GMOs and the Environment

Many people are worried about the impact GMOs could have on the environment. That’s a reasonable concern. Are GMOs increasing the profits of farmers and biotech companies at the expense of the environment? As I have learned more about biotechnology and agriculture, contrary to popular fear, I have found that there is actually no scientific evidence of  harm from GMOs – but it doesn’t stop there. Conversely, I have learned that there are several environmental benefits of biotechnology.

GMOs and CO2 updated

So what does the environment have to gain from biotechnology? I have touched on this topic before, in my piece On farming, animals, and the environment from an organic farming angle, but I believe it deserves a post of its own. Shortly put, GMO crops have been found to increase farming efficiency: higher yields, reduced pesticide use, increased profits, and reduced farm labour.

GMOs help farmers make the best possible use of the land area used for farming. Does that mean that they are using the land somehow too efficiently, resulting in drawbacks for the environment? Not really. Farmers continue working their land for generations. What is best for them is a land that stays healthy and soil that retains its nutrients. On top of that, there are good arguments for farm efficiency being a good measure of its impact on climate change. To clarify what efficiency means in practice, I’ll borrow Marc Brazeau’s words over at Genetic Literacy Project:

High yields are an indicator of efficient use of resources. High yields indicate that water, fuel, fertilizer, pesticides, labor, etc were successfully transformed into food instead of weeds, bug food, and run off.

In our carbon conscious world, most people would consider it a great feat if a large western country such as the UK would manage to cut its car use by more than a third. This is what biotech crops have been doing since 1996 – cutting carbon emissions, in 2013 by as much as 28 000 million kg, or by as much as emitted by 7.4 coal-fired power plants in one year. (Unfortunately none of the biotech-derived carbon savings originate from UK as of yet, however.)

Among the countries responsible for these carbon savings are US, Brazil, Argentina, China, India, Bolivia, Paraguay, Uruguay, South Africa, and Canada. European countries on the other hand, have been slow to adopt biotechnology, but with 5 EU countries growing GMO maize at present, and a total of 49 GMO crops authorised for use all in all, Europe (and the UK) could soon begin taking part of these advances.

You can read more in the report by European Academies Science Advisory Council (ESAC):

Taken together, the published evidence indicates that, if used properly, adoption of these crops can be associated with the following:

• reduced environmental impact of herbicides and insecticides;

• no/reduced tillage production systems with concomitant reduction in soil erosion;

• economic and health benefit at the farm level, particularly to smallholder farmers in developing countries;

• reduction in greenhouse gas emissions from agricultural practices.

Below you can find the sources for the data in my infographic. They present the key environmental impacts that crop biotechnology has had on global agriculture in two studies from 2014 and 2015. Their summary:

The adoption of GM insect resistant and herbicide tolerant technology has reduced pesticide spraying by 553 million kg (-8.6%) and, as a result, decreased the environmental impact associated with herbicide and insecticide use on these crops (as measured by the indicator the Environmental Impact Quotient (EIQ)) by 19.1%. The technology has also facilitated important cuts in fuel use and tillage changes, resulting in a significant reduction in the release of greenhouse gas emissions from the GM cropping area. In 2013, this was equivalent to removing 12.4 million cars from the roads.

They note in the paper that reduced levels of greenhouse gas emissions follow largely from reduced tractor fuel use and additional carbon retained in the soil. So what about GMO farming leads to increased soil organic matter (carbon sequestration)? One of the big benefits is the wider adoption of the no-till method, also known as conservation tillage, which means omitting the plowing or tilling step (a crude means of weed management). The US Department of Agriculture notes that the spread of the no-till method is largely thanks to the adoption of Herbicide Tolerant (HT) crop varieties.

These trends suggest that HT crop adoption facilitates the use of conservation tillage practices. In addition, a review of several econometric studies points to a two-way causal relationship between the adoption of HT crops and conservation tillage. Thus, in addition to its direct effects on herbicide usage, adoption of herbicide-tolerant crops indirectly benefits the environment by encouraging the use of conservation tillage.


Many people may immediately think of pesticide use as the burdensome factor when environmental aspects of farming are mentioned.

