Hunger is a political not a production problem, writes Julia Hinde.

At the launch of the United Nations conference on sustainable development in Johannesburg, South African president Thabo Mbeki called for a new world order in which prosperity was shared, saying that "the survival of the fittest only presages the destruction of all humanity". The conference, which ended on Wednesday, touched on various areas of development, but how to tackle the problem of hunger in many of the world's poorest countries was high on the agenda.

Previous conferences have also sought to tackle one of the world's most intractable problems. But despite good intentions such as the pledge by 186 countries at the 1996 UN World Food Summit to halve the number of undernourished people by 2015, the situation in countries such as Malawi, Angola and Zimbabwe seems to be worsening. Indeed, the UN Food and Agriculture Organisation believes that the 1996 target is unlikely to be met. Despite all our world's technical advances, we appear unable to feed ourselves. In sub-Saharan Africa, for example, according to the International Food Policy Research Institute (IFPRI), a third of children continue to go to bed hungry and "have their mental and physical development compromised by the ravages of hunger".

Of course, people have gone hungry throughout history. Perhaps the earliest mention is the biblical story of Joseph in which famine grips the land now called Palestine. People have also been trying to understand patterns of hunger for centuries. In 1798, clergyman and scholar Thomas Malthus suggested that while food production grew arithmetically, population grew at a geometric rate and hence outstripped the means of production, which inevitably limited population growth. Development theorist Esther Boserup, writing in 1965, was more upbeat. She suggested that demographic pressure promoted innovation and higher productivity and, hence, in contrast to Malthus, argued that food production could keep pace with population growth.

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In his 1981 book Poverty and Famines: An Essay on Entitlement and Deprivation , economist Amartya Sen shows that famine has occurred in recent history even when the supply of food was not significantly lower than during previous famine-free years. He challenged the view that food shortages are the most important explanations of famine. Some 20 years on, most scholars agree that there is sufficient food to feed the world population of 6 billion, with many countries producing food surpluses. Hunger is not a simple production issue.

The green revolution of the 1960s, 1970s and 1980s, which involved the introduction of high-yielding varieties of plant, in addition to fertilisers and pesticides, saw significant increases in production in some developing regions. Artificial fertilisers had been introduced in the 1950s but scientists found that they made traditional wheats grow so tall they fell over. American agricultural advisers working in Japan after the second world war identified dwarf wheat varieties that were brought back to the US and formed the basis of the plant breeding associated with the green revolution. These plants, as well as not falling over, put less photosynthetic effort into producing stems and more into grain production. A similar cross-breeding programme was undertaken with rice. As a result, the number of malnourished people has dropped from 1 billion in the 1970s to 800 million today, a decline from 37 to 18 per cent of world population.

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But increased productivity has not been felt in every developing geographical region, nor uniformly for everyone within each country. Sub-Saharan Africa, for example, has tended - perhaps because of the distinctiveness of crops and farming methods - to miss out on technical developments. As a result, per-capita output has declined since the 1960s, with associated hunger.

Tim Dyson, professor of population studies at the London School of Economics, suggests that widespread political instability, ethnically heterogeneous nation states, neglect of agriculture by governments and extremely rapid population growth are also to blame. Even within individual nations, there can be both food surpluses and hunger. India, for example, has tens of millions of tons of stored cereals, yet is home to one-third of the world's hungry.

These people, explains Jules Pretty, professor of environment and society at the University of Essex, are hungry "because they are poor". They do not have access to food nor to the resources to buy food. What is needed, he says, are the right sustainable, pro-poor policies. With between 70 and 75 per cent of the world's hungry in rural areas, says Per Pinstrup-Andersen, director-general of the IFPRI, the best approach is to increase productivity on small-scale farms by giving farmers access to whatever tools they need. Others stress the need for strategies to increase economic growth and improve health and education for the poor in both rural and urban areas.

