GRAIN The spectre of climate change has been increasingly haunting newspapers, environmental conferences, and diplomatic negotiations the world over. Because of its truly global nature and its outrageous complexity, trying to manage the future of the earth's atmosphere by regulating our own activities on this planet is perhaps the most daunting challenge science and society will have to face together in the immediate future. "Climate change" refers to the complex transformations in weather patterns due to the heating up of our atmosphere -- known as "global warming" -- which is caused by a build up of carbon dioxide and other gases in the atmosphere (see box). Most of these gases -- e.g. 85% of the carbon dioxide -- are produced by industrialised countries, due to energy production using fossil fuels and transport. The greatest producer of carbon dioxide is the United States which releases twice as much per person as Western Europe, ten times as much as the average for India and China, and over 100 times as much as the poor countries of Africa. However, it is likely that the poorest people in the poorest countries and their agricultural systems will suffer most from the effects of climate change. According to World Bank President Barber Conable, speaking at a meeting in Tokyo last December, "The poor will be the hardest hit, because they have the least resources with which to adapt to any change." Some studies of global warming predict simultaneous crop failures in all those regions now considered breadbaskets of the world. The diversity of genetic resources will become even more important in meeting the challenge of food production under new climatic conditions. But on the other hand, the process of climate change itself will become yet another cause of genetic erosion and destroy much of the remaining diversity that nature still has to offer. THE GREENHOUSE EFFECT Gasses around the earth act like a giant greenhouse, keeping the earth warm. Sunlight passes easily through, but the heat radiated back from the earth is, to a large extent, retained. We now produce so much carbon dioxide and other "greenhouse gases" that the system has been thrown out of balance, and the earth is heating up at a rate faster than any time in the last 100,000 years. This is global warming. Other greenhouse gases include methane, nitrous oxides and CFCs (chloro-fluro-carbons). A team of international scientists working at the UN Intergovernmental Panel on Climate Change estimate that average temperatures could rise by 4.5 degrees Centigrade by the year 2050. This is nothing short of phenomenal compared to past variations in global temperature. It will lead to a rise in sea levels as the polar ice caps melt and the seas expand. Weather patterns will change and while it is impossible to predict the exact nature of these changes, there is no doubt that the effects of global warming would be devastating. TROPICAL PLANTS LOSE OUT? The increase of carbon dioxide in the atmosphere will also certainly have an effect on plant growth through changes in photosynthesis and metabolism. Most temperate crops like wheat, rice, soybean, cowpea, cotton and barley -- the so-called C 3 plants -- are projected to benefit from increased carbon dioxide with growth increases of up to 50%. But tropical crops like maize, millet, sorghum and sugarcane -- C 4 crops which have a different metabolism -- will hardly benefit from increased carbon dioxide levels. These effects, however, may well be outweighed by other alterations in climate. "We do have the technology and skills to save the majority of plant species in the world. It is a matter of politics if we choose to do so!" G.L. Lucas, Kew Gardens, speaking at an EC-sponsored conference on biological diversity, Dublin, 1987. Agriculture: The Greenhouse in Action Our uncertainties about magnitudes and effects of global warming stem from our near total ignorance about how the many complex elements of the climate interact. However, the general scenario foresees that sea levels will rise by as much as 1.5 meters in the next 50-100 years, flooding coastal areas and destroying wetlands. This alone could be disastrous, as one-third of the world's current population lives in low-lying coastal areas. Bangladesh could lose almost 20% of its habitable land by the year 2050. Egypt is predicted to lose about as much of its arable land around the Nile delta. The Netherlands would be totally infiltrated by salts, while large cities like Miami, Bangkok and Taipei would have to protect themselves with bulkheads and levees. It is also generally suggested that Northern latitudes will grow warmer and wetter while arid regions, including Mediterranean climates, suffer increased drought. Global warming could have its most dramatic effects on agriculture. Temperature rises will change rainfall and evaporation patterns. What will happen where is uncertain but experts generally point to two possible shifts: in Europe and North America, we will see Mediterranean areas shift northward, as places like Canada, Iceland, Finland and upper regions of the Soviet Union experience wetter winters and warmer summers. Current Mediterranean climates could grow drier and cooler. The wet tropics may grow wetter while the arid and semi-arid tropics, spanning many parts of Africa and