Turning Over an Old Leaf Bryony Yates discusses the value of herbaria with Dr. Lauren Gardiner, Curator of Cambridge University Herbarium “It’s a sort of tutankhamun’s tomb” says Dr. Lauren Gardiner, describing the plant collection she curates. 'I regularly feel like I’m opening the door to a treasure trove and going "Folks? Does anyone realise what’s here?”'. Cambridge University Herbarium is a little-known collection, tucked away in a basement within the Sainsbury Laboratory, on the site of Cambridge University Botanic Garden. It houses an estimated 1.1 million plant specimens that have been dried, pressed, and preserved. The Herbarium (also known by its international herbarium code CGE) forms one node in a global network of over 3,000 herbaria that collectively house an estimated 380 million specimens. One of the largest collections in the UK, CGE is 'laden with the most extraordinary collections' says Dr. Gardiner 'and would be considered to be the national collection in many countries'. It is home to one of the finest collections of British flora and plant specimens collected by famous naturalists including Charles Darwin and Alfred Russel Wallace. The Herbarium also holds many 'type' specimens, an estimated 50,000: each one is the original specimen upon which the description of its species was based. Despite its importance, the collection has received little attention in recent decades. As a result, many specimens are uncatalogued mysteries; some have lain untouched for centuries. 'It is pretty amazing when you find something in the collection… and then you realise you have something really significant' says Dr. Gardiner. 'I quite regularly find these in this collection'. As recently as 2019, previously undocumented specimens collected by Darwin have been discovered, some still wrapped in the newspaper they had originally been collected in. While plants collected by Darwin will excite any keen natural scientist, herbaria are much more than mere curiosities. '[Herbaria] are collected for scientific purposes. They are enormous research datasets' explains Dr. Gardiner. Individual ecological studies tend to be limited by funding cycles, conducted on only a handful of species and locations, and restricted to a few years at most. With herbaria 'others have done a lot of fieldwork over the years and you can do your research on the material they collected. You have specimens that go back over a long time period and have a wider geographic and species range than you could possibly cover in one research project'. Worldwide, the oldest herbarium specimens date from as early as the 16th Century; CGE’s collections stretch back an impressive 300 years. Crucially, this period covers the onset of industrialisation and globalisation, perhaps humankind’s most large-scale and long-term experiments. Plants have witnessed, and bear the scars of, the rapid and intense global changes that have characterised this era: climate change, pollution, urbanisation, biological invasions, and more. Herbaria offer unique insights into such changes because they match the scales at which these processes operate: over decades and centuries, across all species, everywhere. A single specimen contains many layers of information. The preserved morphology (form) of the plant records its life-cycle stage at the time it 10
Turning Over an Old Leaf
was collected as well as characteristics of its growth. Interactions with other organisms may have left their physical mark on the specimen: disease lesions for example, or bite-marks from a hungry herbivore. The plant tissue itself holds information that can be carefully extracted with biochemical methods. Environmental pollutants and nutrients retained in the tissue can paint a picture of the plant’s growth environment. The presence of a plant’s own defensive compounds point to interactions with pests and pathogens. Even the plant’s genetic makeup, its DNA, is largely preserved. Importantly, each specimen is accompanied by metadata, usually at least the plant name, date, location, and the collector’s name. All of the characteristics of each specimen can therefore be mapped to a specific place and time, with varying degrees of accuracy. This allows changes to be tracked over time and correlated with other relevant data, such as climate and land-use. While many specimens remain on shelves and in boxes, leveraging their potential is challenging. 'There’s an international network of herbaria and a UK network as well…We can loan material back and forth between collections' highlights Dr. Gardiner. However, physical exchange of material can only go so far. A global priority for herbaria is the digitisation of specimens. Digital records, made available via online portals, are accessible and usable by researchers around the world. However, digitisation is both slow and requires human resource. Some herbaria are finding creative ways to accelerate the process, using machine learning or engaging the public through citizen science initiatives. CGE is in the process of digitising its priority specimens —those of special historical importance and holotypes — and plans to make them freely available via portals such as the Cambridge Digital Library and JSTOR Global Plants. Wider use of the collections is central to Lauren’s vision for CGE. 'I would like the collection to be much, much more active... particularly to see it embedded in the teaching and research of the [Plant Science] department…part of the department’s day-to-day activities...there’s a lot of research that could use the collection'. She also emphasizes the cultural importance of the collection. 'These kinds of collections were put together, particularly in the 19th century and before that, by polymaths who were interested in everything. We have botanical specimens collected by literary figures known for their writing - all sorts of people'. Other significant items in the collection include original botanical artwork, photographs and portraits. It even holds the teaching materials used by Darwin’s botany Professor, John Stevens Henslow. These materials create even more opportunities to collaborate with other collections: 'I would like to see the Herbarium’s collections represented in exhibitions at the University of Cambridge Museums and the Botanic Garden…to strengthen the links between our collections and to explore the stories behind them'. Despite their exciting potential, the future of herbaria is under threat in many UK organisations. There are immediate threats, such as the Easter 2020
