The ‘Doomsday’ Svalbard Global Seed Vault is nearing one million seed samples after nearly 50,000 samples from around the globe were deposited Wednesday in an effort to safeguard the world’s food supply.

The vault, which opened in 2008, is housed in Svalbard’s Plateau Mountain, on a group of islands located off the northern coast of Norway near the North Pole. Often referred to as the ‘Doomsday Vault,’ the sub-zero bunker was designed to protect seed crops in an apocalyptic event.

The vault, which is managed and operated by the Norwegian government, Global Crop Diversity Trust and the Nordic Gene Bank, received the latest seed deposit on Wednesday from a dozen different countries “despite a backdrop of geopolitical volatility.”

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“Today’s seed deposit at Svalbard…shows that despite political and economic differences in other arenas, collective efforts to conserve crop diversity and produce a global food supply for tomorrow continue to be strong,” Crop Trust executive director Marie Haga said in a statement. “Together, the nations that have deposited their seed collections account for over a quarter of the world’s population.”

Crop Trust executive director Marie Haga scans boxes of ICARDA’s seeds returning to Svalbard after being withdrawn from the vault in 2015. Andrea Gros/ICARDA

Among the seeds sent to the vault for the latest deposit are samples returning from Syria’s agricultural system. In 2015, war-torn Syria was the first country to make a withdrawal from the vault to replace seeds in a gene bank near Aleppo that had been damaged as result of the war.

According to Reuters news agency, samples of wheat, barley and grasses suited to dry regions were requested at the time. The seeds had been requested by the International Center for Agricultural Research in Dry Areas (ICARDA), Reuters reported.

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According to ICARDA, the seeds from the Aleppo collection have traits resistant to drought, which could help breed crops to withstand climate change in dry areas from Australia to Africa.

The seeds were then moved to Morocco and Lebanon so ICARDA could continue replicating the seeds in “safer locations,” according to Crop Trust. A portion of the seeds were returned to the vault on Wednesday.

Why the need for such a vault?

It’s the final back up, as Crop Trust puts it. The vault acts as a kind of insurance policy for the other seed banks and acts as a fail-safe for the food supply of future generations. The vault holds a backup copy of seeds that can be used after a natural or man-made disaster occurs and wipes out agricultural resources.

How many seeds can the vault hold?

According to Crop Trust, the ‘Doomsday Vault’ can house 4.5 million varieties of crops, which contains on average 500 seeds of each variety. Following Wednesday’s deposit, 930,821 seed samples are housed in the vault.

This is a March 2. 2016 file photo of the interior of the Svalbard Global Seed Vault. Heiko Junge/ AP Photo

How are the seeds stored?

As for the seeds themselves, the samples are stored at -18C and are “sealed in custom made three-ply foil packages” which are then placed in boxes and stored on shelves.

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Crop Trust explained that the vault’s low temperature and moisture level allows for the seeds to stay useable for “centuries, or in some cases thousands of years.”

In this photo taken Sunday, Oct. 18, 2015, shows the door to the Global Seed Vault, keeping the temperature inside the vault at -18C, in Svalbard, Norway. AP Photo/David Keyton

The vault has a “black box” system

The vault works on a so-called “black box” system which means that the country or organization that deposits the seed samples still own and control the samples. They are also the only ones that can access and withdraw the seeds.

Why is the vault built on an island 1,300 kilometres from the North Pole?

According to Crop Trust, part of the reason Svalbard was selected for the vault’s location was its climate and permafrost. The vault is located 120 metres into the mountain “ensuring that the vault rooms will remain naturally frozen” in an event the electrical system fails. Essentially the frozen terrain acts as a “fail safe” mode to keep the seeds viable.

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Official opening of the Global Seed Vault in Svalbard, Norway. Hakon Mosvold Larsen via AP

The entire length of the bunker, from the front door of the mountainside to the back of the vault is nearly 146 metres. Each vault is about 10 metres in width, six metres tall and about 27 metres in length.

Some of the samples deposited in these rooms this week include potato, sorghum, rice, barley, chickpea, lentil and wheat.

–with a file from Reuters.