For more than a decade, agricultural seed companies have been selling seeds that are genetically engineered to include (or exclude) genes to produce specific traits. The adoption by farmers of those seeds has been rapid: as of 2010, about 80% of the total corn, cotton, and soybeans seeds planted in the United States are genetically engineered. The plants help farmers compete against two of their most formidable enemies, insects and weeds, because of introduced genes that (1) make them resistant to specific pests; and (2) make them resistant to the herbicide commercially known as RoundUp, which enables farmers to kill weeds with RoundUp without killing the crops.
Many genetically engineered plants are “transgenic”—meaning that they have a gene (or are expressing a gene) from a different species. The inserted genes can come from species within the same kingdom (plant to plant) or between kingdoms (bacteria to plant). For example, the first genetically engineered plants were tobacco plants made resistant to the family of moths and caterpillars that feed on the plants by inserting a gene from a bacteria, Bacillus thuringiensis (Bt). Like the bacteria, the resultant “Bt” plants produce a toxin that kills the moths and caterpillars. In comparison to traditional methods of creating new traits—which include generations of plant breeding or the use of radiation to create genetic changes—these new techniques are fast and targeted for the new desirable traits being sought.
However, this new form of plant breeding has been controversial, particularly in Europe, where people are concerned about issues such as the risk that traits could be introduced, intentionally or unintentionally, into other food crops, or that genetically engineered plants could contaminate organic crops or the natural environment. People are also concerned that a small number of companies producing the seeds could control and financially exploit the genetic stock of key crops.
Over the past ten years, the NRC has produced several reports on genetically engineered crops; most of the early ones evaluated potential risks of genetically engineered (GE) crops. The most recent report, The Impact of Genetically Engineered Crops on Farm Sustainability in the United States, takes a more holistic look at GE crops at the farm-level, including environmental, economic, and social impacts. The report evaluates some key questions: exactly how have farmers benefited, and have all farmers benefited equally? Are the benefits expected to continue, unabated? What environmental consequences might there be?
The report finds some positive trends in the form of economic and environmental benefits, but cautions that mismanagement and overuse of GE crops—or even the irrelevance of available GE technology to many farmers—could limit their further use and potential.
Most farmers who use GE crops have experienced lower costs of production or higher yields, and sometimes both. Although the costs of GE seeds are higher than conventional ones, production costs are lower because farmers don’t have to apply as many insecticides and herbicides as they would with conventional crops. Farmers also save the labor and fuel costs for equipment operations to weed and spray insecticides. Not having to weed or to spray insecticides offers the perceived benefits of increased worker safety, and greater simplicity and flexibility in farm management (time saved is money on the farm). Box 1 provides an example from a study (Rice, 2004) of the estimated benefits of planting 10 million acres of corn that is resistant to the corn rootworm, based on a 2004 study (Rice et al).
Box 1. Estimated Benefits of Planting Insect-Resistant Corn
According to a 2004 study (Rice, 2004), planting 10 million acres of corn that produces toxins against the corn rootworm would have these estimated benefits: :
• Intangible benefits to farmers, including reduced exposure to pesticides, ease and use of handling, better pest control
• Tangible economic benefits, estimated at $231 million from yield gains
• Increased yield protection (9-28% better than no insecticide use, 1.5-4.5% better than insecticide use)
• A decrease of about 5.5 million pounds of insecticide (active ingredient) per 10 million acres.
• Conservation of 5.5 million gallons of water used in insecticide application
• Conservation of about 70,000 gallons aviation fuel.
• Reductions in farm waste, with about 1 million fewer insecticide containers
• Increased planting efficiency
Although the effects on yield of fertilizers, capital, and labor can be directly measured, other effects of the use of insect- and herbicide-resistant crops must be measured indirectly—that is by how much they reduce or facilitate the reduction of crop losses. When GE soybeans, corn, and cotton resistant to RoundUp are planted, along with timely RoundUp applications to control weeds, yields are almost always greater when compared to crop production without weed control.
The benefit of planting insect-resistant crops is more time and location dependent. For example, the use of corn resistant to the European corn borer resulted in annual average yield gains across the United States of 5-10 percent, but that the advantage
varied greatly. Prior to the introduction of insect-resistant corn, many farmers accepted yields losses rather than incur the expense and uncertainty of chemical control. With the adoption of GE corn, yield differences were most notable in years and places when the pressure on crops from pests was high.
