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    Mirids: A Case Study For Indirect Ecological Effects Of GMOs
    By Lindsey Tuominen | May 30th 2010 10:16 AM | 3 comments | Print | E-mail | Track Comments
    About Lindsey

    I am a Doctoral Candidate in Forest Resources at the University of Georgia. The name of my program is about as broad as my interests, but my current...

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    The development of genetically modified organisms has been a potentially explosive topic for those who see themselves as scientists, environmentalists, or just plain eaters-of-food. 

    Although some evidence suggests that GMOs can be enormously beneficial, particularly in developing countries (1), others have suggested that most of the gains are attributable to other factors than the engineered traits (2).  Ever since I first learned about genetic engineering and the court battles between farmers and biotech giants, I have generally thought of the controversy of GMOs as more socially than scientifically controversial.

    Yet sometimes the lack of scientific debate has more to do with a lack of data than anything else.  Indirect effects, while the very meat of systems thinking, can be notoriously difficult to demonstrate in practice without a full survey of an ecosystem's matter or energy flows.  For this reason, there has been little work considering the indirect ecological effects of genetically modified organisms, even though scientists have recognized the need for such research (3).

    An article in this week's issue of Science has now opened up an examination of indirect effects of GMOs, although the results are more convoluted than the article's title might initially suggest.  Researchers in China have tracked mirid bug populations in Heibei province for a decade now, and overall no difference in mirid populations were found between varieties of cotton with or without Bt, a gene used widely in transgenic crops as a built-in insecticide.  This is pretty much what you might expect, since Bt does not affect mirids -- it is engineered into cotton to control cotton bollworm. 

    What's important here, though, is not the genetic background of the crop but the difference in pesticide regimes.  While no difference between mirid populations was observed between
    no-spray Bt cotton and no-spray conventional cotton, the populations were lower in sprayed cotton than in no-spray Bt cotton.  Since cotton bollworm can be managed well with the Bt gene alone, the Bt cotton is not treated with the insecticide sprays that were used to control bollworms before the transgenic cotton became available.  Yet the very benefit of Bt cotton -- the fact that insecticide sprays are not needed to control cotton bollworm -- seems to be its downfall when it comes to mirids.  The sprays are less selective than Bt, and they will typically take out mirids as a sort of chemical "collateral damage" when farmers try to limit bollworm on conventional cotton.  The mirids take no collateral damage from the Bt cotton. 

    As the authors note, this means that fields that previously acted as mirid sinks are now acting as mirid sources.  The cotton fields where mirid populations were once limited by insecticides have now become areas where mirids can thrive, then spread to a range of other crops, necessitating greater levels of insecticide sprays.

    Yes, you read that correctly.  The indirect effect of an environmentally-friendly, theoretically-spray-reducing transgenic crop has actually led to increased levels of sprays for a non-target pest that wouldn't really be a problem if we just used the nasty, broad-spectrum insecticides that take out both cotton bollworms and mirids.  As the proportion of Bt cotton planted increases, so does the mirid infestation on other crops, and so does the use of mirid sprays.

    A person who considers him- or herself a biotechnologist just out to make some money may not be bothered much by this.  It's job security, right?  A new indirect effect pops up, and that becomes an opportunity for the next round of crop development.  On the other hand, for an ecologist this situation may seem rather distasteful.  We have now spent a great deal of our dwindling material resources (think of all those pipette tips and petri plates!) developing a crop that had the promise of reducing our use of chemical sprays, but that promise retreats the more we use the new supercrop.  Instead of shifting resource use from chemicals to plant biotechnology, we are now using resources on both of these. 

    This paper is a good reminder that in ecology, nothing happens in a vacuum.

    References:
    (1) Brookes and Barfoot.  April 2010.  GM Crops:  Global Socio-Economic and Environmental Impacts 1996-2008.
    (2) Gurian-Sherman.  April 2009.  Failure to Yield:  Evaluating the Performance of Genetically Engineered Crops.  Cambridge, MA:  UCS Publications.  44 pp.
    (3) National Research Council.  2008.  Genetically Engineered Organisms, Wildlife, and Habitat:  A Workshop Summary.  Washington, D.C.:  The National Academies Press.  72 pp.
    (4) Lu et al.  28 May 2010.  Mirid Bug Outbreaks in Multiple Crops Correlated with Wide-Scale Adoption of Bt Cotton in China.  Science 328(5982): 1151-1154.