UPDATE: while the reduction in total pesticide use thanks to GMO crops has been noted before especially thanks to eliminating needs for insecticides, some sources have implied the reverse for herbicide use. However, a recent a paper in Nature Communications by the weed ecologist Andrew Kniss analyses herbicide usage trends in the context of GMO crop adoption, finding no such evidence. Andrew Kniss on GMOs and Herbicides: it’s complicated:

In summary, this analysis suggests that GMOs have had a positive effect (or at the very least neutral or non-negative effect) with respect to herbicide use intensity and mammalian toxicity, and I’m sure that will disappoint many folks who don’t like GMOs.

But while GMOs have helped reduce all-over pesticide use, this is actually quite a small part among its ecological impacts of agriculture. As Marc Brazeau puts it over at Food and Farm Discussion Lab:

… pesticides represent a drop in the sustainability bucket when compared to land use, water use, pollution and greenhouse gases. In fact, it may seem counter-intuitive but, pesticides can play a substantial role in mitigating the damage associated with many of those other factors.

These big factors are highlighted in a report published in Science in 2014 (discussed in more depth in the Food and Farm piece above):

We find that a relatively small set of places and actions could provide enough new calories to meet the basic needs for more than 3 billion people, address many environmental impacts with global consequences, and focus food waste reduction on the commodities with the greatest impact on food security.

That sounds encouraging. All in all, science is good news for both farmers, consumers, and the environment. We need every tool in the box to help with the precarious balancing act of human welfare as well as that of the environment.

For easy overview, here a list of the scientific papers and reports included in this essay:

  • Environmental impacts of genetically modified (gm) crop use 1996-2013: impacts on pesticide use and carbon emissions,  Barfoot and Brookes 2015
  • Key global environmental impacts of genetically modified (GM) crop use 1996–2012, Barfoot and Brookes 2014
  • A Meta-Analysis of the Impacts of Genetically Modified Crops, Klümper and Qaim 2014
  • Leverage points for improving global food security and the environment, West et al 2014
  • Planting the future: opportunities and challenges for using crop genetic improvement technologies for sustainable agriculture, European Academies Science Advisory Council 2013
  • A Meta Analysis on Farm-Level Costs and Benefits of GM Crops, Finger et Al 2011 (link to PDF download)
  • Genetically Modified Crops and Household Labor Savings in US Crop Production, Gardner et al 2009
  • Modelling greenhouse gas emissions from European conventional and organic dairy farms, Oelesen et al 2006

About Thoughtscapism

Cell Biologist, volunteer science communicator, and fiction writer.
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18 Responses to GMOs and the Environment

  1. guesscloud says:

    Tha ks for the great gmo post


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  3. Michael Sawyer says:

    Thanks for helping to bring more information to this difficult issue for people to understand


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  10. Phil Harrison says:

    Interesting piece. It doesn’t seem to address the fact that HT crops have hugely increased herbicide use, herbicide resistant weeds are now widespread and requiring more and more heavy herbicide treatment.

    Genetically-modified herbicide-resistant (GMHR) crops a two-edged sword? An Americas perspective on development and effect on weed management
    Genetically Modified Herbicide-Tolerant Crops, Weeds, and Herbicides: Overview and Impact

    The claim the HT crops have resulted in a reduction in overall herbicide use is somewhat misleading. Indeed, this is based on Kovach’s 1992 Environmental Impact Quotient methods which are not great “In its current form, the EIQ is a poor measure of herbicide environmental impact”
    Quantitative Evaluation of the Environmental Impact Quotient (EIQ) for Comparing Herbicides

    Agreed BT crops have been successful at reducing pesticide use so far…however…resistence is common..
    Insect resistance to Bt crops: lessons from the first billion acres


    • Hello Phil Harrison,

      Thanks for stopping by. You might be interested in reading more from the scientist, Andrew Kniss, who wrote the EIQ-criticism paper to which you refer, and from whom I’ve learned a lot – he makes many valid points, both in his published work and in his blog where he makes weed research more accessible for the public. His well communicated insights into weed science aptly point out that things are seldom simple.

      For instance, looking at recent US data (graphs presented in the piece), he wrote: “In fact, the pace of herbicide increase was slower in the GMO crops than non-GMO crops. From these data, one could make a plausible argument that GMO crops have decreased herbicide use, since the increase in herbicide use has been slower compared to non-GMO crops. But this is the problem with trying construct a narrative from imperfect, national-level data. I don’t actually know whether GMO crops have increased or decreased herbicide use (and neither does Mr. Hakim). We can each use different versions of the best data available to fit contrasting narratives. But the answer is far more complex than anything we can derive from data that weren’t explicitly generated with this question in mind.”

