Analysis of USDA data on benefits of GE crops
by Jane Rissler, Union of Concerned Scientists
The USDA Economic Research Service (ERS) has just released new data on the benefits of genetically engineered (GE) Bt and herbicide-tolerant crops. The new report, Genetically Engineered Crops for Pest Management, contains data on pesticide use on GE crops in 1997 and yield of GE crops in 1997 and 1998. The report is available at www.econ.ag.gov/new-at-ers.
Below I have summarized what I learned from the report. My summary is somewhat different from the ERS summary-which emphasized only the results supporting the view that biotechnology is good for the environment and good for farmers.
The data reveal a mixed picture of benefits from crops engineered to control pests. In some engineered crops in some regions, pesticide use may be reduced and/or yields may be increased. But in the majority of crops and regions surveyed, there are no statistically significant differences in pesticide use or yield between engineered and nonengineered varieties. In one case, pesticide use increased on the engineered crop and in another case, yield declined in the engineered varieties.
The ERS collected data on pesticide use in the 1997 growing season in several growing regions on the five most widely planted engineered crops: Bt corn and cotton, herbicide tolerant corn, and herbicide(glyphosate)-tolerant cotton and soybeans. All together data were collected on 12 region and crop combinations, i.e., Bt corn and HT corn in the Heartland, Bt cotton in three regions, HT soybeans in 5 regions, and HT cotton in 2 regions, and their non-engineered counterparts in all the regions.
In the 12 region/crop combinations, 7 showed no statistically significant differences in pesticide use on engineered versus non-engineered crops. Four showed significant reductions in pesticide use on the engineered versus non-engineered crops. In one region/crop combination, Bt cotton in the Mississippi Delta area, significantly more pesticides were used on Bt versus non-Bt cotton.
Bt corn data only from Heartland (IL, IN, IA, parts of SD, NE, MN, MO, OH, KY). The data on insecticide acre-treatments* for all insect pests, including Bt-corn pests, showed no statistically significant difference in insecticide use on Bt versus nonBt corn.
Bt cotton In the Mississippi Delta area, insecticide acre-treatment* for all insect pests on Bt and nonBt cotton were significantly different statistically--53% higher on Bt than on non-Bt cotton.
In much of the south-eastern cotton-growing area, insecticide acre-treatments* for all insect pests on Bt and nonBt cotton were not significantly different.
In the region encompassing the south-western cotton-growing area, Florida, and parts of Texas, insecticide acre-treatments* for all insect pests on Bt and non-Bt cotton were not significantly different statistically.
In the Heartland, there was no significant difference statistically between herbicide use on HT versus non-HT corn.
Data from five growing regions showed a statistically significant decrease in three regions (51%, 23%, 20%) in herbicide acre-treatments for HT soybeans versus non-HT soybeans.For two other regions, herbicide use was essentially the same for HT and non-HT soybeans.
Herbicide-tolerant cotton In the Mississippi Delta, there was no significant difference statistically in herbicide use between HT and non-HT cotton.
In much of the south-eastern growing region, herbicide use was significantly decreased on HT versus non-HT cotton (a 22% decrease).
*An acre-treatment is the number of different pesticides applied per acre times the number of repeat applications.
The ERS collected yield data in 1997 and 1998 for 12 and 18 region/crop combinations, respectively. The crops surveyed were Bt corn and cotton and HT corn, cotton, and soybean and their non-engineered counterparts. In 1997, yields were not significantly different in engineered versus non-engineered crops in 7 of 12 crop/region combinations. Four of 12 showed significant increases (13-21%) in yields of engineered versus non-engineered crops (HT soybeans in 3 regions and Bt cotton in 1 region). One - HT cotton in 1 region - showed a significant reduction in yield (12%) compared with its non-engineered counterparts.
In 1998, yields were not significantly different in engineered versus non-engineered crops in 12 of 18 crop/region combinations. Six crop/region combinations (Bt corn in 2 regions, HT corn in 1 region, HT soybean in 1 region, Bt cotton in 2 regions) showed significant increases in yield (5-30%) of engineered over non- engineered crops. HT cotton (glyphosate-tolerant) was the only engineered crop which showed no significant increase in yield in either region where it was surveyed.