Environmental Risks of Genetic Engineering in Field Crops
E. Ann Clark,
Plant Agriculture, University of Guelph, Ontario N1G 2W1 (email@example.com)
presented to the NAEC workshop Factoring in the Environment for Decisions
on Biotechnology in Agricultural Production. 28 July 98, Ottawa
For clarification, I will define genetic engineering (GE) as the process of artificially moving genes among unrelated organisms (e.g. across normally impenetrable species barriers(1)), which specifically excludes conventional plant breeding or genetic improvement within a species. Genetically engineered organisms (GEO's) or entities are the products of genetic engineering, such as BT corn or herbicide tolerant soybeans. Consideration will be limited to the implications of genetic engineering on field crop agro-ecosystems, excluding livestock and medicinal aspects.
Types of Risk? The types of GE products currently or soon-to-be in the marketplace pose two kinds of risks to agriculture, to primary producers, consumers, and to the environment at large. The first is specific to what the genetically engineered organisms may do themselves, either directly or indirectly. The second concern pertains to genetic engineering as it supports, sustains, and prolongs aspects of contemporary agriculture which have been proven to be incompatible with a healthy environment. Linear thinking, which is the foundation of both genetic engineering and some aspects of contemporary agricultural practice, will be contrasted with the kind of holistic thinking needed both for the sustainability and profitability of future agriculture. An analogy will be made between the growing of GE crops and smoking, to focus the attention of producers, suppliers, and policy makers on the predictable longterm implications of GE in agriculture.
Why Bother? Now, you may think that is it unnecessary for someone like me - or you - to consider the issues of environmental risk vs. benefit from GE organisms, because after all, that is what government is doing - right? Wrong. Contrary to what farmers and consumers might assume, the federal government -via its relevant regulatory agencies - takes no responsibility for ensuring any benefit, at all, of a potential GE entity (or any other agricultural input) to anyone. Their responsibility ends with assessing efficacy (e.g. does it do what it says it will do). As a result, you should not assume that the presence of GE cultivars on the marketplace implies that any sort of risk:benefit analysis has been done by government, because it hasn't. Government doesn't involve itself with benefit, or with risk:benefit analysis.
The Regulatory Impact Analysis Statement(2) published by the Canadian Food Inspection Agency (CFIA) notes that citizens had requested that products covered under the Federal Regulatory Framework for Biotechnology "should be shown to have clearly defined benefits to the environment, consumers, and farmers before the products are evaluated." The response of the CFIA is informative:
"To institute such an approach would be inconsistent with the approaches already taken in the evaluation of agricultural products and those resulted in other jurisdictions, and thus was not accepted. Once any product is approved for commercial release, it is the responsibility of companies involved in selling their product to explain the benefits to consumers so that they can make decisions as to whether or not they will purchase the product" (N.B. emphasis added).
It is critically important that Canadian farmers and consumers understand that they must themselves take responsibility for assessing the balance between risks and benefits, and as I will present below, for assessing both risks and benefits, because government is not doing it for you.
Direct and Indirect Effects of GE Organisms
Potential effects are many, as discussed previously (Clark, 1997a, 1997b, and 1998). Three specific issues will be discussed here, with reference to the environmental assessment protocol currently in use in Canada:
I. sexual outcrossing to wild, weedy ancestors
II. horizontal gene movement, and
III. ramifying side effects.
I. Sexual outcrossing to wild, weedy ancestors. The original protocols for testing GE field crops were based on the premise of isolation - that it was possible to prevent movement of transgenes into the broader environment. We now know this to be impossible. For example, Mikkelsen et al. (1996) demonstrated the ease with which BASTA-tolerance genes could be transferred between transgenic oilseed rape (Brassica napus) and B. campestris, a weedy relative. Fertile, transgenic, weedy plants were produced after just two generations of hybridization and backcrossing. The ability of transgenic potatoes to cross-fertilize - and transfer transgenic traits - to nontransgenic potatoes has been demonstrated for distances up to 1100 m (Skogsmyr, 1994).
