Biotech crops helpful, but take management to remain effective


WASHINGTON — Many U.S. farmers who grow genetically modified crops are realizing substantial economic and environmental benefits — lower production costs, fewer pest problems, reduced use of pesticides, and better yields — compared with conventional crops, says a new report from the National Research Council.

However, biotechnology 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 (link opens .pdf).

And genetically modified crops could lose their effectiveness unless farmers also use other proven weed and insect management practices.

The report provides the first comprehensive assessment of how biotechnology crops are affecting all U.S. farmers, including those who grow conventional or organic crops.

Benefits not universal

“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, and chair of the committee that wrote the report. (Read report summary.)

“However, these benefits are not universal for all farmers. And as more GE 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 U.S. agriculture and the environment.”

Ervin also said gaps in knowledge prevent a full assessment of the environmental, economic, and other impacts of genetically modified crops on farm sustainability.

Biotech background

First introduced in 1996, genetically modified crops now constitute more than 80 percent of soybeans, corn, and cotton grown in the United States.

Biotech 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, corn and cotton plants also are designed to produce bacillus thuringiensis, or Bt, a bacterium that is deadly when ingested by susceptible insect pests.

Takes management

Farmers need to adopt better management practices to ensure that beneficial environmental effects of biotech crops continue, the report says.

In particular, farmers who grow 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 genetically modified crops were introduced, largely because of repeated exposure.

Environmental benefits

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

Insecticide use has declined since biotech crops were introduced, and farmers who grow biotech 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, no infrastructure exists to track and analyze the effects that genetically modified crops may have on water quality.

Insect resistance

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

Practices to prevent insects from developing resistance should continue, such as an EPA-mandated strategy that requires farmers to plant a certain amount of conventional plants alongside Bt plants in “refuge” areas.

Other benefits

In many cases, farmers who have adopted the use of biotech 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, other countries adopt genetic engineering technology, and more traits are incorporated into existing and new crops.

Production costs

The higher costs associated with GE 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 biotech crops provide and the increased safety for workers from less exposure to harmful pesticides.

Impact on organics

The economic effects of genetically modified 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 biotech traits, but their crops’ value could be jeopardized if genes from genetically modified crops flow to non-genetically modified varieties through cross-pollination or seed mingling.


Farmers have not been adversely affected by the proprietary terms involved in patent-protected GE seeds, the report says. However, some farmers have expressed concern that consolidation of the U.S. seed market will make it harder to purchase conventional seeds or those that have only specific biotech traits.

With the exception of the issue of seed industry consolidation, the effects of biotech crops on other social factors of farming — such as labor dynamics, farm structure, or community viability — have largely been overlooked, the report says.

More research

More research is needed on the range of effects biotech crops have on all farmers, including those who don’t grow biotech crops or farmers with less access to credit.

Studies also should examine impacts on industries that rely on biotech products, such as the livestock industry.

Research institutions should receive government support to develop GE 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.


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