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Vol. 10 No. 3 - July 2004

Environmental Impact of Genetically Engineered Crops

By: C.R. Bhatia

Cultivation of food crops began ten thousand years back when humans discovered that the cereal grains they have been collecting from natural stands could be grown in their own backyards. Since then, contemporary knowledge and tools have been used to select the plant types most suited to the human needs. Selection of easily threshing wheat, non-shattering rice, cobs of maize, and fruits with large edible parts are some of the well-known examples. Genetic modification of crops continues even in the most primitive tribal populations. They select the best cobs of maize, and ears of sorghum and millets, and hang them at the entrance of their houses. Domestication brought about large changes in morphological, physiological and biochemical characters by indirectly selecting them, though the process was slow. Rediscovery of the Mendel’s laws of inheritance in 1900, and the birth of the science of Genetics, provided knowledge based plant improvement, and the rate of change accelerated. Hybridization to combine the desired characters from different accessions, exploitation of hybrid vigor, development of polyploids, and amphiploids, induction of mutations, chromosomal translocations using radiations and chemical mutagens added new tools, and further hastened the pace of change. However, in all these methods the genetic manipulations were made at the cell level, and selection was based on the phenotype. In the mid 1970’s it was discovered that the isolated genetic material (DNA) can be cut at defined sites using specific restriction enzymes, cloned, and the desired DNA sequences (genes) can be introduced into the resident genomes, and expressed. This process of precisely manipulating the genetic material at molecular level is known as the recombinant DNA (r-DNA) technology, or as genetic engineering. The new techniques also made it possible to directly select for the presence or absence of the gene(s) and not on the phenotype as in the past.

First such plants expressing a bacterial antibiotic resistance gene were produced in 1983. Since then, a large variety of plants expressing genes from microbes, reproductively isolated plants, animals, and even human genes have been developed. Thus the gene pool available for the improvement of crop plants has been enlarged to include the genes available in the entire biodiversity. Further, the existing genes can be modified at molecular level or new genes can be synthesized. Such plants are popularly referred as Genetically Modified Organisms (GMO’s). Crop plants developed using classical methods of selection, hybridization and mutations are all genetically modified, and hence, the terms Genetically Engineered Organisms (GEO’s) clearly differentiates them on the basis of the technique used for their development.

Soon after the development of GE plants, and the possibilities of their large-scale cultivation, the scientific community expressed different viewpoints illustrated by the following quotes:

“Genetic Engineering represents a radical break from evolutionary history.” - Rissler and Mellon (1993)

“Molecular biologists are making an end run around nature’s restrictions, mixing genes from many distantly related species of organisms to provide progeny that nature would never allow” – Giampietro (1994)

“Crops modified by molecular and cellular methods pose risk no different from those modified by classical genetic methods for similar traits” – NRC (1989)

“Genetic Engineering is nothing more than a simple extension of traditional plant breeding” - OECD (1993)

          It is pertinent to recall that:

  • Most people are apprehensive of things that are new, not experienced by them earlier – the fear of the unknown.

  • New technologies have always been controversial – vaccination introduced by Edward Jenner, and pasteurization of milk are the classical examples.

  • All technologies have some adverse effect on environment. Even food gathering, and hunting, practiced by humans before the dawn of agriculture, was detrimental to the environment and biodiversity.

  • Growing of crops, and animal husbandry was possible only after clearing the natural vegetation from large areas of land, and consequent loss of biodiversity.

  • All technologies have certain risks, and benefits. Humans have learned to minimize, and control risks, and to maximize the benefits.

  • The real risk, and human perception of risk varies. Most people believe that flying has a higher risk than travelling by road, but the statistics show that it is the other way.

Environmental Risks from GE Crops

Environmental risks perceived from large-scale cultivation of GE crops are:

  • Increased invasiveness.

  • Development of new, more virulent strains of viruses on transgenic virus resistant plants.

  • Effect of toxic, transgenic products from insect, and pathogen resistant plants on non-target organisms.

  • Overcoming the resistance mechanism of the transgenes by insect pests leading to more virulent insect biotypes.

  • Transfer of antibiotic resistance genes, used as selectable markers in the process of developing transgenics, to other organisms.

  • Safety of food items obtained from transgenic crops – allergic reactions.

  • Gene flow to other crop cultivars, traditional varieties, land races, wild, weedy related species leading to the loss of biodiversity.

  • Long term effects.

  • Non-foreseeable effects on ecosystems.

          The possibilities of the above-mentioned risks cannot be ruled out on the basis of scientific knowledge. The risk-benefit analyses consider the probability of the occurrence of risk, and the overall benefits of the technology. Out of the above, except the gene flow, the probabilities of their occurrence are extremely low. Moreover, if any transformation events lead to such adverse changes they will be identified in early generation testing, and during biosafety evaluation. While the GE crops were widely accepted in US, the environmental groups in Europe started determined campaigns against the GE crops. Believers in the God’s creation of life say that “humans have no right to tinker with the genetic material which is the creation of God”, and “GE is against nature”. These ideas found wide support in public. At the same time green political parties gained considerable clout in Europe and became part of the ruling coalition Governments. Socio-political and commercial issues underlying the resistance to GE crops in Europe are very different. Human populations are stable or declining in many countries, crop productivity is high with excess production of most farm products, produced by their heavily subsidized farmers. In contrast, population is growing in India, and most developing countries of the world, and average purchasing capacity is low. Additional land can be brought under cultivation only after clearing the already low forest cover, and hence, increased production must come through enhancing the productivity of the existing farmland. GE crops though grown in 18 countries over an area of 67.7 million ha in 2003 is one of the most controversial, and hotly debated issue. People opposing globalization, privatization, multinational companies and new technologies view GE crops as a symbol of all the above, and a means of exploiting the farmers in poor countries.