It could be argued, with validity, that outcrossing to weedy ancestors and relatives is essentially a non-issue in Canada (or the US), because 98% of the food crops grown in North America - and hence, their wild weedy ancestors - evolved elsewhere (e.g. maize, beans, potatoes, tomatoes, and cotton in South America, cereal grains and forages in Eurasia, rice in Asia). We are assured that one needn't worry about outcrossing if there is nothing to outcross with. Thus, it is entirely correct to state, as in Table 1:
Table 1. Clarification of national jurisdiction to Canadian decisions authorizing commercial release of genetically engineered field crop cultivars
Decision Document 97-20:
Determination of the Safety of NatureMark Potatoes' Colorado Potato Beetle (CPB) Resistant Potato (Solanum tuberosum L.) Lines ATBT04-6)
Decision Document DD96-09:
Determination of Environmental Safety of Event 176 Bt Corn (Zea mays L.) Developed by Ciba Seeds and Mycogen Corporation
Decision Document DD95-05:
Determination of Environmental Safety of Monsanto Canada Inc.'s Glyphosate Tolerant Soybean (Glycine max L.) Line GTS 40-3-2,
"The biology of potato... shows that there are no wild relatives in Canada that can naturally hybridize with S. tuberosum. AAFC therefore concludes that gene flow from NewLeafm Atlantic lines to potato relatives is not possible in Canada."
"The biology of corn...indicates that there are no wild relatives in Canada that can freely hybridize with Zea mays L. ...AAFC therefore concludes that gene flow from Event 176 to corn relatives is not possible in Canada".
"The description of the biology of G. max...shows that it is not naturalized in Canada...AAFC therefore concludes that, in Canada, ....there is no potential for transfer to wild species".
As is made clear in the wording, however, such a conclusion is limited just to the geographic territory of Canada.
Now, should we in Canada - or in the US or other nations authorizing the large scale field production of such crops - be taking at least some responsibility for what might happen if herbicide-tolerant soybeans are grown in China or BT potatoes are grown in Peru, where each crop evolved?
At least two reasons could be suggested in the affirmative:
A. The first reason is enlightened self interest. It is in our own best interest to avoid inadvertently obliterating potentially valuable genes, which could very well occur through at least two mechanisms.
B. A second rationale for Canadians to take a less parochial view on this issue would be to give a genuine foundation to the confident pronouncements recorded at the Rio Conference on Biodiversity. Biodiversity means not just spotted owls and peregrine falcons, but the whole genetic fabric that knits together and reinforces the resilience of nature - the ability of nature to respond to change, to cope with calamity, and to adjust to circumstances such as global warming. Releasing fitness-enhancing traits, such as those conferring stress tolerance or the ability to produce BT endotoxins, into the environment could have unimaginable consequences - not just for genes needed for future crop breeding but for species extinction and human health (various, in Grifo and Rosenthal, 1997; also, see below).
Consideration of these and other real-world implications should be informing GE decision-making in Canada and the US. But the federal protocol for evaluating GE applications pertains solely to the national jurisdiction. It is quite true that Canada cannot - and should not - attempt to regulate what happens in Argentina or Iran, but is it at all plausible that Monsanto and Novartis would be expending billions in buying up the global seed trade and developing GE crops if their market did not include North America?
Decisions made in Canada, the US, and Europe will unquestionably impact upon the release of GE organisms in the Third World, incurring risks such as those noted above. Is it our responsibility to consider these downstream realities before sanctioning - indeed promoting - the use of GE crops covering millions of hectares of Canadian (and US) land each year?
-----> How would you answer such a question from your son or daughter?
But the potential for horizontal gene movement into unrelated organisms, including plants and animals, is heightened by the very techniques employed to bring the transgenes into crop plants. The vectors used to carry transgenes into a new species include plasmids, viruses, and mobile genetic elements which normally have the ability to infect a particular host species and insert themselves into the cell's DNA, causing genetic change. This is a natural process. What makes GE different is that these same vectors, many of which cause tumors (e.g. Agrobacterium tumefaciens) and cancers have been specifically modified to overcome host specificity, which means that now, the same vector used to carry the transgenes can enter not just the target cell - e.g. inserting Bt genes into corn - but other species as well. This greatly broadens the potential for dissemination of transgenes into the environment, with implications which have only just begun to be examined.