      I have touched more on the topic of resistance concerning glyphosate in another piece (quoted here below), though I still refer to Mr Kniss pieces for a much more in-depth-look. In a nutshell, resistance is always a problem, even to things as mundane as hand-weeding, and herbicide tolerant crops are just one factor, depending on how they are used they can either increase resistance incidence or help avoid it. One would have to look at a specific crop, area, and pest, to find out in each case which approach is most suitable.

      “is there a problem with glyphosate-resistant weeds? Certainly, weeds developing a widespread resistance against glyphosate would nullify all of its earlier outlined environmental benefits, and farmers would have to revert to tilling as a means of weed control, as well as older, more toxic herbicides. That would be a big blow to the farmers and the environment. Conversely, it would also make the campaigns for a glyphosate-ban redundant, as glyphosate would no longer be used, or its use would be greatly reduced. So… from the perspective of said campaigns against glyphosate, problem solved?

      palmer-amaranthThis is the extent of the resistance problem: if resistance becomes all too problematic, farmers stop using glyphosate. Conversely, most people who worry about glyphosate would not deem cessation of its use an issue at all. Isn’t it rather more problematic (from their perspective) that glyphosate use is not creating enough glyphosate-resistant weeds in order to undermine its usefulness for farmers?

      But putting that seemingly solved dilemma aside, are glyphosate-resistant weeds a problem? Will farmers be able to continue its use? If you would like to read more about the world of herbicide resistance, its history, management tools, and future prospects, you can read several informative pieces on that from, you guessed it, the weed ecology professor Andrew Kniss. For instance: The Cost of Preventing Herbicide Resistance, or Herbicide Resistance Predates Herbicides by 80 Years. In The Large-scale Impacts of Herbicide Resistance, he writes:

      Since the discovery of glyphosate-resistant Palmer amaranth, arguably the most damaging of all the so-called superweeds, cotton yield in the affected states continues to increase.

      To be clear, though, I don’t want anyone to get the impression that glyphosate-resistant Palmer amaranth hasn’t had a major impact. On the contrary, there is ample evidence that farmers in the South have had to adapt to this particular problem by using other herbicides, re-introducing tillage, or using cover crops. These additional weed control practices cost money, and growers with glyphosate-resistant weeds may very well have seen a reduction in their net economic return. There are surely many examples of individual cotton fields where yield was significantly reduced by this weed. But I think it is important to note that these herbicide-resistant weeds have not had the devastating impact on crop yields, at least not on a macro-scale, that is often implied by the sensational coverage of this topic.”

      Thanks for your interest in my piece. Hope you have a great day,


      • Phil Harrison says:

        Hi Iliada

        Thankyou, that is some interesting material. I agree ecology is rarely simple, and predicting the impacts of the introduction of GE crop on the environment is very hard to do with any certainty. Likewise as you point out in your reply, it is even difficult to assess the impacts of GE crops, even when they have been used for some time.

        Accordingly, it seems to me that the certainty about the reduction of herbicide and pesticide use associated with GE crops described in your original blog post, is not backed up by empirical data. Indeed, this point is made by Kniss in your response.
        “I don’t actually know whether GMO crops have increased or decreased herbicide use (and neither does Mr. Hakim).”

        Accordingly, I would recommend that, in the interests of scientific integrity, you edit your statements to reflect this uncertainty.


    • Hi again,

      I happened to find, among the references in another one of the articles you referenced, “Genetically Modified Herbicide-Tolerant Crops, Weeds, and Herbicides: Overview and Impact”, the piece from Andrew Kniss which I was thinking of, but first couldn’t locate. It was referenced in that article, here a quote from it that questions the underlying assumption that HT-crops would have lead to an increase in herbicide-resistant weeds:

      “If GM crops have contributed significantly to the development of herbicide resistant weeds, we would expect the number of unique instances of these superweeds to increase following adoption of GM crops. The figure below illustrates all unique cases of herbicide resistant weeds between 1986 and 2012. I have fit a linear regression to the data from 1986 to 1996 (time period before widespread GM crop adoption) and another regression to the time period 1997 to 2012.

      The slope of the linear regression is an estimate of the number of new herbicide resistant weeds documented each year. In the eleven year period before GM crops were widely grown, approximately 13 new cases of herbicide resistance were documented annually. After GM crop adoption began in earnest, the number of new herbicide resistant weeds DECREASED to 11.4 cases per year. The difference in slopes between these two time periods is probably not very meaningful from a practical standpoint. But based on the best data available, we can be quite certain that adoption of GM crops has NOT caused an increase in development of superweeds compared to other uses of herbicides.”

