Many US farmers who grow genetically modified (GM) crops are realising substantial economic and environmental benefits -- such as lower production costs, fewer pest problems, reduced use of pesticides, and better yields -- compared with conventional crops, says a new report, published this week, by the US National Research Council, which was chartered by the US Congress in 1863.  

However, the report warns that GM crops resistant to the herbicide glyphosate -- a main component in Roundup and other commercial weed killers -- could develop more weed problems as weeds evolve their own resistance to glyphosate.  GM crops could lose their effectiveness unless farmers also use other proven weed and insect management practices. Farmers spray the chemical to kill weeds while leaving the crops unharmed.

First introduced in 1996, more than 80 per cent of the corn, soybean and cotton grown in the United States is genetically modified and the potential benefit of GM technology is in particular in tropical regions of the world, which are most exposed to climate change and difficult agricultural conditions. Most of the resistance comes from well-fed Europeans who do not have to concern themselves about the development of drought-resistant seeds and the bigger threat in tropical regions from insects. Health scare claims have no scientific validity.

The National Research Council report provides the first comprehensive assessment of how GM crops are affecting all US farmers, including those who grow conventional or organic crops.  The report follows several previous Research Council reports that examined the potential human health and environmental effects of GM crops.

"Many American farmers are enjoying higher profits due to the widespread use of certain genetically engineered crops and are reducing environmental impacts on and off the farm," said David Ervin, professor of environmental management and economics, Portland State University, Portland, Oregon, and chair of the committee that wrote the report.  "However, these benefits are not universal for all farmers.  And as more GE (genetic engineering) traits are developed and incorporated into a larger variety of crops, it's increasingly essential that we gain a better understanding of how genetic engineering technology will affect US agriculture and the environment now and in the future.  Such gaps in our knowledge are preventing a full assessment of the environmental, economic, and other impacts of GE crops on farm sustainability."

GM soybeans, corn, and cotton are designed to be resistant to the herbicide glyphosate, which has fewer adverse environmental effects compared with most other herbicides used to control weeds.  In addition to glyphosate resistance, GE corn and cotton plants also are designed to produce Bacillus thuringiensis (Bt), a bacterium that is deadly when ingested by susceptible insect pests.

Farmers need to adopt better management practices to ensure that beneficial environmental effects of GM crops continue, the report says.  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.  To date, at least nine species of weeds in the United States have evolved resistance to glyphosate since GM crops were introduced, largely because of repeated exposure.  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 GE crops and new types of GE herbicide-resistant plants now under development.

Environmental Benefits

Improvements in water quality could prove to be the largest single benefit of GM crops, the report says.  Insecticide use has declined since GM crops were introduced, and farmers who grow GM crops use fewer insecticides and herbicides that linger in soil and waterways.  In addition, farmers who grow herbicide-resistant crops till less often to control weeds and are more likely to practice conservation tillage, which improves soil quality and water filtration and reduces erosion.

However, the report says no infrastructure exists to track and analyse the effects that GM 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. 

The report notes that although two types of insects have developed resistance to Bt, there have been few economic or agronomic consequences from resistance.  

Economic and Social Effects

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 says.  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 GE traits are incorporated into existing and new crops. 

The higher costs associated with GM seeds are not always offset financially by lower production costs or higher yields, the report notes.  For example, farmers in areas with fewer weed and pest problems may not have as much improvement in terms of reducing crop losses.  Even so, studies show that farmers value the greater flexibility in pesticide spraying that GE crops provide and the increased safety for workers from less exposure to harmful pesticides.

The economic effects of GM crops on farmers who grow organic and conventional crops also need further study, the report says.  For instance, organic farmers are profiting by marketing their crops as free of GE traits, but their crops' value could be jeopardised if genes from GM crops flow to non-GE varieties through cross-pollination or seed mingling.

Farmers have not been adversely affected by the proprietary terms involved in patent-protected GM seeds, the report says.  However, some farmers have expressed concern that consolidation of the US seed market will make it harder to purchase conventional seeds or those that have only specific GM traits.  With the exception of the issue of seed industry consolidation, the effects of GM crops on other social factors of farming -- such as labour dynamics, farm structure, or community viability -- have largely been overlooked, the report says.  More research is needed on the range of effects GM crops have on all farmers, including those who don't grow GM crops or farmers with less access to credit.  Studies also should examine impacts on industries that rely on GM products, such as the livestock industry.

Research institutions should receive government support to develop GM traits that could deliver valuable public benefits but provide little market incentive for the private sector to develop.  Examples include plants that decrease the likelihood of off-farm water pollution or plants that are resilient to changing climate conditions.  Intellectual property that has been patented in developing major crops should be made available for these purposes whenever possible.