In a paper published today in Nature Plants, researchers at the Royal Botanic Gardens, Kew, detail for the first time the scale of threatened species that are unable to be conserved in seed banks.
The paper reveals that when looking at threatened species, 36 per cent of ‘critically endangered’ species produce recalcitrant seeds. This means they can’t tolerate the drying process and therefore cannot be frozen, the key process they need to go through to be safely ‘banked’.
Kew’s world-famous Millennium Seed Bank (MSB) based at Wakehurst in Sussex is the largest and most diverse wild plant seed bank in the world and contains 90,000 seed collections. Kew has long been championing the use of cryopreservation alongside to conventional banking at the MSB, and outlined it as a key priority for conserving the world’s seeds in Kew’s Collections Strategy published earlier this year. Cryopreservation is a form of preservation using liquid nitrogen which offers a potential long-term storage solution for recalcitrant seeds. In seed banks, seeds are dried and frozen at -20°C, whereas cryopreservation involves removing the embryo from the seed and then using liquid nitrogen to freeze it rapidly at a much colder temperature of -196°C.
This latest research in Nature Plants, co-authored by Kew scientist Dr John Dickie, former Kew scientist Dr Sarah Wyse, and former Director of Kew Science Prof. Kathy Willis, found that other threatened categories and global tree species list also contain high proportions of species that are ‘unbankable’ using the drying and freezing technique, including 35% of ‘vulnerable’ species, 27% of ‘endangered’ species and 33% of all tree species.
John Dickie, Head of Seed & Lab-based Collections at Kew’s Millennium Seed Bank and one of the authors of the paper, says that
“Ex-situ conservation of plants is more critical than ever, with many threats to plant populations including climate change, habitat conversion and plant pathogens, we need to make sure we’re doing all we can to conserve the most important and threatened species.
As successful as seed banking is for some species, we have always known that it is not suitable for all. This new data shows that we need greater international effort and investment to understand and apply alternative techniques like cryopreservation which have the potential to conserve many more species from extinction.”
The paper builds on research published last year that estimated around 8% of the world’s plants produce recalcitrant seeds. Among these species are important UK heritage trees such as oaks, horse chestnuts and sweet chestnuts, as well as worldwide food staples like avocado, cacao, and mango. This latest research reveals that the scale of plants unable to be conserved in seed banks is much higher for threatened species. The issue is particularly severe for tree species, especially those in tropical moist forests where half of the canopy tree species can be unsuitable for banking. This analysis has also highlighted that the Global Strategy for Plant Conservation (GSPC) target of conserving 75% of the world’s threatened plant species outside of their natural habitat by 2020 is practically impossible.
Kew aims to develop a generic protocol for the banking of recalcitrant seeds and to kick-start large-scale use of cryopreservation by developing a bespoke ‘Cryosphere’ facility at the MSB.
 Looking at the likely ‘bankable’ proportion of species on the International Union for Conservation of Nature Red List of Threatened Species [IUCN Red List]
 Dr Sarah Wyse and Dr John Dickie’s paper in Journal of Ecology (105): “Predicting the global incidence of seed desiccation sensitivity” (2017)
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Research paper details
Article title: “Seed banking not an option for many threatened plants”
Publication: Nature Plants
Link to the paper https://www.nature.com/articles/s41477-018-0298-3
Notes to Editors
The Royal Botanic Gardens, Kew is a world famous scientific organisation, internationally respected for its outstanding collections as well as its scientific expertise in plant diversity, conservation and sustainable development in the UK and around the world. Kew Gardens is a major international and a top London visitor attraction. Kew’s 132 hectares of landscaped gardens, and Wakehurst, Kew’s Wild Botanic Garden, attract over 2.1 million visits every year. Kew was made a UNESCO World Heritage Site in July 2003 and celebrated its 250th anniversary in 2009. Wakehurst is home to Kew's Millennium Seed Bank, the largest wild plant seed bank in the world. Kew receives approximately one third of its funding from Government through the Department for the Environment, Food and Rural Affairs (Defra) and research councils. Further funding needed to support Kew’s vital work comes from donors, membership and commercial activity including ticket sales.