The Use of GM Crops in Developing Countries
Case study 1: Non-food crops – Bt cotton in China and South Africa continued 2
3.34 Reductions in the use of pesticides arising from the cultivation of Bt cotton might lead to less employment for farm workers. However, recent data from the Makhathini Flats have shown that, overall, this can be compensated for by increased demand for farm workers during the harvest, because of increased yields.42 While this issue of labour is not relevant for small-scale farmers who do not employ labourers, it may require consideration in the case of larger farms. Problems could arise if farm workers are not able to obtain employment on other farms during the growing period of the crop.3.35 It is uncertain whether the concept behind Bt crops will prove to be robust over the medium to long term. It is known that pests may eventually acquire resistance to toxins.43 However, the cotton bollworm has been monitored for Bt resistance in China since 1997, and resistant mutants have not yet been reported.44 Nonetheless, resistance is likely to develop if the first generation of plants remains in cultivation for long enough. The use of refuges is one way of addressing this issue. To slow down the emergence of resistance, many regulatory schemes require that sufficient acreage of non-Bt crops are grown close to the Bt crops, to allow refuges for insects which can mate with potentially Bt-resistant insects. There is disagreement about the theoretical and practical effectiveness of refuges. Their success depends on factors such as size, spatial proximity relative to GM crops, the inheritance patterns of the trait that confers resistance to the toxin in pests, and the synchronous emergence of resistant and non-resistant pests.45 The efficacy of refuges is well documented for Bt cotton farms in Australia, where regulatory requirements have been successfully implemented.46 However, while the monitoring of refuges seems feasible for large-scale commercial farms, it may be much more difficult to achieve for numerous small-scale farms in developing countries.47 Other approaches to avoid resistance might be to use two or more Bt genes,48 or to carry out research into new insecticidal genes that could eventually take the place of Bt.49 However, at present Bt varieties have remained resistant to pest infestation for considerably longer than had initially been anticipated.
3.36 In evaluating the risks and benefits of Bt crops it is not sufficient to examine effects solely on the target species. Effective control of, for example, the cotton bollworm may lead to an increase in the numbers of other pests unaffected by Bt. These pests may then require control, which in turn might lead to increased use of pesticides. Such changes in the spectrum of pests have recently been reported in the US, South Africa and China, and require close monitoring.50
3.37 Additional problems might arise from the possibility of gene flow from Bt crops to wild relatives.51 Some fear that the introduced Bt gene may ‘escape’ from the modified plant and change the genetic composition of other plants. It is argued that this may be particularly relevant in the case of countries such as India, which is a centre of diversity for cotton. Centres of diversity often contain landraces, other cultivated crop varieties, as well as wild relatives, and possible outcrossing of Bt crops could irreversibly affect the local gene pool.52 While some argue that these and related issues simply require stringent monitoring and assessment in field trials, others doubt whether such risks should be taken. We consider questions relating to the management of gene flow in paragraphs 4.28-4.34.
3.38 Further concerns have been expressed with respect to the possibility that the use of Bt crops may lead to a decrease in biodiversity. For example, in 1999, researchers undertaking laboratory studies claimed that the pollen of Bt maize negatively affected non-target species, such as monarch butterflies. When these insects were fed milkweed leaves dusted with large amounts of Bt pollen, increased larval mortality, slower development and smaller sizes of monarch butterflies were recorded.53 However, subsequent studies have shown that the risk of acute toxicity to monarch butterflies in the wild is negligible.54 Evidence from Bt cotton field trials in KwaZulu-Natal even seems to suggest that the use of Bt can contribute to enhanced biodiversity, as increased numbers and varieties of insects and insectivorous birds were recorded in Bt fields.55
Examples of improved traits in staple crops
3.39 Cotton is a non-food crop that is grown predominantly for international trade. We now consider examples of food crops that are relevant to both subsistence and commercial farming. In many tropical areas of developing countries, two or three crops a year can be harvested. Temperatures and daylength are often more favourable to the growth of crops than conditions in temperate developed countries and best-case yields are therefore, often higher in the tropics than in highly productive areas of temperate zones.56 However, the average yield of almost all crops grown in tropical regions is significantly lower than in developed countries. This is so because poor farmers and government departments in developing countries are generally not well placed to deal with problems such as poor quality seed, salty or otherwise recalcitrant soil, environmental stresses such as drought and heat, pests and diseases, lack of fertilisers, short-term management of farm land, and inadequate control of water.
