An Email Conversation About GMOs

Post date: Nov 7, 2013 6:57:35 PM

Here's an email exchange that I had with a friend about GMOs. Names are redacted to protect the innocent. Perhaps I could add some citations in here? Perhaps! But to start with, Pilson and Prendeville (2004) wrote a really nice review.

Friend:

I've been having conversations about GMOs, and the consensus is that they are not necessarily harmful for human consumption, but perhaps harmful for biodiversity. Do you have educated information about this? I'm open to the idea, but I'm an evidence/science/data driven thinker. I want to be sure my opinions are not based on talk, but real info.

So will GMOs result in monoculture?

Me:

Are we talking about a monoculture of agricultural species (e.g., wheat, apples)? If so, then the answer is that we already have a monoculture of agricultural species (at least regionally). Agricultural systems already have essentially no species diversity, so GMOs can't reduce that.

If the question is about the surrounding "agroecosystem", then, yes, there is a possibility of some types of GMOs reducing biodiversity. For example, transgene escape could change the genetic diversity of surrounding plant species, in rare cases where there are vectors for gene transfer from transgenic crops species to nearby related wild species. This is a theoretical possibility, but I don't know of any cases where this has happened on a wide and uncontrollable scale. GMOs could also reduce the diversity of surrounding animal populations, by making conditions unfavorable for some species of herbivorous insects, with cascading consequences for their ecosystems. But such changes would be occurring in ecosystems that already have reduced biodiversity due to the widespread use of indiscriminate pesticides, which do much more to reduce invertebrate biodiversity, and have greater consequences on the rest of the ecosystem.

To me, all of the real concerns about agriculture and biodiversity have nothing to do with either GMOs or conventional pesticides/herbicides, but rather with industrial agriculture as a whole. Small scale, organic farming, permaculture - all of these essentially obviate the need for any sort of pest control, whether it is a conventional chemical or genetically engineered, by creating an environment that isn't conducive to epidemic pests. I like to think of this issue the same way that I think of all epidemiology. The way to beat an epidemic is not by giving everyone drugs after they already have the disease, nor by giving everyone new genes to fight the disease. A much better approach is to tell people to cover their mouths when they cough, and not make out with sick people.

And, finally, there are many instances where GMOs can *increase* an ecosystem's biodiversity. More productive GMOs (especially golden rice) can reduce the total amount of land area required for cultivation, allowing for more land area to be kept as a biological preserve. This is a common argument from companies that produce GMOs, and the quick and easy rebuttal is that people don't actually put more land into reserves, they just cultivate more land and make more people. But it's a valid point that more productive GMO crops could be part of an effective plan to conserve biodiversity.

Let me know if you need cites for this stuff, and let me know if I didn't answer your question. (Looking back at what I wrote, it's quite possible that I didn't answer your question.)

Friend:

I'm not 100% sure what my question is, actually…

The comment that got me thinking was this, posed by a friend, and I just don't know the science behind it or the validity of it…

GMO's threaten to severely disrupt the biodiversity of not just our food supply, but the biosphere. Billions of years of evolution have created varieties of plants with incremental, but incredibly important differences. Let's say I grow five varieties of tomatoes and four of them succumb to Verticillium Wilt, a disease, but the fifth is resistant- I don't lose all of my tomatoes and I don't starve. Think about that on a global level. Industrial farming has shown us that monocultures are bad for the environment and can have catastrophic consequences. They are vulnerable to disease, drought, pests, etc. By introducing GMO's we begin a slow pollution of the genetics of all of our plants, not just the ones we eat. And the first places to feel the pain of this won't be the US, they'll be the places we're trying to help, ie the drought-ridden places that these GMO's are allegedly being designed to help. Labeling definitely isn't the answer to solving this problem, but it's a step toward necessary regulation. I don't support the use of GMO's for, well, anything that I can think of. Therefore, I want to be notified of those products that contain them so that I can, at least temporarily, avoid them. And I'm not going to carry my damned phone around scanning everything to be sure. That's like these stupid voter ID laws. You just want to make it more difficult for me to find the information, so you're hoping I'll give up. I'm not going to. I'm looking out for your interests as well, because GMO's are not selective about the plants they pollenate. It won't be long before we hear more and more stories about Organically certified products being threatened because of GMO's. By law, they cannot contain GMO's, but tell that to the wind and the bees. At the very least, GMO's should be required to be engineered so that they cannot pollenate or cross with other non-GMO's. It would be like including a switch in the genetic material, if GMO, pollination can proceed, if not, the genetic material contained in the pollen is inert.

Me:

I will start at the top.

Billions of years of evolution have created varieties of plants with incremental, but incredibly important differences. Let's say I grow five varieties of tomatoes and four of them succumb to Verticillium Wilt, a disease, but the fifth is resistant- I don't lose all of my tomatoes and I don't starve.

