GMOs and pesticide use (an email from Greg Conko)

Here is a further Mark Bittman column on GMOs, arguing against GMOs on the grounds that they lead to greater use of chemicals and pesticides.  I would start with quite a simple point, namely to the extent there is a problem with chemicals and pesticides (as there may be with or without GMOs), let’s regulate that problem directly.  Somehow that option is not put on the table as an alternative to what is widely recognized as a rather dubious referendum.  In any case, I posed the question about GMOs and pesticides to Gregory Conko, who has written a book on GMOs, and he responded to me (Greg’s email goes under the fold)…

GC: Note that “pesticide” is a broad term that includes both insecticides and herbicides, as well as fungicides, nematocides, rodenticides, etc. Use of GE crops has had a measurable impact on insecticide and herbicide use, with insecticide use incontrovertibly down and a mixed record on herbicide use. And because there is much more acreage planted with GE herbicide tolerant varieties than with GE insect resistant varieties, herbicide use trends tend to drown out insecticide use trends.  Critics tend to obfuscate these distinctions by using the term “pesticide”, rather than the more specific sub-types, probably because they know casual readers will think “insecticides”.  But even the herbicide data need some additional context.

When measuring raw quantities of active ingredient, you find herbicide use on herbicide-tolerant GE crops to vary widely with crop species and region. In corn, for example, where atrazine is used extensively on non-GE varieties, a switch to Roundup Ready varieties tends to reduce slightly the quantity of active ingredient used, but mainly results in a switch from one to the other chemical. In soy, on the other hand, where herbicides of any kind are used much less frequently in non-GE varieties, a switch to RR soy almost invariably increases active ingredient use significantly.  And because RR soy is by far the most widely grown GE crop (amounting to well over 60 percent of all the soy grown anywhere in the world), on net across all species, this tends to result in an increase in quantity of active ingredient for GE crops generally.

However, merely saying that GE HT varieties result in higher use of active ingredient says little about the environmental or human impact of that change.  Because glyphosate, the active ingredient in Roundup, has close to zero mammalian, avian, invertebrate, etc. toxicity, and biodegrades rapidly, it has a vastly lower Environmental Impact Quotient (EIQ) than the herbicides it’s replacing.  Thus, a switch to RR soy may result in an increase in “pesticide” use while nevertheless being far better for humans and the environment.  Focusing only active ingredient use without any discussion of EIQ is therefore patently misleading.

It’s also worth noting that there is nothing unique about genetic engineering’s ability to produce herbicide tolerant crop varieties. In fact, there are scores of non-GE herbicide tolerant varieties grown all around the world.  A farmer who wants to plant HT canola or rice but doesn’t want to be beholden to Monsanto, or another farmer who’s tired of waiting for full regulatory approval of Roundup Ready wheat or sunflowers, can buy “Clearfield” branded seed from BASF that’s been bred with induced mutagenesis to tolerate the herbicide imidazolinone. Why are GE opponents not talking about imi-tolerant crops? Because they’re not GE. Plant breeders can expose seeds to mutagenic chemicals or ionizing radiation to scramble the plant’s DNA in entirely unpredictable ways and then put them on the market in the United States without reporting to or asking permission from a single regulatory agency, and not a one environmental activist or consumer group will bother criticizing them for doing so. For some reason, skeptics seem to be fixated on the use of recombinant DNA techniques, even though what they criticize publicly are phenomena that occur with all sorts of plant breeding methods.

See here, for example, for a nice critique of the recent study by Charles Benbrook concluding that GE crops increase pesticide use: And a related discussion, with references
to the literature, can be found here:

For a more general discussion of the impacts of GE crops on pesticide use, see:

National Research Council, Impact of Genetically Engineered Crops on Farm Sustainability in the United States, 2010,
” Generally, GE crops have had fewer adverse effects on the environment than non-GE crops produced conventionally. The use of pesticides with toxicity to nontarget organisms or with greater persistence in soil and waterways has typically been lower in GE fields than in non-GE, nonorganic fields. … When adopting GE herbicide-resistant (HR) crops, farmers mainly substituted the herbicide glyphosate for more toxic herbicides.” (p. 3).  And, ” Targeting specific plant insect pests with Bt corn and cotton has been successful, and the ability to target specific plant pests in corn and cotton continues to expand. Insecticide use has decreased with the adoption of insect-resistant (IR) crops” (p.6).

G. Brookes and P. Barfoot, “Global impact of biotech crops: Environmental effects 1996-2009,” GM Crops Vol. 2, No. 1 (2011) pp.
This paper updates the assessment of the impact commercialised agricultural biotechnology is having on global agriculture from an environmental perspective. It focuses on the impact of changes in pesticide use and greenhouse gas emissions arising from the use of biotech crops. The technology has reduced pesticide spraying by 393 million kg (-8.7%) and, as a result, decreased the environmental impact associated with herbicide and insecticide use on these crops (as measured by the indicator the environmental Impact Quotient (EIQ)) by 17.1 %. The technology has also significantly reduced the release of greenhouse gas emissions from this cropping area, which, in 2009, was equivalent to removing 7.8 million cars from the roads.

TC again: In other words, the charge about chemicals and pesticides is not such a strong one.  As we can see from the earlier Indian farmer suicide accusation, the critics are still just clutching at straws.


Comments for this post are closed