According to Ho and Tappeser (1996), a database search of mainstream journals for "horizontal gene transfer" yielded 75 references between 1993 and 1996, of which all but two gave direct or indirect evidence of horizontal gene transfer(3) among quite different bacteria, between fungi, between bacteria and protozoa, between bacteria and higher plants and animals, between fungi and plants, or between insects.
As one example, Hoffmann et al. (1994) reported the movement of antibiotic resistance genes from GE-rapeseed, black mustard, thorn-apple, and sweet peas into a soil fungus Aspergillus niger, either when the crops were actually grown in the soil and or even when just the leaves of the crops were added to the soil. This means that genes can move from transgenic plants out into unrelated soil organisms, simply by incorporating crop residue into the ground.
Thus, the potential for antibiotic resistance genes (used as markers) or other transgenes to move into a much broader ecological community appears to be significant. As stated by Stephenson and Warnes (1996): "The threat of horizontal gene transfer from recombinant organisms to indigenous ones is....very real and mechanisms exist whereby, at least theoretically, any genetically engineered trait can be transferred to any prokaryotic organism and many eukaryotic ones".
The practical impact of this is that a transgenic corn, potato, or soybean plant need not have compatible near neighbors in order to transfer transgenes into the broader ecological community. It could happen through horizontal gene transfer, as from plant to soil fungi to .......? And then what?
Within the Plant? The dominant assumption of genetic engineering - that a given transgene affects one, and only one trait, and does this consistently in a new genetic background - is implausible given what is already known about genetics (see Fenstar et al. 1997 on the role of epistasis in evolution), and has, in fact, already been disproven in commercial agriculture.
In a recent ruling, the Mississippi Department of Agriculture and Commerce awarded more than $1.9 million to a group of Mississippi cotton growers who had grown Roundup Ready cotton in 1997 and lost their crop. About 25% of the 200 Mississippi farmers licensed to grow cotton complained of losses, most of whom settled out of court with those found responsible - Monsanto, Delta and Pine Land Company, and Paymaster Technology Company ("Monsanto Cited in Crop Losses" New York Times, 16 June 98).
So, what happened? The Roundup Ready genes had apparently affected not simply herbicide tolerance but also boll development itself in 20% of the sown cropland, causing premature boll drop. The transgene had affected more than one trait, and had done so inconsistently in the sown acreage. It is still unknown why some fields were affected and others were not.
Within the Agro-Ecological Community? From a wider perspective, the potential for GE to affect not simply the target organisms, such as Colorado potato beetles in a BT potato field, but to ramify out and adversely affect other nontarget organisms is essentially unacknowledged in current federal protocols for release of GE entities in Canada.
