Companion Publication Biotechnology and Sustainable Development

Chapter 4 

Agricultural Biotechnology, Biodiversity and the Environment

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Public concerns about the risks and benefits of living modified organisms (LMOs) in the environment are based on the fear that when such organisms contain genes introduced from outside their normal range of sexual compatibility, these organisms may present new risks to the environment. Present gene technology enables new and potentially useful traits to be introduced into plants, trees, microorganisms, livestock and fish. Although new strains of all have been developed experimentally, only genetically modified (transgenic) crops are in widespread commercial cultivation in the environment.  

In 2001, approximately 52.6 million ha of genetically modified crops were cultivated commercially by some 5.5 million farmers in 13 countries (James 2001). These crops were mainly genetically modified corn, cotton, oil seed rape and soybean, modified with new genes for insect resistance and/or herbicide tolerance. (Figure 1.1; Tables 1.2, 1.3).

 

Environmental Impact Issues

The issues about the impact of living modified organisms (LMOs) on the environment are about the risks and benefits of direct ecological effects and indirect environmental effects (Johnson 2000). Amongst direct effects, most concern is about the potential impact of LMOs on biodiversity, including their direct impact on non-target species. Amongst indirect effects, these effects may be the result of changing agricultural management practices, particularly those brought about by the use of transgenic crops in intensive crop management systems. There are also beneficial effects of genetically modified crops in the environment, when compared to present agricultural practices and other technology options (Carpenter et al 2002). These benefits also need to be taken into account when undertaking risk/benefit analysis of specific applications in particular environments.

In terms of international obligations, the Cartegena Biosafety Protocol of the Convention on Biological Diversity was agreed in January 1999 by over 100 countries. The Protocol states that nations have the right and responsibility to determine if the applications of modern biotechnology, in particular living modified organisms (LMOs), will have any impact on biodiversity.

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Direct ecological effects of genetically modified plants in the environment

In addressing the risks posed by the cultivation of plants in the environment, five environmentally related safety issues are often raised.  These issues are the potential for:

·    Gene transfer, meaning the movement of genes from a crop through outcrossing with wild relatives to form new hybrid plants
·    Weediness, meaning the tendency of a plant to spread beyond the field where first planted and to estabish itself as a week or invasive species 
·    Trait effects, meaning effects of traits that are potentially harmful to non target organisms.
·    Genetic and phenotypic variability meaning the tendency of a plant to exhibit unexpected characteristics.
·    Expression of genetic material from pathogens, such as the risk of genetic recombinations following mixed virus infections.

Gene flow and transfer of traits to other species: Gene transfer may be  an issue when crops are being grown in areas close to their wild relatives with whom they are able to cross naturally to form inter-specific hybrids. Natural hybridization occurs within 12 of the world’s 13 most important food crops and their wild relatives (the exception being banana since cultivated banana is infertile) (Table 4.1).

Natural hybridization may occur at low frequency when pollen blows or is otherwise transported from crops to wild relatives in the vicinity. Recent research confirms that genes introduced into some genetically modified crops may move  into related native species at low frequency. The difference from natural hybridization is that genes inserted into GM crops are often derived from other phyla, giving traits that have not been present in wild plant populations. The ecological concern is that these genes may change the fitness and population dynamics of hybrids formed between native plants and related GM crops, eventually backcrossing genes into the native species. The importance of pollen transfer from GM crops to wild relatives is not that it occurs but whether the resulting hybrids survive and reproduce and introgress genes back into the native population, and whether these have any negative environmental impacts.  The issue is not so much the rate of gene flow  rather the impact that this might have on agriculture and the environment (Johnson 2000).

Weediness:  Some concerns are that GM plants could have negative impacts on natural ecosystems by increasing weediness by two routes. Firstly, the GM plants could establish self-sustaining populations outside cultivation themselves. The concern is that these plants may become invasive weeds that out compete wild populations and thus lead to further decreases in biodiversity in native plant habitats. Weeds having tolerance to a range of herbicides could also emerge. Secondly, novel genes from GM crops could be introduced into their wild relatives by pollen spread and the survival and reproduction of the resulting hybrids. This may have negative impact on the wild plant population if new genes are introgressed back into the wild plant population. For this to happen, the new genes must increase the plants’ fitness to survive and reproduce in the wild. 

Transfer of certain genes, such as resistance to insects, fungi and viruses may increase fitness (ability to reproduce) of any resulting hybrids. If hybrids acquired insect resistance from GM crops, they could damage food chains dependent on insects feeding on previously nontoxic wild plants. It is possible that "foreign" genes introduced accidentally from GM crops to crop/native plant hybrids would decrease their fitness in the wild, leading to rapid selection of these genes out of the population.

Trait effects: Trait effects are the effects of traits that may be harmful to non-target organisms. For example, plants modified to produce pesticidal proteins such as Bt toxins may have both direct and indirect effects on populations of non-target species. One group of Bt toxins primarily targets Lepidoptera (butterflies and moths, particularly the European corn borer) and the other affects Coleoptera (beetles). The effects of Bt toxin-producing plants on non-pest species amongst these insect groups may vary widely, depending on the sensitivity of different insect species, the concentration of Bt toxin in the transgenic plants and environmental conditions.

For example, laboratory experiments demonstrated that the larvae of Monarch butterflies (a relative of the European corn borer) were susceptible to pollen from Bt corn when ingested in large amounts. Subsequent field experiments in several locations in North America found that there were no significant differences between Monarch butterfly survival in areas planted with Bt corn and those planted with conventional crops grown under current agricultural practices. Ecological studies published by the US National Academies of Science also show that presently cultivated strains of Bt corn pose little risk to Monarch butterflies (Zangerl et al 2001).

