Recently, Italian researchers published a review of studies concluding planting genetically modified (GM) maize (corn) over the past 20 years has increased the agricultural yield of this popular and important staple food. In this context, it is important to remember one of the most popular myths perpetuated about GM crops: that they aren’t boosting yields. In fact, in 2016 the media mentioned this point when the National Academy of Sciences of the United States (NAS) published an extensive review of about 1,000 studies about the safety of GM crops. Apart from concluding that GMOs are as safe as conventional crops, the review mentioned that “there was no evidence that transgenic crops had changed the rate of increase in yields.”
That phrase was enough for many journalists to erroneously publish news mentioning that GM crops “were useless to increase agricultural yield.” New York Times reporter Danny Hakim even published a controversial article around that claim, which was widely criticized by academics and researchers. While this point about “no change in yield” is real, it was omitted that GM crops currently harvested at the commercial level haven’t been modified to directly increase agricultural yield, such as increasing the number of grains, pods, fruits or size of the plant. The GM crops that have been commercialized since 1996 were designed for two main traits: resistance to insects (or diseases) and/or tolerance to herbicides. In recent years, new traits such as drought-tolerance and non-browning have been commercially approved.
Insect-resistant Bt crops, and those that confer virus-resistance, like the Hawaiian papaya, reduce crop losses and require fewer phytosanitary products compared to conventional susceptible crops. In the case of herbicide-tolerant GM crops, they allow a better control of problematic weeds and facilitate the adoption of more environmentally friendly phytosanitary products, as well as sustainable no-till farming practices. The reduction of losses by pests, viruses and weeds that compete for soil nutrients, together with savings in phytosanitary products and fuel, indirectly increase the final yield when compared with conventional crops.
These advantages were previously documented in two major academic reviews by agricultural economists. The first, which was published in 2014 and included the review of 147 studies, concluded that GM crops have allowed an average increase in agricultural yield by 22 percent and increased farmers’ profits by 68 percent, with profit margins even larger in developing countries.
The second review is a study published annually covering the data of the global GM crops production. The last version, published in 2017, indicates that between 1996 and 2015, GM crops increased global production by 357.7 million tons of corn, 180.3 million tons of soybean, 25.2 million tons of cotton fiber, 10.6 million tons of canola and about a ton of sugar beet. In addition, the report mentions that GM crops significantly reduced the use of agricultural land due to this higher productivity. In 2015 alone they prevented almost 20 million hectares from being used for agricultural purposes, thus reducing the environmental impact cultivating forests or wild lands. This is a great environmental benefit derived from the higher agricultural yield.
Apart from these two major revisions, there is the new one referenced at the start of this post: a paper that was published a couple of days ago by Italian researchers, who reviewed more than 6,000 studies over 20 years of GM corn harvest. They concluded that GM crops allowed an increase in yield of 6 percent to 25 percent, depending on the country, with the additional benefit of reducing mycotoxin levels by one-third. These toxins contributed to major economic losses and cause serious health problems.
If GM crops didn’t provide a significant yield benefit to farmers, they would simply choose to use conventional seeds. However, the amount of arable land planted with GM crops has multiplied 100-fold in the last decade, from 1.7 million hectares in 1996 to 185.1 million hectares in 2016. These crops were planted by 18 million farmers in 26 countries, making GM the fastest adopted crop technology worldwide in recent times. This impressive increase in the adoption rate speaks for itself, in terms of its sustainability, resilience, extra income and the significant yield benefits available to both small and big farmers.
Genes for better yield
The only GM crop designed for higher yield that has received commercial approval is a GM eucalyptus developed in Brazil, which was approved in 2015. A gene from the model plant Arabipdopsis thaliana was inserted into the eucalyptus, which produced 20 percent more wood and reduced the time to maturity from 7 to 5.5 years.
Outside the forestry sector, although there are still no commercially available GM plants specifically designed to maximize yield (in terms of, for example, grain production or plant biomass), there are already several developments at the experimental or regulation stage.
A very promising example is the so-called “C4 rice” developed by scientists from the International Rice Research Institute (IRRI) in the Philippines, with collaboration from researcher groups all over the world. Because rice has C3 photosynthesis (3-carbon pathway), which is much less efficient than the C4 photosynthesis (4-carbon pathway) of crops such as corn or sugar cane, scientists work on inserting genes to express the metabolic pathway of C4 photosynthesis in rice plants. This accelerates plant growth by capturing carbon dioxide and concentrating it in specialized cells in the leaves, allowing the process of photosynthesis to work much more efficiently.
The technology that is being applied experimentally in rice and wheat — two crops that have already reached their peak of yield and feed the majority of the world’s population — would increase yield by 50 percent. In addition, it would be possible to use much less water and fertilizer to produce the same amount of food. This project has already had its first positive results.
Another project is the Realizing Increased Photosynthetic Efficiency (RIPE), an international research effort that is also engineering plants to photosynthesize more efficiently to increase crop yields. They have already succeeded increasing yields with model plants such as tobacco and Arabidopsis, and they are now transferring the technology to crops important in developing countries, such as cassava, rice and beans.
There are other projects under way that address the optimization of the photosynthesis process. For example, a University of Illinois initiative achieved a 20 percent higher yield in tobacco by overexpressing three genes protecting damage at times when more light is obtained. Other research managed to increase the yield of soy under conditions that emulate the higher temperatures and carbon dioxide levels expected in the year 2050.
There are also various GM crops in the experimental stage that can directly maximize the yield trait. These include a wheat with 20 percent higher yield, developed by Rothamsted Research in the United Kingdom, and another GM wheat with larger grains developed by the Austral University in Chile; a soybean with 36 percent more grain developed by Washington State University; a mustard with 25 to 34 percent more seeds developed by the University of Delhi in India; a corn with 50 percent larger kernels and an increased number of grains developed by the Cold Spring Harbor Laboratory (CSHL) in the United States; and a rice with a 54 percent higher yield developed by public sector researchers from the United Kingdom and China.
Other GM traits and gene editing
Additionally, a series of GM crops have modified to express traits like an efficient use of soil nitrogen, which directly increases agricultural yield while reducing the use of fertilizers, and the new generation of diverse drought-tolerant, heat-tolerant and salinity-tolerant crops, which will increase the final yield in soils that face water scarcity, warm climates or high salt levels.
And we can’t leave aside the new breeding techniques (NBTs), which also offer tools for improving yield. In fact, at the end of last year a review was published that analyzed 52 studies using the gene editing technology known as CRISPR from 2014 to mid-2017. The results showed that 15 crops were studied for the application of CRISPR. The most studied crop has been rice, followed by tobacco, Arabidopsis and corn. The majority of CRISPR applications were to improve crop yields, followed by improved nutrient content (biofortification) and tolerance to biotic/abiotic stresses.
An example of these developments is the modification of the structure of the plant, the size of the frui, and the architecture of ramification in tomato through CRISPR by CSHL scientists.
All of these crops deliver benefits not only for farmers, but also for the environment by reducing land use and general environmental impact, and for consumers by supporting global food security. It’s estimated that to feed a growing population, we will need to increase the food supply by 60 to 70 percent by 2050, which is why we need to use all possible technologies to boost agricultural production while reducing the environmental impact. However, the ability of society as a whole to enjoy the benefits of this technology depends in large part on decision makers, governments and the regulatory frameworks of each country. Let’s hope they don’t react too late, since it requires at least a decade and a lot of investment to take GM crops from the laboratory into the field, and the goal to significantly expand global food production is just around the corner.