Arctic ice to house doomsday seed vault

It is impervious to global warming, would survive a nuclear winter or an asteroid impact and is guarded by polar bears. And if catastrophe does engulf the planet, it might just save humanity.

Norway announced detailed plans yesterday for a repository for the world's agricultural diversity. The "doomsday vault", as it has been nicknamed, will hold 3m seeds be built 120 metres into the side of a frozen mountain on a remote Norewegian island. "Every day that passes we lose crop biodiversity," said Cary Fowler, executive director of the Global Crop Diversity Trust, which will co-fund operation of the vault. "We must conserve the seeds that will allow agriculture to adapt to challenges such as climate change and crop disease."

Construction begins in March and should be completed by September. The task of filling it with seed samples will begin soon afterwards, but the official opening will not be until around March 2008.

The remote site on Svalbard, inside the Arctic Circle, was chosen partly because it is perpetually frozen at between -4C and -6C. So even if cooling units that drop the temperature to -18C fail, the seeds will not germinate. If global warming raises air temperatures significantly, the permafrost at the heart of the vault will stay frozen. Designers have also planned for the possibility that sea levels could rise significantly due to climate change. The entrance to the vault is 130 metres above sea level, so a rise of seven metres resulting from potential collapse of the Greenland ice sheet would pose no threat.

Scientists consider such a rise highly unlikely, but even the very worst case scenario of a total meltdown of Antarctica leading to a 61-metre rise would leave the vault intact.

The vault's entrance is deliberately conspicuous with a striking triangular shape and reflective panels to catch the summer midnight sun. "In winter it will emit a quiet glow so that you can sense it in the landscape," said project manager Magnus Bredeli Tveiten. "We have been very conscious about giving this a design that will signal its identity and importance."

But to keep the £1.7m facility tamper-proof the concrete lined tunnel to the pair of vaults at the core will have a series of reinforced doors. There are also no windows and the site will be under continuous video surveillance.

The UN food and agriculture organisation estimates that 75% of the genetic diversity of global agricultural crops has already been lost.