The genetic diversity of our agriculture is rapidly vanishing, leaving our crops prone to pest and plague Rob Edwards, Stuttgart
IN the middle of the last century, about one million people starved to death in Ireland because the potato crop failed. The potatoes were wiped out by a pandemic of Phytophthora infestans, commonly known as blight, which rotted the crop. The potato was Ireland's staple diet. The harvests of 1845, 1846 and 1848 failed completely. Many Irish people died or emigratedmostly to America. Now there are newer, more dangerous breeds of potato blight. A new strain of the disease, R infestans A2, hit potato crops in Europe, Asia and Latin America in the 1980s. In 1992, the most virulent version of blight so far was discovered in Mexico. By 1994, it had spread to North America, where it was named R infestans US-8. P infestans US-8 overpowers the genes that have been bred into potatoes to resist blight. No known fungicide can harm it. It rapidly mutates to combat new resistance genes or fungicides. "While large-scale starvation seems unlikely, at least here in the northern hemisphere, millions of dollars in crops are threatened, and many people could become destitute," says Gail Schumann, professor of plant pathology at the University of Massachusetts. It is the threat of a 20th-century version of the Irish potato famine that lies behind this year's attempts to conserve the genetic diversity of the world's food. In June, 150 governments meeting in Leipzig agreed a global emergency plan to stem a dramatic fall in the diversity of agricultural plants. In November, heads of state will meet for the first World Food Summit in Rome running at the same time as the UN Convention on Biological Diversity in Buenos Aires. But developing countries and Third World groups fear that without funding from richer nations, much of the world will go hungry. Food crops made up of only a handful of genetically distinct varieties are vulnerable to disease, pests and severe weather. As well as the potato, genetically uniform crops of wheat, maize, sugar, banana and clover have been severely damaged in recent years. In 1970, a new breed of leaf blight wiped out 15 per cent of the maize crop in the US. Ten years later, more than a million tonnes of Cuba's sugar crop were destroyed by cane rust. And the production of bananas in Central America was nearly halved in the 1980s by a fungal disease, black sigatoka. The UN Food and Agriculture Organization (FAO) has recently completed the most comprehensive assessment of the world's plant genetic resources. The conclusions of its recent 336-page roundup of detailed reports from 154 countries were bleak: the world depends on too few crops. Many thousands of genetic varieties have been lost, and a million more will die out unless urgent action is taken. The FAO says that there are about 30 000 edible plants in the world, 7000 of which have been grown or collected for food. Cultivated over thousands of years, many crops developed a huge genetic diversity. Potatoes last century were white, yellow, red, blue and black-inside and out-and small communities in the Andes can still grow 178 varieties. One species of rice-Oryza sativa-has 100 000 distinct varieties. Today, however, the world depends on a small number of crops and a shrinking range of genetic varieties. About 95 per cent of our protein and calories come from 30 crops. More than half of our energy intake from plants is derived from only three crops: wheat, rice and maize. A single genetic strain of wheat-Sonalike-was grown on 67 per cent of wheat fields in Bangladesh in 1983 and 30 per cent of Indian wheat fields in 1984. A report from the US's National Academy of Sciences in 1991 said the country's main crops depended on fewer than nine varieties. The FAO warns that European barley's resistance to mildew could be wiped out "in a single evolutionary step" because it depends on one gene and one fungicide. "We must learn to diversify our crops," says Schumann. "This is something scientists have been saying for years, but the message doesn't seem to be getting through."
The genetic diversity that agricultural plants have evolved over thousands of years has withered in this century. Since 1903, the US has lost most of its 20 000 varieties of agricultural plants (see Diagram). China told the FAO that in the 1970s it had a thousand strains of wheat in production, compared with 10 000 in 1949. Four-fifths of maize varieties have been wiped out in Mexico since 1930. The FAO says "the spread of modem commercial agriculture" is the main cause of the current gigantic loss of diversity. More than 80 countries re port that a wide range of locally grown varieties are being replaced by a few profitable alternatives from abroad. Seeds, instead of being cultivated by peasant farmers, are being supplied in bulk by multinational companies such as Pioneer, Sandoz and ICI. The world's response to this crisis has been to set up an international network of gene banks using refrigerators to conserve threatened seed varieties. But the FAO's report reveals that in many countries the refrigerators are in such a poor state that a million of the plant varieties they contain are threatened with extinction (This Week, 27 April, p 5). More than half the world's 1300 stores are "perhaps incapable at pre sent of performing the basic conserva tton role of a gene bank", says the FAO. However, the most important prob lem is that frozen seeds gradually lose their viability. Every ten years or so, most varieties must be regenerated by planting them out. But the process of germination, cultivation and collection is tabour intensive and expensive. Many gene banks, including those in Germany, India, Brazil, Korea, Ethiopia and the US, are not regenerating enough seeds because they are short of staff and money. Some countries also told the FAO that more effort should go into the traditional method of conserving seeds-by cultivating them on farms. In the run-up to the 150-nation conference in Leipzig, the FAO drafted a Global Plan of Action to save plant genetic resources. A section on financing estimated that between $1 billion and $3 billion would be needed over the next decade to upgrade gene banks and enhance conservation on farms. One of the first decisions of the delegates in Leipzig was to scrap the entire section of the plant. Developing nations argued that it was an underestimate of the likely cost, while developed countries were anxious to avoid any commitment to extra funding. In a long series of late-night private meetings in Leipzig, delegates from the south pleaded in vain with Japan, Europe and the US to provide more money. "In the current economic climate we cannot offer any more," one member of the British delegation told New Scientist. "But it is hard to convey that to the developing countries." The text eventually agreed at Leipzig does little more than reiterate the promise made by the developed nations at the Earth Summit in Rio de Janeiro four years ago to provide "new and additional funds". It also urges countries to "make every possible effort" to provide financial support. These lukewarm formulas left many delegates from developing countries disappointed. "We did not get all that we wanted," says Lim Eng Slang, head of the Malaysian delegation. According to Third World groups, the Global an of Action is now "hanging in a financial void". Miges Baumann from Genetic Resources Action International in Barcelona argues that it has not taken the world any further forward. "If there are no funds for the Global Plan of Action, there is no way all its nice suggestions can be implemented," he says. Cary Fowler, until last month head of the FAO's secretariat on plant genetic resources, is irritated by these criticisms. He says that specific funding commitments were never on the agenda at Leipzig, but will be considered in December at a meeting of the FAO's Commission on Genetic Resources in Rome. "The Leipzig conference is not the end of the process, it is probably closer to the beginning," he says. In one sense, Fowler has to be right. The plan agreed in Leipzig will also be conveyed to the World Food Summit in Rome in November, an unprecedented gathering of world leaders aimed at reducing food shortages. The draft plan prepared by UN officials for the summit says that unless the causes of hunger are tackled by governments, nearly 700 million people will still be chronically undernourished in 2010. The draft plan, available on the Internet, talks vaguely of the need to "promote the conservation and sustainable use of the diversity of species and genetic resources for food production". One of the many reports produced by UN organisations for the summit argues that food supplies must increase 75 per cent by 2050 to feed an extra four billion people in the world. But, as at Leipzig, the richer nations will not want to make any concrete commitments to extra funding. The influential American pressure group, Rural Advancement Foundation International, describes the summit as a holding operation. The group's spokesman, Edward Hammond, says: "Anyone who thinks that a food summit convened at this point in history will be an unfettered offensive against hunger is not living in the real world."