This is barely true, because life on this planet has evolved over billions of years. Plants have only been around for about 500 million years, though. The particular plants in the author's example, tomatoes, were domesticated about three thousand years ago - again, not billions of years, but plenty of time for some substantial evolutionary changes to take place. Any modern varieties that the author is talking about growing, however, are likely quite new. Heirloom varieties are usually 150-200 years old, while most varieties grown are the product of intensive selective breeding, and are probably about 50-70 years old, maximum. (One of my favorite tomatoes to grow in Oregon, the Santiam, is commonly referred to as an heirloom tomato. Jim Baggett invented it at OSU in the 1970s by crossbreeding small determinate tomatoes with large Russian indeterminate tomatoes.) Many modern fruits and vegetables have only been in production for a few decades. Some never even get to reproduce on their own. Many fruit trees, for example, are bred entirely in greenhouses, and planted with one species as the root, and another species as the fruiting stem. Such species are therefore never subjected to natural selection, and aren't evolving in concert with a surrounding ecosystem at all. Even for species that have been reproducing in the fields for a couple decades, that still isn't really enough time for them to be co-evolving with other species around them. So this assertion - that GMOs will disrupt a careful balance of coevolved biodiversity - ignores the fact that there is often little or no co-evolutionary history between crop species and their agroecosystems.

Industrial farming has shown us that monocultures are bad for the environment and can have catastrophic consequences. They are vulnerable to disease, drought, pests, etc.

Yes, this is certainly true, but this has nothing to do with GMOs. Non-GM crops are almost always planted in monoculture, as I mentioned in the last email. Moncultural planting leads to many problems with disease, drought, and pests, and those problems would occur with both GMOs and non-GM crops. 

By introducing GMO's we begin a slow pollution of the genetics of all of our plants, not just the ones we eat.

I assume that what the author means is GM alleles showing up in non-GM plants. As I mentioned, this is a theoretical concern, but one that has yet to be realized on a large scale. If GMOs are widely planted, there will be increased gene flow from GM species to wild neighbors. It is important to keep in mind, though, that there have already been many examples of genes moving from conventionally bred species to wild neighbors, both by horizontal gene transfer and by hybridization. This gene flow has resulted in some ecological disruption, loss of biodiversity, and a shift toward "weediness" in plant species surrounding agroecosystems. Should transgenes escape into wild populations, the effects would likely be similar. But once again, this is not a problem that is particular to GMOs. Conventional breeding creates the exact same problems.

I don't support the use of GMO's for, well, anything that I can think of

I don't want to get too far away from the biology, here. But I would encourage the author to consider the example of golden rice. I think this is an important example because, with golden rice, there is really no biological reason not to grow it. There are many social and political reasons to avoid golden rice, and many social and political reasons to cultivate golden rice as widely as possible. To me, that's what makes it such a good example in the GMO debate. It forces us to recognize that our reluctance to use GMOs has no scientific basis. Having said that, there may be plenty of good reasons to avoid GMOs. They just aren't scientific reasons.

GMO's are not selective about the plants they pollenate. It won't be long before we hear more and more stories about Organically certified products being threatened because of GMO's. By law, they cannot contain GMO's, but tell that to the wind and the bees. At the very least, GMO's should be required to be engineered so that they cannot pollenate or cross with other non-GMO's. It would be like including a switch in the genetic material, if GMO, pollination can proceed, if not, the genetic material contained in the pollen is inert.

It is true that GMOs can hybridize with conventionally bred crops. I don't know how to engineer these plants so that they can't spread pollen, but many people are working on it. A law requiring that GMOs contain molecular mechanisms for preventing hybridization is probably a good thing, in my opinion - but again, this is a policy issue, not a scientific one. Having said that, however, these are biological systems that can and will mutate, so perfect containment of transgenes is impossible. With that in mind, how much transgene escape is acceptable? This, again, is a political question, a question about values, and is not amenable to scientific analysis. And, as I have mentioned many times, this issue already exists with conventional crops, whose genes can easily move from one species to another. All gardeners know that it's hard to recover seeds from brussels sprouts, because there is a good chance that they have hybridized with some cabbage pollen, and are going to grow into a weird (and not delicious) plant. If I am growing "heirloom" tomatoes, and my neighbor is growing a modern tomato, and I want to save seeds from my heirloom plant but can't because they're all weird hybrids now, do I get to sue my neighbor? Should my neighbor be prohibited from growing his modern tomato varietal? What if we're commercial farmers? I think that this is an interesting issue. As I've have said many times, however, I don't think it's a scientific issue.

Here's one more thing to think about, and then I'll get back to doing work. Consider natural selection, which made wild Asian rice hundreds of thousands of years ago, artificial selection, which made domesticated Asian rice about 14,000 years ago, and genetic engineering, which made golden rice about a decade ago. What are the mechanistic differences among these processes? What the ecological consequences of these processes? I always try to have my evolution and ecology students answer these questions. And the most important question that I ask my conservation biology students is: what do you want to conserve, and why do you want to conserve it? I think that the answers to these questions should help us understand the role of biology in the debate over GMOs.