Genetic and phenotypic variability: Genetic and phenotypic variability is the tendency of a plant to exhibit unexpected characteristics in addition to the expected characteristics. This trait is well known from conventional breeding, but becomes an identifiable hazard if the variability leads to one of the other biosafety issues, such as greater weediness or greater tendency for outcrossing in the genetically modified organism.

Expression of genetic material from pathogens: Another potential hazard is the possibility of recombination of a virus gene expressed by the plant with genes from another virus infecting that plant. This risk is similar to the risk of genetic recombinations following mixed virus infections, which also occur in nature.

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Indirect environmental effects of genetically modified plants

Genetically modified crops and agricultural intensification: effects on biodiversity: The management of some genetically modified crops is likely to differ from conventional intensive agriculture or organic farming.

The use of more effective pesticides (including herbicides) over the past 20 years has been a major cause of the decline in farmland birds, arable wild plants, and insects in several European countries. The more widespread use of broad-spectrum herbicides may accelerate this trend. This may be of more concern in Europe where farming, wild landscapes and wildlife habitats are in closer proximity to one another than in other areas with more broad-scale agriculture, such as North America and Australia (Johnson 2000).

Besides the aesthetic and scientific reasons for conserving biodiversity within and around agricultural crops, there is another important utilitarian reason for doing so. This is the possibility of losing the food chain links between native species and crop systems. This link is vital to preserve the early warning function of biodiversity, whereby damage to feeding species (eg birds) signal warning of dangers in food crops or the chemicals used to manage them (Johnson 2000). .

There is evidence accumulating that the use of GM crops with insect resistance is reducing the volume and frequency of pesticide use on cotton, corn and soybean in North America (Carpenter et al 2002). Similar transgenic crops are also having demonstrable beneficial effects on human health in China and South Africa (Pray et al 2000.

The future development of new crops with improved tolerance to abiotic factors (such as drought, salinity and frost) and the advent of ‘pharmed’ crops that may be used to produce vaccines and industrial products, may also change crop management practices. These new crops may either increase or decrease demand for arable land in the long term. They may also put further pressure on natural biodiversity when crop cultivation extends into presently marginal lands, or into areas not presently used for agriculture. For example, salt tolerant rice may be able to be cultivated in coastal areas where mangroves presently grow, with resulting ecological changes in land and water use and associated plant and marine life.

Biotechnology can also contribute to the characterization and conservation of biodiversity. Increasing the productivity of crops can reduce pressure on biodiversity by reducing the need for agriculture to move into forests and marginal lands.

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New scientific developments

There are some promising new developments in R&D that may assist in the design of future genetically modified crops that would have clear benefits to the environment and that would mitigate some of the environmentally damaging effects of agricultural intensification (Johnson 2000). Some R&D challenges for the future might include: 

·  Securing fungal resistance in adult plants by switching on resistance genes that are active in the seed, but not currently in adult plants.

·  Achieving insect resistance by altering physical characteristics of plants, perhaps by increasing hairiness or thickening the plant cuticle.

·  Altering the growing characteristics of crops, for example by shortening the growing season or changing the timing of harvests, offers the prospect of allowing more fallow land and less autumn planting.

·  Using new discoveries from functional genomics to identify useful genes within species, and understanding how better to regulate them to control useful traits. This approach will place more emphasis on the control of genes already existing within species rather than on inter-specific gene transfers, especially those that require gene movement  amongst distantly related species.

The greater understanding of the environmental risks and benefits posed by gene technology may lead to the better design of future genetically modified crops. For example, where gene flow is a risk in out-crossing crops growing in their center of diversity, close to wild relatives with which they may cross, it may be possible to include genetic mechanisms of pollen incompatibility to limit the risk of gene flow. Also, where crops are to be used for industrial purposes to produce products such as vaccines, or industrial polymers, the crop of choice should be one with which there is no risk of gene flow to related edible crops or wild species in the area of cultivation (Johnson 2000).

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Future ecological research needs

There is a need for further ecological research and developing agreed standards and protocols to enable the continuing monitoring of the behavior of genetically modified crops after their experimental (small-scale) and commercial (large-scale) releases into the environment. There is a need to set up effective monitoring systems to detect gene transfer and research to assess its ecological impacts. Most of the present research has been undertaken in Europe and North America. Little has been undertaken in tropical environments, which are the centers of diversity of most of the world’s major food crops (Table 4.1).

Such ecological research will require additional support by national governments and international agencies in their efforts to develop methodologies and undertake participatory field studies on the environmental impact of GM crops. These assessments should be undertaken using participatory approaches so as to involve local communities in the evaluation of the risks and benefits of new technologies.

Additional data would then feed back into risk assessments, so as to inform future decisions on the decisions on the appropriate technology choices in addressing specific problems, including the development and management of genetically modified crops for agricultural purposes.

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Future role of the international agricultural research centers

There is a need for greater science-based understanding of the risks and benefits in the applications of biotechnology in agriculture and the environment. The international agricultural research centers supported by the Consultative Group on International Agricultural Research (CGIAR) may have an important role to play here. The centers represent a unique resource in addressing these issues, as they constitute:

·  The world’s largest collection of plant genetic resources and their wild relatives held in trust by the Centers. 
·  A geographically dispersed network of research centers, located throughout the world’s major agro-ecosystems, and across the centers of diversity of the world’s major food crops. 
·  Data and research capability in the use of geographic information systems that could be used to model and evaluate the likely behavior of living modified organisms in different environments and assess the risks and benefits associated with particular traits in those environments.
·  Research capabilities in the applications of gene technology to crops, livestock, forestry and fisheries, and associated socio-economic, policy and management expertise.

Further information and references

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