Largest-ever study reveals environmental impact of genetically modified crops

September 16, 2016 by Caroline Newman
Credit: University of Virginia

According to new research from University of Virginia economist Federico Ciliberto, widespread adoption of genetically modified crops has decreased the use of insecticides, but increased the use of weed-killing herbicides as weeds become more resistant.

Ciliberto led the largest study of and pesticide use to date, alongside Edward D. Perry of Kansas State University, David A. Hennessy of Michigan State University and GianCarlo Moschini of Iowa State University. The four economists studied annual data from more than 5,000 soybean and 5,000 maize farmers in the U.S. from 1998 to 2011, far exceeding previous studies that have been limited to one or two years of data.

"The fact that we have 14 years of farm-level data from farmers all over the U.S. makes this study very special," Ciliberto said. "We have repeated observations of the same farmers and can see when they adopted seeds and how that changed their use of chemicals."

Since 2008, have accounted for more than 80 percent of maize and planted in the U.S. Maize seeds are modified with two genes: one kills insects that eat the seed and one allows the seed to tolerate glyphosate, a commonly used in weed killers like Roundup. Soybeans are modified with just one glyphosate-resistant gene.

Unsurprisingly, maize farmers who used the insect-resistant seeds used significantly less insecticide – about 11.2 percent less – than farmers who did not use genetically modified maize. The maize farmers also used 1.3 percent less herbicide over the 13-year period.

Soybean crops, on the other hand, saw a significant increase in herbicide use, with adopters of genetically modified crops using 28 percent more herbicides than non-adopters.

Ciliberto attributes this increase to the proliferation of glyphosate-resistant weeds.

"In the beginning, there was a reduction in herbicide use, but over time the use of chemicals increased because farmers were having to add new chemicals as weeds developed a resistance to glyphosate," Ciliberto said.

Maize farmers, he said, have not yet had to address the same level of resistance, in part because they did not adopt genetically modified crops as quickly as their counterparts in the soy industry. However, the study did find evidence that both maize and soybean farmers increased herbicide use during the last five years of the study, indicating that weed resistance is a growing problem for both groups.

From 2006 to 2011, the percentage of hectares sprayed with only glyphosate shrunk from more than 70 percent to 41 percent for soybean farmers and from more than 40 percent to 19 percent for maize farmers. The decrease resulted from farmers having to resort to other chemicals as glyphosate-resistant weeds became more common.

"Evidence suggests that weeds are becoming more resistant and farmers are having to use additional chemicals, and more of them," Ciliberto said.

Insects do not appear to have developed a similar resistance, in part because federal regulations require to have a "safe haven" in their fields that is free of genetically modified crops. Insects and worms in those safe havens have no need to develop resistance, and because they interact and breed with insects in other parts of the field, they help prevent the development of resistant genes.

Despite the decrease in insecticide use, continued growth in herbicide use poses a significant environmental problem as large doses of the chemicals can harm biodiversity and increase water and air pollution.

Ciliberto and his colleagues measured the overall environmental impact of the changes in chemical use that have resulted from the adoption of genetically modified crops, using a measure called the environmental impact quotient, or EIQ, to account for chemicals' impact on farmworkers, consumers and the environment. Comparing adopters to non-adopters, they found little change in the impact on farmworkers and consumers. However, the adoption of genetically modified soybeans correlated with a negative impact on the environment as increased herbicide use also increased contamination of local ecosystems.

Overall, Ciliberto said he was surprised by the extent to which herbicide use had increased and concerned about the potential .

"I did not expect to see such a strong pattern," he said.

Explore further: 'Superweeds' linked to rising herbicide use in GM crops

More information: E. D. Perry et al. Genetically engineered crops and pesticide use in U.S. maize and soybeans, Science Advances (2016). DOI: 10.1126/sciadv.1600850

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humy
2.6 / 5 (5) Sep 16, 2016
I should point out that genetic engineering of crops isn't all necessarily about and often isn't all about making the crop insect pest resistance or herbicide resistant for the are MANY completely different kinds of advantage that could be genetically engineered into the crop that have nothing to do with insect pest resistance nor herbicide resistant.

I should also point out that the same crops could have been created to have those traits, albeit with vastly much more time and cost and very inefficiently, by selective breeding and with exactly the same impact on the environment, thus rendering the question of "what is the environmental impact of genetically modified crops" a completely wrong question and an irrelevant question. Any study that tries to answer that flawed question is flawed as a result. It is just like a study that tries to answer the question of "what is the environmental impact of selectively bred crops"; it is completely flawed for the same reason.
humy
3 / 5 (4) Sep 16, 2016
A less flawed albeit still a very badly flawed question for a study to try and answer would be "what is the environmental impact of crops with a certain trait" where that "trait" might be, for example, insect pest resistance. BUT even that question would be extremely badly flawed for the impact would just depend on a vast number of variables and factors. I think to try and make that question specifically about genetically engineered crops rather than merely selectively bred ones makes the question completely idiotic; why pick on engineered crops in particular rather than selectively bred ones or, say, red-leafed or hairy-leafed ones, or some other completely arbitrary and irrelevant chosen characteristic the crop may have?
PsyProf
5 / 5 (2) Sep 17, 2016
Also more important: how fast do the herbicides break down. Just saying "more herbicides are used" is meaningless without taking that variable into account. If they disappear in a short enough time, no harm done. If they persist and accumulate, it's trouble.
electronism
5 / 5 (1) Sep 17, 2016
It is possible to get this right eventually, but we clearly need extremely tight standards for testing and application of any toxic substances to food production. But that needs enlightened government!
optical
Sep 17, 2016
This comment has been removed by a moderator.
gkam
1.8 / 5 (5) Sep 17, 2016
We are killing ourselves with poison for the profit of farmers and chemical manufacturers.
humy
5 / 5 (3) Sep 18, 2016
The spreading of alergenic bacterial proteins and virus vectors into the wild is probably the most significant problem of GMOs.

