by Jordan Wilkerson
figures by Brian Chow
Summary: In the history of agriculture, no technology has been adopted so quickly and completely as genetically engineered crops. Particularly useful crops are ones that have an engineered resistance to herbicides. These crops have alluring benefits: reduced crop damage when herbicides are sprayed, easier weed management, and even the potential for environmental benefits. So what’s the problem? Herbicide-resistant weeds. The benefits gleaned from these crops begin to disappear as these superweeds gain prominence on farmlands across world. However, to fully appreciate the current predicament, it is necessary to understand what led to the difficult problem of superweeds. And it starts with the most common herbicide used in agriculture: Roundup.
Roundup and the crops that resist it
Chances are you’ve heard of Roundup, a common weed killer used by farmers and homeowners alike. Roundup is the brand name for the herbicide, glyphosate. Glyphosate works by preventing plants from being able to make the proteins they need to survive. Since virtually all plants make these essential proteins the same way, glyphosate affects nearly all plants. For this reason, glyphosate is deemed a “broad-spectrum” herbicide [1].
Of course, this is a double-edged sword. While Roundup is a great weed killer, its broad-spectrum effects make it a decent crop killer, too. That’s no good. If our crops aren’t resistant to Roundup, can we figure out a way to make them resistant? In fact, the agriculture company Monsanto did just that.
In 1996, Monsanto introduced the Roundup Ready soybean, a genetically engineered crop resistant to glyphosate. In the few years after, Roundup Ready cotton, maize, and various other crops also made their debut. While almost all plants are susceptible to glyphosate’s grip, the beautiful thing about genetic engineering is that the genes need not be from similar organisms [2]. In this case, the gene allowing resistance to glyphosate was taken from a type of bacteria called Agrobacteria [3]. With the introduction of this organism’s relevant gene into the desired plant genetics, a Roundup Ready crop is born (Figure 1).
Figure 1. Roundup contains glyphosate, which is toxic to standard plants that contain its target protein. The plants containing this protein are destroyed upon exposure to glyphosate, indicated by the red X. Roundup Ready crops have been engineered to contain a gene from Agrobacteria, making them immune to the herbicide.
While companies are developing these brand new plants, one question that naturally arises is this: do Roundup Ready crops directly affect the environment? Based on the large amount of scientific evidence so far, the short answer is no. There are two ways in which scientists and the public speculated these crops could have an effect on their surrounding environment [4].
One is the possibility that Roundup Ready crops may crossbreed with weeds to produce glyphosate-resistant weeds. This is slightly possible for some crops such as oilseed rape and sugar beet, but in most cases, the weeds present are not sexually compatible with the crops present, so crossbreeding cannot occur [2].
The other possibility is that dead, Roundup Ready plant matter could be different from normal plant matter. This could be a problem if this difference results in plant tissue that is toxic to organisms in the surrounding ecosystem. However, evidence strongly suggests that the two plant types have very similar composition, and their fast breakdown renders the final products that enter the environment basically identical [2].
A win for farmers and the environment
Assuming that farmers only use Roundup at the recommended rates in their weed management techniques, results show that farming practices associated with Roundup Ready crops actually have a lower environmental impact.
One reason for this is that they are able to reduce their pesticide use and replace more harmful pesticides with glyphosate [1]. The harmfulness of a pesticide is assessed by exposing organisms to higher and higher concentrations of the pesticide until it appears to inhibit their ability to survive. Glyphosate is considered less harmful because much higher concentrations are required to hurt aquatic animals and plants than with other herbicides [5]. When herbicides are considered relatively non-toxic to ecosystems, this means that the concentrations that could enter the environment from the recommended application of the herbicide is usually lower than the minimum concentration for that chemical to be toxic.
Another reason Roundup Ready crops theoretically result in a new environmental benefit is that farmers no longer have to till their cropland. While tilling has other benefits, its primary purpose is to mechanically destroy weeds present on the land before the crops are planted. However, this comes with a price. Tilling the land loosens the soil, which causes more of it to run off into nearby water bodies when there’s rain or even a strong wind. Soil on a farm plot is different from natural soil in that it contains much higher concentrations of fertilizer and residual pesticides [6].
