The yield improvements reduced the need to convert forests to farmland, a process that typically involves burning trees and other plants, which generates carbon dioxide and other greenhouse gases, the announcement said.

The researchers estimated that if it wasn't 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, which is 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 Proceedings of the National Academy of Sciences.

Burney is a postdoctoral researcher with Stanford's Program on Food Security & the Environment. Steven Davis from Stanford's Carnegie Institution was co-author.