The absence of ecologically meaningful testing for environmental risk in contemporary assessment protocols is discussed by Kareiva and Parker (1995) and Rissler and Mellon (1996). The environmental impact "assessment criteria" stipulated for GE crops(4) in Canada, typical corresponding responses found in the Decision Documents themselves, as well as a critique of each, are presented below:
Table 2. Critique of criteria used to assess environmental impact of GE crops in Canada
How Addressed in Decision Documents
1. potential...to become a weed of agriculture or be invasive of natural habitats
*unmodified plants of this species are not invasive, and the GE entity exhibits reproductive and survival params within the norms for the unmodified plants, therefore, the GE entity is deemed to be not different from an unmodified plant * novel traits have no intended effect on weediness or invasiveness; therefore, the new GE entity will have no altered weed or invasiveness potential compared to current cultivars (N.B. emphasis added)
*little or no actual testing is reported; inferences are made from measurements as plant height, stem count, and vigor * no recognition of potential unintended interactions or side effects apart from the intended trait (see Stewart et al. (1997) on increased fitness of Bt oilseed rape
2. potential for gene-flow to wild relatives
*no wild relatives; no sweat
* trait confers no ecological advantage, so won't be retained in the wild
*parochial perspective, ignoring global, downstream implications * little or no testing reported; inferences are made * unaware of work of Tabashnik et al. (1997) showing that resistance to Bt was retained in target pests through >100 generations, in the absence of Bt; see also Stewart et al. (1997) showing Bt DOES confer ecological advantage
3. potential ...to become a plant pest
* the GE entity is not substantively different from the unmodified plant, and the unmodified plant is not a pest, so the GE entity will not be a pest
*ignores potential for unintended side effects, apart from the intended trait
4. potential impact...on non-target species, including humans
* the GE entity is not substantively different from the unmodified plant, and the unmodified plant is not a harmful, so the GE entity will not be harmful
* results of some type of monitoring is presented, including visual observations, of effects on beneficials - results almost invariably favorable to the GE entity (e.g. positive effect on beneficials, contrary to independent European reports)
*ignores potential for unintended side effects, apart from the intended trait (see below)
* little or no consideration of soil biota (see below)
* no apparent testing of human impact
* no consideration of horizontal gene transfer (see below)
* no consideration of ramifying effects on enemies of target pests
* no assessment of secondary pest creation
5. potential impact on biodiversity
* no novel phenotypic characteristics which would extend current geographic range
* plant pesticide could reduce insecticidal sprays and increase potential for IPM
* therefore, net effect is always neutral or positive
* ignores essentially all ecological interactions, and decades of evidence on cascading effects, secondary pest creation; see also Johnson and Gould, 1992.
Of general concern across the entire Canadian protocol are two items, the exclusive reliance on industry data from which to gauge environmental risk(5), and the heavy reliance on assumptions - many of which are already known to be faulty - rather than targeted field testing, to assess the potential for environmental risk.
Item 1. The absence of independent, objective, third party evaluation. All of the data used to make each assessment is provided by the proprietor of the GE entity, whose scientific protocols, replication, and analyses are not reported in the Decision Documents. The CFIA simply reviews and accepts the environmental risk data submitted by the manufacturer - while conducting no independent studies to check or verify the manufacturer's findings.
While reasonable, in principle, the independence and objectivity of government regulators have been challenged by recent events, including both the debacle over the dismantling of the health regulatory system in Canada in 1996 (see Michelle Brill-Edwards presentation, same workshop), and the controversy at Health Canada over several drugs, including rBST, a GE product that is injected into dairy cows to stimulate milk production
In a 29 May 98 article in the Toronto Star, Eggertson reported that top officials within Health Canada were attempting to suppress an internal report written by four scientists questioning the adequacy of data used by Health Canada to assess risks of BST to human health. The scientists had concluded that the original drug review by Health Canada had not been as thorough as required by the Food and Drugs Act. According to the report, Monsanto - the manufacturer of rBST or "Posilac" (to be sold as "Nutrilac" in Canada) - had not submitted any of the "normally required long-term toxicology experimentation and tests for human safety, nor at any time did the chief of human safety division, Dr. M.S. Yong, appear to have asked for these tests from this or any other manufacturer of rBST submissions".
As of 29 May 98, four senators, as well as the Toronto Star itself, had been refused access to the dissenting Health Canada report. On 13 July 98, one of the dissenting scientists, Dr. Shiv Chopra, received a registered letter forbidding him to speak in public about the report without first getting approval from his superiors. The original four (now six) scientists have reportedly felt so strongly about the implications of their situation that they have taken the almost unprecedented step of filing a formal grievance, which will be heard later this summer.
To private citizens, such actions render hollow the pronouncement of Margaret Kenny of the Canadian Food Inspection Agency that "if we thought there was a health and safety concern with these foods, then they would not be getting into the marketplace" (The Province, Vancouver, 27 May 98).
Item 2. The heavy reliance on assumptions and inferences rather than actual field testing for most aspects of invasiveness, potential to transfer genes - sexually or horizontally, effects on nontarget organisms (with some exceptions), and effects on biodiversity.