No it isn't. There is no evidence n rational reason to believe this at all.
see;

https://www.genet...lergies/
"....
According to a recent national survey, the potential that GMOs might cause allergies is a prime concern of consumers. The survey was conducted by GMO Answers, an initiative of the Council of Biotechnology Information, an industry trade group. Scientists and experts provide answers but are not paid to do so. The answer to that question is "no", writes Lisa D. Katic, a food policy consultant:

No commercially available crops contain allergens that have been created by genetically engineering a seed/plant. And the rigorous testing process ensures that will never happen.

..."

There have merely been a few irrational scares from people scared by GM.
humy
5 / 5 (4) Sep 18, 2016
We are killing ourselves with poison for the profit of farmers and chemical manufacturers.

There is absolutely no evidence we, in general, are all dying or will ever die from poisons from chemical manufacturers.
In fact, quite the opposite; the chemical manufacturers are helping to prevent pests causing devastating crop failure + they make fertilizers thus help with food security and reduce world hunger and poverty + many life saving medicines are made from chemical manufacturers etc. thus, for most of us, making our lives longer and better.
optical
Sep 18, 2016
This comment has been removed by a moderator.
humy
5 / 5 (2) Sep 18, 2016
Standard GMO tests for toxicity required by FDA and done by Monstanto are just ninety days long.

-and those tests are not the only ones done so that is irrelevant.

Your link is totally moronic; there is NO evidence of a causal link between GMO and allergy.
Try going to proper scientific websites no authored by loonies with a political agenda who are just historically vomiting out hateful propaganda crap but rather REAL scientists and came back to us.

Kelly_From_Killane
5 / 5 (4) Sep 18, 2016
We are killing ourselves with poison for the profit of farmers and chemical manufacturers.


What does that even mean? Actually we are killing ourselves with over population. There is a point where we will not be able to keep pace using more efficient crops. Until you get the population under control, all the other problems will never be resolvable.

CO2? Poisoned water? Climate change? Air pollution? Pfffft, none of those can be solved with the population increasing exponentially decade after decade. But the news is not all bad. After we are gone, surely some bacterium will be left to began the process all over again. Does anyone truly believe the Universe actually requires our presence?
optical
Sep 18, 2016
This comment has been removed by a moderator.
humy
5 / 5 (2) Sep 18, 2016
there is NO evidence of a causal link between GMO and allergy
Many scientific studies are linked https://www.genet...lergies.

Nope, they are not.
Try going to REAL science links i.e. based on ACTUAL scientific research which use rigorous modern scientific methods and scrutiny to establish actual causal links rather than stupid propaganda links from people with a political agenda that say any crap for political reasons. The REAL science shows absolutely no causal link.
humy
5 / 5 (1) Sep 18, 2016
I demand PHYSICAL/MEASURABLE EVIDENCE from proper SCIENTIFIC studies, not mere hearsay and innuendos from obviously propaganda web links with an obvious political agenda, which, obviously, counts for absolutely nothing. Whether inside science or outside science, mere hearsay and innuendos isn't evidence for causation of anything and should be immediately dismissed as trash.
optical
Sep 18, 2016
This comment has been removed by a moderator.
humy
5 / 5 (1) Sep 18, 2016
You already got it, or not? How many links to scientific articles my link contains? http://www.agbiow...ubs.html


You could show a trillion more such unscientific propaganda links with lies and unscientific innuendos and it would makes absolutely no difference; they would STILL be all irrelevant.
The only links that count are the truly scientific ones i.e. the ones not there just to push a political agenda via misinformation and propaganda but rather backed up with REAL science based on unbiased research and backed up by ACTUAL PHYSICAL EVIDENCE. This is just the way REAL science works.
You have yet to so any ACTUAL PHYSICAL EVIDENCE for your claim.
EnricM
5 / 5 (2) Sep 19, 2016

I should also point out that the same crops could have been created to have those traits, albeit with vastly much more time and cost and very inefficiently, by selective breeding and with exactly the same impact on the environment, thus rendering the question of "what is the environmental impact of genetically modified crops" a completely wrong question and an irrelevant question.


