The study, published Friday, Feb. 7, in the journal Science, holds particular promise for small-scale, low-income farmers in developing nations, said the researchers. These farmers, especially those in tropical regions, regularly risk large, pest-related crop losses because they cannot afford to use the pesticides available to larger farms.
"Many critics have questioned whether genetically modified crops would be economically and environmentally beneficial to farmers in developing countries," said David Zilberman, UC Berkeley professor of agricultural and resource economics and co-author of the study. "Our research indicates that transgenic crops should be a viable option. This is the first paper to show such a substantial increase in yield for bioengineered crops."
The researchers reported the results of field trials conducted on 157 farms in three major cotton-producing states in India during the seven-month cotton season that began in June 2001. The field trials were initiated by the Maharashtra Hybrid Seed Company (Mahyco), which has been studying Bt hybrids in India since 1997.
The farm sites contained three adjacent plots that measured 646 square meters each. One plot was planted with cotton bioengineered with a gene from the insecticidal bacterium Bacillus thuringiensis (Bt), the second with the same hybrid of cotton but without the Bt gene, and the third with a cotton hybrid traditionally grown in the local area.
The Bt cotton, produced by the Monsanto Company and Mahyco, is resistant to the three species of bollworm that plague crops in India. Prior studies in India show that crop damage from bollworm attacks averaged 50 to 60 percent.
In the study, the researchers found that average yields for Bt cotton were a remarkable 80 percent greater than their non-Bt counterparts, and 87 percent greater than the local cotton hybrids. In addition, the Bt cotton crops were sprayed against bollworms three times less often than both the non-Bt and local cotton crops.
For the sucking insects - such as aphids, jassids and whitefly - that Bt does not protect against, there were no significant differences in pesticide applications among the three types of crops.
"We are reporting on cotton, but the results are easily transferable to food crops since the type of pest damage they would sustain would be the same," said Matin Qaim, assistant professor of agricultural and development economics at the University of Bonn's Center for Development Research and the study's lead author. "With populations in developing countries growing exponentially, and available farmland stagnating, there is an urgent need to find ways to increase crop yields on the land that is available."
While transgenic crops have been shown to reduce the use of certain chemical pesticides, they have not been known to substantially increase crop yields in the countries where they have been grown. For example, the yield gains of insect-resistant cotton crops in the United States and China average less than 10 percent. Bioengineered corn and soybeans have even less impressive gains, and in some cases, the yield effects are negative.
Why the difference in India? The answer seems to be that the region suffers from a significantly higher pressure of crop-destroying pests, and that there has not been a widespread adoption of chemical pesticides in India to control crop damage. Transgenic crops would likely have greater potential to increase yields in such regions, said the authors.
"The large scale applications of genetically modified crops in the United States or China are not truly representative of what would happen if the crops were grown in the small farm sectors of poor countries in tropical and subtropical climates," said Qaim, who conducted the research while he was a post-doctoral fellow at UC Berkeley's Department of Agricultural & Resource Economics, which is within the College of Natural Resources. "The results we see in India are much more representative of what would happen if transgenic crops were used in sub-Saharan Africa or Southeast Asia."
The temperature and humidity of tropical regions produce ripe conditions for insects that munch on crops. Absent the regular use of pesticides, crops in those regions are defenseless against pests.
Qaim said the reason China has not seen significant yield gains in its transgenic crops is that the country has long had a well-developed infrastructure to support pesticide use for its farmers. Since pesticide sprays are widely used for non-transgenic crops, the loss of yield is not as severe.
But for the majority of developing nations, the high cost of pesticides makes them too risky an investment for small, non-commercial farmers, the authors argued. In addition, chemical pesticides are much more harmful to farmers' health and the environment, and require a significant amount of technical knowledge to be used properly, they said.
"Many of the rural poor in developing countries are undereducated," said Qaim. "If they had effective pesticides, they would still have to know that the proper time to spray would be when the bollworms are in a certain larval stage, a window of opportunity that lasts a mere two to three days."
"Understanding how to use pesticides properly is difficult, but replacing the type of seed used is easy and thus more desirable," Zilberman added. "The bottom line is, biotechnology has the potential to positively impact the lives of small, poor farmers in developing nations. It would be a shame if anti-GMO (genetically modified organism) fears kept important technology away from those who stand to benefit the most from it."