Apart from the economic losses which have already occurred in field crop agriculture, what evidence is available to suggest that the assumptions-based process used by CFIA is actually missing key elements in the potential impact of GE entities on the environment? Does assumptions-based assessment provide an overly simplistic perspective on potential risk, or is this much ado about nothing? Following are three examples:
Decomposition/Nutrient Cycling. One example of an overlooked risk is what happens to the active pesticidal ingredients in these GE entitites after they have done their "job". Tapp and Stotzky (1995) demonstrated that active BT-endotoxins (as are synthesized by Bt-plants) can persist for extended periods in the soil, bound to clay particles where they are resistant to breakdown by soil microbes. There is thus the potential for the accumulation of active BT endotoxins in the soil, with unknown long-term effects on soil processes. Understand that these are active toxins, rather than the inactive prototoxins which are synthesized by the original soil bacterium Bacillus thuringiensis itself, and which require solubilization and enzymatic cleavage to yield active toxins.
An additional risk is the horizontal movement of the Bt transgenes themselves into unrelated organisms, which could also
prolong the synthesis of Bt in the environment beyond the crop year itself, affecting nontarget organisms and promoting
resistance in target insects.
In a related study, Donegan et al. (1997) studied the post-harvest effects of proteinase inhibitor I - another insecticidal protein - in buried GE tobacco residues. Compared to unmodified (parent plant) tobacco residues, transgenic residues altered the species composition of the soil biota responsible for organic matter decomposition and nutrient cycling.
Evidence from this paper suggests that integration of the transgene for proteinase inhibitor I had affected not simply insect resistance - the intended trait - but also had unintended and unanticipated side-effects on plant factors affecting the processes of decomposition in the soil. Consider the downstream implications of a technology that leaves products - and genes - in crop residues that could affect the process of decomposition and nutrient recycling?
Compatibility with IPM (Integrated Pest Management). Official pronouncements on sustainable agriculture usually include something about reducing dependence on pesticides. One widely cited approach is IPM. Hence, it is reasonable to ask how inserting transgenes for pest resistance into a cultivar might affect the susceptibility of the target pest to natural control agents, as by parasites and predators. In other words, how compatible is GE resistance with IPM? And further, what effect does the interaction between GE resistance and natural control agents have on development of target pest resistance to the host plant GE resistance genes?
Published studies cited in Johnson and Gould (1992) reveal that the interaction of host plant resistance genes with natural control agents under field conditions can produce a whole range of outcomes ranging from antagonistic to additive to synergistic. In these studies, pest control could be worsened, improved in an additive way, or improved more than would be expected by simple addition of the control agents, depending on the species and environment. Thus, one cannot predict how a given transgene might affect IPM control agents, without testing.
In their own research, Johnson and Gould (1992) found that genes expressing low levels of Bt toxin in tobacco had the effect of increasing parasitism of the tobacco budworm (Heliothis virescens) by natural enemies. Thus, at least on the surface, Bt genes interacted favorably and synergistically with natural control agents, producing better pest control than would be expected from adding together their independent effects. However, subsequent analysis of their data with a population genetics model revealed that the level of synergism detected in the field trials w ould actually accelerate pest resistance to the Bt genes
So, while the initial response was favorable, the effective lifespan of the Bt genes - which is already in question - was shortened by exposure to natural pest enemies. None of these types of considerations are evident in existing federal protocols.
Toxin Transfer Among Trophic Levels. Another type of risk that does not appear to have been acknowledged is the potential for transfer of the insecticidal proteins to non-target enemies of the target organism, with potentially adverse effects on natural biocontrol agents. Independent researchers in Scotland, Switzerland, the US, and elsewhere in Europe have already published evidence of deleterious effects on survival and fecundity of organisms which have the misfortune of eating the target organisms of GE biocides (see Clark, 1997b for references), e.g.
