Despite already providing substantial economic and environmental benefits ranging from lower production costs and reduced use of pesticides to better yields compared to conventional crops, the report noted these benefits have not been universal, some may decline over time, and potential benefits and risks may become more numerous as the technology is applied to more crops.

David Ervin, professor of environmental management and economics, Portland State University, Portland, Ore., and chair of the committee that wrote the report, said that the industry was entering a "pivotal time in the evolution of genetically engineered crops".

The authors state in particular, farmers who grow GM herbicide-resistant crops should not rely exclusively on glyphosate and need to incorporate a range of weed management practices, including using other herbicide mixes.

Federal and state government agencies, technology developers, universities, and other stakeholders should collaborate to document weed resistance problems and develop cost-effective ways to control weeds in current GM crops and new types of GM herbicide-resistant plants now under development.

Improvements in water quality could prove to be the largest single benefit of GM crops, the report said.

However, no infrastructure existed to track and analyse the effects that GE crops may have on water quality.

The US Geological Survey, along with other federal and state environmental agencies, should be provided with financial resources to document effects of GM crops on US watersheds.

In many cases, farmers who have adopted the use of GM crops have either lower production costs or higher yields, or sometimes both, due to more cost-effective weed and insect control and fewer losses from insect damage, the report said.

Although these farmers have gained such economic benefits, more research is needed on the extent to which these advantages will change as pests adapt to GM crops, other countries adopt genetic engineering technology, and more GM traits are incorporated into existing and new crops.

The study was funded by the National Research Council. The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council make up the National Academies.