With Roundup Ready crops, farmers can spray glyphosate on their land instead of plowing their entire area to get rid of the weeds. Furthermore, since their crops are resistant to glyphosate, farmers can replace outdated, more harmful herbicides with glyphosate, which breaks down quickly and is not very toxic to aquatic organisms [6]. Thus, runoff is reduced overall, and the small amount that may occur has less harmful effects.
Possible concerns about Roundup Ready crops
These benefits only occur if spraying Roundup is the only weed management technique required. As early as the 1960s, scientists have known that the tactic of only spraying one pesticide has strong potential to push weeds to develop resistance to it. Resistance to an herbicide occurs when one weed has a mutation that allows it to survive a Roundup spraying. If this resistant weed reproduces, it can pass its mutation to its offspring. Soon, a cluster of superweeds can quickly spread across acres of cropland, rendering Roundup largely ineffective [7].
One strategy that would reduce the probability of weeds developing resistance is to periodically use another herbicide that kills weeds through a different route. Therefore, resistant weeds would have to establish two mutations to survive the herbicidal spray [6,7]. However, this strategy would periodically eliminate the Roundup Ready crop, too, making it not much better than using non-resistant crops.
Another approach that is even more environmentally friendly is to change what crop is grown on the land each year. Different crops are planted at different times, deplete different nutrients, and root into the soil differently. This makes the environment much less stable and therefore less habitable for weeds to prosper [8]. However, this technique requires much more work of farmers.
Soon after the introduction of Roundup Ready crops, several research articles were published concluding that there is no benefit to using a portfolio of weed management strategies such as crop rotations and herbicide rotations mentioned above, one of which was cited by Monsanto in an advertorial they published [9]. Therefore, most farmers believed that employing much less convenient weed management just seemed unnecessary.
Rise of superweeds, return to old farming practices
Unfortunately, these studies had one major problem: the croplands they created for their experiments were rather small [1]. Industrial croplands, on the other hand, can be on the order of a million acres. Therefore, even though developing resistance to Roundup is not probable for any individual plant, there are a massive number of weeds growing that have the potential to resist its poison: this significantly increases the probability of at least some Roundup resistant weeds developing [7,8].
We do not have to go into detail about probabilities to assess whether superweeds will form – we already have confirmation that they have. Twenty-four cases of glyphosate-resistant weeds have been reported around the world, 14 of which are in the United States [7]. Farmers are now back to tilling their farmlands and spraying more toxic herbicides in addition to Roundup in an attempt to control the superweeds spreading across their farmlands [8].
Additionally, because many of the superweeds can still be killed by glyphosate if it is sprayed in higher doses, many farmers are spraying more glyphosate and other herbicides to combat the weeds. The attraction is that this is much less labor intensive than plowing and handpicking weeds out of the soil [9]. Consequently, a report drawing from US Department of Agriculture data on pesticide use estimated that an additional 383 million pounds of herbicides have been used than if Roundup Ready crops were never introduced [6]. This increased use of glyphosate heightens the likelihood of higher concentrations of the chemical running off into nearby ecosystems. At these elevated concentrations, glyphosate may be capable of causing environmental damage.
Furthermore, the practices of tilling and increased herbicide use are similar to what they were 20 years ago (with even more reported herbicide use). This is both an environmental problem and a financial problem for farmers who must now revert to spending more on herbicides and labor costs to till the land [10].
While Roundup Ready crops themselves have not caused environmental damage, they are certainly responsible for the Roundup-intensive weed management practices that have accompanied them. The environmental benefits – reduced tilling and reduced use of more toxic herbicides – are fading because the weeds Roundup was supposed to control have sprung up in revolt.
More complex weed management strategies than the ones mentioned here can be employed to help reverse this, and they’re already being used by some farmers [6]. These and other techniques mentioned previously may be worthwhile for realizing the benefits of adopting Roundup Ready technology on a larger scale. However, it is up to farmers to decide whether to invest in complex weed management practices. They are less convenient, but can help reduce risk of resistance in the future. This was a hard decision when Roundup was so effective. However, the advent of glyphosate-resistant weeds has shown that just spraying Roundup is not sufficient – not for farmers and not for our environment.