Now, why should one worry about toxin transfer among trophic levels? Does it matter if the lifespan, fecundity, or activity of some unintended species is reduced? Yes, it does matter.
A given species of insect does not exist in isolation from other species, but rather, in a multifaceted, competitive equilibrium that is maintained by the integrative forces of all organisms interacting together. In other words, potentially pestiferous organisms are held in check by other natural control agents. A pest is not a pest until its population becomes excessive. So, what would it mean to a commercial producer if a community of insects became "unbalanced", releasing the population of minor pest species from the natural forces which formerly held them "in check"?
Linear Thinking: the Achille's heel of contemporary agriculture
Secondary pests are created by the linear thinking which characterizes much of contemporary pest management, and most especially, genetically engineered pest resistance - e.g. control the pest and the problem will be solved. For example, 24 of the 25 top agricultural pests in California were originally minor secondary members of the biotic community. They became major pest species when indiscriminant use of broad-spectrum biocides eliminated the natural controls on their numbers, allowing them to proliferate to pestiferous proportions (Van den Bosch, 1980).
This reference is nearly 20 years old, and one might be tempted to think that this is flogging a long-dead horse - like, we don't do that anymore, right? Think again.
As recently as 1995, the joint federal-state Boll Weevil Eradication Program (BWEP) applied up to 15 applications of insecticide to control boll weevil on cotton in a 200,000 ac region of Texas (Benbrook, 1996). As a result of this farmer-driven, governmentally sanctioned process(6), populations of cotton aphids, beet armyworm, and sweet potato white flies exploded, reducing cotton yield within the spray zone by 80%. A team of ARS scientists charged with determining what went wrong in the sprayed BWEP zone - as compared with the normal yields experienced in surrounding areas - concluded:
|"The (data) overwhelmingly implicate heavy pesticide usage as the primary causal factor for dramatic differences observed in pest and beneficial insect complexes. Furthermore, these differences were primarily responsible for the catastrophic crop losses experienced" (USDA, 1995, cited in Benbrook, 1996).|
Genetically engineering plant pesticides into crop plants to control a pest, whether corn borers or Colorado potato beetles, is no better and may well be worse than just applying a chemical spray. Quite apart from the development of resistance, it is entirely likely that selectively depressing one or more species within the pest community will unbalance macro- and microbiota, promoting the proliferation of other organisms to potentially damaging levels - just as occurred in the decomposition of cotton and tobacco (Donegan et al., 1995 and 1997, respectively) and in the Texas BWEP story (Benbrook, 1996).
In practical terms, this is what it means to unbalance a population of organisms. The outcome is the same, whether it is done with a spray or with a plant pesticide, because the thinking is the same - LINEAR. Nature doesn't work linearly. When we try to apply linear thinking to an "open" system (e.g. not in a sealed processing vat), Nature fights back, and remember, Nature bats last.
This is but one of the many (many) reasons why GE will not only NOT feed the world - a mantra some are fond of repeating - but will actually exacerbate global food production problems. If you have ever lived in a Third World country, you can appreciate the implications of unleashing biotic diversity on a crop.
It is therefore particularly disturbing to read in the British Times (13 July 98) that Monsanto (and others) have commissioned Global Business Access - a Washington lobbying firm that boasts a staff that includes 140 former ambassadors - to elicit the endorsement of leading Third World politicians for a major new advertising campaign. The campaign will reportedly be mounted under the slogan - LET THE HARVEST BEGIN - and will claim that slowing the acceptance of biotechnology "is a luxury our hungry world cannot afford".
Apart from its transparent inaccuracy - people are hungry for many reasons which have remarkably little to do with the lack of genetically engineered food crops - the greater tragedy in this kind of argument is that national leaders, producers, and consumers are led to believe that biotechnology is the only way to address food production problems - that there are no other alternatives. Wrong. As discussed in Clark (1998), a more holistic approach to problem avoidance could call upon a whole range of proven agronomic practices, including crop rotation and tillage, rather than solving problems after the fact with pesticides - whether chemically applied or plant pesticides.
