I’m standing in a bomb-proof vault. Its reinforced concrete walls are designed to withstand floods, radiation and even a direct hit from an aircraft.
The underground stronghold is wired with alarms and automated systems. Yet I’m not surrounded by cash, gold or jewels, but something far more valuable to humanity: seeds.
This is the Millennium Seed Bank (MSB), which sits beneath the wild botanical gardens of Wakehurst in Sussex, UK – a site managed by the Royal Botanic Gardens, Kew.
The true figure is unknown, but the scientists who work here estimate there are over 6.6 tonnes of seeds in the vault, which covers a space the size of three tennis courts.
The seeds range in size from those almost as large as your fist (the palm tree Hyphaene thebaica, at 8.5cm wide) to the microscopic: Chinese orchid seeds, measuring just 0.07mm across – the width of a human hair. Some are kept in their dozens, some in their millions.
Some are spiky and hairy, while others curl in on themselves like intricate pasta. Some come with ‘quarantine’ labels (for those not permitted to be in the country except in this vault), or hazard signs to warn users of irritant – or even poisonous – contents.
It’s literally freezing in here (-20°C, -4°F) and I’m clad in a snow coat and gloves. A timer counts down my visit – stay more than 10 minutes and security is automatically triggered.
It’s key-card access only to get into the airlock and the vault. After all, says Sharon Balding, seed collections manager at the bank, “These collections are invaluable.”
Indeed, the Millennium Seed Bank holds a handful of species that are extinct in the wild, and many that are critically endangered – but also some that are highly prized by collectors.
“We don’t want to release their location information,” says Balding.
High security extends to the storage system; the seed containers aren’t labelled, so if you were to, say, break in and look for valuable – or perhaps dangerous – seeds, you’d have no idea what they were without access to the computer system.
Yet the alarm isn’t there to stop theft, but to stop me from freezing to death. Even so, I’m likely to feel it before security is called; before going in, I signed a waiver about my heart stopping.
This sub-zero temperature helps the vault keep seeds in a suspended state, ready to spring back into life when needed. It’s the same principle used in more than 1,700 seed banks around the world.
Seeds stored all over the world
All these so-called ‘doomsday vaults’ serve different purposes. The Svalbard Global Seed Vault, for example, on a remote archipelago of Norway, prioritises edible plants and crops – it’s considered the ultimate safety net for food security.
There’s a vault in Colorado in the US that stores American crops in cryogenic tanks, and one in Pisac, Peru, to protect Indigenous crops. Around the world, local seed banks also serve smaller communities that regularly deposit and withdraw seeds.
And then there’s the Millennium Seed Bank: the largest ex-situ collection of wild plant seeds in the world.
It has locked away copies of 40,150 different plant species (at the time of writing) with deposits from most countries, making it the biggest backup of the world’s seed collections, including those of other vaults.
After all, even Svalbard – an epic, James Bond-style lair half-buried in a mountain and built to withstand rising sea levels, earthquakes and nuclear war – was breached by meltwater from warming permafrost in 2017.
No seeds were lost, but the threat made one thing clear: when it comes to doomsday, one backup isn’t enough.
The oldest seeds in the Millennium Seed Bank date from the 1950s, but the seed bank opened in its current form in (as its name suggests) the year 2000, with the aim of making copies of as many of the world’s seeds as possible.
The idea was that these would be stored in the doomsday vault until some kind of disaster – species on the brink of extinction, for example, or the loss of an essential food crop – made their withdrawal necessary.
But seed bank researchers are no longer waiting for doomsday. It’s already here.
When to make doomsday withdrawals
When the seed bank opened 25 years ago, the idea was to keep the seeds for a ‘break glass in case of emergency’ situation. Back then, the crisis was vague, hypothetical. Today, it’s intensely clear.
“Mini crises are happening all the time,” says Charlotte Lusty, head of seed collections at the Millennium Seed Bank.
“Even more importantly, we’re losing diversity before our eyes – we’re losing trees and flowers without really noticing. We’re seeing rapid destruction, fire and flooding, and there’s also this gradual decline.”
Threats including climate change, habitat loss, war and wildfires have increasingly put species at risk of extinction, and the loss of certain species has a trickle-down effect on others, with a knock-on hit to crops, pollinators and animals (including humans).
This, Lusty says, is “so much more critical” an emergency than the idea that there will be a single, terrible disaster that would force the opening of the vault.
When one of the most catastrophic seasons of wildfires hit Australia in 2019–2020, the seed bank leapt into action.
Their ‘emergency bushfire recon mission’ involved rapid surveys, propagation, germination and collections, says Dr Aisyah Faruk, the seed bank’s conservation partnership coordinator for Oceania and Europe – “but obviously there wasn’t really much to collect, because everything was gone.”
Kangaroo Island, in South Australia, was hit particularly hard during the so-called Black Summer, as fires ripped through 211,474 hectares (522,563 acres) of land – almost half the island. The area, once full of threatened species, was decimated.
But 12 years before, the South Australian Seed Conservation Centre in Adelaide had collected thousands of seeds from this area and sent them across the world to be deposited in the vault below the Sussex garden.
The deposit would end up rescuing whole plant populations from extinction over a decade later.
One plant, for example – a pea species called Glycine latrobeana that was already listed as ‘vulnerable’ – was entirely wiped out in the area during Black Summer. The local seed bank’s collection wasn’t enough to repopulate the species.