Because pest pressure varies across regions, not all farmers have realized an equal benefit. In addition, genetically engineered seed is much more expensive than conventional crops (see Figure 1). That means that productivity gains have to offset those additional costs, which may not occur, for example, if a farmer lives in an area where weeds and insects are not intense.
The decision to adopt GE crops may have far-reaching effects on other farms. For example, livestock producers, who are the biggest buyers of corn and soybeans, are major beneficiaries of reductions in crop price from better yields in GE crops. However, to date, there have been no quantitative estimates of those savings. Farmers who don’t plant GE crops do benefit from the regional use of GE technology that reduces pest populations. However, those farmers also might suffer from the development of weeds and insects that have acquired pesticide resistance in fields planted with GE crops. Without more research on these issues, the wider effects of GE crops on other farmers are difficult to determine.
GE crops can benefit the environment when properly used. One of the biggest potential benefits is improvement of soil and water quality. The use of RoundUp-resistant crops has helped reinforce the growing trend to practice conservation tillage, because it eliminates weed control as one of the reasons to use conventional tilling. (see Figure 2) With conventional tillage, farmers turn plant stalks and stubble into the soil while at the same time disrupting the growth of weeds. The problem is that conventional tilling can erode and compact soil and form a crust that repels water. The result is increased runoff from farms that carries sediments and agricultural chemicals into rivers and other waterways. With conservation tillage, at least 30% of crop waste remains on top of the field. This includes the practice of “no till,” which is no tilling at all; the seeds are “drilled” into the ground amidst the stubble of the last crop. The end result is less runoff and better water quality.
A major benefit from the use of insect-resistant crops has been the decreased use of insecticides. Since the advent of GE crops, the pounds of insecticides (active ingredient) used per acre has decreased. This benefits the environment because most spray insecticides kill most types of insects, even beneficial ones such as honey bees or natural predators of pests. But GE crops that target specific pests with Bt toxins in corn and cotton have been used very successfully, targeting only the pests that feed on those crops. To combat the possibility that repeated plantings of Bt crops could lead to the emergence of Bt resistant insects, the U.S. Environmental Protection Agency mandated a “refuge strategy”: a certain percentage of every Bt field must be planted with non-Bt seed to ensure that a population of insects susceptible to Bt will survive.
The report finds that the reliance on plants that are resistant to only one herbicide (RoundUp) could be problematic. RoundUp does have several environmental advantages over other herbicides because it kills most plants without substantial adverse effects on animals or on soil and water quality. However, repeated applications of it could allow naturally–occurring glyphosate-resistant weeds to thrive. Continued and constant exposure to RoundUp can also speed the evolution of resistance to it in weeds previously susceptible. A trend in the occurrence of RoundUp-resistant weeds has already been detected in the United States and abroad (see Figure 3). Combating the growth of herbicide-resistant weeds would require more diverse weed management practices, for example rotating the use of different types of herbicides.
Research on earlier technological developments in agriculture suggests that there are likely to be social impacts from the adoption of GE crops. For example, it’s possible that farmers with less access to credit or those who grow crops for smaller markets would be less able to access or benefit from GE crops. Genetic-engineering technology could affect many aspects of farming, including labor dynamics, farm structure, and farmers’ relationships with each other, but little research has been conducted to date on those social effects.
Another concern is how the market structure of the U.S. seed market may affect access to and the development of GE traits. Today, a handful of large, diversified companies dominate the market. They have invested significantly in the research, development, and commercialization of patent-protected GE traits for the large seed markets of corn, soybean, and cotton, but, so far, they have chosen not to commercialize GE traits in many other crops, either because the market size is insufficient to cover the necessary R&D costs, or due to concerns about consumer acceptance of the crops and their risks. Research to date has found no adverse effects on farmers’ economic welfare from this market structure. However, the trend toward seeds with multiple “stacked” traits is causing concern that access to seeds without GE traits or with traits of particular interest will become increasingly limited.
The public debate over genetic-engineering technology of plants will continue for the foreseeable future as seed companies and farmers seek to produce and use new crops with new combinations of traits, while others continue to raise concerns about contamination of organic crops and potential loss of markets where GE crops are not allowed, among other issues. Also driving this debate will be efforts by the agricultural community to address some of the biggest global challenges, for example, helping to fight global food insecurity by developing plants with improved nutritional qualities and resilience to climate change.
Next year, the division plans to release materials that explain in lay terms more about GE crops and the expert findings from the National Research Council.