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GE Food & the Environment

Center for Food Safety

Despite the misleading claims of companies selling them, Genetically engineered (GE) crops will not alleviate traditional environmental concerns, such as the chemical contamination of water, air or soil. Far from eliminating pesticides, GE crops have actually increased this chemical pollution. Plants engineered to tolerate herbicides closely tie crop production to increased chemical usage. Crops engineered with Bt genetic material to protect against specific insect pests may decrease the efficacy of this important nonchemical pesticide by increasing resistance to it. This could mean the widespread conversion of this sustainable method of farming to chemical-intensive methods.

Meanwhile, genetic engineering has brought an entirely new slate of environmental concerns. Altered genes engineered into commercial plants are escaping into populations of weeds and unaltered crops. Genetically enhanced “superweeds” may well become a severe environmental problem in coming years. Even now, GE corn, canola and, to a lesser extent, soybeans and cotton are contaminating their non-GE counterparts. This is causing major economic concerns among farmers and is resulting in the loss of U.S. agricultural exports. The biological pollution brought by GE crops and other organisms will not dilute or degrade over time. It will reproduce and disseminate, profoundly altering ecosystems and threatening the existence of natural plant varieties and wildlife.

Despite these troubling and unprecedented environmental concerns, the U.S. government has allowed companies to grow and sell numerous gene- altered crops. Yet no government agency has thoroughly tested the impact of these crops on biodiversity or farmland and natural ecosystems. No regulatory structure even exists to ensure that these crops are not causing irreparable environmental harm. The FDA, our leading agency on food safety, requires no mandatory environmental or human safety testing of these crops whatsoever. Nonetheless, officials at the FDA, EPA, and USDA have allowed, and even promoted, GE crop plantings for years.

The lack of government oversight is troubling. Each decision to introduce these biological contaminants into our environment is a dangerous game of ecological roulette. The extent of irreversible environmental damage grows greater with every new acre of GE cropland and every new GE variety.

Biological Pollution

The term "pollution" evokes thoughts of factory smokestacks capped by billowing columns of acrid smoke or lifeless streams foaming with putrid agricultural or industrial runoff. For decades environmentalists have focused on reducing or eliminating these and other forms of chemical pollution. Now, the commercialization of biotechnology has raised concerns among scientists, farmers and the public over a much more subtle yet potentially more insidious form of pollution––the biological contamination of wild species, organic crops and other agricultural products.

Unlike chemical pollutants, biological pollutants reproduce, disseminate and mutate. They do not degrade over time as chemicals do, but rather multiply exponentially. Disastrous U.S. experiences with exotic bio-invaders such as Dutch elm disease, chestnut blight and the kudzu vine attest to the pernicious problem of biological pollution. As demonstrated by these exotics, once biological pollutants enter the environment, the results are irreversible and ecosystems are forever changed.

Plant geneticist Dr. Norman C. Ellstrand describes the difference between chemical and biological pollution: "A single molecule of DDT remains a single molecule or degrades, but a single crop [gene] has the opportunity to multiply itself repeatedly through reproduction, which can frustrate attempts at containment." Even as agricultural biotechnology brings with it an unprecedented increase in potential biological pollution, its current uses are also likely to increase the use of agricultural chemicals.



A major biological pollution problem of GE crops is the creation of "superweeds.” Almost all of the world's leading food crops have formed hybrids in nature with weedy relatives. Published research confirms varying degrees of gene flow from domesticated crops to weedy wild relatives for varieties of beets, canola, corn, grapes, millet, radishes, rice, squash and sunflowers. Several studies demonstrate that GE plants are likely to share this propensity, and some may have a strong tendency to pass along traits that could create more persistent, more damaging weeds.