      “Almost any way you look at the data, it appears that GM crops are no greater contributor to the evolution of superweeds than other uses of herbicides. Which makes sense, because GM crops don’t select for herbicide resistant weeds; herbicides do. Herbicide resistant weed development is not a GMO problem, it is a herbicide problem.

      It is important to note that the glyphosate-resistant weed species that have had the most economic impact are those that evolved first in GM crops (in particular, the Palmer amaranth noted in Ms. Gilbert’s article). But this is primarily because it is these weed species that were the most economically damaging to begin with (before they acquired their super-powers). But the Palmer amaranth narrative is what leads many people to conclude that glyphosate-resistant weeds are primarily a problem in GM crops. Certainly, Roundup Ready crops have increased the amount of glyphosate used in cropland, and this increased glyphosate use has contributed to the evolution of some new glyphosate-resistant weeds. No one can dispute that. But glyphosate-resistant weeds evolved due to glyphosate use, not directly due to GM crops. And to date, there have been more new cases of glyphosate-resistant superweeds documented in non-GM crops/sites than in GM crops. So it is difficult to make the case that GM crops are any more problematic than other uses of herbicides with respect to superweed development. Unless, of course, you rely on dogma and speculation.”

      Hope you find the information interesting.
      Best regards,


      • Phil Harrison says:

        Hi Again,

        I had a look at the weedfreak website. There is some good stuff in there. He really tears to pieces the EIQ, which features prominently in the “evidence” you provide to suggest that GEs have reduced pesticide use, in you blog post!

        In the interests of brevity, I will summarise his finding “is the environmental impact quotient better than nothing? NO it is no more effective that a random number generator!


      • Hello Phil,

        One thing that is important to distinguish here, is that in my piece I talk about reduction in *pesticide* use. The use of genetically modified crops has most of all resulted in a reduction in insecticide use – this is not questioned by the discussion whether or not herbicide use is down or up, and reduction in insecticide use brings the total of pesticide use down. I believe there are no sources disputing GE crops impact on reducing insecticide (and thus pesticide) use.

        While the EIQ metric was mentioned once in a quoted article in the piece above, EIQ itself is not a central tenet of my article. In fact, there is no doubt, qualitatively speaking – not relying on the EIQ – that GE crops have helped farmers shift to using less harmful herbicides, especially glyphosate. I have written more about it here:

        “… most of the pesticides in use today are significantly less toxic than those used even a few decades ago, and despite what many might think, glyphosate is actually among the safest of the bunch. If you look at the doses that have proven lethal to half of the laboratory animals tested, the so called Lethal Dose 50 (LD50), you find that some of the most common organic herbicides, such as clove oil, acetic acid, and cinnamon oil, are also more toxic than glyphosate. In fact, when it comes to the lethal dose, even table salt is more toxic than glyphosate (see table below: 3000 vs 4900 mg/kg – toxicity studies on glyphosate LD50 can be found at EPA here, and studies determining the No Observable Adverse Effects Level (NOAEL) here). Other common substances and their LD50 values described here.”

        “Agricultural scientist and journalist Steve Savage has written in detail about the kinds of pesticides in use today. Using pesticides in California as his example, he illustrates the major shift toward essentially non-toxic substances, and he compares changes in amounts and toxicities of pesticides used between 1990 and today. He writes:

        Most pesticides today have oral ALD(Acute Oral Toxicity)50s of more than 5,000 mg/kg (Category IV) and are less toxic than table salt, vinegar, citric acid, vanillin and many other familiar food ingredients.

        University of Florida Pesticide Information Office has also put out a report on this trend towards much more harmless herbicides, called Herbicides: How Toxic Are They? In it, they write:

        Although there have been pesticides that were toxic and dangerous to handle, most of these products are no longer used and have been replaced by newer chemistry. Pesticides now must go through rigorous testing by the U.S. Environmental Protection Agency (EPA) before they can be sold. This has led to many herbicides that possess little or no mammalian toxicity and are less harmful than many everyday household products (Table 1). Surprisingly, household chemicals that many of us store under the kitchen sink pose more risk to the handler than herbicides.”

