Modern high-yield farming lowered the amount of greenhouse gases pumped into the Earth's atmosphere toward the end of the 20th Century by a massive amount, according to a surprising study from researchers at Stanford University.

Technological advances in agriculture helped reduce greenhouse gas output by reducing the need to convert forests to farmland, the study said. Such conversion involves burning of trees and other naturally occurring carbon repositories, which increases emissions of carbon, methane and nitrous oxide.

If not for yield improvement techniques, which have dramatically helped corporate farms produce more crops with less land, authors of the study said an additional 13 billion tons of CO2 would have been loosed into the atmosphere per year.

"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 on high-yield farming to be published online by the Proceedings of the National Academy of Sciences.

Overall, the study estimated that new farming methods averted emitting as much as the equivalent of 590 billion metric tons of CO2. That translates into as much as a third of the world's total greenhouse gas output since 1850, a date often cited as the start of the Industrial Revolution in the West.

The production and use of fertilizer has led to significant greenhouse gas emissions, Burney said, but that increase pales in comparison with what might have been had more forests and grasslands been shifted to agricultural uses.

"Every time forest or shrub land is cleared for farming, the carbon that was tied up in the biomass is released and rapidly makes its way into the atmosphere," said Burney, who is a postdoctoral researcher at Stanford.

A co-author of the paper at Stanford, Steven Davis, added that the evidence points to spending on agricultural research as one of the best and cheapest ways to prevent new emissions of CO2 and other greenhouse gases.

To conduct the study, the academics looked at agricultural production between 1961 and 2005 and compared it to hypothetical models that estimated the amount of land that might have been converted if not for the so-called "green revolution" in modern farming. They found that improvements kept at least 317 billion tons of CO2 out of the atmosphere and possibly as much as 590 billion tons.

The researchers conclude by arguing for improvement of crop yields as part of any policy meant to reduce greenhouse gases.
