Advances in conventional agriculture have dramatically slowed the flow of greenhouse gases into the atmosphere, in part by allowing farmers to grow more food to meet world demand without ploughing up vast tracts of land, a study by three Stanford University researches has found.

The study which has been embraced by many agricultural groups but criticized by some environmentalists, found that improvements in technology, plant varieties and other advances enabled farmers to grow more without a big increase in greenhouse gas releases. Much of the credit goes to eliminating the need to plough more land to plant additional crops.

The study’s authors said they aren’t claiming modern, high production agriculture is without problems, including the potential for soil degradation through intense cultivation and fertilizer runoff that can contaminate fresh water.

But some environmentalists said the study is flawed, arguing it’s based on unrealistic scenarios of what would have happened if yields hadn’t increased during the study period. The yield is the amount of a crop grown per acre.   

The other authors are Jennifer Burney, a physicist who focuses on energy and food security research at Stanford’s Program on Food Security and the Environment, and David Lobell, an assistant professor of environmental science at Stanford who has studied the effects of food and bio-fuel production on the environment.

The three decided to look at the impact of agriculture on greenhouse gases – carbon dioxide, methane and nitrous oxide. Agriculture accounts for about 12 per cent of greenhouse gas emissions generated by human activity.

The researchers set up hypothetical models in which the world’s growing population was fed by cultivating even more land. Those models were then compared with actual agricultural production between 1961 and 2005.

Yields for major crops like corn and soybeans have increased dramatically over the study period. Midwestern corn farmers for instance now average well over 160 bushels an acre. That’s roughly double what they produced in the early 1960s, according to US Department of Agriculture statistics.

Without those increases, it would have taken an additional 4.35 billion acres to feed the world according to the study. The cultivation of that land including the release of carbon in the soil and burning of brush and trees that covered it would have released an additional 317 billion to 590 billion tons of greenhouse gases, the authors wrote.

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