While strategies to end hunger focus on such political and geographical solutions, science still has a role. World population is predicted to rise by 33 per cent to 8 billion by 2030 and will coincide with increased urbanisation, an ageing population in some areas, and changing tastes. People will consume more meat - a less efficient use of cereals - as economic prosperity grows. In addition, water scarcity, soil degradation and climate change, which could cause desertification, could affect farmers' production capabilities.

Anthony Trewavas, professor in the Institute of Cell and Molecular Biology at the University of Edinburgh, and Oxford University's Christopher Leaver argue that over the next 50 years, food production will have to double or triple on the same area of land, with decreasing water supplies and without damaging the environment. "If we keep technology at 1993 levels, to feed people in 2025 we will have to plough up another 800 million hectares of forest," Trewavas says. "But we don't have huge new lands."

He argues that further improvements in agricultural technology are needed to increase crop yields.

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Over the past 20 years, new understanding of how cells and organisms work has revolutionised plant science. Where conventional plant breeding relies on crossing similar species to bring about hybrids with desired traits and is constrained by the traits already contained within a species and its close relatives, scientists can now select one or more genes from a species and transfer them directly into another species. They can even take genes from other organisms such as bacteria and introduce them into plants.

This technology allows scientists to, for example, make specific plant processes more efficient by introducing genes to improve yields. Or they can introduce genes to increase resistance to pests and pathogens, which kill 40 per cent of crops, or to abiotic stresses such as heat and drought.

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Worldwide, 44 million hectares of transgenic crops were grown in 2000. This first generation of transgenics, under cultivation mostly in the US, but also in significant quantities in Canada, Argentina and China, has involved relatively straightforward manipulation of single genes to confer resistance to herbicides and insect pests. But it has caused huge controversy in Europe, where consumers are seen to benefit little and where there are concerns for the environment and human health. The worldwide environmental pressure group Greenpeace, for example, opposes all releases to the environment of genetically modified organisms.

The balance of benefits and risks may be very different for transgenic crops in the developing world, says Gordon Conway, president of the Rockefeller Foundation, a US charity that over 15 years has put $100 million (?65 million) into plant biotech research. He calls for a doubly green revolution "that repeats the successes of the old but in a manner that is environmentally friendly and much more equitable". The Rockefeller Foundation estimates that of the $2.5 billion spent on research and development biotechnology for agriculture, just $75 million is spent in the developing world. This new revolution, he says, should include applying modern biotechnology "to help raise yields, to produce crops resistant to drought, salinity, pests and diseases, and to produce crops with greater nutritional value".

Perhaps the most interesting genetic achievement so far has been the introduction of genes that produce beta-carotene - the precursor to vitamin A - into rice grains. Beta-carotene is present in the leaves of rice plants but conventional plant breeding has been unable to put it into grain. Scientists in Zurich have done this using one bacterial gene and two daffodil genes, producing a rice plant - Golden Rice - with the potential to provide sufficient beta-carotene to meet human vitamin A requirements. About 150 million children in the developing world lack vitamin A, leading in some cases to permanent blindness and even death.

Inserting specific genes through genetic engineering can achieve in a few years what could take decades with traditional plant breeding. Florence Wambugu, one of Africa's leading plant geneticists, who is working on a biotech solution to sweet potato virus, has suggested that genetic modification may also work better for Africa than green revolution technologies because all the technology to control insects is packed within the seed. There is no need to educate farmers on the use of fertilisers. She is concerned that antipathy to genetic modification in Europe, where transgenic crops are not needed, could stall its introduction in Africa.

Again it becomes a political issue. For Pinstrup-Andersen, what is lacking is not understanding of how we can end hunger but the political will to do it. "Those in power don't have malnourished children," he says. "They are not giving food a high enough priority."

Mary Warnock, Janet Radcliffe-Richards and Martin Rees will be speaking at a panel discussion on the Big Questions in Science , chaired by Nancy Cartwright, at the BA Festival of Science at 2pm on 12 September 2002.

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The Big Science Questions is published by Jonathan Cape on October 3.

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