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Synthesis/Regeneration 18   (Winter 1999)

The Ecological Risks of Releasing Genetically Engineered Crops

Promiscuity, Pollination, and Genes

by Sonja Schmitz, University of Vermont

Gold beads blast from the barrel of a gun at 1000 mph. Their target-soft plant tissue nestled in a sterile petri dish. The golden bullets blast their way through thick cell walls, membranes, and cytoplasm of the plant cells. Finally, they penetrate the nuclear membrane and deliver the information with which they have been coated-cloned genes that insert themselves randomly along the chromosomes. Only a fraction of the cells will survive the bombardment. Only one in a million will express the new genetic information correctly. That cell will be grown to maturity and eventually, after years of nurturing in the hands of plant breeders, it will produce fields of genetically engineered plants.

Vandana Shiva, the director of the Research Foundation for Science, Technology and Natural Resource Policy in India, describes the genetic engineering of plants as the latest manifestation of colonization: this time, invasion of the seed. Since the process of colonization uses weapons to exploit other cultures, the gene gun (bioblaster) symbolizes the weapon of biotechnology. To many scientists it represents a technological advance that will revolutionize agriculture.

Many genetically engineered organisms (GEOs) contain genes from the same species-altered in some way. For instance, the Flavr Savr tomato has a cloned tomato gene put in backwards. This prevents the tomato from making the enzyme that causes the fruit to ripen-hence you get a tomato that has a longer shelf life. Cloning also allows scientists to mix genes between organisms; bacterial genes in plants, fish genes in tomatoes, pea genes in corn. This aspect of genetic engineering disturbs many people who believe that mixing genes between animals, plants, and bacteria violates the natural integrity of living things. Even if this doesn't bother you, the safety of consuming foods that are genetically engineered is another concern. For environmentally minded folks, the ecological risks of releasing GEOs are significant.

The gene revolution of the 1990s is transforming agriculture. Forty-five million acres of genetically engineered crops were grown in the US during 1998. To the agricultural industry these events herald a revolution in biotechnology. But not everyone is impressed. During the summer of 1998, groups in England, France, and Germany targeted test plots of GEO plants and pulled them out of the ground in protest. In the USA, overwhelming public objection to inclusion of GEOs as part of the Organic Standards influenced the USDA's decision to exclude genetically engineered foods from being labeled organic. The success of genetic engineering rests on public acceptance and the industry is nervous about it. They have invested billions of research dollars during the last 15 years and its time for it to pay off. This is my biggest problem with biotechnology. Are genetically engineered crops really a better way to grow food or are they a risky commodity being forced on the public in order to pay a hefty research bill?

Are genetically engineered crops really a better way to grow food or are they a risky commodity being forced on the public in order to pay a hefty research bill?

I once worked for the industry as a genetic engineer. The projects on which I worked did not seem to be about feeding a starving world. For instance, there was the "novel starch" project: genetically engineering corn to produce modified starches. Although scientifically challenging, the end product was destined for food processors that fill grocery shelves with such creatively designed items as instant puddings, gravies and frozen dinners. Then there were the "fartless" soybeans, a project we jokingly called cloning the "fart 1" gene. The fartless soybeans contained smaller amounts of the sugars, which normally result in human flatulence, to put it politely. How was this work part of an agricultural revolution?

Although scientists are creating many different kinds of genetically engineered plants that will end up in our food supply like insect- and virus-resistant vegetables, and herbicide tolerant crops (HTCs) represent the most popular group. Herbicides kill plants. They are intended for the eradication of weeds. Plants that are engineered for herbicide resistance have bacterial or plant genes that allow them to survive in the presence of herbicide. HTCs are sold together with their corresponding herbicide as a treatment system. They are marketed as sustainable, environmentally friendly additions to chemical agriculture. According to Monsanto, the largest agri-chemical company in the US, these herbicides degrade faster in the environment, leave negligible residues on crops, and have the potential to reduce the amount of herbicide applied to farmland by one third. But that doesn't mean these claims are true.

Herbicide tolerant crops have nasty environmental side effects. Most obviously, they continue the legacy of chemical agriculture, a crop production system that has contaminated our soil, water, and food supply. Furthermore, HTCs may actually increase chemical contamination. Their rapid degradation could result in the need to apply herbicide more often, as weeds emerge after they degrade. Also, since these herbicides are sprayed directly onto crops they are more likely to drift onto neighboring fields. This could induce other farmers to switch to the same herbicide to protect their crops, thereby, increasing overall herbicide use. Furthermore, no herbicide kills every kind of weed. Farmers must use several kinds of herbicides to combat all their weed problems. HTCs don't change the need to use other herbicides.

