Two main concerns about the effects of genetically-modified food plants on the environment are that the new plants will become pernicious weeds or that they will transfer their new genes to wild relatives or similar crops growing nearby with unforeseen effects. A great deal of research has been carried out by ecologists to determine whether or not these worries are likely to be substantiated. This is one of the major reasons for carrying out field trails of GM crops.
Evidence from thousands of field trials suggests that the new plants will behave just like the varieties currently in cultivation. There is also evidence to suggest that the transfer genetic material from transgenic crops to their wild relatives or unmodified plants occurs, although the frequency of such transfer and its significance is still debated.
The ecologists involved in such work have emphasised the need for caution and the importance of case-by-case analysis (in other words, it is difficult to generalise about the impact of GM crops).
A further concern is whether plants with introduced genes that enable them to resist insect attack will quickly lead to the establishment of resistant populations of pests. Because of the intense selection pressure (favouring naturally-resistant individuals) that crops carrying for example, Bt genes will exert, refugia of susceptible plants are usually grown alongside transgenic crops. Indeed, this has been a legal or voluntary requirement in the USA and Australia where transgenic, insect-resistant cotton has been grown. To date, there have been no confirmed cases of resistant populations developing, but it is generally accepted that without measures such as the limited use of a range of pesticides and the use of refugia, resistant pest populations will certainly develop. With this in mind, in January 1999, four major producers of Bt maize plants (Monsanto, Pioneer Hi-Bred, Novartis, and Mycogen-Dow AgroScience) proposed that 20% of farmland should be set aside for non-transgenic crops when Bt maize is grown.
There are also concerns, expressed by English Nature, the RSPB and others, about the wider impact of GM crops on farmland wildlife.
Food safety: marker genes
The current generation of genetically-modified organisms sometimes contains 'marker' genes. These are short, easily-detected sequences of DNA put there so that the researchers can tell which organisms have taken up the introduced genes. Among the questions that regulatory authorities have asked are whether the marker genes permit their recipient to make a new protein and if so, what levels of that protein (if any) would be expected in the food. Could that protein have any unwanted effects? Finally, is it at all likely that the marker gene could be transferred to other organisms such as microbes in the intestine of the consumer?
The Food Safety Unit of the World Health Organisation and a working party of the OECD has looked specifically at the safety issues associated with marker genes in plants that are to be consumed as foods. The need for marker genes was accepted and the impracticality of removing these genes (at present) was recognised.
The marker genes in plant varieties approaching commercialisation are restricted to two markers that break down specific antibiotics and a few herbicide tolerance markers. The presence of marker genes per se (the DNA itself) in food was not thought to constitute a safety concern. There is DNA in abundance in almost all the food we eat, but no recorded evidence for the transfer of genes from plants to microorganisms in the gut or to any other living things (including humans).
However, the recent introduction and approval of maize with a bacterial marker conveying resistance to the antibiotic ampicillin has raised new fears, particularly in the European Union. Recent scientific advice has suggested that as a precaution, the use of antibiotic resistance markers in commercial crops (rather than in contained research) should be phased out, and this is indeed happening.
Both the possibility of DNA transfer and the production of proteins from marker genes, and their possible effects, are considered on a case-by-case basis by the regulatory authorities in the USA and Europe.
Changes in farming structure
Biotechnology has the potential to affect world agriculture dramatically. Although great benefits may come, it has been suggested that there might also be accompanying disadvantages. Several of these disadvantages are no different to existing trends in world agriculture, such as the shift towards larger farms and more capital-intensive farming systems. This tends to favour, for example, wealthy farmers in the Northern hemisphere who can invest in new technologies rather than those in the impoverished South. In the developed world, there are concerns about over-production of food, although these worries are unlikely to be shared by those countries where the growth in population far outstrips the capacity of farmers to provide sufficient food. Biotechnology, alongside other changes and technologies offers a realistic prospect of long-term sustainable agriculture to farmers in the Third World. At least, this is the finding of several recent independent investigations into the topic (see 'Publications').
Plant breeding methods have produced plants with greatly improved characteristics compared with the old cultivars. Biotechnology might encourage the production of a far wider variety of new crops, increasing biodiversity. Modern agriculture has been so successful in increasing the yield of food that farmers in the USA and Europe are paid to take land out of cultivation or to grow new crops, again increasing diversity. Because it has the potential to reduce waste, biotechnology may accelerate this trend.
The opposing argument is that plant breeding will increasingly fall into the hands of just a few companies, and that the plant varieties they offer to the farmer will be correspondingly reduced. This could make crops more susceptible to attack by pests and diseases, and lead to a reduction in the use of important old cultivars and their wild relatives.
However, biotechnologists depend upon the genetic resources of the World for their raw materials, and thus have a vested interest in maintaining biodiversity. The techniques of plant tissue culture are already used to help maintain rare and endangered plant species. Some argue in favour of patents on living organisms as they might allow Third World countries to obtain payment for the use of their genetic resources. Provisions for such payments in the 'Biodiversity Treaty' of the Brazil Earth Summit are widely thought to be one reason that the USA refused to sign this treaty at first.