One example of such research is a 2-year trial on plant/weed hybridization conducted by Dr. Ellstrand and Dr. Paul E. Arriola of the University of California, Riverside. The trial demonstrated substantial hybridization between sorghum and johnsongrass, a noxious weed that plagues various field and orchard crops. Extreme johnsongrass infestation can reduce corn, cotton and soybean yields by nearly half. Arriola and Ellstrand found sorghum/johnsongrass hybrids growing as far as 100 meters from the nearest sorghum crop, and judged these plants to be as hearty as non-hybrid johnsongrass.

Crops engineered to tolerate herbicides are of particular concern. The biotechnology industry has long known of the potential for its crops to create “superweeds.” In fact, scientists at Calgene, the company that introduced the first commercial GE crop, were among the earliest to predict this danger. They noted in 1985, "The sexual transfer of genes to weedy species to create a more persistent weed is probably the greatest environmental risk of planting a new variety of crop species." Since that time, field trials and the experiences of commercial growers have borne out their fears. To control herbicide resistant weeds, farmers are now spraying more toxic herbicides (6 to 8 different types in extreme cases), resorting to more soil-eroding tillage operations, and hiring weeding crews to hoe weeds by hand in cotton-growing states. In Illinois, weed scientist Patrick Tranel predicts that waterhemp resistant to as many as four families of herbicide may soon make it impractical to grow soybeans in some Midwestern fields.

Besides hybridizing with weeds, genetically engineered crops themselves can become superweeds. Once again the major concern is herbicide resistant plants. In the late 1990s, canola farmers in Alberta, Canada, began planting three distinct types of GE seeds specifically designed to withstand the application of certain commercial pesticides. One variety exhibited resistance to Monsanto Co.'s Roundup herbicide, another to Aventis LP's Liberty herbicide, and another to Cyanamid's Pursuit and Odyssey herbicides. By early 2000, all of these varieties had cross-pollinated to the extent that farmers were finding triple-resistant canola, exhibiting the resistance traits of all three GE varieties, growing in and around their fields. This resistance means farmers have to rely on older, more toxic herbicides to eradicate weeds and volunteers.

Chemical Dependence

Since 1996, Roundup Ready systems—Herbicide Resistant (HR) crops resistant to glyphosate, the active ingredient in Monsanto’s weed killer Roundup—have been the mainstay of GE crop plantings. Scientists, environmentalists and agricultural experts warned that reliance on the Roundup Ready system would create weeds that would build resistance to the herbicide, based on the same Darwinian principle by which overused antibiotics foster drug-resistant bacteria; that is precisely what has happened. Massive use of glyphosate with Roundup Ready crops has created an epidemic of glyphosate-resistant weeds. Now, farmers across the country are struggling to deal with these resistant weeds on over 10 million acres of cropland. 

Eighty-four percent of the GE crops planted today are designed to withstand massive applications of herbicides without dying. HR crops are the chief focus of biotechnology development efforts for 2 basic reasons.

First, all of the major biotech companies are pesticide firms that have acquired seed companies. Biotechnology = pesticides + seeds.Second, herbicides are far and away the most heavily used form of pesticide, comprising two-thirds of agricultural pesticide use in the U.S.

HR crops thus create incredibly profitable synergies for Monsanto, Dow and the other pesticide-seed firms, which profit twice by selling both expensive GE seeds and the large quantities of the herbicide(s) used with them.

Now, in a misguided effort to fix the weed resistance problem created by first generation HR crops, biotechnology companies are racing to genetically engineer new crops resistant to ever more toxic herbicides. For example, Dow Chemical Company is currently requesting USDA approval of a GE version of corn that is resistant to 2,4-D, an ingredient in the highly toxic “Agent Orange” used during the Vietnam war. Commercial approval of Dow’s corn would trigger a large increase in 2,4-D use. The chemical arms race with weeds triggered by these HR crops entails an ever-escalating spiral of pesticide use and pollution, and attendant adverse impacts on public health and the environment.

Genetic Contamination

Superweeds are not the only consequence of unwanted gene-flow. Volunteer crops, cross pollination, and poorly segregated seed stocks have led to widespread contamination of non-engineered crops. This is potentially devastating for organic farmers and others wishing to keep their crops free from GE contamination. The pervasiveness of genetic contamination effectively denies farmers and consumers the ability to choose to avoid growing and eating GE crops and foods.

