Chakravarthi Raghavan
Geneva, 12 Aug - Genetic Engineering suggests new avenues for production of useful products and organisms, but it also poses hazards to the environment and health. Delineating these hazards is complicated and difficult, but important at every level of decision-making on risk assessment and risk-management - a process where sometimes use of scientific information is distorted by economic interests and the political contexts of decision-making.
This was a major thrust of discussions and scientific papers at a symposium on 'Genetically Engineered Organisms: Hazardous or Beneficial - How We Find Out', organized as a part of this year's annual meeting of the Ecological Society of America (ESA), at Spokane in Washington on 8 August. The symposium was jointly organized by Prof. Deborrah Letourneau of the University of California at Santa Cruz and Beth Burrows, President of the Edmonds Institute, Washington State.
The papers and discussions and related articles are to be published in a book form. But a summary of abstracts of papers at the symposium have been made available by the Edmonds Institute (Burrows contact: beb@igc.org).
The ESA in 1989 had produced an influential report, 'The release of Genetically Engineered Organisms', including ecological considerations and recommendations on the matter. Ten years later, the issue remains a hotly debated topic, and was the subject of the symposium at this years ESA meeting.
The symposium under the overall title, 'Theoretical and Practical Considerations for Assessing Ecological and Human Health Effects of Genetically Engineered Organisms', featured a variety of case studies on GEOs, covering a diverse group of GEd plants, along with a discussion of their resistance to pests and herbicides.
An overall symposium abstract said GE suggests new avenues for production of useful products and organisms, but also poses hazards to the health of the environment and the public.
'Delienating those hazards is complicated, difficult and important at every level of decision-making in risk assessment and risk management. Sometimes, the use of scientific information is distorted by economic interests and the political contexts of the decision-making,' says abstract. 'Risk assessment and risk management may be further complicated by the need to discover more or more detailed information than is usually available and by the oddities of the regulatory testing regimes that may preclude the possibility of getting timely information.'
One paper at the symposium, by Andrew Spielman of the Harvard School of Public health, discussed the problems of genetic engineering of arthropods as tools in the battle against vector- borne diseases such as malaria, but concerns about use of these types of arthropods included the possibility of the engineered insects themselves becoming pests. Spielman said that numerous research efforts now seek to develop bases for suppressing the transmission of such vector-borne human infections as malaria and dengue by releasing genetically modified, pathogen-incompetent, vector insects. Examining the prospects for the successful deployment of this technology and identifying possible risks to human health, Spielman says that success depends upon the attainment of a level of incompetence that has not yet been specified and on a non-structured distribution of wild-type and of released insects. If the released insects must be nurtured, regulatory considerations should insure that they should not transmit other infections and that they should not be pests. If a drive mechanism is to be used, the efficacy of future releases must not be compromised. If insecticide resistance is to be used to displace wild-type vector insects, future use of those or other insecticides should not be compromised. If 'Bti' toxin is to be used in transgenic plants, combinations of toxin should be presented in order to protect native 'Bti' against induced resistance in surviving target populations.
On the issue of risk assessment, a paper by Anne R. Kapuscinski of the University of Minnesota, discussed risk assessments of GEOs in ecosystems and examined the controversy surrounding these evaluations. The available guidelines, she pointed out, had some weaknesses. Kapuscinski also discussed a new Manual for Assessing Ecological and Human Health Effects of GEOs. The manual (available at www.edmonds-institute.org) produced by the Edmonds Institute, was the result of a cooperative effort between scientists and public interest organizations.
Kapuscinski said in her paper: 'That biosafety guidelines should be 'science-based' is the claim of parties seeking approval for large-scale releases and transboundary trade of genetically engineered organisms across the globe. Yet the United Nations guidelines, which set the standard during negotiations of the International Biosafety Protocol, are so vague that they are scientifically meaningless. They failed, for instance, to identify the ecological hazard posed by a transgenic bacterium and documented in the scientific literature. The authors of the 'Manual for Assessing Ecological and Human Health Effects of Genetically Engineered Organisms', Kapuscinski said reclaimed the meaning of 'science-based' by designing a process of appropriate scope covering ecology and other relevant life sciences (getting the right science) and of reliable content (getting the science right). In providing in-depth assistance on how to assess virtually any GEO in any ecosystem, we had to guard against use of the manual as a cookbook.'
In a paper, 'Variability in gene flow contributes to uncertainty in estimation of risk of transgene spread,' Terrie Klinger said that gene flow between engineered populations and their wild or unengineered relatives can introduced the GE genes into non- target populations. For crops, gene flow by pollen represents a major pathway by which engineered genes can be transferred to non-target populations.
While the average relationships between the probabilities of gene flow and the distance from a source is often described as a monotonicaly declining function, Klinger points out that the actual measure of gene flow indicate that considerable variability in distance-dependent gene flow also exists. Sources of variability in gene flow from crops include factors such as species and cultivar composition and genotype; size, density and geometry of donor and recipient populations; specific habitat and environmental variables; and mating systems, pollen vector and pollinator abundance and behaviour.