Jordan Wilkerson is a third year graduate student in the Department of Chemistry at Harvard University.
This article is part of the August 2015 Special Edition, Genetically Modified Organisms and Our Food.
References
- Devos, Y., et al., 2008. Environmental impact of herbicide regimes used with genetically modified herbicide-resistant maize. Transgenic Res. 17:1059-1077.
- Dale, P., et al., 2002. Potential for the environmental impact of transgenic crops. Nature Biotechnology 20: 567-574.
- Padgette S. R. , Kolacz K. H. , Delannay X. , Re D. B. , LaVallee B. J. , Tinius C. N. , Rhodes W. K. , Otero Y. I. , Barry G. F. , Eichholz D. A. , et al. (1995) Crop Sci. 35:1451–1461.
- Ackerman, J. Food: How Altered? National Geographic. http://environment.nationalgeographic.com/environment/global-warming/food-how-altered/
- Herbicides. United States Environmental Protection Agency. http://www.epa.gov/caddis/ssr_herb_int.html
- Eight Ways Monsanto Fails and Sustainable Agriculture. Union of Concerned Scientists. http://www.ucsusa.org/food_and_agriculture/our-failing-food-system/genetic-engineering/eight-ways-monsanto-fails.html#.Vaa1h8ZViko
- Selection Pressure, Shifting Populations, and Herbicide Resistance and Tolerance. University of California, Agriculture and Natural Resources. http://anrcatalog.ucdavis.edu/pdf/8493.pdf
- Boerboom, C and Owen, M. Facts about Glyphosphate Resistant Weeds. The Glyphosphate, Weeds, and Crops Series. https://www.extension.purdue.edu/extmedia/gwc/gwc-1.pdf
- Hartzler, B. Weed Science. (December 2004). http://www.weeds.iastate.edu/mgmt/2004/twoforone.shtml
- Neuman, W. and Pollack, A. Farmers Cope with Herbicide Resistant Weeds. New York Times. (May 2010) http://www.nytimes.com/2010/05/04/business/energy-environment/04weed.html
Note that a previous version of this article stated that the estimate of 383 million pounds of increased pesticide use came directly from the USDA. This has been corrected.
Ok. This was a well-written calmly argued and well substantiated article. However, would like to make a couple general comments. One, the development and spread of a lot of herbicide resistant weeds, particularly pigweed (amaranth and waterhemp), in the US is a fact and has posed challenges for a number of farmers to the point that they are having difficulty managing them with chemicals. Two, in the long run having vast monocultures is not sustainable as they are inherently prone to being disrupted by various pathogens, insects, and undesired plants.
Hi Jordan, in parts of this article you use the words ‘herbicide’ and ‘pesticide’ interchangeably. Was this intentional? I’m struggling to get my head around this rather vital concept, especially in the context of pharmacokinetics/dynamics and safety testing. The main question being is the mechanism for glyphosate’s destructive effect on plants the same mechanism that can cause problems in mammalian cells?
Pesticide is a general term that can apply to something that kills any pest (in agriculture, this usually means weeds or insects). Herbicide is more specific, as something that kills plants (or in this case weeds). So glyphosphate is both a pesticide and a herbicide. You can read more about this here: http://sitn.hms.harvard.edu/flash/2015/gmos-and-pesticides/
Lovely article. I only wish it had addressed the potential human health impacts of having so much glyphosate in our food supply. With so much corn, soy, wheat, canola oil, and sugar being eaten by Americans each day, exposure levels and their consequences deserve a closer look.
Soil minerals ( all if them) are the answer, look up the papers of William Albrecht.
This is a great explanation! As a health professional, I find myself reminded of the similar problem of antibiotic resistance in bacteria. It makes me wonder if the farming community will do better at combating this looming issues than the medical community has with antibiotic overuse.
Or, as Ian Malcolm would say, Life finds a way… That sneaky b******.
Exactly what I thought of!
