Some organic farming advocates and public pundits have characterized modern agriculture as a major contributor to global warming.

Not true, say two agricultural economists.

Quite the contrary: As one of these economists stresses, the advances in farming technology within the past 50 years have dramatically reduced the acreage needed for production, which, in turn, has substantially reduced farming's carbon footprint. This holds especially true for grains, the world's principal food crop.

For example, using modern methods, U.S. farmers routinely produce corn yields of 250 or more per acre.

"That's at least 100 bushels more than can be grown by farming back in the good old days," says Robert Goodman, an Alabama Cooperative Extension System economist and Auburn University associate professor of agricultural economics.

"By growing twice as much on your land, you're freeing up the other half for parks, wildlife preserves, bird sanctuaries or whatever you desire," he says, stressing that this preservation and conservation is made possible by what he describes as the "tremendously high level of production efficiency.

Ironically, Goodman says, the development of synthetic nitrogen fertilizer, produced using mostly carbon-based petroleum production, made this high-yield grain production possible.

Conversely, the lack of this critical plant nutrient remains one of the biggest challenges in organic production.

"And with so-called organic production, you would produce less than half that amount — roughly 60 to 70 bushels per acre with corn — and that only in an exceptionally good year," Goodman says.

On the other hand, to produce 250 bushels of corn with organic farming would require more than three acres instead of the single one needed with modern technology, he says.

In essence, the extra land freed by modern methods amounts to what Goodman describes as "money in the bank," a resource that can be used some other way or preserved for later use, depending on the need.

"This is the one benefit of modern agriculture that is often overlooked, especially by those who tout the environmental benefits of traditional, small-scale and organic farming," he says.

Goodman's colleague, Max Runge, says there is another way of looking at the effects of these advances to underscore how they have helped reduce farming's environmental impact.

"Nationwide, we are farming roughly the same number of acres we did in the 1920s, even though our population has increased from roughly 100 million to more than 300 million ," Runge says.

The substantial acreage increases that would be required to produce grains using organic farming practices would result in the release of substantial additional amounts of greenhouse gas — a fact borne out by the findings of a recent Stanford University study.

The Stanford findings maintain that high-yield agriculture, made possible by a myriad of advanced farming methods, have reduced the need to convert forest into cropland, which translates into a saving of some 590 billion metric tons of carbon dioxide.

While farming currently accounts for about 12 percent of human-caused greenhouse emissions, the output of these emissions would have been considerably higher without the adopting of modern farming practices.

Without the yield gains associated with advanced farming, Stanford University researchers estimate that additional clearance of forestland to support farm output would have resulted in greenhouse gas emissions equivalent to roughly a third of that released since the advent of the industrial revolution in the mid-19th century.

"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 — usually by being burned," says Jennifer Burney, a post-doctoral student and lead author of a paper describing the study that will be published online by the Proceedings of the Academy of National Sciences.

While there is a place for organic farming, Goodman says its benefits are limited by the lack of one critical factor.

"There are lots of things we can grow well with organic farming practices — carrots, for example," he says. "But with grain production, we can't sustain yields without massive amounts of nitrogen fertilizer.

"There are no organic fertilizers available that can produce similar yields."

Runge cites advances in reduced-tillage practices as another major factor in reducing farming's environmental footprint.

"Reduced-tillage certainly is one of the reasons why we've become so efficient," he says. "Over time, we've learned to build soil in the course of production. Not only have we increased seed and fertilizer capability, but we've also imparted to farmers the importance of protecting soil."

But this wasn't always the case. In fact, he says roughly a century ago in the South, much of the insufficiently managed cropland soil washed off by heavy rains ended up in the bottom of the Gulf of Mexico.

"We're still paying for those mistakes even as we take steps to preserve what remains. We still have a long way to go, but we've made tremendous strides over the last few decades."