The Independent recently published an article with the startling headline:
Exposed: the great GM crops mythWow. That's a pretty bold statement. Let's look further into it, shall we?
Major new study shows that modified soya produces 10 per cent less food than its conventional equivalent
Genetic modification actually cuts the productivity of crops, an authoritative new study shows, undermining repeated claims that a switch to the controversial technology is needed to solve the growing world food crisis.Hmmm.
The study – carried out over the past three years at the University of Kansas in the US grain belt – has found that GM soya produces about 10 per cent less food than its conventional equivalent, contradicting assertions by advocates of the technology that it increases yields.
Professor Barney Gordon, of the university's department of agronomy, said he started the research – reported in the journal Better Crops – because many farmers who had changed over to the GM crop had "noticed that yields are not as high as expected even under optimal conditions".I've noticed in the past that news organizations don't always do the best job with science stories, so let's look at the original citation, shall we?
But first, some background (yes, yes, I know that the Independent wouldn't require any background, but they also wrote a factually wrong, irresponsible, scaremongering article, so we'll do some background). Soybean plants have been genetically modified in recent years to be resistant to a broad-spectrum herbicide called Roundup (aka glyphosate). This provides a neat trick for farmers, because they can grow their Roundup resistant soybeans, and spray them with Roundup to kill any weeds (without killing the soybeans). This is a neat trick, because Roundup isn't very toxic to people, and breaks down pretty readily in the soil, providing a neat way for farmers to decrease weeds in their fields, without having to use more expensive and toxic compounds.
Ok, so what was the question that Dr. Gordon asked? From the paper:
There is evidence to suggest that glyphosate may interfere with Mn metabolism and also adversely affect populations of soil micro-organisms responsible for reduction of Mn to a plant-available form. Manganese availablity is also strongly influenced by soil pH. As soil pH increases, plant-available Mn decreases. It is unlikely that Mn deficiencies will occur on acid soils. It stands to reason that the addition of supplemental Mn at the proper time may correct deficiencies and result in greater GR soybean yields.Ok, so he wanted to ask if there are manganese deficiencies in plants that are treated with glyphosate. And what did he see?
He sees that he can increase yield of soybeans by applying manganese to the soil. Cool, huh? Now, if you're a journalist at the Independent, you may look at that graph and say, "Hey, wait, the conventional soybeans have higher levels of production than the Roundup resistant soybeans!". Well, you could say that, but you'd be wrong. You can't ask that question from these data. Firstly, these strains aren't isogenic. Meaning that their genetic content isn't just differentiated by the fact that the GM strain is Roundup resistant, so increased growth could be due to different genetic content. Secondly, the Roundup resistant strain was sprayed with Roundup. And the other one wasn't. That's a rather large difference. Indeed, the conventional strain of soybean is really only a control to show that increasing manganese levels doesn't increase yield in the absence of Roundup. Thirdly, both these crops were worked over by hand to remove weeds, as they were interested in only studying the effect of manganese on the experiment, not on the effect of weeds in the crop. So this experiment simply can't be used to ask "Do Roundup resistant crops produce more or less than conventional crops?" The experiment wasn't designed to ask that question, and you can't use these data even incidentally to ask that question. And what does the Independent say?
The GM crop – engineered to resist Monsanto's own weedkiller, Roundup – recovered only when he added extra manganese, leading to suggestions that the modification hindered the crop's take-up of the essential element from the soil.Hmmm.... but they applied Roundup to the Roundup resistant plants. That's another pretty huge difference.
Indeed, the author of the study, Dr. Barney Gordon, concurs. From an e-mail he wrote me:
The article you saw in the Independant was a total distortion of the research. My research concerned manganese application on soils that are known to respond to Mn application. We used one conventional variety and a glyphosate-tolerant near isoline (not genetically identical). The objective of the research was to improve soybean yields under optimum management conditions, not to make any statement about GM crops.Now, I can almost hear the anti-GM crowd crowing now, "Just because he didn't ask that question, doesn't mean you can't extrapolate from the data he gathered", but as I've outlined above, you can't even extrapolate. The experiment isn't properly controlled to ask that particular question, just to ask the question about manganese suplementation.
And it's rather disingenuous of the Independent to say otherwise.