To illustrate the commercial reality of non-chemical approaches, compare the disastrous chemical approach used by the BWEP to control boll weevil in Texas with the highly effective, agronomic alternative which was implemented for the same purpose in CA, AZ, and Mexico (G. Johnson, personal communication, 1998). Cotton growers themselves initiated this multi-state initiative to reduce the high cost of the increasingly ineffective chemicals used to control the same pest - cotton boll weevil. Starting in 1988, cotton growers were required to plow under all cotton plants and residues by a certain date, which varied with elevation and climatic regime. A six-week "host-free" period was observed each year. After three years, boll weevils were considered "eradicated" from this large geographic zone and pesticide costs had dropped from $147 to $69/acre.
The technique was so successful that neighboring states of TX, OK, and NM have now undertaken their own comparable programs. To maintain their economic advantage, cotton growers in the original zone continue to plow under residues by specified dates, although the host-free interval has been reduced to 2 weeks.
The longterm legacy of the current "all-eggs-in-one-basket" preoccupation with genetic engineering may well be the loss of a generation or more of scientific energy and producer creativity in dealing with the REAL problems facing producers today - the shrinking profit margins that necessarily pertain when inputs-based agricultural methods are used to increase yield when demand for food is inelastic (see Clark, 1997c).
Smoking and GE Crops - Concluding Comments
Before you decide to grow a GE crop next year, I'd encourage you to think about an analogy between growing a GE crop - say Round-up Ready rutabagas - and smoking.
Now, how does that relate to genetic engineering?
But unlike smoking, the harm from GE crops will persist long after the crop is dead and gone, in the form of Roundup resistant weeds and Bt resistant cornborers and Colorado potato beetles. Which leaves the grower with what choice, if s/he wants to continue growing with pesticides...........?
We as a society have decided to discourage smoking, for the public good. I would urge you to make the same personal commitment the next time you consider growing a GE crop.
Benbrook, C.M. 1996. Pest Management at the Crossroads. Consumers Union. 272 pp.
Clark, E. Ann. 1997a. A Luddite's view of biotechnology. Presented to the Select Seed Growers Annual Meeting (http://plant.uoguelph.ca/faculty/eclark/biotech.htm
Clark, E. Ann. 1997b. Risks of genetic engineering in agriculture. Presented to the National Farmers Union, Saskatoon. http://plant.uoguelph.ca/faculty/eclark/risks.htm
Clark, E. Ann. 1997c. Farming at the agriculture-environment interface. Presented to the Agroecosystem Management workshop at OARDC, Wooster, Ohio (http://plant.uoguelph.ca/faculty/eclark/ohio.htm
Clark, E. Ann. 1998. Genetic engineering: wrong answers to the wrong questions. Presented to the Ohio Ecological Food and Farm Association. http://plant.uoguelph.ca/faculty/eclark/wrong.htm
Donegan, K.K. et al. 1995. Changes in levels, species and dNA fingerprints of soil microorganisms associated with cotton expressing the Bacillus thuringiensis var. kurstaki endotoxin. Applied Soil Ecology 2:111-124.
Donegan, K.K., R.J. Seidler, V.J. Fieland, D.L. Schaller, C.J. Palm, L.M. Ganio, D.M. Cardwell, and Y. Steinberger. 1997. Decomposition of genetically engineered tobacco under field conditions: persistence of proteinase inhibitor I product and effects on soil microbial respiration and protozoa, nematode and microarthropod populations. J. Applied Ecology 34:767-777.
Fenster, C.B., L.F. Galloway, and L. Chao. 1997. Epistasis and its consequences for the evolution of natural populations. TREE 12(7):282-287.
Grifo, F, and J. Rosenthal. 1997. Biodiversity and Human Health. Island Press, Washington, D.C. 379 pp.
