Page 283 - Environment: The Science Behind the Stories

What are the benefits of GM foods? producing Roundup, Monsanto engineers seeds for crops that
survive spraying with Roundup. For years farmers have loved
Genetically modified foods have long been promoted as a these Roundup-Ready crops because they reduce labor and
means for assisting people in developing nations. If foods can boost yields: Simply spray fields with Roundup, and the weeds
be made more nutritious, then malnutrition can be alleviated. die while the crops thrive. However, widespread and extended
If crops can be made tolerant of drought or of salinized soils, use of Roundup and other glyphosate-based herbicides
then small farmers can more easily produce crops on marginal is resulting in the evolution of resistance (Figure 10.27b).
land. However, most of these noble intentions have not yet Scientists have confirmed glyphosate resistance in 24 weed
come to pass. This is largely because the agrobiotech corpora- species so far, and farmers feel the number is higher than that.
tions that develop GM varieties cannot easily profit from sell- As glyphosate-resistant weeds fill their fields, farmers are
ing seed to small farmers in developing nations. Instead, most dousing their plants with more chemicals, including additional
biotech crops have been engineered for insect resistance and herbicides that are more powerful.
herbicide tolerance, which improve efficiency for large-scale
industrial farmers.
Regardless, proponents of GM foods maintain that these What are the impacts of GM foods?
foods bring environmental and social benefits, assisting efforts Although many people worry about health impacts from eating
toward sustainable agriculture in several ways:
GM foods, persuasive scientific evidence for health impacts
• Raising food yields while lowering production costs for has been elusive. Indeed, many millions of Americans eat GM
farmers enhances food security for society. foods every day without obvious signs of harm. For the most
• Crops that increase yields on existing farmland help con- part, the public’s anxiety over potential health impacts from
serve biodiversity and ecosystem services because they GM foods has not been corroborated by research. Increased
reduce pressure to clear forests and convert natural lands herbicide applications do pose potential health risks, however.
for agriculture. Most scientists feel that ecological impacts of GM foods
are a greater issue than health impacts. Many conventional
• Crops engineered for drought tolerance can help save crops can interbreed with their wild relatives (rice can breed
water by reducing the need for irrigation.
with wild rice, for instance), so there seems little reason to
• GM crops that reduce fossil fuel use during cultivation believe that transgenic crops would not do the same. In the
help to lower greenhouse gas emissions and mitigate cli- first confirmed case, GM oilseed rape was found hybridizing
mate change. An example is herbicide-tolerant crops that with wild mustard. In another case, creeping bentgrass engi-
help enable no-till farming, freeing farmers from having neered for use on golf courses—a GM plant not yet approved
to till to control weeds. No-till farming can reduce ero- by the USDA—pollinated wild grass up to 21 km (13 mi) away
sion, cut down on fossil fuel use, and bring other benefits from its test growing site in Oregon. Most scientists think
(pp. 215, 226–228). transgenes will inevitably make their way from GM crops into
wild plants, but the consequences of this are open to debate.
In addition, supporters of GM crops maintain that these
crops also help to reduce chemical pollution from pesticides. Because biotechnology is rapidly changing, and because
Indeed, adoption of insect-resistant Bt crops appears to reduce the large-scale introduction of GMOs into our environment is
the use of chemical insecticides, because farmers use fewer recent, there remains much we don’t yet know about the conse-
insecticides if their crops do not need them. In India, Bt cotton quences. As a result, it is still too early to dismiss concerns about
has enabled 7 million farmers to increase their yields while
decreasing their insecticide use. Is it safe to eat genetically
With herbicide-tolerant crops, however, most studies FAQ
find that these crops tend to result in more herbicide use, modified foods?
because farmers often apply more herbicide if their crops can In principle, there is nothing about the process of genetic
withstand it. A 2012 study by Washington State University engineering that should make genetically modified food any
scientist Charles Benbrook using USDA data calculated that less safe to eat than food produced by conventional methods.
as GM crops expanded in the United States between 1996 Simply because technology is used to move a gene, this does
and 2011, insecticide use declined by 56 million kg (123 not make the gene unsafe. Thus, to determine whether GM
million lb), but herbicide use increased by 239 million kg foods pose any health risks, studies must be done compar-
(527 million lb). ing those foods with conventional versions, one by one—just
This rise in herbicide use is accelerating, according to as researchers would study any other substance for health
Benbrook’s analysis, and the prime reason is that weeds are risks (Chapter 14). Thus far, no study has shown undeniable
evolving resistance to herbicides, causing farmers to apply evidence of health impacts from any GM food, but this does
even more of them. Just as insects can evolve resistance to not guarantee that all GM foods pose no risks. A great deal
insecticides (see Figure 10.18, p. 255), weeds can evolve of research is controlled by the companies that develop GM
resistance to the chemicals used to kill them. Worldwide, foods, and we will never be able to test all foods for all poten-
over 200 weed species have evolved resistance to herbicides tial effects. However, most scientists agree that the potential
(Figure 10.27a). health impacts of genetic engineering are likely of less concern
The most widely used herbicide is Monsanto’s Roundup, than the potential ecological impacts.
282 which contains glyphosate as its active ingredient. Besides

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