    Comments

    The use of GMOs has been an area of much debate. Things to consider or test before introduction of a GMO would logically be what are the internal biochemical effects within the GMO caused by this modification? How does producing a GMO affect the evolution of the organism? How does it affect neutral mutations within the species? If a plant is GM for pesticide properties (lets say we make the plant unpalatable to a particular organism) how does that affect the co-evolutionary coupling of that plant and organism. This wouldn't be so relevant in crops since we would prefer genetically identical crops to maximize yield, but breeding such species for unique genotypes, or the GM species pollinating wild species, how would the inclusion of a gene coding for unpalatability affect such cases... Ecological techniques need to be stringently applied in such cases. If we want a crop species to be resistant to a type of pest, firstly natural defences against similar pests and ecological functioning in wild populations need to be considered. Why had this plant not developed this trait before? Is there perhaps a selective disadvantage to possessing such a trait naturally? In crop species much of the natural variation has been selected out by humans resulting in crops that may not be able to evolve defense mechanisms since they may lack the essential groundwork. Other fundemental questions to be answered would be how sustainable are these practices? Does the cost outweigh the benefits? Are there no natural means of eliminating the effects of the pest? Biological control agents perhaps? I think that GM crops and organisms should respresent a last resort and not a way to cut costs of agriculture compromising the integrity of natural diversity. Micropropagation of genotypes that are largely beneficial with high crop yields and breeding of crops for selectively advantageous traits are sufficient sustainable pathways of propagation. The use of gene banks to preserve genotypes that are unique may be a better way to promote natural diversity and exploit traits that are naturally occuring within that species. Honestly i think that putting fish genes in potatoes to make them more resistant to chilling may have effects downstream that would not have been predicted. Perhaps someone could enlighten me on what may happen if genes are inserted into a different genome. My molecular biology is quite rusty. I would imagine that be inserting a gene into a genome that is significantly different may increase the incident of mutations within that area of insertion or even mutations in other parts of the genome. is this a common phenomenon? is the stabilty of the genome compromised? can there be mutations occuring in that gene after generations of breeding? taking the potatoe and fish idea, if a fish gene were inserted into a potatoe is it possible that a mutation may occur in the fish gene that would promote different or other fish traits? I know my questions seems juvenile but I've always been told that there's no such thing as a stupid question, only an uninformed one. lol.

    The use of GMOs has been an area of much debate. Things to consider or test before introduction of a GMO would logically be what are the internal biochemical effects within the GMO caused by this modification? How does producing a GMO affect the evolution of the organism? How does it affect neutral mutations within the species? If a plant is GM for pesticide properties (lets say we make the plant unpalatable to a particular organism) how does that affect the co-evolutionary coupling of that plant and organism. This wouldn't be so relevant in crops since we would prefer genetically identical crops to maximize yield, but breeding such species for unique genotypes, or the GM species pollinating wild species, how would the inclusion of a gene coding for unpalatability affect such cases... Ecological techniques need to be stringently applied in such cases. If we want a crop species to be resistant to a type of pest, firstly natural defences against similar pests and ecological functioning in wild populations need to be considered. Why had this plant not developed this trait before? Is there perhaps a selective disadvantage to possessing such a trait naturally? In crop species much of the natural variation has been selected out by humans resulting in crops that may not be able to evolve defense mechanisms since they may lack the essential groundwork. Other fundemental questions to be answered would be how sustainable are these practices? Does the cost outweigh the benefits? Are there no natural means of eliminating the effects of the pest? Biological control agents perhaps? I think that GM crops and organisms should respresent a last resort and not a way to cut costs of agriculture compromising the integrity of natural diversity. Micropropagation of genotypes that are largely beneficial with high crop yields and breeding of crops for selectively advantageous traits are sufficient sustainable pathways of propagation. The use of gene banks to preserve genotypes that are unique may be a better way to promote natural diversity and exploit traits that are naturally occuring within that species. Honestly i think that putting fish genes in potatoes to make them more resistant to chilling may have effects downstream that would not have been predicted. Perhaps someone could enlighten me on what may happen if genes are inserted into a different genome. My molecular biology is quite rusty. I would imagine that be inserting a gene into a genome that is significantly different may increase the incident of mutations within that area of insertion or even mutations in other parts of the genome. is this a common phenomenon? is the stabilty of the genome compromised? can there be mutations occuring in that gene after generations of breeding? taking the potatoe and fish idea, if a fish gene were inserted into a potatoe is it possible that a mutation may occur in the fish gene that would promote different or other fish traits? I know my questions seems juvenile but I've always been told that there's no such thing as a stupid question, only an uninformed one. lol.

    Gerhard Adam
    The problem doesn't surprise me.  We live in an environment where there are millions of species in existence that we haven't even identified, with scores more that have gone extinct before we can identify them.  Consequently there are a significant number of parameters that we simply don't know anything about regarding broad interactions.  When this is coupled with an environment that has reached its current state over hundreds of millions of years of evolution with all manner of variation exerting its influence to produce some element of stability.  Into this we inject nearly 7 billion human beings behaving as if the world were their personal workshop and dumping ground.

    Amidst this we begin tinkering with some elements of the natural environment with literally no understanding beyond the reductionist controls and then presume that there are no external consequences?  To steal from Newton, "every action has an equal opposite reaction", doesn't just apply to physics, but rather it can be loosely paraphrased to every situation in which unintended or unknown consequences occur because of a particular action. 

    The trouble is that we don't even know what we don't know, but we intend to move ahead with sweeping changes anyway.  In small localized areas, such activities could make sense, but when we are attempting to operate on nearly a global scale, our ignorance becomes clear. 
    Mundus vult decipi