Asia, are claimed to be under great threat of increased drought, as the climate becomes drier and rainfall patterns ever more erratic. Thus the very centres of genetic diversity are in the zones most susceptible to changes in climate patterns. These predictions owe a lot to speculation but imply enormous modifications that world farming could undergo. The first logical question is how cropping patterns might change. In the North, maize and soybean production could shift to higher latitudes. In the Saskatchewan region of Canada, for example, the growing season could be extended and the ripening period of popular spring wheat varieties reduced by up to 2 weeks. But because of the interplay of precipitation and mid-summer heat waves, Canadian farmers might be faced with a new, two-part growing season more favourable to winter wheats and maize. Likewise, the area under barley production in Finland could virtually double. Japan's rice stock might also increase substantially, as Hokkaido enjoys warmer weather, exacerbating surpluses of their particular javanica rice that has a limited export market. In the South, where arid regions may grow drier, and moist regions even wetter, drought tolerant crop types like millets, sorghum, maize and Vigna will have to better compensate for scantier moisture availability. Deep water rices might maintain production in low lying areas of several Asian countries. According to M.S. Swaminathan, President of the International Union for the Conservation of Nature and Natural Resources (IUCN), the same greenhouse factors that promote rice production in the South could harm wheat production, particularly in India. The Role of the Greenhouse Genes Despite these uncertainties, it is clear that resource management, farm practices and government policies will have to adapt quickly to such far-reaching and profound transformations. The cornerstone of our capacities to adjust agriculture to these extreme changes will greatly rely on genetic resources and the breeding of new crop types. Never before has the strategic importance of genetic diversity taken on such proportions, as the new challenges provoked by climate change will be global, fast arising and unpredictable. Agriculture will have to adapt to new complex factors. Alterations in available water, heat and sunlight will not only affect plants. Crop pathogens, soil structures, predators and animals will also change under the new ecological conditions. Just because it seems the Sahel will grow drier does not mean we simply need to improve on drought resistant crops. Unforseen pest adaptations to drought conditions and new diseases could arise as well, so it could prove necessary to breed resistance to these threats into new crops as well. As well, while the combination of rainfall and temperature modifications could render northern regions of the North more suitable for growing southern crops, soil types and local biota might well confound any such simple shift. Weather can have profound effects on crop pathogens. Around 1980, unusually cool and damp weather spurred on the outbreak of a blue mould epidemic in the US and Canada's tobacco fields, costing North American farmers over $240 million in losses. The disease rapidly moved south and nearly decimated Cuba's cigar crop, with reported losses of 90% of the harvest. Korea also suffered a temperature-related epidemic of rice blast in 1980, which severely struck that crop and forced the Koreans to import a lot of rice. The weather-inspired pathogen was so damaging because, according to T.T. Chang, Director of the International Rice Research Institute's gene bank, three-quarters of Korea's rice area were sown to modern, "high-yielding" varieties that were nearly genetically identical. The complexity, unpredictability and speed of such changes combined obviously forces us to develop priorities for genetic resource conservation and devise breeding programmes to incorporate new characteristics into crops for sustained and improved production. What we conserve is largely a matter of subjective choice determined by available resources and production goals. Conservationists from IUCN or WWF (World Wide Fund for Nature) might argue that is it necessary to preserve as much as possible, that all genetic resources have potential value and should be actively protected. They are firm advocates of in situ conservation where plants can evolve in their natural ecosystems. On the other side of the dividing line, the International Board for Plant Genetic Resources (IBPGR), which spearheaded the ex situ genebank movement, argues that priorities and limitations must be set in collecting efforts. But the ex situists disagree amongst themselves as to whether or not enough genetic resources have already been collected. In a recent conference on the subject of "Climate Change and Plant Genetic Resources", Trevor Williams, ex-Director of IBPGR, pleaded that "Neither habitat degradation nor climate change should be used as an argument to amass huge collections of wild relatives simply because they are thought to be valuable." His colleagues Ford-Lloyd and Jackson from the University of Birmingham, which trains gene bank people for IBPGR, are a bit more cautious. They argue that wild collections are in fact under-represented in gene bank collections