Inside the Millennium Seed Bank: Protecting Global Plant Diversity at Wakehurst

Short Summary

In a subterranean but central repository near Wakehurst, the Millennium Seed Bank at Kew Gardens preserves the world’s plant diversity by safely drying, storing, and testing seeds. The facility acts as a global backup, receiving collections from partners around the world and maintaining a 15% relative humidity, -18 to -20 degree storage regime to keep seeds viable for years or decades. Volunteers and scientists work together to clean, inspect, and germinate seeds, ensuring that rare and threatened species can be restored if landscapes are lost to wildfires, droughts, or other climate-driven stresses. The seed bank is not just a vault; it is an active center supporting restoration and research across dozens of countries.

Overview

The Guardian Science Weekly episode documents a visit to the Millennium Seed Bank at Wakehurst, a bunker-like facility designed to endure century-scale preservation of plant life. Inside, researchers and volunteers process seeds from around the world, preparing them for long-term storage and potential future restoration projects. The aim is to prevent plant extinction and enable the use of stored seeds to restore habitats and understand plant properties for research and practical applications.

Location, Design, and Operations

Located near Gatwick Airport in Sussex, the seed bank sits beneath a garden-like surface and is engineered to withstand accidents and ensure longevity. A 24/7 security presence guards a complex of labs, drying rooms, and cold storage spaces. On arrival, seeds are dried, cleaned, and inspected using advanced imaging and X-ray techniques to assess viability before freezing at cryogenic temperatures. The bank’s dry room maintains low humidity and cool temperatures to minimize damage during handling.

Dr. Eleanor Breman, a senior seed conservation researcher, describes a hybrid model where volunteers and scientists collaborate on seed collections. Seeds flow in from partners across continents—Africa, Europe, Asia, and the Pacific—while a safety duplicate is stored at Wakehurst as a global insurance policy for biodiversity. The facility also serves ongoing needs, with UK collections alone sending out about one germplasm collection per working day for research and restoration projects.

Seed Collection and Genetic Diversity

Collections target thousands of seeds, aiming to capture genetic diversity from many individuals while avoiding impacts on natural regeneration. The core idea is to preserve seeds from at least 50 individuals and to avoid removing more than a fraction of mature seeds on any given day. The bank currently stores tens of thousands of species, representing a global biodiversity dataset that can be accessed for restoration and study.

Storage, Testing, and Access

When seeds arrive, they are dried and gradually transitioned to low humidity and cool temperatures, before being archived in ultra-cold freezers. The facility uses a hospital-grade X-ray to verify seed viability and to detect empty or waterlogged tissues. Periodic germination tests are performed in Germany and elsewhere to check whether stored seeds can still sprout after long periods in cold storage. While many seeds may eventually be incinerated to prevent invasive releases, the most threatened species are prioritized for bulking up and propagation inside the vault or nearby nurseries.

Impact and Future Roles

Seed banks like Wakehurst provide a lifeline against climate-driven losses, enabling the revival of populations after wildfires or habitat destruction. A notable case involved the glycine clover in Australia, where seeds stored in Wakehurst were later used to reestablish plants after extensive fires, resulting in high survival rates in restored landscapes. The episode emphasizes the human stories behind seed conservation: field researchers travel across difficult terrain, sometimes risking safety to secure germplasm that could sustain life on Earth. The Millennium Seed Bank embodies a philosophy of stewardship and practical science, balancing risk management with active use to safeguard habitats and the plants that support broader ecosystems.

Quotes from the episode provide insight into the mission and challenges:

"these seeds here, whilst they are a kind of ultimate last resort, they're also available for use all the time." - Patrick Greenfield

"we are holding it in trust for 190 different countries." - Dr. Eleanor Breman

"we're losing plants 500 times faster than before humans existed." - Madeleine Finlay

"you can't leave seeds in wet fruit because they'll start to go moldy." - Madeleine Finlay