carbon dioxide and other greenhouse gases.
The researchers estimate that if not for increased yields, additional greenhouse gas emissions from clearing land for farming would have been equal to as much as a third of the world's total output of greenhouse gases since the dawn of the Industrial Revolution in 1850.
The researchers also calculated that for every dollar spent on agricultural research and development since 1961, emissions of the three principal greenhouse gases – methane, nitrous oxide and carbon dioxide – were reduced by the equivalent of about a quarter of a ton of carbon dioxide – a high rate of financial return compared to other approaches to reducing the gases.
"Our results dispel the notion that modern intensive agriculture is inherently worse for the environment than a more 'old-fashioned' way of doing things," said Jennifer Burney, lead author of a paper describing the study that will be published online by the Proceedings of the National Academy of Sciences.
The researchers calculated emissions of carbon dioxide, methane and nitrous oxide, converting the amounts of the latter two gases into the quantities of carbon dioxide that would have an equivalent impact on the atmosphere, to facilitate comparison of total greenhouse gas outputs.
Burney, a postdoctoral researcher with the Program on Food Security and the Environment at Stanford, said agriculture currently accounts for about 12 percent of human-caused greenhouse gas emissions. Although greenhouse gas emissions from the production and use of fertilizer have increased with agricultural intensification, those emissions are far outstripped by the emissions that would have been generated in converting additional forest and grassland to farmland.
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