Biosafety regulations

          Biosafety regulations were first brought out in the USA to find science-based answers to the possible risks. Since then a large number of countries have evolved their own regulatory mechanisms for conducting experiments with GE plants, their field evaluation and commercial cultivation. In India, rules for the manufacture, use, import, export, and storage of GEO’s, the Ministry of Environment and Forests framed cells and plants under the Environment Protection Act in 1989. Based on the recommendations of the Recombinant DNA Advisory Committee, the r-DNA safety guidelines were issued in 1989 by the Department of Biotechnology. They were revised in 1994, and more detailed guidelines for transgenic crops were issued in 1999.

          Three level of approvals is followed, first the Institutional Biosafety Committee (IBSC) that approves and oversees the GE research within the Institute / Company. At the second level is the Review Committee on Genetic Manipulation (RCGM) that permits and oversees contained as well as small plot (one acre) field experiments. The design and layout of the field experiments is approved by RCGM that also appoints Monitoring and Evaluation Committees (MEC) to visit each of the field experimental sites and report to RCGM. At the third level Genetic Engineering Approval Committee (GEAC) functions under the Ministry of Environment and Forests Large-scale field experiments, and final approval for commercial production are authorized by the GEAC. Besides the above, there are State Biotechnology Coordination Committees for each state, and District Level Committees (DLC) in each district (county), mainly to ensure implementation of the biosafety guidelines.

General Consensus Among Scientists

          Some common issues in safety evaluation have emerged for which there is widespread agreement in the scientific community. The Ecological Society of America has also included them in their position paper on GEOs in 2004.

  • The environmental benefits and risks associated with GE crops should be evaluated with appropriate baseline – GE versus conventional crop.

  • The risk is dependent on the trait, and not on the method used for developing such cultivars.

  • Each crop-gene combination, and transformation event, should be evaluated independently.

Leading Science Academies of India, China, Brazil, Mexico U. S. National Science Academy, the Royal Society, London, and the Third World Academy of Science after considerable deliberations brought out their common report on GE crops. Others have also considered the ethical, and socially sensitive issues such as transfer of animal, and human genes into plants the public acceptability for which would vary in different societies. The food safety issues were also extensively examined among others by the British Medical Association, their 2004 statement says that the safety concerns for GE foods apply equally to other conventional foods.

Genes Versus Genomes

          Out crossing is ubiquitous even in highly self-pollinated plants. Occasional out crossing and consequent gene flow is a means of enlarging the genetic diversity of the species. Out crossing between cultivars of the same species, cultivars to wild, weedy relatives and vice versa happen all the time when they grow nearby (Sympatric populations). It has been a matter of concern in the seed production programs, and appropriate measures have been evolved to minimize the pollen flow into seed production plots. GE crops do not differ from the traditional crops in this respect. However, some environmental scientists have projected scenarios to scare the public, even going to the extent that GE crops will destroy biodiversity, and the land races will be lost forever. Gene flow can only enhance biodiversity by enlarging the gene pool, it cannot destroy it. Genomes (complete set of genes) are constantly changing even in nature due to mutations and recombination. In the past, the whole genomes with about 30,000 genes each, as per the recent estimates, have been introduced as food, fruit or ornamental crops with no apparent damage to local biodiversity. Potato, tomato, tobacco, chillies, groundnut, maize, tetraploid cotton, soybean, rubber are introduced crops extensively grown in the country. Similarly many introduced species of fruit and agro-forestry trees, and ornamentals (Bougainvillea) are grown all over the country. Botanical gardens claim with pride the new exotic species they have introduced. All such introductions of new genomes have not caused any appreciable harm to the local biodiversity, how the introduction of few genes can destroy biodiversity? Of course, precautions are necessary in dealing with herbicide resistance – natural or engineered, and other such characters for which there is no previous experience. Identification, management and plans for mitigation of environmental risks should be well thought out and investigated in parallel with the development of GE crops.

Conclusions

          GE crops, approved for cultivation by the regulatory agencies, are as safe as any other conventionally bred cultivars for human consumption, as well as for the environment. Occasionally they may transfer their genes into other cultivars in the neighboring fields or wild related species through out crossing, like other cultivars. Cross-pollination, even in highly self-pollinated species, is part of the nature to enhance biodiversity. It occurs in the natural stands of the ancestral species of the crops, and has been going on between the cultivated and their related wild species since domestication.

Dr. C. R. Bhatia is former Secretary, Department of Biotechnology, Government of India, New Delhi. e-mail: neil@bom7.vsnl.net.in

The first transgenic plants in India were developed at BARC.


This article has been reproduced from the archives of EnviroNews - Newsletter of ISEB India.


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