Seeds of Hope – Establishing the National Seed Bank

By Darren Reidy

Article was posted in Spring 2025 Journal

Figure 1: Germination trials.

Globally, 40% of plant species are threatened with extinction. In Ireland, fifteen of our 1047 native and archaeophyte (colonised Ireland pre-1500 AD) species have been declared extinct in the wild. A further 106 species (9%) are threatened with extinction, while 98 species (8%) have undergone such decline that they are considered ‘near threatened’. In fact, over half of Ireland’s native species have declined in abundance and range since the year 2000, largely because of habitat loss and degradation by land use change, agricultural intensification, commercial afforestation, excessive nutrient input and the drainage of wetlands. Indeed, 85% of Ireland’s protected habitats are considered to be in poor condition. It is widely recognised that radical conservation interventions are required to halt the loss of biodiversity and restore our natural ecosystems. In the face of the global ecological crisis botanic gardens and herbaria are responding by adapting their collections to also ensure the conservation of the global flora. Seed banks are an efficient method of ex-situ plant conservation, capable of conserving floral diversity outside of their natural environments, should it be lost in the wild.

It is the biology and structure of a seed that makes them such ideal candidates for long term ex-situ conservation of wild flora. They consist of an embryonic plant, enclosed in a bundle of nutritive tissue and a protective outer layer. This tiny plant embryo contains all of the genetic information required for a plant to develop, survive and reproduce.

The storage and preservation of seed is not new technology; As long as humans have been harvesting seed for food, they have also been storing them. Farming and domestication of crop plants first emerged between 10-12,000 years ago in the ‘Fertile Crescent’, but there is evidence indigenous Americans and Australian Aboriginal peoples cultivating plants as far back as 15,000 years before present. Of course, the practise of storing seed to feed your family and resow emerged around the same time. Simultaneously seed was being buried in tombs of the deceased, across multiple cultures, for their future use in the next life or the afterlife.

But how does seed storage translate to seed conservation? The answer to this comes down to a key survival strategy known as dormancy. Seed dormancy is a temporary suspension of embryo development, allowing seed to survive hostile environmental conditions until suitable conditions return. We are all familiar with the scenes of barren desserts bursting to life after the rains. In some cases, seed can persist in the soil seed bank for decades until germination conditions are right. In other cases embryo suspension is short lived and rely on seed energy reserves rather than becoming truly dormant.

How long exactly can seed survive in this form of suspended animation? Archaeological digs near the Dead Sea have uncovered dried seed of the Judean Date Palm (Phoenix dactylifera) which were buried over 2000 years ago. After laying dormant for two millennia these seed have successfully been germinated by researchers and cultivated into viable plants. A more extreme example of seed survival comes from Siberia, where seed of the Narrow–leafed Campion (Silene stenophylla) was uncovered from a squirrel’s burrow which had been frozen in the permafrost for almost 32,000 years. Here, researchers were able to regenerate viable plants from maternal fruit tissues which had remained frozen at -7°C. These two examples illustrate that as long as seed are stored cool and dry they can remain viable for extraordinarily long periods.

The concept of long term seed storage for conservation purposes was developed by Nikolai Vavilov (1887-1943), a botanist, geneticist and crop scientist from Russia. He was heavily influenced by the many repeated famines experienced across the Soviet Union, and believed that the preservation of genetic diversity of crops held the answer food security in the face of environmental perturbations, diseases and climatic events. Under his leadership, the world’s first seed bank was established at the Bureau of Applied Botany, Leningrad, Russia, in 1917. He, together with a dedicated team of botanists, amassed some 380,000 collections of seed from the centres of origin of cultivated plants throughout the globe. The faith of world’s first seed bank at the hands of the Nazi’s during the Siege of Leningrad and the anti-science persecution of Vavilov by Stalin, is a tragic and emotive story which you can read about in detail in the recently published book by Simon Parkin “The Forbidden Garden of Leningrad”. Vavilov’s legacy and the science of seed conservation has survived however. Today the Global Seed Vault (also known as the Doomsday Vault) in Svalbard, Norway, safeguards over 1,214,827 seed samples from almost every country in the world. This includes Irish deposits made by the Dept. of Agriculture, including some 32 potato varieties. Closer to home the Irish Seed Savers Association does extremely important work in conserving the genetic diversity and heritage varieties of Irish apple trees and other crop plants.

