Pressed for space

Herbarium collections give snapshots into the history of plant life. But their future usefulness relies on their equity and accessibility.

A recent announcement from the Royal Botanic Gardens at Kew describing plans to move their world-famous herbarium collection¹ is gaining mounting controversy. One of the largest collections in the world, the herbarium houses over seven million dried plant specimens with 20,000 more being added each year. While the managing directors at Kew hope that this move will secure the future of the expanding collection — protecting these samples from fire, flood and pests — scientists have criticized these plans as being short-sighted and as failing to take into consideration the value gained from having these specimens on site with researchers². A relocation like this doesn’t come cheap either and is estimated to cost the British taxpayer £200 million. The remonstrations from the scientists at Kew and the astronomical costs of moving the collection invite questions as to the intrinsic value of herbariums. What do we gain from studying them and how do we ensure equitable access to these collections in the future?

Herbarium specimens from Patagonia collected by Charles Darwin at Royal Botanic Gardens, Kew, London, England. Credit: horst friedrichs/Alamy Stock Photo

A launching pad of botanical research for centuries, documentation of herbarium specimens has allowed scientists to preserve biodiversity, examine the evolutionary history of flora and, increasingly, predict how plants will respond to global change. Last year for instance, we published a study describing the best candidates for de-extinction from seed currently housed in herbarium collections — an attractive concept in light of current biodiversity extinction rates³. Meanwhile, for extant species on the brink, herbarium samples can be used to assess the risk of ecosystems to threat from fire, invasive plant species and increasing temperatures — a step that is key to developing effective conservation strategies^4,5,6.

In a study published in Nature Plants in 2019, researchers at Oxford University combined classical monographic research with DNA sequencing to rewrite the taxonomic history of the genus Ipomoea. This analysis revealed that, rather than being an outcome of domestication, edible storage roots evolved independently in over sixty Ipomoea species, thereby predisposing plants like sweet potato to agricultural cultivation⁷.

As with many scientific disciplines, studies using herbarium samples have been rejuvenated by the availability of high-throughput genomic sequencing and advanced computing methods. The latter has allowed improved imaging analysis of digitised specimens, more accurate species identification, and automated extraction of phenotypic and phenological traits⁸. Perhaps more importantly, digitisation has given immediate access to researchers unable to visit a herbarium’s rich facilities in-person.

Great efforts are currently being taken to digitise herbarium specimens; access to online biodiversity data depositories, such as the Global Biodiversity Information Facility, are improving the democratisation of the knowledge that can be gained from these samples. Earlier this year, Kew announced that it had digitised one million specimens — a feat that other herbarium collections across the globe are striving to emulate⁹.

While an admirable achievement, the Kew digital collection represents just a small fraction of the 400 million herbarium samples currently archived world-wide. A recent study in Nature Human Behaviour shows that these efforts have a long way to go. By assessing over 85 million specimen records from 92 physical herbariums, Charles Davis at Harvard University and colleagues found that only 30% of these specimens had been described online and just 10% had been digitised¹⁰.

This study uncovered another striking disparity. Although some of the most biodiverse ecosystems in the world are found in the tropics of the Global South, the vast majority of herbarium specimens are housed in the Global North. Another study published in Plants, People, Planet also reported this discrepancy, finding that just 12% of Global Biodiversity Information Facility specimen data were deposited from a country within the native-taxa range of the plant specimen¹¹. A legacy of colonial exploration, herbarium collections were born from the desire to uncover the medicinal, culinary and industrial properties of plants — the exploitation of which further cemented the economic dominance of imperial nations. While historical institutions, such as the British Museum, have been held under the spotlight for their retention of looted artefacts, seemingly little attention has been given to how the disparity in equitability of plant collections can be rectified.

Nature recently reported on how the Royal Botanic Garden at Edinburgh is confronting its colonial past, moving to recognize the contributions of indigenous peoples to the establishment of their collections and lay bare the historical links between botany and racism¹². A similar acknowledgement of the colonial legacy of herbariums will be key to improving their equitability.

But we need to go further. Improved rates of specimen digitisation and investment into infrastructure that can house herbariums closer to their sites of collection could represent a small step forward in making plant sciences more inclusive. While the importance of preserving these invaluable resources is clear, the strong opinions being voiced over the relocation of Kew’s collection highlights the even greater value of their accessibility. We still have a long way to go in making that access fair for all.