by Marion Nestle
Apr 20 2009

Does GM (genetic modification) increase crop yields?

The answer to this question depends on whom you ask.  If you ask the Union of Concerned Scientists, the answer is no. Just out is this group’s report, Failure to Yield: Evaluating the Performance of Genetically Engineered Crops. Its conclusion: traditional genetic crosses outperform genetically modified crops by a wide margin.  Monsanto, as you might guess, has a rather different take on this issue, one that now faces a serious challenge.

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  • Jon

    Well, they don’t really genetically modify it to increase yields. It’s for herbicide resistance and things like that; particularly disturbing is marketing crops with traitor genes in them as having higher yields.

    At best, GMOs might improve yields under laboratory conditions, which (as you might imagine) never exist on a farm, due to things like the weather. I know people who live in the Midwest, and they could tell you which fields had GMOs last year: The ones that failed to survive the storms.

  • Lisa

    Really? I was actually impressed with what they reported, such as (page 19):
    “In summary, when levels of ECB infestation are low or even moderate, most research reviewed here suggests that there is typically little or no significant yield difference between Bt varieties and their NI counterparts, even without insecticide treatment of the NI. When infestation levels are high, Bt corn provides yield advantages of about 7–12 percent compared to typical alternative practices used by conventional (non-organic) farmers.”

    Since it is about resistance and not yield that seemed worthwhile to me. What would be considered a good value?

  • It is interesting to note that the paper concludes that the Bt trait has increased yields overall, but the press release states that GE has not. Also, this paper only examined two traits in two species, but makes sweeping conclusions based upon those traits. I haven’t completed my analysis of the paper yet, but I made a few points here:
    http://www.biofortified.org/2009/04/union-of-concerned-scientists-ge-crops-have-not-decreased-yields/
    Curiously, there is apparently a GE yield trait that has undergone field trials, yet Gurian-Sherman at the UCS was not aware of it.

  • Anne

    I attended your lecture on Saturday (thank you!) and remembered a question that you were asked related to the increase in food allergies. I just read an artcile about GMO’s, and how in the process of of modifying say the soybean, the genetic material of the roundup-resistant bacteria is paired with a CMV (cauliflower mosaic virus). The CMV acts as a promoter (in order to ensure that genes are expressed, or turned on). And the CMV could easily latch on to a protein that, say, causes an allergy in some people. And when Roundup Ready Soybeans were introduced in the UK, a 50% increase in soybean allergies was tracked shortly thereafter. Perhaps GMO’s are the cause for huge increases in wheat, soy, and peanut allergies.