        There are also practical examples of different spraying schedules on GE vs non-GE here:

        “If you listen to the sugar beet farmers who are hurt by companies yielding before popular fears of glyphosate and biotechnology, the risks are great indeed. In the NPR piece As Big Candy Ditches GMOs, Sugar Beet Farmers Hit A Sour Patch:

        Part of Grant’s intense interest in [GMO] beets definitely stemmed from his own farm’s experiences with the “traditional regimen” of herbicide products and application timing and methods. “It was a nightmare,” he recalls of those pre-Roundup days. “We had failures all the time — fields that would become unharvestable because of our failure to control weeds. We had an army of people applying herbicides around the clock or just at night. We did micro-rates, we did maxi-rates, you name it.”

        “We had one sprayer for every 500 acres, so eight sprayers running around,” Grant relates. “They would work whenever they could. It might be all night long; it might be 24 hours straight because they had a window.

        “It was a horrible life. Just last spring (of 2011), as the Roundup litigation was progressing through the courts and it was unclear whether we’d be able to plant Roundup Ready seed, my sugarbeet manager flat-out told me, ‘If we have to be conventional again, I’m quitting. I can’t do it.’”

        And more detailed info on it here:

        In the developing world, the effect has also been pronounced:

        “GE crops have helped reduce harsher pesticides in the developing world, where safe pesticide handling is most at question. A study on the Impact of Genetically Modified Maize on Smallholder Risk in South Africa finds lower risk for farmers using biotech crops, and International Food Policy Research Institute makes the following assessment:

        Savings in terms of increased gross margins (114%), reduced pesticide costs (62–96%), beneficial human and environmental effects, and improved yields (18–29%) over conventional crops in the presence of pest pressure have been documented for small-scale African farmers growing commercial GM crops. This despite high variation among crops, time, and geographies.

        The European Academies Science Advisory Council’s (ESAC), in their report summary in Planting the Future, also highlights how the technology offers significant economic and health benefits at the farm level, particularly to smallholder farmers in developing countries, not least because of the associated decreases in pesticide use.

        For perspectives of farmers in the developing world, you can read about a brinjal-farmer in Bangladesh or a cotton-farmer in India, who speak about their switch to GE-brinjal and GE-cotton, and the resulting dramatic decrease in pesticide use on their farms. These trends have also been scientifically reported, here articles about these developments in China: Widespread adoption of Bt cotton and insecticide decrease promotes biocontrol services, and India: Bt cotton cuts pesticide poisoning.”

        Thanks for reading,


      • George Norman says:

        Sorry to jump in here: doesn’t it strike you that we should be talking in terms of the entire system here? Does it really matter WHERE the resistant weeds are developing, because sooner or later they will be growing in GM crops? At that point, wouldn’t not only the herbicide become useless, but also the genetic modifications that made that plant resistant to the herbicide in the first place? Unless you can direct me differently, I can see nothing but a future of chasing a new silver bullet every time the old one becomes ineffective.


      • Hello George,

        Thanks for your interest in my blog! I think you might be interested in this article, where I touched more on resistant weeds – most of all, I recommend reading more from weed ecology Professor Andrew Kniss (several good pieces linked to his work from my article), a fantastic perspective into weed science for laypeople and scientists alike.

        You are right in that fighting weeds has always been a chase, much like antibiotic use against pathogenic bacteria. Weeds develop resistance to most methods, even hand weeding. But there are many things we can do to slow this down and stay ahead, and having more tools in our toolbox is crucial for that, as is knowing how to use them. GE crops do not change the fundamentals of weed development, they are simply a way to diversify our tools.

        Hope you find the information helpful.
        Thanks for reading!


    • Ah, finally, a paper I’ve been waiting for from the weed ecologist Andrew Kniss, on herbicide usage trends in the context of GMO crop adoption (note not about pesticides in total where studies show GMOs have lead to a reduction thanks to insecticides, just the herbicide subcategory) just published in Nature Communications.

      “In summary, this analysis suggests that GMOs have had a positive effect (or at the very least neutral or non-negative effect) with respect to herbicide use intensity and mammalian toxicity, and I’m sure that will disappoint many folks who don’t like GMOs.”

      Long-term trends in the intensity and relative toxicity of herbicide use in Nature Communications:

      GMOs and Herbicides: it’s complicated (Andrew’s blog)

      Here is his tweet thread summary:

      – comment from there: “this bit is REALLY important, but also really difficult to quantify rigorously: Banning glyphosate would likely increase chronic toxicity hazard, since would likely be replaced with more toxic herbicides”


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