How the survival of vital food sources can be ensured

The future of humanity could lie in a large room to be hewn out of a frozen mountain just 1,000km from the North Pole over the next few months. The concreted room is to be a "doomsday vault", set in permafrost, guarded by polar bears and designed to hold seeds from all of the world's great crops, some three million samples.

The idea is that, in the event of a nuclear, climatic or disease disaster that wipes out the world's food supply, survivors will be able to track down the vault and its contents, and start civilisation afresh.

Over the past 10,000 years or so, the world's farmers have bred millions of varieties of food crops such as rice, wheat, beans and potatoes from wild plants. Most come from a handful of ancient geographical heartlands known as "Vavilov centres", after the Russian agricultural scientist Nikolai Vavilov, who first identified them. Modern industrial farming means that fewer and fewer of these traditional crop varieties survive in fields. But many are held in a network of 1,400 national and international refrigerated seed banks.

They remain valuable because their genes contain vital traits needed by plant breeders to improve modern varieties and protect them against new diseases. But many of these gene banks are poorly run. Some have lost collections when power supplies have failed. And all would be doomed by any global cataclysm that could switch off freezers for good. Hence the need for the Arctic doomsday vault to preserve duplicates of the seeds for posterity. Here are the major Vavilov centres where seeds must be saved:

WHEAT, BARLEY

Where grown Middle East.

On the hills of the West Bank and through Lebanon, Turkey, Syria and Iraq, wild ancestors of wheat and barley still grow, much as they have since the crops were first bred from wild grasses 12,000 years ago. The region is also the ancient home of the lentil, fig, date, olive, lettuce, onion, carrot, cabbage and melon.

Threat faced For every surviving ancient plant variety, with its irreplaceable store of genes to fight pests or inoculate crops against climate change, hundreds have disappeared.

How the seeds are being saved The International Centre for Agricultural Research in Dry Areas, in Aleppo, Syria, holds 24,000 varieties of barley, 30,000 varieties of wheat and 7,000 varieties of lentil. It is also home to the seeds rescued from Iraq's national seed bank at Abu Ghraib. Before Saddam's fall, Iraqi scientists shipped out their precious ancient wheat, chickpea and lentil seeds. They were wise. Following the US invasion, the seed bank was destroyed by looters.

WALNUT, APPLE, APRICOT

Where grown Central Asia. It's the original home of many of the world's fruits and nuts. In Turkmenistan, there are still wild pomegranate forests; in Kazakhstan there are apple (right) and apricot forests; in Kyrgyzstan, walnuts grow wild.

Threat faced Thousands of wild, ancient varieties have gone as farmers destroy orchards to grow wheat or opium.

How the seeds are being saved In Turkmenistan, former Soviet scientists tend orchards containing more than 1,000 uncatalogued pomegranate varieties. A farmer in Uzbekistan has one of the world's largest collections of watermelon. But apple collections in Kazakhstan and Turkmenistan are badly neglected. And Afghanistan's seed banks - containing ancient almonds, for which the country is a world centre - have all been destroyed abandoned or confiscated by warlords over the past 25 years.

POTATO, COTTON

Where grown The Andes. The first potatoes grew in the Peruvian Andes, where most varieties remain. The Andes are the original home of cotton, ancient grain crops such as amaranth, and wild tomatoes. Peanuts were first cultivated on Bolivia's Andean slopes. Threat faced Andean farmers still grow most of their old potato varieties. But many wild tomatoes no longer exist. Deforestation may have exterminated the original wild peanut; since commercial peanuts have lost their ability to fight many pests, researchers say the only hope is to find their wild ancestors.

How the seeds are being saved The International Potato Centre in Peru holds the world's largest collection of potatoes, including 200 wild and 5,000 cultivated varieties. The collection is now vital in fighting a renewed outbreak of potato blight.

CASSAVA, MILLET

Where grown West Africa. A handful of crops stand between Africans and widespread starvation. Some, like maize, are imports, but others are native. They include cassava (below), millet, beans and a rice bred independently from Asian varieties. Africa badly needs a "green revolution" to boost yields of these old crops, and the genes in many ancient varieties still survive to provide the genetic feedstock.

