The NAs' report, entitled Genetically Engineered Crops: Experiences and Prospects, provides a comprehensive review of existing scientific evidence. Although they hedge their answers, as befits the complexity of published studies, the NAs conclude that evidence for negative consequences of GE crops is generally lacking. They suggest that the economic effects lean to the positive side of the cost/benefit ledger:
The available evidence indicates that GE soybean, cotton, and maize have generally had favorable economic outcomes for producers who have adopted these crops, but outcomes have varied depending on pest abundance, farming practices, and agricultural infrastructure. Although GE crops have provided economic benefits to many small-scale farmers in the early years of adoption, enduring and widespread gains will depend on such farmers receiving institutional support, such as access to credit, affordable inputs such as fertilizer, extension services, and access to profitable local and global markets for the crops.
The NAs concluded that neither humans nor animals appear to have been harmed by consuming food derived from GE crops:
The committee carefully searched all available research studies for persuasive evidence of adverse health effects directly attributable to consumption of foods derived from GE crops but found none. Studies with animals and research on the chemical composition of GE foods currently on the market reveal no differences that would implicate a higher risk to human health and safety than from eating their non-GE counterparts. Though long-term epidemiological studies have not directly addressed GE food consumption, available epidemiological data do not show associations between any disease or chronic conditions and the consumption of GE foods.And, the NAs found little evidence that GE crops harm the environment:
The use of insect-resistant or herbicide-resistant crops did not reduce the overall diversity of plant and insect life on farms, and sometimes insect-resistant crops resulted in increased insect diversity, the report says. While gene flow – the transfer of genes from a GE crop to a wild relative species – has occurred, no examples have demonstrated an adverse environmental effect from this transfer. Overall, the committee found no conclusive evidence of cause-and-effect relationships between GE crops and environmental problems. However, the complex nature of assessing long-term environmental changes often made it difficult to reach definitive conclusions.
Nevertheless, the NAs do warn that biotechnology is a dynamic and evolving set of techniques, and suggest ongoing regulatory oversight:
Emerging genetic technologies have blurred the distinction between genetic engineering and conventional plant breeding to the point where regulatory systems based on process are technically difficult to defend. The committee recommends that new varieties—whether genetically engineered or conventionally bred—be subjected to safety testing if they have novel intended or unintended characteristics with potential hazards.This report will not be the final word on GE crops. In fact, the popularity among consumers of food they perceive as "non-GE" represents a substantial, continuing challenge to GE crops, with increasing demands by the public and national regulators that GE and non-GE crops be carefully sequestered from one another to avoid cross-contamination. Time will tell whether or not scientific assessments such as the NAs' will change public opinion. In the meantime, both supporters and opponents of GE crops have the benefit of this new and authoritative source of evidence and analysis from the NAs.
