Tuesday, July 2, 2013

GM Oh No! Part 2 of 3: Environmental considerations

A blog of Bridge Environment, updated most Tuesdays

This entry is the second in a three-part series about genetically modified organisms (GMOs)

Not quite the zombie apocalypse, but should we worry
about the ecological effects of a GMO invasion?
Two weeks ago, I discussed human health concerns surrounding genetically modified (GM) foods, also known as GMOs. Last week, I followed up with a scathing critique of a new study on pigs that claimed to show health problems from GMOs. In both entries, I argued that we do not have scientific evidence to suggest GMOs would pose widespread accute health problems, but that there is the possibility of long-term effects and rare allergic reactions. We need more testing to resolve those concerns. Today, I write about environmental effects, which are more complicated and potentially worrisome because GMOs are designed to have novel ecological characteristics and their effects will reach beyond the farms where they are raised. Morevoer, the nature of ecological science makes the consequences of these characteristics harder to monitor and distinguish from background noise.

GMOs can be made with nutrition or flavor in mind, but most are designed to change the ecological balance of a farm. Many GM crops have genes that provide chemical defenses against insects, shifting the balance towards healthy crops and away from infestations. Others have high tolerance of herbicides, which encourages farmers to use more harmful chemicals to keep weeds at bay. Still others are designed to grow faster and more efficiently, creating a super population. While these three ecological changes have been goals of farmers for millennia, GMOs raise more urgent concerns about potential ecological effects because they can be such a quantum leap from their predecessors. GMOs raise three major ecological concerns: direct toxicity of GMO chemical traits on non-pest animals, indirect toxicity of pollution emanating from GMO farms, and the spread of GMOs themselves beyond their farms or enclosures.

Let’s start with the concern about GMOs’ effects on non-pest animals. In theory, internal chemical defenses seem like a wonderful idea. Put the pesticide inside the plant in a form that doesn’t affect toxicity in humans, and keep pests down without having to spray as many chemicals. However, concerns have been raised about the effect these plants may have on non-pest organisms. Honeybees particularly stir this controversy. Since late 2006, honeybee hives have suffered increased rates of colony collapse disorder. Research has identified a number of common characteristics of collapsing hives, particularly a higher pathogen load in individual bees. Rather than representing a new epidemic, though, bees are apparently succumbing to diseases because of increased stress, much in the same way that people don’t die directly from HIV/AIDS but from diseases they can no longer fight off. The source of stress is still unclear, with some signs pointing to the increased use of a certain class of pesticide called neonicotinoids. However, the cause is still unresolved and many casual observers believe the culprit is pollen from pesticide-containing GM crops. Even if GM crops are not to blame in this case, it does seem plausible that crops engineered to be toxic to pest insects might affect non-pest ones as well.

While certain crops are designed to reduce the need for insecticides, others are made to tolerate higher concentrations of herbicides, allowing farmers to use chemistry to fight weeds more aggressively. Thus, while insecticide use has generally dropped with the advent of GM crops, herbicide use has increased and is leading to tougher weeds that are harder for non-GMO farmers to contend with (Benbrook 2009, but keep in mind this report was not peer reviewed). Though the overall change in chemical use is complicated, it is safe to say that the use of GM crops has changed the sort of chemical pollution coming off of farms.

Crops are not the only GMOs being developed for food consumption. AquaAdvantage salmon, also known as the Frankenfish, have been approved by the US’s Food and Drug Administration. Until now, these GMOs have been raised in contained systems. However, they will no doubt replace more natural versions of Atlantic salmon in penned farms around the world (primarily in Norway, Chile, the UK, Canada, and the US). These pens let seawater flow through, and that water carries uneaten food, salmon fecal matter, and diseases from the pens to surrounding oceans, bays, and river mouths. Current studies suggest that it requires less food to produce GM salmon than their non-GM counterparts. On the surface, this characteristic appears to be an environmental benefit. Salmon feed typically contains substantial amounts of wild-caught forage fish, and more efficient salmon production would mean lighter pressure on the forage fish stocks and less pollution because of GM technology. These gains would quickly turn to losses, though, if GM technology spurs more intensive salmon farming. This is a likely scenario if the technology makes these practices more profitable. Disease is a greater concern. Epidemics occur when diseases have a high chance of infecting new hosts before the original one’s immune system fights it off or it dies trying. Farms are prone to epidemics in the same way that classrooms are—the concentration of potential hosts mean that one infection can become dozens in short order. GM salmon are likely to have a harder time fighting off disease because there are usually fundamental trade-offs in what an organism can do. Because GM salmon grow so quickly, their immune systems are likely to be weaker. As a result, GM salmon farms are likely to have a higher rate of epidemics than non-GM farms. When disease outbreaks occur, farms can potentially expose nearby natural populations. Given the poor state of salmon stocks around the world, disease from farms poses a real threat.

Finally, let’s consider the effects that GMOs may themselves have. Farms are rarely sealed off from surrounding environments. Plants naturally disperse by broadcasting pollen and later, seeds by wind or animal carrier. In this way GM genes and whole individuals can be carried or blown into adjacent farms, forests, and fields, where they can crowd out natural competitors or contaminate non-GM crops. And though GM salmon are designed to be sterile females, the pens they are kept in are fairly flimsy and prone to damage from storms and from hungry sea lions. Large-scale salmon escapes are common, and their pressure on the food web and crowding of natural habitats can potentially further degrade the poor state of natural salmon stocks.

All of these concerns are prevalent in non-GM salmon production and the changes GM salmon would induce are speculation. Nevertheless, they represent real risks that haven’t been the focus of much debate because concerns over food safety have dominated. By focusing on our most prominent fear (lack of control of our food system and our immediate health), opponents of GMOs have distracted us from more realistic and challenging concerns.

These challenges are further exacerbated by the difficulty in identifying clear signs of environmental harm. Environmental systems are notoriously variable, affected by many non-GM-related influences (e.g., natural climate variability and human-induced climate change). This variability makes it exceedingly difficult to tease out the ecological effects of GMOs. Here, much more study is needed that combines micro-view studies of chemical flows in farm-influenced ecosystems with macro-views of ecological changes occurring on and around farms.

As much as ecological concerns require our attention, GMOs have important economic and political effects that may be of even greater concern. Stay tuned. They will be the subject of next week’s blog entry.


For more information, read our other blog posts and visit us at Bridge Environment.


  1. This comment has been removed by a blog administrator.

  2. In discussing ecological effects of GM crops, I failed to point out a major consideration: pest resistance. Just as bacteria evolve to resist antibiotics, pests have a knack for evolving resistance to pesticides. As would be predicted, a recent study found this phenomenon occurring in GM crops.

    One of today’s most widely used genetic modifications in crops takes insect-repelling genes from a bacteria, Bacillus thuringiensis, and inserts it into plants. In 2005, Bt crops did an excellent job of repelling insects. Only one of 13 common pests showed resistance. Today, five of these 13 have resistant populations.

    The lesson here is that nature is dynamic and capable of adaptation. The field of ecology is filled with stories of arms races between predators and prey. The ecological changes discussed in this particular blog entry are bound to select for insects and weeds that defy our efforts to control them, and which may do collateral damage to other farms and nearby ecosystems.