The World's Biggest Seed Bank Is Hidden Beneath Your Feet

The famous ‘Doomsday Vault’ – formally known as Norway’s Svalbard Global Seed Vault – may be the most recognisable seed bank on Earth.

Containing more than a million seed samples from plant species in nearly every country, this imposing stronghold serves as a kind of worldwide insurance scheme. It provides essential seed reserves for growing food and other crucial crops in an unpredictable future.

Yet, remarkable as the Doomsday Vault’s collection is, it is dwarfed by nature’s own store.

The soil seed bank beneath our feet

The planet’s largest seed bank lies beneath our feet. Known as the soil seed bank, it is nature’s enormous cache of seeds waiting in the soil, on the ground, or amid fallen leaves.

Whereas Svalbard receives carefully organised deposits, additions to the soil seed bank are far less orderly. Seeds land by chance, blown by wind, swept along by floods, or simply dropped onto the earth.

New research indicates that, despite this apparent disorder, the resulting seed reserve is extraordinarily vast.

In research published in Nature Communications, scientists examined a worldwide soil seed bank database with 3,096 records of soil samples gathered in 94 countries on all seven continents.

Across roughly 1,400 studies, researchers counted and identified millions of seeds and seedlings in these samples.

This huge seed reservoir can now be expressed in numbers.

The researchers’ estimates indicate that, worldwide, soil contains an average of more than 5,000 hidden seeds per square metre across terrestrial, wetland and aquatic environments.

“In the broadest sense, if you put your finger to the earth, you are likely to be pointing at a seed,” the researchers explain in their paper, led by co-first authors and ecologists Alistair Auffret from the Swedish University of Agricultural Sciences and Emma Ladouceur from the University of Prince Edward Island in Canada.

“The high density of seeds in the soil is a testament to the formation of soil seed banks as an important component of plant population and community dynamics, and a valuable strategy for many plant species to facilitate establishment following disturbance.”

Seed density and diversity vary worldwide

However, the data also revealed a pattern that may restrict how effectively the soil seed bank can fulfil its important role in restoring vegetation after disruption. Severe weather, for instance, can destroy plants growing above ground.

Scientists have long understood that plant density and diversity differ between habitats: deserts contain relatively little vegetation, while rainforests are densely populated. But it has been less clear whether the same pattern applies to the soil seed bank, particularly at the global level, because most soil seed bank studies have focused on individual regions.

Drawing on their global database, which was compiled by some members of the same team and first published in 2024, the researchers identified an unexpected difference between seed populations in different places.

“Across the world's biomes and ecosystems, patterns in species richness in the seed bank often diverged from patterns of seed density,” the team reports.

Put simply, soils with seeds representing many different plant species did not necessarily contain large quantities of seeds. Equally, places with dense seed stores often lacked high species diversity.

Tropical ecosystems illustrate this contrast: their soil seed banks had high species richness but low seed density. At the opposite end were arable, or farmland, ecosystems, where species richness was low while seed density was high.

Human activity may affect the soil seed bank

More worryingly, the team found signs that human activity may be harming the soil seed bank, particularly by reducing the diversity of seed species within an environment.

“Strikingly, we also found that the richness of soil seed banks appeared higher in undisturbed compared to degraded habitats, suggesting how across the world's ecosystems, soil seed banks also reflect the ongoing depletion of biodiversity as a result of anthropogenic activities,” the researchers write.

“This indicates that the potential for seed banks to contribute to the recovery and restoration of degraded ecosystems might be limited.”

Should additional research confirm this result, it would offer another view of the biodiversity crisis already visible among plants above ground – now reflected in the seed precursors concealed below the surface.

“Our findings are concerning,” the researchers explain, “matching general trends of reduced biodiversity in the established vegetation over time, and have consequences for the potential of passive restoration to reverse biodiversity losses.”

The findings are reported in Nature Communications.

This article was fact-checked and edited by Clare Watson. Although we take pride in our process, we are only human. If you notice an error, please tell us.