This last Wednesday, the public radio show Marketplace did a story on how GMO crops are damaging tractor tires and a company is now making Kevlar tires in response. This story doesn’t seem to be inaccurate. But the explanation of the cause — tough GMO corn (or soy) stubble — is so simplistic that it leaves you misinformed. The glib explanation represents a missed opportunity to genuinely inform the public. Instead, people will think GMOs are so scary they can destroy tires that don’t have bullet-proofing. Reality is far more interesting.
The Glib Version
The glib version of this story goes like this: GMO crops are engineered to be tough to pests and stand up to drought. The stubble (the cut off stalks left after harvest) is really sharp and hard to breakdown. When farmers try to run a tractor over them, it cuts up the tires much faster than before the GM crops. Tractor tires are expensive and farmers have to buy a lot of them. Now companies are making even more expensive Kevlar tires so they don’t wear out so fast.
The Marketplace story itself is fairly innocuous and so short I would call it fluff driven by a tire maker. But now it’s also going around via twitter (especially from activist anti-GMO groups) and other news organizations have posted similar stories. All of them seem to be repeating the same basic information. The WSJ story (which I can’t read all of) even cleverly titled their story story Genetically Engineered Tires.
Less Glib Possibilities
If you’re paying attention (or read a few pages on wikipedia), you’ll know that in the United States, the main transgenic traits that have been incorporated into commercially available corn are traits to produce Bt toxins (damaging to certain insects) and herbicide tolerance (usually glyphosate). The main trait in transgenic soy is herbicide tolerance. Neither of these traits are likely to be changing the “toughness” of the plant in a fundamental way (such as making the plants literally taller or stiffer). There’s just no clear mechanism how that would be. But if you google around, you’ll find that farmers widely believe that Bt corn is harder on their equipment and will even mistake non-GMO corn for GMO corn by judging the stubble (see the end of previous link). However, controlled research isn’t showing that Bt corn decomposes any differently which might be expected. But some studies show higher lignin content which could cause tougher stalks, though it’s not clear what the cause would be. Another study speculates lignin differences might be due to random insertion of the Bt gene elsewhere in the genome.
So the evidence is pretty ambiguous that that “tough” stubble is caused by GMO traits. But could it be true due to something else, but possibly still related to the GMO traits? I don’t think there is any firm evidence but there are some good possibilities:
- Bt corn is more resistant to root and other damage. A healthy plant is going to be stronger and larger.
- Similarly, Bt corn is going to resist root damage. Stronger roots means it won’t be easy to push over or uproot.
- Herbicide tolerance means the young plant doesn’t have to compete as much and can grow stronger and larger.
- Modern corn or soy lines that have transgenic varieties may have been previously bred for “toughness” such as being taller and thicker.
Most of the above are basically side effects of the crops being more resistant to pests or not having to compete with weeds. In other words, the toughness might be due to “effective pest control”, not “GMO genes”. I’m not saying the above are definitely the cause of “tough” plants, but they seem like better explanations than unproven claims of an unexpected genetic change due to transgenic methods1
The Missed Opportunity
Marketplace, by choosing to do a glib story emphasizing the fancy Kevlar tires and glossing over the explanation of “tough” GMO plants, has done a disservice to their listeners. A quick google search shows that it’s not at all clear that the transgenes in corn are “the” cause. Misinforming listeners is bad enough. The simplistic explanation of “GMOs are tough” means listeners don’t know why or how they are tough. It’s just another thing “wrong” with GMOs that is costing farmers money. In reality, tough plants are probably what farmers want. Marketplace implies this by citing the kinds of traits the plants might have2, but the emphasis on the expensive Kevlar tires washes out that understanding. This is a missed opportunity to actually improve knowledge of agriculture and the kinds of trade-offs we are making.
Of course, this is all too common. Stories with simple explanations are easier to write and easier for readers to enjoy and understand. But too simple a story can misinform as much as blatant inaccuracy or outright lies. Obviously it doesn’t matter much in this case. It’s a fluff story that few will care about a week from now and the harm to a listener who isn’t otherwise interested in agriculture is minimal. Current GM crops probably are “tougher” in some ways than older varieties. But for those inclined to believe scare stories about agriculture and food, this will become another unshakeable story about the horrors of transgenic technology.
Thanks to many people on twitter and biofortified for discussion on possible explanations for “tough” corn. I hope I’ve summarized them well enough. Special thanks to cropdoc2, geneticmaize, Brian Corkill and Brian Scott. ↩
They mention drought tolerance as one of the tough traits. Transgenic drough tolerance trait only got approval last December so if it’s being grown commercially this year, it would be the first time so previous years “tough” crops couldn’t be due to that trait. Of course, non-transgenic crops with drought tolerance features have been available for years. ↩