As a society, we struggle to satisfy the global demand for food. One in nine people across the globe suffer from hunger, and in order to keep pace with the rate of population growth, we will need to be able to produce 70 percent more food by 2050. We can increase agricultural output by allotting more wilderness to farms and pastures, or by making existing farmland more productive. Crop technologies such as genetic engineering—the transfer of foreign genes by nonsexual methods—can help to satisfy the global demand for nutrients by optimizing the productivity of agriculture to increase the accessibility of food worldwide.
The ethical debate about genetic engineering and its products, genetically modified organisms (GMOs), has been divisive. Many of the criticisms of genetically engineered (GE) foods center on potential risks to human health, the environment, and socioeconomic dynamics, and are typically variations on the following statement:
Nature is complex; the human body is a black box, ecosystems are chaotic, and socioeconomic networks are highly interdependent. Introducing variables into these systems can perturb them in ways that are difficult to predict, with consequences that may only emerge over time.
This principle is invoked liberally throughout anti-GMO rhetoric. It is ostensibly reasonable, scientifically impossible to disprove, and fundamentally flawed.
Our food supply is already the product of millennia of human-driven modifications to nature. Selective breeding exploits random mutations, combined with controlled sexual reproduction, to create extreme variations in traits over generations. Although breeders select for specific traits, gross untargeted changes to the genome—including the addition of entire chromosomes—arise and are preserved.
Since the 1920s, breeders have been exposing seeds to radiation and chemical mutagens in order to increase the amount of genetic variation per generation. The induced mutations, which are largely untargeted, have been used to improve several major crops, leading to the creation of over 2700 “non-GMO” varieties, many of which may be labeled as organic.
The ancient technique of grafting—the joining of plant tissue from two plants—has been shown to result in the exchange of entire genomes between plants cells. Additionally, the same process of gene transfer from bacteria to plants implemented in genetic engineering occurs ubiquitously in nature. Evidence of such horizontal gene transfer has been discovered in common staple crops, such as the sweet potato and tobacco, demonstrating how nature has been creating its own “GMOs” all along.
Within this context, it becomes clear that sweeping ethical judgments of genetic engineering as a technology are unreasonable. The scientific consensus is unambiguous—the process of genetic engineering is no riskier than the above means of genetic optimization. Rather than debate the relative merits of these inherently related technologies, let us examine how the genetic engineering of crops is being applied in the real world. Weighing the benefits of GE crops on their health, environmental, and socioeconomic risks can inform how they can play a role in improving our food system.
Hundreds of safety studies have established that GE crops present no significant safety hazard. After reviewing the body of scientific evidence, the National Academy of Sciences, American Medical Association, World Health Organization, European Commission, and American Association for the Advancement of Science have all concluded, no credible evidence exists that any GMOs are unsafe. Not a single verified case of illness, allergy, or adverse effect has ever been attributed to the genetic modifications in GE crops. There is no scientific basis for imposing standards on GMOs that are not applied to foods developed using substantially similar methods, such as selective breeding (which is known to give rise to unintended effects). Doing so would mean denying society the benefit of products that would not otherwise be available, when the perceived risk is not supported by the data.
“Scientific and regulatory agencies around the world have repeatedly and consistently found crops and foods improved through biotechnology to be as safe as, if not safer than those derived from any other method of production.”
Consider the papaya, an important source of vitamins, minerals, and fiber in the developing world. The papaya ringspot virus (PRSV) is a major limiting factor for papaya cultivation globally and, in the 1980s, an epidemic of PRSV in Hawaii ravaged the crop. The transfer of the gene encoding the coat protein (CP) of PRSV into the genome of papaya was shown to effectively vaccinate the crop against PRSV. Today, genetically engineered papaya accounts for a lot the papaya production in Hawaii and remains the only means of growing papaya resistant to the virus. PRSV-resistant papaya is now grown throughout the world.
There is no evidence of any toxicological effect of the CP gene. In fact, the protein has been shown to break down into its constituent amino acids within seconds in gastric fluid. Moreover, people have been eating conventional papayas containing entire viruses for decades, in concentrations of viral protein eight times higher than those found in GE papaya.
Crops engineered to be pest resistant provide another salient example. Bacillus thuringiensis (Bt)—a bacterium naturally toxic to many insects (but not to mammals)—expresses Cry protein. Cry solubilizes in the alkaline pH of the insect digestive tract, binds to gut receptors found in insects (but not humans), and lyses gut cells through the formation of pores in the cell membrane, resulting in death to susceptible hosts. Bt sprays have been widely used as a pesticide in conventional and organic farming since the 1960s, with an abundance of research establishing their safety. In 1996, American farmers began growing corn, potatoes, and cotton engineered to express Cry protein from Bt.
The benefits of Bt transgenic crops are compelling. Their cultivation has resulted in a 42% reduction in insecticide use, lessening the burden of conventional insecticides on non-target organisms. Bt crops have also increased the economic return to farmers in the US and abroad. A specific health benefit of Bt corn has been the reduction in the incidence of Fusarium ear rot, which is transmitted by the corn borer and produces carcinogenic toxins.
Given that Bt sprays and injections have been applied safely by farmers for decades, and that the quantity of Cry toxin produced by Bt crops is no more than the amount of Bt pesticide applied to an equivalent amount of farmland, it is highly unlikely that Bt crops would pose any safety hazard. The empirical data overwhelmingly support this conclusion.