Fig. 2: Ripe seed of the Fen Violet (Viola stagnina), a rare species in Ireland.

More recently, seed banking techniques have been adapted for the conservation of wild flora. This has been spearheaded by the Millennium Seed Bank (part of the Royal Botanic Gardens Kew), who, through their international partnerships, now house over 2.4 billion seed from around the globe. In Ireland in 2019, the Office of Public Works, in response to the declaration of a ‘National Climate and Biodiversity Emergency’ committed to the establishment of the National Seed Bank for the conservation of the Irish flora. This has since become a key target with statutory backing under the ‘National Biodiversity Action Plan, 2023-2030’. The National Seed Bank is located in the herbarium at the National Botanic Gardens. The facility employs international best practise and aims to bank a collection of seed from all native species. It is currently prioritising those species that are most immediately under threat.

The seed banking process begins with identifying which plant populations may require conservation intervention. This is done in consultation with the National Parks & Wildlife Service. It is important to maximise the genetic diversity of seed collected, as it is this genetic diversity that holds the capacity to adapt to future scenarios and ensure long term survival. This is achieved by sampling populations as widely as possible. The selected populations are assessed to ensure that seed can be safely collected without compromising the population in the wild. It is essential that seed banking does not accelerate a species’ extinction. A critical rule is thus that no more than 20% of available seed is collected on any occasion. This threshold is reduced to 10% if a population is particularly vulnerable. Seed is only collected from protected plant species under license from NPWS. Members of the public should be aware that it is not permitted to interfere with protected plant species or protected habitats unless authorised to do so.

After seed are collected they are returned to the lab. Here they are kept cool and dried to an equilibrated relative humidity of 15%. This is a critical moisture level as it ensures the seed are dry enough to maximise storage potential, but not so dry that the seed is killed. As a general rule, for every 1% relative humidity the moisture content of the seed is reduced, it doubles the lifespan of the seed in storage. Once dry, the seed are cleaned and counted. A portion are then dissected under a microscope to check for fully developed embryos, and the presence of pests or pathogens. A further subset are then rehydrated and germinated to calculate what proportion of the seed are viable. Ideally there would be a target of 10,000 viable seed per banked species, but this figure can be difficult to achieve for rare or threatened species. The conditions under which seed are germinated can be adjusted to suit the ecological preferences of the species, and sometimes dormancy must be broken in order to accurately calculate viability rates. Any germinated seedlings of species of conservation concern are sent to the native plant nursery to be cultivated as part of the living collection. After establishing viability the remaining dry seed are sealed in foil packets, assigned a unique barcode identifier and frozen at -20°C where they can theoretically survive in perpetuity.

Fig. 3: Germinating seed of Hairy St John’s-wort (Hypericum hirsutum), vulnerable to extinction in Ireland.

To date the National Seed Bank has preserved seed from >200 populations of 124 different species. This represents 12% of the Irish flora. A quarter of these banked species are red listed, and represent 13% of Ireland’s threatened flora. The intent is that, should these species or populations ever be lost from the wild, the seed preserved at the National Seed Bank will be available to assist in the propagation, restoration or reintroduction of populations unique to a given area. Of course, any species reintroduction efforts must follow the removal of the drivers of extinction and be combined with the appropriate habitat restoration measures. This will require a whole of society approach in many cases, with diverse stakeholders such as landowners, local communities, local industries, local authorities, public bodies and NGOs working together to address regional environmental concerns. Until then the National Seed Bank will act as a critical piece of infrastructure and an ark for the survival of some of Ireland’s most unique and threatened flora.