Can you direct me to peer reviewed studies comparing the effects on humans of synthetic pesticides like glyphosate and 2,4D to the natural pesticides used in organic farming? Can you direct me to studies showing the long term environmental impact of the above mentioned pesticides both natural and synthetic?
Thanks
By now the health impact of using glyphosate pre-harvest on nearly all the food staples of the USA is clearly visible. Please Youtube the lectures of Dr Stephanie Seneff.
See our article here for more info on that, too: http://sitn.hms.harvard.edu/flash/2015/gmos-and-pesticides/
Stephanie Seneff has a PhD in computer science, not medicine, pathology, physiology, or any other biological science. She is unqualified fear-monger.
She switched her focus and educated herself in their, just like we all could if we decided to . William Albrecht started off as a medical student but switched his major to AG when he decided he could do more to help more people in the world by promoting healthier farming practices and producing more nutritious food. Look him up. He has the answer to the NPK farming frailties and super insecticides. Soil minerals are pretty cheap but provide the basics that help plants resist insects. If I didn’t see it with my own eyes, I might not believe it, but we all have to test these theories for our own satisfaction.
I am very familiar with the work of William Albrecht, but you obviously don’t. He promoted the use of cation exchange capacity and base saturation for making fertilizer recommendation. You should look him up and actually try to understand what he wrote. You should consider a very basic soil science class if you are going to chat about this topic.
Larry, what is your educational background focused in? If you don’t have a PhD in computer science, I don’t think you are qualified to post comments on an internet forum such as this. Without a background in computer science, anything you post really has no validity.
Makes sense, right???
You make no sense. Seneffs MO ia to dredge through data and make correlations and then claim that “correlation proves causation”. This is an error that anyone with even an extremely basics stats class would be aware of.
Does that make sense??? If not let me know and I will try to simplify the explanation even more.
I have a PhD in agronomy which is the topic of this article. So, what I post is more scientifically valid than what a computer programmer writes about pesticides.
Makes sense, Right???
In the caption for Figure 1, I believe you have a mistake. Roundup is an herbicide, not an insecticide.
Thanks! You’re correct–while the figure shows Roundup acting as an herbicide, it says insecticide–oops!
@Jordan Wilkerson
This appears to be the best, most informative, and least biased article I’ve ever read on this subject. Thank you.
@Stuart Smythe
> … GM crops are now the most sustainable form of crop production in existence.
Maybe it’s sustainability of topsoil with corporate farming you meant. That would make more sense. I don’t mean to put down what you said. It’s just when people read ‘sustainable’, certain things immediately come to mind.
GM crops are typically patented. Patented crops are not sustainable without permission (if something requires permission and/or money to buy license to use it, that’s a lot of risk and overhead). Also, it sounds like many of these crops are sterile, which further degrades their sustainability (since they can’t be reproduced without their creator corporation, who for all we know, may not be around a few years from now, especially if there’s an apocalypse, a severe war, or something). Sustainability implies independence. GM crops, as they currently stand, imply reliance on whoever owns the intellectual property, and the (probably) expensive/proprietary means to make them. This isn’t an inherent trait of GM crops, though, but it is an inherent trait of how they’re being made and used today.
Additionally, glyphosphate seems to suffer similar problems with sustainability.
And nobody has mentioned anything about the dangers of GMO products consumed by other organisms including humans. Several studies have proven that if Monsanto, Pioneer, and other GMO grain seed providers had continued testing their grain feed for just a few more months on laboratory rats; they would’ve found high numbers of their test subjects had developed cancerous tumors.
This is infuriating,. Can you direct me to those studies? Thank you.
He can’t. They don’t exist.