3.40 Often, substantial improvements can be achieved cost-effectively in one or more of these areas by means of better irrigation, integrated pest management, or agricultural extension services. However, these approaches have limitations. Furthermore, with regard to improved seeds, there are a number of cases where conventional, non-GM approaches have achieved little progress. For example, sorghum and maize in Africa have shown scant improvement in yield. Maize hybrids, which are high-yielding with adequate water and nutrient conditions, have proved very vulnerable to even short delays in the rains during flowering. Hence, it may be worth exploring the potential contribution of GM crops for raising ‘yield potential’ (that is, the maximum attainable crop yield from a given soil-water regime), and yield stability of crops (see paragraphs 4.20-4.27 of the 1999 Report).
3.41 We now discuss several examples of research on food crops relevant to the developing world which may contribute to increasing yield in terms of quantity and quality. The first three concern research on genetically improved traits in rice, a staple food for over three billion people, in other words, half the world’s population.57
Footnotes50 Bacheler JS (2003) Managing insects on cotton, in 2003 North Carolina Cotton Production Guide (North Carolina State University), Chptr 11. Available: http://ipm.ncsu.edu/Production_Guides/Cotton/chptr11.pdf. Accessed on: 20 Oct 2003; Joubert GD et al. (2001) South African Experience with Bt Cotton, International Cotton Advisory Committee Technical Seminar of the 60th Plenary Meeting 16-21 Sept 2001 (Victoria Falls, Zimbabwe). Available: http://www.icac.org/icac/cotton_info/tis/biotech/documents/techsem/SAexperience_tis01.pdf. Accessed on: 20 Oct 2003; Glover D (2003) Bt Cotton: Benefits for Poor Farmers? Genetically Modified Crops in Developing Countries Briefing Series Briefing 9 (Brighton, UK: Institute of Development Studies). Available: http://www.ids.ac.uk/ids/env/PDFs/Briefing9.pdf. Accessed on: 20 Oct 2003; Wu K, Peng Y and Jia S (2003) What we have learnt on impacts of Bt cotton on non-target organisms in China,
AgBiotechNet 112. 51 The transfer of genes via pollen to or from a cultivated crop to other crop plants, wild relatives, other plant species or other organisms.
52 Nester E et al. (2002) 100 years of Bacillus thuringiensis: a critical scientific assessment, at 100 Years of Bacillus thuringiensis, a Paradigm for Producing Transgenic Organisms: A Critical Scientific Assessment, 16-18 Nov 2002 (Ithaca, NY: American Academy of Microbiology Colloquium); Shiva V (2002) speech at the Soil Association’s International Sir Albert Howard Memorial Lecture 27 March 2002. Available at: http://www.soilassociation.org/web/sa/saweb.nsf/librarytitles/vandanashiva.html. Accessed on: 20 Oct 2003.
53 Losey JE, Rayor LS and Carter ME (1999) Transgenic pollen harms monarch larvae, Nature 399: 214.
54 Sears MK et al. (2001) Impact of Bt corn pollen on monarch butterfly populations: a risk assessment, Proc Natl Acad Sci USA 98: 11937–42; Hellmich RL et al. (2001) Monarch larvae sensitivity to Bacillus thuringiensis – purified proteins and pollen, Proc Natl Acad Sci USA 98: 11925–30; Pleasants JM et al. (2001) Corn pollen deposition on milkweeds in and near cornfields, Proc Natl Acad Sci USA 98: 11919–24; Stanley-Horn DE et al. (2001) Assessing the impact of Cry1Ab– expressing corn pollen on monarch butterfly larvae in field studies, Proc Natl Acad Sci USA 98: 11931–6; Oberhauser KS et al. (2001) Temporal and spatial overlap between monarch larvae and corn pollen, Proc Natl Acad Sci USA 98: 11913–8; Zangerl AR et al. (2001) Effects of exposure to event 176 Bacillus thuringiensis corn pollen on monarch and black swallowtail caterpillars under field conditions, Proc Natl Acad Sci USA 98: 11908–12; Committee on Environmental Impacts Associated with Commercialisation of Transgenic Plants (2002) Environmental Effects of Transgenic Plants: The Scope and Adequacy of Regulation (Washington, DC: National Academy Press).
55 Thomson J (2002) Genes for Africa: Genetically Modified Crops in the Developing World (Cape Town: University of Cape Town Press), p169; Head G, Freeman B, Moar W, Ruberson J and Turnipseed S (2001) Natural enemy abundance in commercial Bollguard® and conventional cotton fields, Proceedings of the Beltwide Cotton Conferences, Anaheim, California, National Cotton Council, Memphis, Tennessee.
56 For example, best-case yields for wheat have been obtained in Amritsar and Ludhiana in the Indian Punjab, and in Sonora and Sinaloa, Mexico; similarly ideal conditions prevail for rice in parts of Taiwan.
57 Lantin R. Compendium on Post-Harvest Operations. FAO. Available: http://www.fao.org/inpho/compend/text/ch10.htm. Accessed on: 20 Oct 2003.