The National Academy of Sciences has released a massive study of genetically modified crops. This has been a tough issue to discern the facts because there has been a lot of corporate propaganda coming from one side, and a lot of emotion from well-meaning but not-all-that-scientific activists from the other side. I would consider the NAS to be pretty close to an impartial, science-based source, although you could argue that the academics involved probably do a lot of research funded by the agriculture industry. Still, it is a very large number of academics involved and is very thoroughly peer-reviewed, so I think you could regard this as the academic consensus.

First, on human health effects, they offer some reassuring news:

There have been claims that GE crops have had adverse effects on human health. Many reviews have indicated that foods from GE crops are as safe as foods from non-GE crops, but the committee reexamined the original studies of this subject. The design and analysis of many animal-feeding studies were not optimal, but the large number of experimental studies provided reasonable evidence that animals were not harmed by eating food derived from GE crops. Additionally, long-term data on livestock health before and after the introduction of GE crops showed no adverse effects associated with GE crops. The committee also examined epidemiological data on incidence of cancers and other human-health problems over time and found no substantiated evidence that foods from GE crops were less safe than foods from non-GE crops.

You could still argue, as the Europeans do, that the precautionary principle means new technologies must be treated as guilty until proven innocent. It is somewhat the opposite here in the big-business-friendly U.S. Still, there is no smoking gun here.

Nor is there a smoking gun on the ability of genetic engineering to deliver yield increases. Some are arguing that the smoking gun is evidence showing it has not really done this yet. That is somewhat disappointing, but with biotechnology continuing to accelerate I don’t think you can point to progress so far as evidence that no further progress will be made. That is like saying we have not cured cancer to date, so it is time to give up.

There is disagreement among researchers about how much GE traits can increase yields compared with conventional breeding. In addition to assessing detailed surveys and experiments comparing GE with non-GE crop yields, the committee examined changes over time in overall yield per hectare of maize, soybean, and cotton reported by the U.S. Department of Agriculture (USDA) before, during, and after the switch from conventional to GE varieties of these crops. No significant change in the rate at which crop yields increase could be discerned from the data. Although the sum of experimental evidence indicates that GE traits are contributing to actual yield increases, there is no evidence from USDA data that they have substantially increased the rate at which U.S. agriculture is increasing yields…

One of the critical questions about the new traits that may be produced with emerging genetic engineering technologies is the extent to which these traits will contribute to feeding the world in the future. Some crop traits, such as insect and disease resistance, are likely to be introduced into more crop species and the number of pests targeted will also likely increase. If deployed appropriately, those traits will almost certainly increase harvestable yields and decrease the probability of losing crop plantings to major insect or disease outbreaks. However, there is great uncertainty regarding whether traits developed with emerging genetic-engineering technologies will increase crop potential yield by improving photosynthesis and increasing nutrient use. Including such GE traits in policy planning as major contributors to feeding the world must be accompanied by strong caveats.

The don’t talk too much about one of my questions, the extent to which corporate profit-driven genetic engineering reduces genetic diversity, potentially making the global food system less resilient in the face of future shocks. They don’t seem concerned about the possibility of genetically engineered crops escaping and wreaking havoc in our remaining natural ecosystems.

I’ll reproduce one graphic I found interesting, distinguishing between the concepts of potential and actual yield. One point they seem to be making is that the focus of genetic engineering to date has been on reducing crop losses to weeds, pests, and diseases. This does not increase the plant’s ability to make full use of water, nutrients, and ultimately sunlight more efficiently than the naturally-derived crop has in the past. So this is why there is still the potential for a lot of progress, as well as the potential for risks to diversity, resilience, human health and ecosystems. This also reinforces my general sense that medical biotech is farther along than agricultural biotech.

National Academies of Sciences, Engineering, and Medicine. 2016. Genetically
Engineered Crops: Experiences and Prospects. Washington, DC: The National Academies Press. doi:
10.17226/23395.