The 53% decrease in environmental impact describes the herbicides used, not the intrinsic environmental impact of the HR crops. As I state in my article, the HR crops themselves do not affect the environment any differently than conventional crops. Therefore, the assessment in the paper you cite is based on weed management practices. It is true that herbicides such as glyphosate are more benign than older herbicides, which I do state in the article. Therefore, this weed management practice is better for the environment as you stated in your comment (and as I stated in the article, actually). However, spraying these new herbicides alone strongly pressures the development of herbicide-resistant weeds. When these weeds dominate the cropland, the weed management practice described in the paper (just spraying the new herbicides) is no longer tenable, and the reduced environmental impact is largely lost because farmers must revert to tilling and intensifying their herbicide use, which includes the application of outdated herbicides. To be clear, my ultimate point is not that we should eschew HR crops. It is that we should consider adopting more complex weed management practices to reduce the frequency that HR weeds develop on croplands, so we can get closer to realizing the full potential of HR crops’ environmental superiority.
Your view of weed control is over simplistic. Organic production relies heavily on tillage which increases erosion potential, requires greater amounts of fuel, causes compactions, . . .
You’ve done a good job of presenting this issue, but for one item. Glyphosate has reduced the environmental impact of crop production and GM crops are now the most sustainable form of crop production in existence. An article published in 2011 based on a large GM canola farmer survey in Canada revealed that the environmental impact of GM canola production was 53% lower in 2006 compared with 1995 when no GM canola was grown. The reference is:
Smyth, S. J., M. Gusta, K. Belcher, P. W. B. Phillips and D. Castle. 2011. Changes in Herbicide Use Following the Adoption of HR Canola in Western Canada. Weed Technology 25: 3: 492-500.
Organic crops require tillage to control weeds, which is incredibly environmentally damaging. In 2006, 67% of canola was produced using zero tillage, up from 11% in 1995. The high toxicity levels of chemicals that the organic industry are allowed to use in their crop production are multiple times higher than glyphosate which has an environmental impact quotient of 15.3.
When combining the changes in tillage and chemical EIQ’s, GM crop production is the most sustainable means of producing crops.
Nice article Jordan. I agree that more sophisticated levels of weed control management are required. What are these strategies? Different chemicals and crop rotation? The problems run so much deeper than switching chemicals and crops in any given year. How do you think that would work exactly (besides being “more work for farmers?” You are basically proposing a chemical merry go round. Would it not just be easier to create and grow more stacked GE crop varieties that you can alternate sprays on? I think you need to talk to more farmers in different areas of the country to get a better idea (if that’s what you are interested in) of what farming entails. While you present a fine case with some fine citations (although some of them are not the best).
Also, the vast majority of farmers still disc or chisel (or both) their land every year. Farming no or low till is more common but requires specialized equipment. We can talk all we want about the environment, but round up for most farmers is convenient and easy to use and that is why they use it. They do not use it because it is better for the environment or to till their land less.
Actually, many farmers do use glyphosate to reduce tillage. They use glyphosate to control weeds, not just for the enjoyment. You mention a “chemical merry go round”. Are you concerned about the tillage merry go round of organic farming. There are multiple trips per year destroying the soil structure.
I’ll take my corn and wheat WITHOUT bathed in glyphosate thank you.
JC , no you prefer organic corn with worse pesticides then glyphosate, neither will effect you though since its only trace amounts.
Roundup is applied at <1lb/acre. An acre is approx the size of a football field including endzones. If that is considered "bathed", I'd hate to consider your hygene habits.
False………………..
I actually farm 36,000 acres in southwest Kansas 15,000 acres in eastern Colorado and 12,000 acres in Washington state I actually quit using round up ready grains to the fact that I have noticed I have a hard time getting a good kill with round up like I used to. Round up is an absolutely safe fantastic product for no till Applications or for borders and or corners of circles pivot points field roads etc. The worst product that we have to use to control overgrowth which most people in large cities don’t understand you can’t just go out and pull every weed. That product is called Gramoxone/paraquat/agent orange since Vietnam they have added die and smell but we use this on a consistent basis because it burns down quick. The chemical that’s in Gramoxone has been used for thousands of years to poison people and or a suicide Potion! We had a field covered in grasshoppers one time Ariel Applied Gramoxone I went out there a week later and there was dead grasshoppers everywhere. When we handle this product on the farm we use Tyvek suits facemasks and respirators as well as rubber gloves look up the ingredients do your research! But due to the fact that the federal government and the liberal activists have pushed most Farms across the country to go no till versus old conventional farming Because of the dust pollution now you guys have to deal with the chemical pollution we put out in the air dust settles and hits the ground. because of the dust pollution now you guys have to deal with the chemical pollution we put out in the air dust settles and hits the ground. Just left wing liberal agenda tree huggers thinking they know everything have actually done more harm to this planet and good by not thinning out the forest Causing forest fires almost every year but the good thing is it’s created lots of jobs with DNR. Nobody gets it and nobody ever will tell there’s nothing left! The government pretty much pays us to no till it’s covered over 70% of our equipment costs allowing us to ramp up production by picking up more ground we have produced more jobs that way but again no till for the most part creates what Farmers call chemical foul and or Chem follow Rather than just summer foul which we kept weed free with a Rod Weeder Or a summer plow/sweep. Anyways hope this helps!