The occurrence of low-frequency, large-magnitude pollination events have now been observed in several agricultural and experimental settings, the paper says. Such events should be accounted for in the formulation of risk assessments. Reliance on average measures of gene flow could impart negative bias in the estimation of risk when variability in gene flow is high. 'Risk- averse strategies therefore should seek to minimise uncertainty by incorporating variability in distance-dependent rates of gene flow,' the paper recommends.
On the issue of 'Introgression of escaped transgenes and their ecological effects on weed populations,' Allison A. Snow of the Ohio State University, says in a paper that crop-to-wild gene flow is known to occur in many species complexes, especially when crops are broadly defined to include plants grown for forage, timber, and landscaping purposes.
'In the past,' says the paper by Snow, 'the 'escape' of genes from cultivated plants has received little attention from weed ecologists. Very little is thus known about whether weedy relatives have benefited from the acquisition of crop genes. Now, however, the pace of crop improvement is quickening due to greater use of molecular techniques, and ecologists are taking notice.'
'Soon, many cultivated plants will possess transgenic resistance to several types of herbicides, insects, diseases, and environmental stress. These transgenic characteristics will likely be inherited as dominant Mendelian traits, with little or no fitness costs.'
Summarising some recent studies demonstrating that crop genes are expected to persist in weedy populations of johnson grass, sunflower, squash, mustard, and radish, Snow said 'further research is needed to show whether suites of transgenic traits confer a strong fitness advantage to recipient weeds, and - more importantly - whether these traits could allow the weeds to become more competitive or widespread.'
Conducting field experiments to test for increased invasiveness would be difficult, in part because government regulations require containment of transgenes during pre-commercial field trials. Thus, the most relevant studies of this problem would likely take place after transgenic crops have been deregulated and long after biotechnology companies have invested heavily in their development.
In another paper, Joy Bergelson of the University of Chicago, pointed out that ecological concerns surrounding transgenic organisms include the risk of creating weedier plant populations. In order for this risk to be manifest, introduced genes must spread via pollen to recipient weeds and subsequently confer a fitness advantage.
Bergelson adds: 'Our Studies performed on transgenic 'Arabidopsis thaliana' that express a gene conferring resistance to the herbicide, chlorsulfuron, reveal an enhanced level of gene spread via pollen relative to mutants expressing the same chlorsulfuron resistance gene. Our experiments furthermore reveal a fitness advantage of resistance in the presence of herbicide. Both of these characteristics exhibit variation among transgenic lines in the fitness effects of the introduced resistance gene.'
In another paper, 'Resisting resistance: theory, practice and the barriers between', David Andow of the University of Minnesota(who is working on Bt corn) notes that transgenic insecticidal crop varieties are being rapidly developed. Although they have many advantages, including good levels of pest control, a concomitant risk is that the pests will evolve resistance to the crops. A substantial body of theory exists to provide a sound conceptual basis for management of resistance evolution, but much of it is too general to provide much specific guidance. Moreover, the ecology of many of the pests has been intensively studied, yet many of the important ecological details for effective resistance management remain virtually unknown. Consequently, resistance management is a problem in evolutionary ecology, science policy, and decision-making under uncertainty.
Bt corn, Andow says about his studies, has been transformed to express a protein endotoxin gene from the bacterium 'Bacillus thuringiensis'. Models of intermediate complexity were developed
to project the dynamics of resistance evolution in European corn borer. Measurement of population structure and local inbreeding was critical for supporting specific management recommendations. Finally, methods for measuring rare allele frequencies in field populations are being developed. These will provide a basis for adaptive resistance management. Evaluation of mating behaviour in the field has not yet been addressed, despite its recognized importance in resistance evolution. Developing effective resistance management practices has been complicated, partly because the scientific information is continually challenged and economic interests are sometimes at odds with the scientific recommendations.
In another paper, Philip J. Regal of the University of Minnesota, emphasized the social and political aspects of decision-making involving GEOs. The paper also examined the long, problematic history of 'confused scientific analysis' which in the past had led to both fear and complacency regarding the dangers of GEOs.
Regal notes that the 'biohazard' controversies of the 1970s excluded ecologists and evolutionary biologists. Molecular biologists of the 'Asilomar era' created a legacy of confused scientific reasoning, including confused reasons leading in some cases to excessive fears and in other cases to excessive complacency about the dangers of genetic engineering. Only in the 1980s did ecologists join the debates and begin a scientifically informed literature. The generic safety arguments of molecular biologists and the generic 'monster' fears of others were shown to be based on outdated or inappropriate ecological and evolutionary principles.
Ecologists were then called upon by government agencies to advise on the implications of new eco/evolutionary perspectives, and phase-outs of National Science Foundation funding by the Reagan administration for mainstream ecology and systematics were cancelled. Thorough ecological assessments remained nevertheless problematic: in many cases intellectually difficult, less than certain, and potentially expensive. So they have been resisted by industry. An urgent need for more basic conceptual and experimental work to support analysis of ecological and health risks remains. The politics and rhetoric surrounding risks and regulation became even more complicated in the 1990s with global efforts to develop an International Biosafety Protocol and with the increasing politico-economic power of transnational corporations and their increasing control over biotechnology. (SUNS4498)
The above article first appeared in the South-North Development Monitor (SUNS) of which Chakravarthi Raghavan is the Chief Editor.
Article first published 26/07/00
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