HTCs have the potential to create more weed problems than they solve. They exacerbate weed problems in two ways: (1) by the natural evolution of herbicide resistant weeds through repeated exposure to herbicide and; (2) by gene escape from crops to natural populations of plants. The evolution of herbicide resistant weeds has been a problem of chemically based agriculture for decades. In the last 10 years the number of weed populations resistant to an array of herbicides has increased. So, although chemical application was designed to combat weeds, the continual emergence of new herbicide resistant weeds demonstrates that herbicide technology is only temporarily effective.

The escape of herbicide resistant genes from crops to their wild relatives will create new weeds and disrupt ecosystems.

Aside from the continued use of chemicals, my biggest concern is the genetic pollution of natural populations with engineered genes. The escape of herbicide resistant genes from crops to their wild relatives will create new weeds and disrupt ecosystems. Genes have mobility. They move from organism to organism of the same species during reproduction. Encapsulated in pollen grains, they drift in the spring breeze and coat the bodies of insects.

Pollination is promiscuous business. Wind-dispersed pollen lands indiscriminately on all kinds of plants. Pollinating insects visit many species of flowers, not just one. Because the reproductive barriers in plants are more lenient than in animals, it is possible to transfer genes between different species. Successful cross-pollination is further made possible by the close proximity of compatible species. Remember that agriculture emerged as a result of domesticating wild, native plants. Even though cultivated varieties of plants dominate today's agricultural landscape, their wild relatives and progenitors exist in populations often growing nearby. Therefore, the opportunity for cross-pollination is very high. Plants also migrate to new habitats through dispersal of their seeds. The seed that flows down stream of the parent population or is carried to a neighboring field on the fur of a deer eventually grows to maturity and yields pollen to be dispersed by wind or insects. The range for potential gene transfer is thus expanded. This is how genes get around in the plant world and why ecosystems will be affected by the introduction of new genes through biotechnology.

Scientists who study the relationship between crops and their wild relatives are increasingly concerned about the commercialization of genetically engineered crops. Forty-five million acres of GE crops produce a lot of pollen with the potential to contaminate wild populations of plants. Eleven out of 18 of the world's worst weeds are also grown as crops, which means that genes are easily exchanged. Crop genes have been detected in natural populations over a half-mile from cultivated stands and can persist there for generations. One study showed that after 10 years, 28% of wild sunflowers growing nearby harbored genes received from cultivated sunflowers. Gene escape from cultivated plants is documented for crops including cotton, cucumber, corn, millet, canola, quinoa, radish, rice, sorghum, strawberry, sugarbeets, and watermelon.

What are the ecological consequences of gene escape? It depends upon the nature of the engineered trait. Traits that enhance survival like genes for herbicide, pest and disease resistance have the potential to create new invasive weeds. All commercially grown GE crops, with the exception of one, fall into this category. Plants that are engineered to withstand environmental stresses such as drought, cold, or salt tolerance would also increase the survival of wild plants. When exposed to herbicide or to natural predators like insects, viruses, fungi, bacteria, or worms, the plants that receive the resistance genes gain a survival advantage over plants that do not. This could upset the ecological balance of natural populations. The invasion of these wild plants-turned-weeds into cultivated fields would require further chemical treatment. It doesn't seem ecologically sound for either agriculture or wild plants!

Eleven out of 18 of the world's worst weeds are also grown as crops, which means that genes are easily exchanged.

The creation of new weeds by continued use of chemicals or gene escape invites the kinds of solutions the chemical industry is eager to provide. The industry's response to the emergence of herbicide resistant weeds is to implement an integrated weed management (IWM) program. This means rotating HTCs and herbicides. For example, if Round-Up Ready soybeans are grown one year, they should be rotated with Liberty Link corn the following year. The response to the ecological risks associated with gene escape to natural populations is to design plants that are sterile and can't pollinate (male sterile corn).

Who should bear the responsibility for the ecological risks posed by introducing genetically engineered plants to the environment? Federal officials at the USDA believe that because chemical companies have an incentive to protect their investments, they will naturally bear the responsibility. Companies risk losing a portion of the herbicide market if resistance genes are transferred to wild relatives because it renders the herbicide obsoletes. But; if new weeds are created by the transfer of herbicide resistant genes, it forces the farmer to purchase other herbicides. The chemical companies can rely on the sale of traditional herbicides or offer the farmer a different seed/herbicide system for purchase. The agricultural chemical companies have an army of chemists constantly developing new herbicides and just as many molecular biologists probing the metabolism of crop plants for genes that will confer resistance.

At a time when organic farmers are making tremendous strides in providing chemical free food and corporations are increasingly held accountable for environmental destruction, why are corporate efforts and government research dollars continuing to be spent on an agricultural system that not only causes chemical contamination but threatens genetic pollution of ecosystems? Because they are primarily interested in cloning profits. In the meantime, pollen and seeds carrying new genetic information are mixing with wild populations in the biggest experiment the global environment has yet been forced to bear.

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