There, at the end of a tunnel 120 metres (390 ft) into the side of a mountain, 80 metres above estimated sea levels even if all polar ice melts, and 18 degrees Celsius (-0.40F) below freezing, they will stay like a bank security deposit.

"It will be the best freezer in the world by several orders of magnitude. The seeds will be safe there for decades," said Cary Fowler of the Food and Agricultural Organisation's Global Crop Diversity Trust.

"Svalbard is a safety backup -- and we hope we never have to use it."

The Norwegian government is footing the US$5 million construction bill and the Global Crop Diversity Trust is providing the estimated US$125,000 a year running costs.

"We are going back to the older varieties because that is where you find the largest genetic diversity ... and diversity is protection," Fowler told Reuters in London.

Svalbard will not find and sort the seeds. That is being left to the various seed banks around the world in the front line of the battle to protect biodiversity.

The function of the Arctic Noah's Ark will be to hold samples of all the food crop varieties in case disaster strikes any of the banks -- like the typhoon that wiped out the Philippines agri crop gene bank in October.

It will also ensure a pristine source of research material for the world's botanists struggling to create crop varieties that will be able to withstand the massive changes in rainfall patterns and temperature that may come with global warming.

NEW VARIETIES

The scientists from around the world predict that global average temperatures will rise by between 1.8 and 4.0 degrees Celsius this century due to human activities, putting millions at risk from rising sea levels, floods, famines and storms.

"Current crops are adapted to the current climate. Start changing that and you change everything," Fowler said. "Plant breeders will have to be designing totally new varieties."

"We already have a water crisis with agriculture and climate change will make it worse. It is not a simply matter of migrating crops northwards. Everything changes -- sunlight, temperature, insects, diseases, pollinators," he added.

He said the Svalbard seed collection would not include modern hybrid varieties because by and large they had genetic diversity bred out of them.

But it would also not rule out genetically modified organisms on the simple grounds that it would be virtually impossible to screen them out and in any case they would never amount to more than a tiny fraction of the total.

The vaults on the remote archipelago 1,500 km north of the Arctic Circle should have been dug and lined with metre-thick concrete by October ready for systems installation and a formal opening early in 2008.