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 Summer 2009

Genetically engineered crops were supposed to help meet the world’s growing food needs. New UCS research shows that these crops have yet to deliver on that promise.

By Doug Gurian-Sherman and Emily Robinson

When food prices soared to record highs in 2007 and 2008, localized food shortages sparked rioting in Bangladesh, Egypt, Haiti, and other countries. These price spikes and shortages, combined with increasing global population and food consumption, have prompted calls to boost agricultural productivity, or yield—the amount of a crop produced per unit of land over a specified amount of time.

For two decades, biotechnology companies have maintained that genetic engineering (GE)—inserting genes with desirable traits into organisms such as food crops—is the technology needed to meet this goal. Monsanto recently claimed that its engineered seeds “significantly increase crop yields.” UCS set out to test such claims with a comprehensive and up-to-date study of the overall effect GE has had on crop yields relative to other technologies in the United States. Our report, Failure to Yield: Evaluating the Performance of Genetically Engineered Crops, found that the industry’s promises have largely proven to be empty, and are likely to remain so for the foreseeable future.

Hitting the Productivity Ceiling
When evaluating a crop’s potential productivity, it is important to understand the critical distinction between intrinsic and operational yield—concepts that are often conflated by the biotechnology industry and misunderstood by policy makers. Intrinsic (or potential) yield refers to a crop’s maximum production under the best possible conditions. Operational yield refers to actual production levels after accounting for losses due to pests, drought, and other environmental factors. While operational yield is important, intrinsic yield must be improved in order to increase the maximum amount of food a crop can produce.

In Failure to Yield, UCS reviewed more than two dozen academic studies of corn and soybeans, the two primary GE food and feed crops grown in the United States. GE soybeans comprise more than 90 percent of the domestic crop, while GE corn comprises more than 60 percent of the domestic crop. The three most common types of these GE crops are: herbicide-tolerant soybeans, herbicide-tolerant corn, and insect-resistant corn (known as Bt corn because it is engineered with a gene from the bacterium Bacillus thuringiensis, which kills several kinds of insects).

Our analysis found that these crops have failed to increase intrinsic yields. Herbicide-tolerant soybeans and herbicide-tolerant corn have also failed to increase operational yields compared with conventional methods; Bt corn has provided a marginal operational yield increase of 3 to 4 percent. Since Bt corn became commercially available in 1996, its yield advantage averages out to an increase of 0.2 to 0.3 percent per year. To put that figure in context, overall U.S. corn yields over the last several decades have increased approximately 1 percent each year—considerably more than what the Bt trait has provided.

A Better Path Forward
So GE has made a paltry contribution to crop productivity, but not for lack of trying. Over the past 20 years the industry has spent billions of dollars on research and carried out more than 3,000 field trials that have not resulted in any widely grown commercialized genes; thousands of additional trials on herbicide tolerance and insect resistance have come up with only two types of engineered genes in widespread use—and neither of those has raised potential yields. Though GE could conceivably increase crop yields in the future, it makes little sense to support this technology at the expense of other technologies and practices already proven to increase yields, such as marker-assisted breeding (using specific markers in plant DNA to breed for desirable traits).

What Price Productivity?

As genetic engineering becomes more high-tech, could growing food crops become more high-risk?

There are many genetic interactions that take place in a plant as it grows, each of which can influence the function of other genes and potentially change the plant’s properties. Many newer engineered genes have been selected for agriculture because they influence crop genes responsible for intrinsic yield or drought tolerance (which affects operational yield). But because genetic interactions are so complex, altering the function of crop genes can lead to side effects far removed from the desired effect. For example, a promising engineered gene for drought tolerance was recently found to increase susceptibility to several plant diseases. Commercialization of this gene may therefore help increase yield, but increase the use of pesticides in order to avoid disease outbreaks.

Similar side effects could make it difficult to successfully increase yields without some degree of harm. Even genes that work as expected could sometimes cause significant unintended consequences for food safety and the environment. Because these potentially harmful effects could go undetected under current U.S. biotechnology regulations, improved oversight is needed to ensure such effects are discovered and prevented.

This argument is further bolstered by evidence from recent studies that suggests developing countries—which have the most urgent need for higher crop yields—may be better served by low-cost farming methods and conventional seeds than GE seeds. Organic and similar sustainable farming methods can double crop yields in many developing countries while saving money (since they require less pesticide and synthetic fertilizer).

It should also be noted that most of the genes being considered for future GE crops cause more complex interactions with plants’ genes than genes in current GE crops. These interactions often cause genetic “side effects” that could produce undesirable—or even harmful—properties (see the sidebar).

The United States should therefore fund solutions that have a track record of boosting crop yields in an efficient and sustainable manner. UCS recommends that the U.S. Department of Agriculture, state agricultural agencies, and universities increase research and development for modern conventional plant breeding methods, sustainable and organic farming, and other sophisticated farming practices. We also recommend that U.S. food-aid organizations make these more promising and affordable alternatives available to farmers in developing countries. Together, these actions can help farmers worldwide meet the goal of higher yields while preserving natural resources for future generations.

Doug Gurian-Sherman is a senior scientist in the Food and Environment Program. Emily Robinson is a press secretary.