Sep 22 2020

GMO Crops and Yield

The issue of genetically modified organisms is interesting from a science communication perspective because it is the one controversy that apparently most follows the old knowledge deficit paradigm. The question is – why do people reject science and accept pseudoscience. The knowledge deficit paradigm states that they reject science in proportion to their lack of knowledge about science, which should therefore be fixable through straight science education. Unfortunately, most pseudoscience and science denial does not follow this paradigm, and are due to other factors such as lack of critical thinking, ideology, tribalism, and conspiracy thinking. But opposition to GMOs does appear to largely result from a knowledge deficit.

A 2019 study, in fact, found that as opposition to GM technology  increased, scientific knowledge about genetics and GMOs decreased, but self-assessment increased. GMO opponents think they know the most, but in fact they know the least.  Other studies show that consumers have generally low scientific knowledge about GMOs. There is also evidence that fixing the knowledge deficit, for some people, can reduce their opposition to GMOs (at least temporarily). We clearly need more research, and also different people oppose GMOs for different reasons, but at least there is a huge knowledge deficit here and reducing it may help.

So in that spirit, let me reduce the general knowledge deficit about GMOs. I have been tackling anti-GMO myths for years, but the same myths keep cropping up (pun intended) in any discussion about GMOs, so there is still a lot of work to do. To briefly review – no farmer has been sued for accidental contamination, farmers don’t generally save seeds anyway, there are patents on non-GMO hybrid seeds, GMOs have been shown to be perfectly safe, GMOs did not increase farmer suicide in India, and use of GMOs generally decreases land use and pesticide use.

Further, adoption of GMOs does, in fact, increase ultimate crop yield. The myth that they don’t is mostly due to the persistent anti-GMO smear campaign, largely funded by the organic industry, but is helped by several layers of confusion on this issue. First, we always have to be cautious when discussing “GMOs” because they are not one thing. Genetic modification is a technology, not an application. Yet anti-GMO propaganda has successfully tied the technology to just one application – use of herbicides. Many opponents still conflate the two in their mind. It is true that the first widely adopted GMO traits were for pest resistance (such as Bt) and herbicide tolerance (specifically glyphosate), and so some opinions are based on this 20 year-old impression of GMOs. But the number and type of GM traits is expanding significantly in recent years, so that impression is out-of-date.

But even if we just consider these two early applications, it is clear that Bt varieties have decreased pesticide use, and herbicide tolerant varieties have increased glyphosate use but decreased the use of more toxic herbicides. They have also increased yield – but indirectly, which is the next layer of confusion. Some studies and reviews conclude that these early GMO applications did not increased crop yield, but this is only true in a limited sense.

These early GMO traits were never designed to directly increase yield. They were designed to help farmers by reducing their need to apply pesticide, or by making it easier to apply herbicide and reduce the need for tilling or expensive hand weeding. So it is a non-sequitur to say that traits never designed to increase yield did not increase yield. That is like criticizing air bags because they don’t increase fuel efficiency.

But even more importantly – these traits did increase crop yield, indirectly. A recent review found:

The analysis of over 6,000 peer-reviewed studies covering 21 years of data found that GMO corn increased yields up to 25 percent and dramatically decreased dangerous food contaminants. The study, published in Scientific Reports, analyzed field data from 1996, when the first GMO corn was planted, through 2016 in the United States, Europe, South America, Asia, Africa and Australia.

Mainly the increased yield was from decreased crop loss, but all that matters is the calories and nutrition produced per acre and per inputs, such as water and fertilizer. In addition, the GMO crops reduced human exposure to mycotoxins, a significant source of crop contamination.

A study that frequently gets misinterpreted by GMO opponents is this review which concluded that the last 20 years of GMO technology did not change the rate of increase of crop yields. This has been misstated at GMOs did not increase yields, but read that sentence more carefully – it did not alter the rate of increase. What this means is that yields have been steadily increasing for decades, with various technological improvements contributing to that increase. GM technology is just the latest technology allowing for this steady increase.

This pattern is true of many industries, like computer processing speed or battery energy density. These have been steadily increases for decades as well, but no individual technology has increased the rate of increase – they are responsible for the steady increase. You can’t just keep doing the same thing and get never-ending benefits. You have to keep pushing the technology forward.

And again, we have to consider GM a technology, not an application. The early applications, which were not specifically designed to increase yield contributed to the steady increase in yield anyway, and have better net yields than farms that do not use GM varieties. But the future looks even brighter, as scientists develop and we start to use GM applications that are designed specifically to increase yield. This will help to continue the trend, feed the world, reduce land use, and reduce the carbon footprint of agriculture.

For example, C4 rice and wheat could make a huge contribution. Some plants use C3 photosynthetic pathways, while other use C4, which is more efficient. Rice and wheat use C3, but if we can engineer them to use C4 we could get a 50% increase in yield with fewer inputs.

Recent applications already in the field, that reduce browning and improve drought tolerance, already increase yield. Other GM applications, such as golden rice, improve the nutritional quality of staple crops, reducing malnutrition.

To reinforce this main point – GM is a technology, and we have to judge each application and each GM crop on its own merits. We also have to think about the whole system, not just the crop. When you do it is clear that GM technology is incredibly powerful and useful, and is our best hope for meeting the nutritional needs of the world population while minimizing our carbon and land footprint.

The good news is, that while popular opposition continues (based on demonstrable misinformation), the science is progressing in the background and farmers are adopting GM crops because of their obvious benefits. Farmers are not stupid, nor are they being manipulated. They buy GM seeds because it is to their advantage to do so.

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