Genetically modified crops have reached a high rate of adoption in the U.S., but more than 15 years after their commercial introduction, the USDA Economic Research Service in a new report says questions still exist about their potential benefits and risks.
The study, which looks impacts of GE technology on seed and tech suppliers, farmers and consumers, reviews price changes, adoption rates and general trends that have developed in the years since GE crops first hit the market.
The study is intended to update a 2006 ERS report, The First Decade of Genetically Engineered Crops in the United States.
U.S. farmers continue to adopt GE seeds at a high rate, ERS says. HT corn accounted for 85% of corn acreage in 2013, and HT cotton constituted 82% of cotton acreage. Meanwhile, farmers planted insect-resistant cotton on 75% of U.S. acreage and Bt corn 76% of corn acres.
The adoption of Bt crops increases yields by mitigating yield losses from insects. However, empirical evidence regarding the effect of HT crops on yields is mixed, the report said.
Generally, stacked seeds tend to have higher yields than conventional seeds or than seeds with only one GE trait. GE corn with stacked traits grew from 1% of corn acres in 2000 to 71% in 2013. Stacked seed varieties also accounted for 67% of cotton acres in 2013.
Planting Bt cotton and Bt corn seed is associated with higher net returns when pest pressure is high. The extent to which HT adoption affects net returns, however, is mixed. It depends primarily on how much weed control costs are reduced and seed costs are increased, the report said.
Insecticide and resistance
Farmers generally use less insecticide when they plant Bt corn and Bt cotton. Corn insecticide use by both GE seed adopters and non-adopters has decreased—only 9% of all U.S. corn farmers used insecticides in 2010.
Refuge use has helped delay the evolution of Bt resistance. However, there are some indications that insect resistance is developing to some Bt traits in some areas.
The adoption of HT crops has enabled farmers to substitute glyphosate for more toxic and persistent herbicides, but there are questions about weed resistance.
"An overreliance on glyphosate and a reduction in the diversity of weed management practices adopted by crop producers have contributed to the evolution of glyphosate resistance in 14 weed species and biotypes in the United States," the report says.
The price of GE soybean and corn seeds grew by about 50% in real terms – adjusted for inflation – between 2001 and 2010. The price of GE cotton seed grew even faster, ERS says.
The yield advantage of Bt corn and Bt cotton over conventional seed has become larger in recent years as new Bt traits have been incorporated and stacked traits have become available. Planting Bt cotton and Bt corn continues to be more profitable, as measured by net returns, than planting conventional seeds.
In reviewing GE crops' effect on seed suppliers, the ERS used the number of field releases for testing of GE crops reviewed by the USDA Animal and Plant Health Inspection Service.
The number of releases peaked in 2002, but biotech firms continue to develop new seeds rapidly. As of September 2013, about 7,800 releases were approved for GE corn, more than 2,200 for GE soybeans, more than 1,100 for GE cotton, and about 900 for GE potatoes, ERS says.
Monsanto leads the number of field releases at 6,782, Pioneer/DuPont is second with 1,405, Syngenta is third with 565, and USDA's Agricultural Research Service rounds out the top four with 370.
Overall, biotech continues to evolve – releases of GE varieties with agronomic properties (like drought resistance) jumped from 1,043 in 2005 to 5,190 in 2013.
Consumer acceptance of foods with GE ingredients varies with product characteristics, geography, and the information that consumers are exposed to, ERS says. Most studies in industrialized nations find that consumers are willing to pay a premium for foods that don't contain GE ingredients. However, studies in developing countries yield more mixed results.
ERS says that some studies, including some with a focus on GE ingredients with positive enhancements like nutrition benefits, find consumers to be willing to try GE foods and even to pay a premium for them, while others find a willingness to pay a premium for non-GE foods.
Most studies have shown that willingness-to-pay for non-GE foods is higher in the EU, where some retailers have policies limiting the use of GE ingredients. Non-GE foods are available in the United States, but there is evidence that such foods represent a small share of retail food markets.
View the ERS' full study, Genetically Engineered Crops in the United States, online.