Our agricultural system—including deforestation and land use change—accounts for one-third of all greenhouse gas emissions. By reducing the amount of crop lost to insects and weeds, genetic engineering of pest-resistant or herbicide-tolerant strains increases the productivity of existing farmland and resources. Furthermore, the cultivation of herbicide-tolerant crops provide farmers with a wide variety of options for weed control.
Objectively considered to be among the most benign herbicides in existence, glyphosate kills actively growing plants by inhibiting a plant enzyme 5-enolpyruvoyl-shikimate-3-phosphate synthetase (EPSPS), involved in the synthesis of aromatic amino acids. A version of the EPSPS enzyme discovered to be resistant to glyphosate was first transfected into soy, and this glyphosate-resistant (GR) soy was made commercially available in 1996.
Today, over 90% of all soy, cotton, and corn produced in the US are GR, which allows the application of glyphosate to control weeds while preventing damage to the productive crop. By reducing the need to till farmland, GR soy and corn have prevented 41 billion pounds of carbon dioxide from being released in the atmosphere between 1996 and 2013.
Criticisms against GR crops are generally aimed at glyphosate itself, which has unsurprisingly increased in usage since the commercialization of GR crops. Considering the totality of scientific evidence, glyphosate and glyphosate formulations are not likely to pose adverse risks to human health or to the environment at realistic exposures. Importantly, the herbicides that have been displaced by increasing use of glyphosate are known to be more hazardous.
The emergence of herbicide-resistant weed species has been cited as a consequence of the increasing adoption of GR crops. In reality, herbicide resistance in weeds is caused by using herbicides, which are not unique to GR crops. Indeed, hundreds of weed species resistant to herbicides aside from glyphosate have been discovered, many predating the development of GR crops. Although the increased utilization of herbicides in both GR and non-GR agriculture continues to foster the evolution of resistant weeds, current levels of herbicide usage are likely lower than would be the case if GR crops did not exist.
Herbicide-resistant weeds are known to emerge upon repeated application of herbicide, as a consequence of evolution. However, resistant weeds are not unique to glyphosate (the herbicide applied to genetically-engineered, glyphosate-resistant crops), and were observed before the advent of glyphosate-resistant crops.
American farmers grow twice as much food per acre as the world overall, mainly because they can afford superior fertilizer, pesticides, and farm equipment. In the developing world, the positive impacts of GE crops on crop productivity, the environment, and health are even more pronounced. For instance, the introduction of Bt cotton in India in 2002 enabled increases in cotton yields by 24%, and gains to farmer profits of 50%.
The resulting income gains among smallholder farm households improves food security and dietary quality. The adoption of Bt crops also reduces the application of toxic insecticides, saving 2.4 million farm workers per year in India from insecticide poisoning. Although seeds for GE crops are more expensive than conventional seeds, the marginal costs are offset by savings in pest control. Importantly, 90 percent of all farmers planting GE crops are resource-poor farmers in developing countries—amounting to 14.4 million farmers in 2010. Such evidence illustrates the tangible socioeconomic benefit delivered by GE crops to the developed world.
These socioeconomic benefits can extend beyond lifting farmers out poverty. Consider, for example, vitamin A deficiency, which kills an estimated 670,000 children under the age of 5 each year. In many areas of the world affected by vitamin A deficiency, rice—a crop whose grains are woefully deficient in many essential micronutrients—is an important staple crop. Although rice plants possess the machinery to produce β-carotene, a pre-cursor to vitamin A, the pathway is not active within the grains. The insertion of genes for two enzymes, a plant phytoene synthase and a bacterial phytoene desaturase, enables β-carotene to accumulate in the grain.
A single serving of the resultant product, golden rice, is an effective source of vitamin A, providing 60% of the recommended daily value in children aged 6-8. Developed as a humanitarian product, golden rice has nonetheless met staunch opposition, despite the absence of any evidence of harm in any safety or field tests. In 2013, anti-GMO activists destroyed a field trial of golden rice in the Philippines, and continue to stymie regulatory efforts to approve the crop. The impact: the lack of golden rice over the past decade has caused the loss of over 1.4 million life years in India alone.
Although GE crops have been on the market for 20 years, are being grown on over 170 million hectares, and have concurrently been the subject of intensive research, consumer perception lags behind scientific consensus. There is sufficient data from controlled studies and real-world applications to conclude that their adoption has been a net positive. The fact that there is still controversy over GE crops must then stem from an under-appreciation of their benefits and an over-estimation of their risks.
GMOs currently on the market provide ample cases of tangible benefit with relatively negligible risk. The pipeline of GE crops highlights the worthy efforts to continue delivering more nutritious, sustainable, and efficient crops, including blight-resistant chestnuts, bacteria-resistant oranges, high-calcium carrots, non-allergenic peanuts, rice with lower methane emissions, and drought-tolerant corn, sugar, and wheat. That the benefits are largely societal, and perhaps more difficult for the individual consumer to appreciate, illustrates the importance of considering the societal impact of our food choices.
The misperception around risk follows from a lack of awareness of the historical context of our food system. Our crops and livestock have always been in a state of genetic flux, and agricultural production incorporates many technologies with nonzero risk. By iterating on less precise tools, genetic engineering enables more efficient and targeted means of genetic alterations and improves upon more hazardous or unsustainable non-genetic crop technologies. From this perspective, it is clear that many of the popular arguments against GE foods are, at best, arguments against non-GE agriculture.
Grave challenges face the future of our food system. There is a palpable cost to denying society the value of GE crops when the risk-benefit calculus is so overwhelming in their favor. Our scientists continue to evaluate GMOs in light of the available data, and relative to the practical alternatives. If we as a society aspire to improve upon our existing food system, it is critical that consumers do the same.