as well as diversity from specific regions like arid or Mediterranean zones, which should provide useful resources in face of climate change, especially for forage crops. Williams and company do concur, though, and in a frightening manner, that we cannot predict what kind of resources we would need. Without even questioning the status of what is being stored today, they revert to ludicrous suggestions of how breeders will have to react. For Ford-Lloyd and Jackson, "The immediate response (to climate change) in terms of crop production may well be to move existing cultivars about, as in a game of chess." Regarding oil crops, they talk about "juggling" with current varieties around the changing regions of the globe to spare global warming breeding efforts. It all sounds like a plant breeding casino where crop varieties are scrambled and relocated along the lines of Russian roulette: Egyptian wheats should work in Finland, Surinam rice will be better for the Chinese, Mozambican maize could be transferred to Iowa and let's see what happens. Despite tacit understandings that the two methods are complimentary, the in situ / ex situ war is bound to rage again, as both camps are on the attack. The ex situists point to climate change as the ultimate proof that conservation is cheaper, safer and more effective in static conditions. They score out global warming as a sure source of destabilisation of ecosystems, thereby undermining the very logic of "vulnerable" in situ reserves. Further still, they now have biotechnology to fill in the conservation gaps where certain types of crops could not be stored as viable seed for any long period of time. With in vitro methods and cryopreservation (liquid nitrogen), it is now possible to put any type of genetic material into "deep sleep". Whether it can ever wake up again is another matter. The in situists, however, are rolling up their sleeves and have a lot to argue in favour of trying to safeguard earmarked plant material in biosphere reserves and other types of setups despite and because of the climatic changes pending upon us. Global warming threatens wild resources, the relatives of our crops, especially in arid zones of the Near East and Mediterranean region which are the centres of diversity of many important cereals, pulses, fruits and vegetables. Severe droughts could wipe many wild species but it might also facilitate the evolution of increasingly better drought resistant genotypes among them. It depends on the rate of climate change and whether or not resistant strains can evolve. Aside from the raw material that breeders need to provide adapted crop types for new conditions, debate is open as to how fast conventional breeding can respond. It is argued that with temperature rises of 0.1% per annum, breeders should be able to keep up with climate change and churn out new cultivars within current time periods of 10-15 years from first cross to the farmer's fields. The role genetic engineering could play is probably rather limited. Tissue culture can certainly help diminish plant multiplication time, but the factors that will need to be bred for are so complex that the single-gene approach of biotechnology will be of restricted value. It is one thing to screen for drought resistance genes; it is quite another to adapt the many factors that influence root activity in drought-stricken soils. The greenhouse crisis may bring back into the forefront the structural, ongoing genetic resources management crisis. As climate models grow more precise and people grow aware of the potential problems, stronger public pressure should be brought to bear on how we are managing genetic diversity and for whose benefit. In the 1980s, it became clear that capital-intensive agricultural development models and the plant breeders that made monoculture possible were undermining their own resource base: genetic diversity. The same is now being said about global warming as we face yet another major threat primarily of our own making. The two crises conjugated could be disastrous for the future of world food production especially in the developing countries, which have fewer resources to adapt to rapid changes. It is imperative that concerted action be undertaken to slow down the buildup of greenhouse gases, and that we come to terms with how we are to manage our biological resource base of the future. SOURCES AND FURTHER READING: Ø The literature on global warming is already plethoric, mostly in the form of magazine/newspaper articles and conference proceedings. Much information for this article was derived from the press clipping service of the International Organisation of Consumer Union's (IOCU) "Consumer Interpol Memo". The Consumer Interpol Memo disseminates news on health and safety issues to participants in IOCU's Consumer Interpol programme. For further information contact: Consumer Interpol Coordinator, IOCU Regional Office for Asia and the Pacific, P.O. Box 1045, 10830 Penang, Malaysia. Ø Quotes taken from M. Jackson, B.V. Ford-Lloyd, M.L. Parry, editors, "Climate Change and Plant Genetic Resources", Belhaven Press, London, 1990; and M.S. Swaminathan, "Genetic Manipulation in Crops -- Scientific, Social, Economic and Ethical Implication", in "Review of Advances in Plant Biotechnology, 1985-1988", CIMMYT/IRRI, 1989.