Environmental Impact

Chemical and seed companies’ assurances that GMO crops would decrease the need for weed killers have been proven wrong. In fact, the widespread adoption of GMO corn and soybeans – America’s most popular crops – have led to an increase in herbicide use since they were first planted nearly two decades ago.


GMOs are crops modified to withstand weed killers that would otherwise damage the crop. The GMOs are then planted seasonally and sprayed year after year with the weed killers that are meant to kill all the plants in the field other than the GMO crop.

At first this process seems to work: most of the weeds die and the GMO crops thrive. But those few weeds that are hardy enough to survive the chemical onslaught are the only weeds in the field left to reproduce. So over time, this process ends up favoring the most difficult weeds to kill. These herbicide-resistant weeds are known as “superweeds.” And they end up requiring more weed killers to manage.

Superweeds, have now become an epidemic on farmland in many locations across the country.

The most common superweeds are resistant to glyphosate, the active ingredient in Monsanto’s popular herbicide Roundup, but resistance is appearing to herbicides used with other GMO crops as well. Today, more than 61.2 million acres of U.S. farmland are infested with weeds resistant to Roundup, which has been the world’s best-selling weed killer for more than 30 years. A 2012 survey showed that 49 percent of U.S. farmers reported finding superweeds in their fields.

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As weeds became resistant, growers have applied still more herbicides to try to control them. A recent study found that over the 16 years from 1996 to 2011, the use of GMO crops increased herbicide use by 527 million pounds, putting consumers and the environment increasingly at risk.

The emergence of glyphosate-resistant superweeds has led growers to turn to older and more toxic weed kills such as dicamba and 2,4-D, resulting in the emergence of weed species that are resistant to multiple chemicals.

Already, a recent study found, 28 species worldwide are resistant to 2,4-D and/or dicamba.  By 2019, the study concluded, these trends could result in enormous additional increases in herbicide use, such as a 30-fold increase in the amount of 2,4-D applied to the American corn crop.

Both dicamba and 2,4-D are volatile chemicals that evaporate and can drift well beyond their targets, especially in warmer weather, posing a significant public health risk to nearby rural communities. Studies have linked exposure to 2,4-D to reproductive problems, Parkinson’s disease and an elevated risk of non-Hodgkin’s lymphoma.

Children’s Health At Risk

The introduction of GMO crops able to withstand being doused in the toxic weed killer 2,4-D puts people closest to these crops – especially children  – at greater risk of exposure to a defoliant known to be hazardous to human health and the environment.

The Environmental Working Group did an analysis that shows where children would be most likely in harms way once 2,4-D tolerant corn and soybeans GMOs hit the market. EWG found more than 3,200 elementary schools close (within 1,000 feet) of corn or soybean fields. Nearly 500 of those schools are incredibly close (within 200 feet) of fields that could soon be blanketed in 2,4-D.

Click the interactive map below to see where these schools are located.

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The emergence of superweeds resistant to multiple herbicides has demonstrated that the strategy of combatting weeds by modifying crops that can withstand herbicides and then blasting fields with those chemicals is no match for evolutionary adaptation. This approach leads to a dangerous, toxic deadend, one that will leave the landscape infested with evermore varieties of resistant superweeds.

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