There I agree with you. The issue is not the way the crops are engineered but the whole industrial system for food production. GMO or not is not really relevant (yet I understand that people may be somewhat reluctant to eat maize that kills insects) but the herbicides, wast amounts of fertilizers. monoculture and the "one size fits all" policy for crop planning... adding that to the enormous waste and the fact that up to 60-70% of the calories of these crops are wasted feeding them to livestock (of which 50% goes to landfill too).

Actually, the whole discussion is moot.
EnricM
5 / 5 (1) Sep 19, 2016
increased the use of weed-killing herbicides as weeds become more resistant
The spreading of https://www.reddi...t_sr=on.


???

I struggle to understand the "virus vectors" part. Are you aware that "virus vector" literally means something that transmits virus? Like a bird or a person? Do you mean that the GMO crops spontaneously create life?

Whoaa, now I'm scared!

humy
5 / 5 (2) Sep 19, 2016
I struggle to understand the "virus vectors" part. Are you aware that "virus vector" literally means something that transmits virus? Like a bird or a person? Do you mean that the GMO crops spontaneously create life?


https://en.wikipe...l_vector

However, despite that, what he said about "viral vectors" there STILL makes absolutely no sense whatsoever and is pretty much complete gibberish.
He obviously has complete ignorance of the basic science and doesn't know what he is talking about.
humy
5 / 5 (2) Sep 19, 2016
The issue is not the way the crops are engineered but the whole industrial system for food production.

I agree completely.
It is currently extremely wasteful and I want something to be done about that.
I should know because I was once a farmer myself.
humy
5 / 5 (2) Sep 19, 2016
when I was a farmer some years ago, I and other neighboring farmers were often greatly angered by being forces to plough perfectly good food crops into the ground because of politics and/or because the market for that crop, without warning, had completely collapsed. Meanwhile, on the other side of the world, people, including young children, starve that would be saved if that wasted food was sent to them. If you really care about the environment, it is exactly THAT kind of thing you should try and put a stop to rather than be concerned with this totally irrelevant non-issue of GM.
Arrowstone
5 / 5 (1) Sep 19, 2016
To Humy re: traits introduced artificially vs those hybridized over time:
While indeed traits might be created via hybridization which are otherwise indistinguishable from those introduced via deliberate genetic modification, there is no guarantee that the hybridized genome will be the same as or even particularly resemble the genetically modified one. Thus either approach may produce unintended side effects not seen in the other. As hybridization is usually a much lengthier process, it is more likely that adverse side effects will be recognized before mass adoption of the resulting crops.
leetennant
5 / 5 (1) Sep 19, 2016
You already got it, or not? How many links to scientific articles my link contains?


http://www.nejm.o...eMethods

Four subjects. FOUR. And their conclusion is that the so-called allergen is 'probably' an allergen and that it 'may' be transmitted to GMO soybeans. The study was in 1996.

http://www.gefree...s-05.pdf

Showed a response in mice to do with a protein increasing their response to other allergens. Conclusion was that all crops need to have allergen testing and be assessed on a case by case basis. In fact, CSIRO decided to discontinue developing the alpha- amylase inhibitor GM peas because of that. No idea why you would link to that since it shows that any kind of immune response to the product leads to its development being discontinued!

http://www.ask-fo...2005.pdf

Is the same research with the same protein on the same pea.
leetennant
5 / 5 (1) Sep 19, 2016
there is NO evidence of a causal link between GMO and allergy
Many scientific studies are linked https://www.genet...lergies.


The weird thing is, I was expecting that link to be to some green ink site. Otherwise why link to it? But it's not too bad. And the hilarious thing is that the one piece (not science - opinion) I found on allergens and GMO cited only the two examples you did and cited them in relation to anti-GMO scaremongering NOT as evidence of GMOs and allergens. In fact, it concludes that GMOs are probably not the cause of a rise in allergies.

So are you channelling these beliefs from your spirit guide or something? Because nothing you've linked to supports your contention. Like, even a little bit.

https://www.genet...lergies/
humy
5 / 5 (1) Sep 20, 2016
To Humy... As hybridization is usually a much lengthier process, it is more likely that adverse side effects will be recognized before mass adoption of the resulting crops.

Why wouldn't adverse side effects be recognized immediately anyway i.e. before mass adoption of the resulting crops?
GM crops are ALWAYS tested before mass adoption thus any visible side effects should be spotted.
As for any invisible side effects; I presume they won't be spotted regardless of how lengthy the process.
I really fail to see any creditable danger here.

optical
Sep 20, 2016
This comment has been removed by a moderator.
doucette_arthur
5 / 5 (1) Sep 20, 2016
This is based on an EIQ of 15.3 for Glyphosate, and that's supposedly because of negative impacts to birds, bees and fish. But Glyphosate is non-toxic to bees, the runnoff levels (as determined by the USGA) in our streams are ~1/7,000th the level we allow in our drinking water, and based on EPA tests it is non-toxic to upland birds. Given a realistic EIQ value the report would show what we can readily see in the environment. Use of GE crops is not harming the environment, and our ability to go to No-Till farming because of glyphosate has significantly reduced run off.
optical
Sep 20, 2016
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optical
Sep 20, 2016
This comment has been removed by a moderator.

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