Animal health and welfare
Classical animal breeding has done much to improve the productivity and well-being of farmed livestock. Changes in characteristics such as maturity, fecundity and the distribution of muscle tissue are noticeable in many modern breeds compared with their wild ancestors and old domestic breeds.
The majority of features in livestock are controlled by many genes, each with a small effect. Just which genes should be altered to improve animal productivity or health is therefore difficult to predict and the modification of animals by genetic engineering is still in its infancy. This area requires very careful consideration. Developments in livestock production that compromise animal welfare are increasingly unlikely to be accepted by regulatory authorities or the public. There are currently no products of animal biotechnology in food shops, nor do we know of any proposals to introduce them anywhere in the world. Several retailers in the UK already have specific policies regarding biotechnology and animal welfare.
In the immediate future, most benefit is likely to come from the development of new diagnostic agents, vaccines and therapeutic agents for veterinary medicine.
Agriculture in Europe and North America already produces sufficient food for the indigenous population. Looking to the future, the real benefits from improved animal production might be seen in the Third World. For example, it may one day be possible to introduce disease resistance into otherwise vulnerable animals. There are well-advanced animal genome projects which parallel the successful mapping of the entire human genome. The Bovine Genome Project could result in, for instance, resistance to trypanosomiasis being introduced into more productive breeds of cattle from their naturally-resistant African counterparts.
If the numerous surveys that have been undertaken in Western Europe are to be believed (and there is no reason to think that they are inaccurate), the vast majority of the population here does not wish to consume GM food.
The first GM product in Europe (the Zeneca tomato purée) presented no problem in this respect, as the cans were both clearly-labelled and always offered alongside a similar non-GM product. The problem arose when GM food ingredients that are traded as bulk commodities entered the market. First GM soya, then maize started to be grown in the USA and traded internationally. This presented UK retailers, who had planned carefully for the introduction of the tomato purée, with an unforeseen problem.
Initially, the amount of GM maize and soya grown was very small, forming just a fraction of the total US harvest. It was impossible, with GM and non-GM material being mixed after harvesting, to devise a statistical sampling regime that would reliably permit the detection of the GM material in bulk shipments. UK retailers therefore assumed that GM material would be present in any maize or soya obtained from the USA, and labelled their products accordingly. The major retailers prepared leaflets, that were available to shoppers, explaining this decision and the reasons for it. This unavoidable decision fed right into the hands of anti-GM campaigners, who claimed that up to 65% of processed food sold in the UK was made with GM ingredients -- and the food packets in the shops seemed to bear this out. Consumers were being denied a choice. Newspaper articles and even entire books were devoted to lists of GM-containing and GM-free products, although they were often rather misleading.
As the proportion of GM soya and maize on the world market increased, food producers and retailers tried to obtain certified non-GM material. In August 1999, the UK firm Marks and Spencer estimated that the cost of obtaining crops that were segregated at source added 10-15% to the cost of the food sold in their shops.
Within a few months, however, all of the major UK food producers and retailers had obtained GM-free material, aided by lists of suppliers prepared by the (then) Ministry of Agriculture, Fisheries and Food. The GM-free material was routinely tested using the sensitive PCR method which is, in theory, able to detect as little as one molecule of DNA. The very sensitivity of technique caught out some producers who had unwittingly incorporated GM material into their products, but in fact the levels detected were usually below those (1%) which would at that time have triggered the necessity under UK law to label the products. [The level of 'contamination' permitted in the EU has since been lowered to 0.5%. This figure compares with 5%, which is the permitted level of 'contamination' of organic produce with conventionally-grown crops. And of course, unlike GM material, there is no way of detecting such non-organic 'contamination'.]
Today the situation is rather different. Almost all food in the shops is non-GM and it could be argued that it is those who would wish to buy GM food who are being denied a choice. It seems very likely that producers and retailers will continue to obtain certified non-GM material to meet consumer demand. The 2003 EU labelling regulations are now even stricter than before, and consumers will definitely have a choice about whether or not they eat products of modified crops.
The new problem is whether, if GM crops are to be grown commercially in the UK, organic farm produce will be compromised. Pollen from GM crops, spread on the wind and by insects, could find its way in organic fields and beehives. At least in the UK, there probably aren't any genuinely organic beehives. Bees range over too wide an area to be able to guarantee they have foraged only on organic sources. There is debate about this, and one large-scale Scottish beekeeper believes his product to be organic due to the isolated nature of his operation (he supplies the 'Duchy Originals' range). But for the rest of the country, the predominant use of non-organic crop husbandry precludes the description 'organic' being applied to honey and bee products.
The distances required to prevent pollen transfer between crops are the subject of controversy and disagreement, although such measures have been commonplace in conventional seed production for many decades. Transfer is likely to occur, but given stringent separation distances some claim that it should be possible to limit the range and degree of any spread.
It remains unclear whether those who oppose the commercial production of GM crops because of potential 'contamination' do so though a fundamental opposition to GM technology, or for well-founded concerns for the status of organic farming.