The Millennium Seed Bank sent their collection back to where they’d come from, and about 80 per cent of the seeds germinated. Thanks to the withdrawal from the doomsday vault, G. latrobeana barely scraped by local extinction.
“It would have been devastating to have lost them in the fires if we hadn’t collected them,” says Faruk.
Ever since, Faruk says, the South Australia seed bank has been making more regular withdrawals from the Millennium Seed Bank to build up the diversity of its seed collections.
And it’s not just natural disasters that threaten these vital resources. In 2015, the International Center for Agricultural Research in the Dry Areas forced the first ever withdrawal from Svalbard to replant vital crops lost during the civil war in Syria.
In fact, seed stocks are so important to a country’s food security that they’re often strategically targeted. The Iraqi seed bank, for example, was looted and destroyed following the US invasion in 2003. And, in August 2025, the Palestinian seed bank in Hebron, in the West Bank, was destroyed.
“They’ve lost all of their collections,” says Faruk, adding that the Millennium Seed Bank has some copies of Palestinian seeds but not everything.
Withdrawals triggered by war are on the rise, she continues.
“The collections that we have here, and the in-country collections, are going to become more and more valuable. We live in such an unstable time that any safeguard to local and global biodiversity is going to be important.”
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The frozen future of cryotechnology
Back at ground level above the seed vault, in a concrete-enclosed corner of a huge glasshouse, smoke billows from a giant metal tank. It’s not cold in this room – not as cold as the seed vault. But inside the tank, the temperature is -196 °C (-320.8°F).
You’d need more than an alarm system if you were to get trapped in there.
A blue-gloved hand pulls out a small, metal chest and the tank whirrs shut. This is postdoctoral research associate Dr Namrata Pradhan’s favourite part.
The drama makes her feel like “you’re actually doing something” – by comparison, cutting out the seed embryos before depositing them here is tricky and time-consuming.
Pradhan is working on the seed bank’s next frontier: new advances in cryotechnology. When she plunges a seed into liquid nitrogen, all biological activity stops.
In this suspended state, almost all ageing is halted: in theory, the seed could stay there as long as it needs to. When it comes out, Pradhan places the seed in a nutrient-rich medium and waits to see if it germinates.
Cryopreservation isn’t the same seed storage solution the Millennium Seed Bank has been perfecting for the last 25 years.
While seed saving has been going on for as long as humans have grown things, there’s a particular – and significant – group of seeds humans have never been able to store. If we don’t find out how to soon, your morning coffee could be at risk.
That’s because the seeds of many trees and plants we consume for food – including coffee, mango, cocoa and many crop species – are ‘recalcitrant’.
This means they’re not able to survive the cold and dry conditions of the seed bank. The avocado is a classic example: a big embryo covered in a very thin seed coating and surrounded by a fleshy fruit.
But, for most of the foods we eat, we rely on just one or two cultivated varieties.
Take coffee: whatever you’re drinking, it’s either from the Arabica or the Robusta plant. The higher quality and more popular arabica species – accounting for two-thirds of consumption – is under threat, with 50 per cent of its growing locations set to become unsuitable by 2050.
If we want to protect these seeds into the future, we need to find a new way of storing them. Cryopreservation could be the answer.
Wakehurst currently has only three tanks, containing about 5,000 species – making it more of a research facility than somewhere like the National Laboratory for Genetic Resources Preservation, in Fort Collins in the US, which has capacity to store 750,000 seed samples in its fleet of tanks.
The Colorado lab is also racing to figure out how to store the world’s 30,000 recalcitrant species before we lose them.
Creating new ways of existing
Meanwhile, the Millennium Seed Bank has also been storing and testing seeds that show resilience to high temperatures, droughts and floods in the face of climate change.
Recently, a withdrawal was made to cultivate a Columbian bean species that has hurricane-resistant roots. And, here in the UK, the vault secured seeds from trees that were discovered to be resistant to the deadly ash dieback disease.
“We have a very key resource for food and agriculture here. I think we’ll play an important role in the way that our future food systems are shaped,” says Lusty. “There are some interesting species that could prove really important.”
Then there are the opportunities we don’t even know we don’t know about, including using seeds to find new chemicals and materials.
This is called bioprospecting, involving the exploration of plant tissues to find useful compounds, often with the help of machine learning.
Most medicines come from these kinds of discoveries in plants or fungi.
Warfarin, for example, was discovered in a poisonous chemical produced by decomposing sweet clover hay, which killed hundreds of cows in the US in the 1920s. It’s now used as a common blood thinner to prevent blood clots and treat heart issues.
Lusty says other vital chemical compounds could be lying in wait that could solve key issues in healthcare and energy – particularly in the poisonous coatings of certain seeds.
“We have a lot of materials that are completely unique taxonomically that we know very little about,” she says. “It’s a frontier – a pioneering area of research that’s getting quite strong at the moment.”
Yet, currently, we’re losing species faster than we can grasp their potential value. Protecting these seeds, of course, gives us more options for the future – but there are also research projects underway around the world to actively look for new biochemicals within them.
That’s why, Lusty says, “I don’t see us in a kind of one-way street towards extinction. I see us as evolving together with our plant kingdom, creating new ways of existing and thriving.”
Bioprospecting, she says, could be part of that – alongside the cooling effects on the climate and increased oxygen if we restore forests and habitats.
“I truly believe that we have a future and it will be because we’ve used plants. We don’t necessarily know how, but we will find the solutions there.”
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