Threat faced Less than in many places. African farmers grow a huge variety of different crops, and they still experiment with interbreeding in their fields, and swap varieties in a way that happens nowhere else in the world.

How the seeds are being saved The International Institute of Tropical Agriculture in Nigeria is a world centre for collecting traditional African crops such as yams, cowpeas and cassava. But, in Africa more than anywhere else, the real seed banks remain in farmers' fields.

PEPPER, SUNFLOWER

Where grown Mexico. The ancient heartland of maize, the world's most widely grown crop. Also the original home of peppers, beans, sweet potatoes and sunflowers.

Threat faced About 80 per cent of traditional varieties of maize have been lost as farmers switch to high-yielding varieties.

How the seeds are being saved The world's biggest store of maize seeds, at the International Maize and Wheat Improvement Centre in Mexico City, holds 20,000 varieties, most of them no longer grown in farmers' fields. It is also a world centre for wheat, holding 95,000 varieties. A meeting at the centre earlier this year heard that many collections of maize held around the world are worthless, having been stored so badly that they will never germinate.

CUCUMBER, AUBERGINE, PIGEONPEA

Where grown South Asia. Home of long-grained rice, bred by ancient farmers from wild grasses some 9,000 years ago, as well as mango, aubergine and black pepper.

Threat faced Thousands of ancient varieties of rice have been lost already as farmers have switched to modern high-yielding varieties - an estimated 7,000 varieties have disappeared from Bangladeshi paddies alone. India is also one of the original homes of the banana, the world's most popular fruit, which is threatened by a global fungus epidemic. Breeders say traditional farmers' varieties may contain genes to fight the fungus, but many have disappeared.

How the seeds are being saved India's National Bureau of Plant Genetic Resources, one of the world's largest national collections, has more than 80,000 varieties of wheat, maize, rice, millet, okra, aubergine, ginger, sugar cane, mango, banana, citrus fruits, black pepper and turmeric.

COCONUT, RICE, SUGAR CANE

Where grown South-east Asia. Home of sticky short-grained rice varieties, along with buckwheat and soybean, the world's most-grown legume.

Threat faced Thousands of traditional rice varieties have been lost in recent decades - especially during Pol Pot's regime in Cambodia, when traditional paddies were turned over to collective farming. The new crops invariably failed, and many of the old varities had been grown only in Cambodia and were lost forever.

How the seeds are being saved The International Rice Research Institute in the Philippines houses more than 1,000 varieties of the world's favourite food. Thirty years ago, it used its huge store of ancient seeds to develop the high-yielding "green revolution" varieties that fed the world's rapidly growing population. But such was their success that many traditional varieties necessary for future plant breeding have been lost. They survive, if at all, only in the IRRI freezers.

Global seed banks

Fort Collins, Colorado, US

America's seed Fort Knox. The National Center for Genetic Resources Preservation is the world's largest gene bank and holds almost half a million samples of most of the world's major crops.

St Petersburg, Russia

The Vavilov Institute was set up in the 1920s by Nikolai Vavilov. Though some of the collections are decaying, it remains the world's second-largest seed bank. The institute holds a major collection of wheat varieties that could prove vital in fighting a new fungus called Ug99, which is spreading from Africa and threatening India's food supplies.

Kew Gardens, England

The Kew Millennium Seed Bank Project is collecting wild plant seeds from around the world rather than crop varieties. But many of these plants are the wild ancestors to today's food crops, and their genes could one day prove vital in the fight to feed the world. It currently has 750 million seeds from 14,000 species of plants, and hopes to double that by 2010.

Svalbard

The "doomsday vault". When it opens in late 2007, it will have room for up to three million seeds, and will, it is hoped, hold duplicates of all the seeds in all the world's collections - a fail-safe repository to be used only as a last resort. The vault will be owned by Norway but the seeds will remain the property, in trust for the world, of an international network of seed banks and agricultural research centres.

Fred Pearce's new book, The Last Generation, is published by Corgi, £12.99