For all the discussion surrounding genetically modified foods, there have been strikingly few comprehensive studies that put a numeric value on the costs and benefits.
Now there’s more to talk about.
By analyzing two decades’ worth of corn yield data from Wisconsin, a team of CALS researchers has quantified the impact that various popular transgenes have on grain yield and production risk compared to conventional corn. Their analysis, published in Nature Biotechnology, confirms the general understanding that the major benefit of genetically modified (GM) corn doesn’t come from increasing yields in average or good years—but from reducing losses during bad ones.
“For the first time we have an estimate of what genetically modified hybrids mean as far as value for the farmer,” says CALS and UW-Extension corn agronomist Joe Lauer, who led the study.
Lauer has been gathering corn yield and other data for the past 20 years as part of the Wisconsin Corn Hybrid Performance Trials, a project he directs. Each year his team tests about 500 different hybrid corn varieties at more than a dozen sites around the state, with the goal of providing unbiased performance comparisons of hybrid seed corn for the state’s farmers. When GM hybrids became available in 1996, Lauer started including them in the trials.
“It’s a long-term data set that documents one of the most dramatic revolutions in agriculture—the introduction of transgenic crops,” says Lauer, who collaborated with CALS agricultural economists Guanming Shi and Jean-Paul Chavas to conduct the statistical analysis, which considered grain yield and production risk separately.
Grain yield varied quite a bit among GM hybrids. While most transgenes boosted yields, a few significantly reduced production. At the positive end of the spectrum was the Bt for European corn borer (ECB) trait. Yield data from all of the ECB hybrids grown in the trials over the years showed that ECB plants out-yielded conventional hybrids by an average of more than six bushels per acre per year. On the other hand, grain yields from hybrids with the Bt for corn rootworm (CRW) transgene trailed those of regular hybrids by a whopping 12 bushels per acre. But even among poor-performing groups of GM corn, there are individual varieties that perform quite well, Lauer notes.
Where transgenic corn clearly excels is in reducing production risk. The researchers found that every GM trait package—whether single gene or stacked genes—helped lower variability. For farmers, lower variability means lower risk, as it gives them more certainty about the yield levels they can expect.
Lauer equates choosing GM crops with purchasing solid-performing, low-risk stocks. Just as safe stocks have relatively low volatility, yields from GM crops don’t swing as wildly from year to year, and most important, their downswings aren’t as deep.
GM crops help reduce downside risk by reducing losses in the event of disease, pests or drought. Economists Shi and Chavas estimated the risk reduction provided by modified corn to be equivalent to a yield increase ranging from 0.8 to 4.2 bushels per acre, depending on the variety.
Risk reduction associated with GM corn can add up to significant savings for farmers—as much as $50,000 for 1,000 acres, calculates Lauer. “It depends on the price that farmers can receive for corn,” he says.
But the two factors quantified in this study—yield and production risk—are just part of the overall picture about GM crops, says Lauer. He notes there are other quantifiable values, such as reduced pesticide use, as well as ongoing concerns about the safety and health of growing and eating genetically modified foods.
“There’s a lot of concern about this biotechnology and how it’s going to work down the road,” says Lauer, “yet farmers have embraced it and adopted it here in the U.S. because it reduces risk and the yield increases have been as good as—or some would argue a little better than—what we’ve seen with regular hybrid corn.”