mf went “false” without elaborating, what a king <3
The trouble with this whole issue is the use of the word “sustainable”. We can take the same data, and arrive at opposite conclusions, not because of the data itself, but what that data is indicating. For example, if less tillage was the only indicator of sustainability, then GM is the way to go. The same is true for less herbicide use, and so on. But to reach the conclusion that GM crops are more “sustainable” requires ignoring a whole host of other indicators; increased cancer rates, reduction of mineral content in food, etc.
GM crops do not have increased rates of cancer and there is no reduction in nutrient content. Some particular GM crops specifically have higher nutrient content.
Where are the proven facts upon which you are making a bold statement produce the facts & data that will prove your statements on cancer and nutrient content and we’ll see what the results are .
There have been many epidemiology studies done.
roundup is cancerous. It ends up in our food. When 95%+ of our corn, wheat, and rice production is treated with roundup, there is no way to dodge the bullet. If you eat food, you now are forced to consume some amount of this cancerous roundup. Even applied in the best practice and even when food is washed thoroughly before processing, inevitably the herbicide will end up being consumed to a certain degree. I find this to be a sad description of ‘sustainability’.
David,
Its not proven even to even be a probable carcinogen and your exposure is very small from food. You seem extremely worried about this so i ask you, do you live in a city and use sealed gas mask when you go outside ? because particles from traffic is actually proven to increase risk of cancer. Do you fry food in a pan or eat chips ? The science for this being carcinogenic is much stronger than glyphosphate although actual risk is not established.
People have lived thousands of years sustainably in America without herbicides and here we are after only a few hundred years of living amongst these invasive lazy slave drivin foreigners they want us to believe that we absolutely need herbicides…I say its not invasive plants we should worry about…Its invasive people by far who are our biggest threat…
Oop period. You slayed bro
You neglect the environmental damage to soil critters, bacteria and fungal mycorrhiza by glyphosate. Interruption of the mutual relationships within soil communities is a recipe for disaster:
https://www.soilassociation.org/media/7202/glyphosate-and-soil-health-full-report.pdf
https://www.researchgate.net/publication/263765119_Glyphosate_herbicide_affects_belowground_interactions_between_earthworms_and_symbiotic_mycorrhizal_fungi_in_a_model_ecosystem
Glyphosate is a very simple molecule. Soil microbes eat it (decompose it) for lunch.
I thought the point of organic crops and promotion of them is that the farmers are not allowed to use chemicals ? Organic crops all a con ?
The point of organic crops is to scare consumers into paying more for something with no additional value.
Your reply is rediculous because organic farming prohibits the use of any commercial chemicals.
Thee are a number of chemicals allowed in organic farming. Organic farming is a marketing scam.
Woolworths South Africa has moved to near organic production for its fruit & veg for all 540 of its stores. Woolworths went on to win best supermarket chain in the world in 2014 for quality of produce, and their produce throwout rate reduced by 58%, saving them tens of millions due to the higher nutritional value in the produce, making it last longer on the shelf.
https://www.koonara.com/55-years-of-farming-left/
Your point has noting to do with conventional vs organic. And, people can give awards to their buddies for anything.
Reading this thread 2 years later. I hope you have learned to chill out since then. I am not comforted by hearing that POPs on my food are there in “trace amounts”