The proliferation of GE varieties has ensured that contamination of non-GE crops, either through cross-pollination or the failure to properly segregate seeds and harvests, is rampant. David Gould, who serves on organic certification committees in California and North Dakota, reported that as early as 2000, virtually all the seed corn in the U.S. was contaminated with at least a trace of genetically engineered material, and often more. Even the organic lots are showing traces of biotech varieties. Controlling the spread of GE contamination has proven all but impossible.

Beyond Gene Flow

Bacillus thuringiensis (Bt) is a family of bacteria that serves as a natural pesticide, because its various subspecies produce proteins (such as Cry9C) toxic to a variety of crop pests. Typically, Bt degrades quickly and poses few toxicity risks to humans, wildlife, or beneficial insects. Therefore, it has become a favored low-impact pesticide for occasional agricultural use. Because Bt is not a manmade pesticide, it is particularly important to organic farmers. Genetically engineered Bt crops constantly produce an activated form of Bt toxin. A published study on Bt cotton states, "This system amounts to a continuous spraying of an entire plant with the toxin, except for the application is from the inside out." Not surprisingly, concentrations of protein toxins are much higher in the tissues of Bt crops than in sprays that farmers apply topically.

Harm to Non-Target Insects

Crops engineered to produce Bt toxins or other insecticides are likely to affect a variety of insects, including those that are not crop pests. A highly publicized study led by Dr. John E. Losey of Cornell University determined that pollen from Bt corn can dust milkweed leaves near cornfields and reduce the survival rate of monarch butterfly larvae that feed on the milkweed. Some scientists have challenged the so-called “monarch study,” arguing that Losey's results in a controlled experiment do not translate to real world settings. Subsequent research, however, suggests that natural dusting of milkweed by Bt corn pollen can indeed reduce the survival of monarch larvae up to 10 meters from the edge of a GE cornfield. A study involving Novartis’ Event 176 varieties of Bt corn found that they interfered with the normal development of the non-target black swallowtail. Research into how Bt crops' toxicity to non-target insects affects wider ecosystems is incomplete. For example, it is uncertain whether high levels of Bt produced by GE crops could have a counterproductive effect by killing beneficial insects and parasites that naturally reduce crop pests. One study found that Bt Cry1Ab toxin is harmful to the green lacewing, a beneficial predator that feeds on aphids.

While non-target butterflies and moths affected by Bt corn do not prey on crop pests, they do feed on weedy plants, function as pollinators, and sustain populations of beneficial predators by providing an additional food source. Non-target insects also serve as prey for birds and bats. One study found spraying forests with conventional Bt toxin impacted the food supply of the black-throated blue warbler, resulting in reduced breeding activity by the birds and causing their rate of reproduction to fall below their rate of mortality.

Bt Resistance

Most researchers and farmers consider Bt resistance to be a serious threat. For about 30 years Bt toxin has been applied on the spot… and only when there are signs of infestation of the crops by insects. It is the most successful biological insecticide control system we have and would probably retain its potency against pests for many more years to come. The primary strategy for preventing Bt resistance relies on planting refuges––sections of fields growing non-Bt crops in proximity to the Bt varieties. The theory is that pests attacking the refuge crops will mate with those feeding on the Bt crops and prevent resistance from being passed to the next generation. However, it seems unlikely that farmers will maintain sufficient refuge fields close enough to all of their Bt fields to ensure crossbreeding between the various pest populations. We have already begun to see Bt-toxin resistance in those insects that are constantly in contact with these monocultures and feed on them.

The rise of Bt resistance would have an extreme impact on many organic farmers. Without Bt, many of these farmers would suffer greater crop losses or choose more expensive pest-control methods, both of which could increase consumer prices for organic foods. Some organic farmers would undoubtedly turn to chemical pesticides or go out of business, potentially reducing the availability of organic products.