Ho, Mae-Wan and B. Tappeser. 1996. Transgenic transgression of species integrity and species boundaries. Presented at the Workshop on Transboundary Movement of Living Modified Organisms Resulting from Modern Biotechnology, Aarhus, Denmark, 19-20 July, 1996. http://userwww.sfsu-edu/ ~rone/GEEssays.html
Hoffmann, T., C. Golz, and O. Schieder. 1994. Foreign DNA sequences are received by a wild-type strain of Aspergillus niger after co-culture with transgenic higher plants. Curr. Genetics 27:70-76.
Ingham, R.E., J.A. Trofymow, E.R. Ingham, and D.C. Coleman. 1985. Interactions of bacteria, fungi, and their nematode grazers: effects on nutrient cycling and plant growth. Ecol. Monog. 55(1):119-140.
Johnson, G. 1998. Arizona Department of Agriculture, IPM Cotton/Organic Specialist. Personal communication.
Johnson, M.T. and F. Gould. 1992. Interaction of genetically engineered host plant resistance and natural enemies of Heliothis virescens (Lepidoptera: Noctuidae) in tobacco. Environ. Entomol. 21(3):586-597.
Kareiva, P. and I. Parker. 1995. Environmental risks of genetically engineered organisms and key regulatory issues. An Independent Report preapred for Greenpeace International.
Mikkelson, T.R., B. Anderson, and R.B. Jorgensen. 1996. The risk of crop transgene spread. Nature 380:31.
Redenbaugh, K. et al. 1994. Aminoglycoside 3'-phosphotransferase-II (alph(3')II) - review of its safety and use in the production of genetically-engineered plants. Food Biotechnology 8:137-165.
Rissler, J. and M. Mellon. 1996. The Ecological Risks of Engineered Crops. MIT Press, Cambridge.
Skogsmyr, I. 1994. Gene dispersal from transgenic potatoes to conspecifics: a field trial. Theor. Appl. Genetics 88:770-774.
Stewart, C.N. et al. 1997. Transgenic insecticidal oilseed rape on the loose. pp. 137-144 in G.D. McLean et al. (ed) Commercialization of Transgenic Crops: Risk, Benefit and Trade Considerations. Coop. Res. Center for Plant Science and Bureau of Resource Sciences, Canberra, Australia.
Stephenson, J.R. and A. Warnes. 1996. Release of genetically-modified microorganisms into the environment. J. Chem. Tech. Biotech. 65:5-16.
Tabashnik, B.E., Y-B Liu, N. Finson, L. Masoson, and D.G. Heckel. 1997. One gene in diamondback moth confers resistance to four Bacillus thuringiensis toxins. Proc. National Acad. Sciences 94:1640-1644.
Tapp, H. and G. Stotzky. 1995. Dot blot enzyme-linked immunosorbent assay for monitoring the fate of insecticidal toxins from Bacillus thuringeiensis in soil. Applied and Environmental Microbiology 61(2):602-609.
Van den Bosch, R. 1980. The Pesticide Conspiracy. cited in National Research Council (1989) Alternative Agriculture.. Ch. 2 pp 89-134. National Academy of Science, Wash. D.C.
1. It is recognized that single celled organisms may have never recognized the sovereignty of species barriers
2. Regulatory Impact Analysis Statement Environmental Assessment of Biotechnology Field Releases. Biotechnology Strategies and Co-ordination Office, Canadian Food Inspection Agency. http://www.cfia-acia.agr.ca/english/food/biotech/enviroa.html
3. Of the two that failed to find evidence of horizontal gene transfer, one came from Calgene (Redenbaugh et al., 1994),
who found that the kanamycin resistance gene used in the Calgene transgenic tomato was stable
4. in the Regulatory Directive Dir94-08: Assessment Criteria for Determining Environmental Safety of Plants with Novel Traits; Plant Biotechnology Office, Variety Section, Plant Products Division. http://www.cfia-acia.agr.ca/english/food/pbo/dir9408c.html
5. data produced either by the life science firm itself or by a separate company paid by the life science firm
6. which was, by the way, effective in controlling boll weevils
7. or may not, see economic analyses reviewed by Clark (1997a)
8. 812 of the 993 breeding objectives encompassed by transgenic field trials in Canada in 1997 (Clark, 1998)