Results of the study will appear in the April 29 issue of the journal Science.
"This paper studies two of the four GM varieties that are now in farm-level preproduction trials, the last step before commercialization" says study co-author Carl Pray, an agriculture, food and resource economics professor at Rutgers' Cook College who specializes in the economics of technology change in the agriculture of developing countries. "Farm surveys of randomly selected farm households that are cultivating the insect-resistant GM rice varieties demonstrate that when compared with households cultivating non-GM rice, small and poor farm households benefit from adopting GM rice by both higher crop yields and reduced use of pesticides, which also contributes to the improved health of farmers."
China began doing research on genetically modified agricultural crops in the 1980s. Although it has aggressively commercialized "Bt cotton," genetically modified to produce a natural pesticide against the bollworm, China has not developed any genetically modified food crops for the commercial market.
"This study provides China and other nations with objective, research-based information about whether GM food crops can actually improve farmer welfare," Pray said.
He and colleagues set out to conduct an economic analysis of data from eight rice pre-commercialization field trials in China. Their goal was to determine whether genetically modified rice was helping farmers reduce pesticide use in the fields, increasing yield and having any identifiable health effects on the farmers growing the genetically modified rice strains.
They examined data from field trials involving two genetically modified rice strains: the Xianyou 63, created to be resistant to rice stem borer and leaf roller through insertion of a Bacillus thuringiensis (Bt) gene, and the Youming 86 variety, which is insect-resistant due to introduction of a resistance gene from the cowpea plant. Both varieties have been in pre-production field trials since 2001.
These field trials in China were designed to identify the effects of the genetically modified crops on farm households before the new crops are commercialized. The field trials of Xianyou 63 are being conducted by farmers in seven villages in five counties and of Youming 86 in one village in Fujian province.
The farmers received no compensation for participating in the two-year study. They grew the rice without help or advice from technicians, making all of their own decisions on whether or not to apply pesticides on both genetically modified insect-resistant rice and non-genetically modified rice. They based their decisions on whether to apply pesticides on observations of the severity of pest infestations, rather than on any prescribed dosages of pesticide.
The 2002 survey included 40 farmers who devoted all or part of their acreage to a genetically modified rice strain and 37 farmers who planted all non-genetically modified rice. In 2003, because more insect-resistant rice seed had been distributed, the survey included 69 farmers who planted all OR part of their fields to genetically modified rice and 32 farmers who grew only conventional rice varieties.
Data from the surveys revealed that the characteristics of the farm households were nearly identical, regardless of what type of rice they were growing. For example, there was no statistical difference between the farms in terms of size, share of rice in the farm's cropping pattern, or in the farmers' age or education.
The main difference between the farm households was in the level of pesticides they used. The study showed that the farmers applied the same types of pesticides, regardless of what type of rice they were growing. However, the farmers growing the genetically modified rice strains applied pesticides less than once per season, while farmers growing conventional rice varieties applied pesticides 3.7 times per season.
Measured on a per hectare (2.471 acres) basis, the quantity and cost of pesticides applied to the conventional rice was 8 to 10 times as high as that applied to the insect-resistant genetically modified rice.
In short, use of the genetically modified rice enabled the farmers to reduce pesticide use by 15 pounds per acre, an 80-percent reduction when compared with pesticide use by farmers using conventional rice varieties.
The survey data also showed that there was a difference in yields between the genetically modified and non-genetically modified rice varieties. Yields of the genetically modified Xianyou 63 variety were 9 percent higher than those of conventional rice varieties. Yields of the genetically modified Youming 86 were not significantly different from those of conventional varieties, however researchers note that there were relatively few observations of this variety because it was grown in only one village by comparatively few farm households.
Pesticide related illnesses
Because there is a high incidence of pesticide-related illness in households of developing countries, including China, the researchers were interested in tracking the health effects of insect-resistant genetically modified rice. They asked farm family members if they experienced any headaches, nausea, skin irritation, digestive discomfort or other health problems during or after spraying pesticides on their farms. If so, the researchers asked them if they had visited a doctor, gone home to recover or taken other actions to deal with the symptoms. If they had, it was recorded as a case of pesticide-induced illness.
The survey indicated that none of the farmers who had completely planted their farms to genetically modified insect-resistant rice varieties reported experiencing adverse health effects from pesticide use in either 2002 or 2003.
Of those farm households that grew plots of the genetically modified rice and plots of conventional rice varieties, 7.7 percent reported pesticide-induced illness incidents in 2002, and 10.9 percent reported such cases in 2003. None of those households reported being affected after working on plots planted to the genetically engineered varieties.
Among the farm households that used conventional rice varieties, 8.3 percent in 2002 and 3.0 percent in 2003 reported adverse health affects related to pesticide use.
This study was funded by the National Natural Science Foundation of China and the Chinese Academy of Science.
Research participants, in addition to Pray, included Jikun Huang and Ruifa Hu, both of the Center for Chinese Agricultural Policy of the Chinese Academy of Sciences in Beijing, and Scott Rozelle of the University of California, Davis.