What's in a collection? The Herbarium at Kew

The initial reaction of most visitors to the Herbarium at Kew is an audible gasp. The transition from the modern foyer into the extraordinary Victorian three-storey ‘vault’ known as Wing C, with its elaborate ox-blood ironwork, spiral staircases, floor-to-ceiling wooden cupboards, boxes and bundles of specimens wrapped in newspaper from the four corners of the globe, and the elusive odour of innumerable exotic dried plants, gives the sensation of walking back in time.

It would be no great surprise to find Darwin bent over a microscope in one of the many window bays, quietly poring over a rare South American sedge.

Innumerable is about right, we’re still not exactly sure how many herbarium specimens are held at Kew. It’s somewhere in the region of seven million, with about thirty thousand new additions every year. Roughly every thirty years since its original construction in the 1870s, another wing has had to be built to house this expanding library of the world’s plant diversity. The latest is a state-of-the-art affair with temperature-controlled vaults and compactor shelving, designed for optimum storage conditions and minimum risk of pest damage.

Maintaining this collection in good order is a huge and expensive task. This needs to be justified. Natural history collections were all the rage in the 19th century, when documenting and describing the natural world was seen as a justifiable end in itself. Nowadays, institutions such as Kew are expected to demonstrate how their collections, and the work of their scientists, are helping to solve global challenges. This is as it should be, and it isn’t hard to do. First and foremost these specimens, in the right hands, allow us to name plants accurately. An accurately named plant opens the doors to a wealth of information: its distribution, its uses and its ecology. Effective conservation, sustainable use of natural resources, climate change adaptation, ecosystem restoration – all are dependent on this ability.

Challenges ahead

The challenges, now, are harvesting and interpreting this massive ‘database’, and making the information widely and easily accessible. Natural history collections around the world, Kew included, are feverishly ‘digitising’ their specimens for access via the Internet, making high-resolution images and comprehensive databases available for all. For collections the size of Kew’s this is a gigantic endeavour, but in the course of doing so we’re disinterring vital information that’s been lurking behind cupboard doors for decades or even centuries, while facilitating botanical research in countries without access to the specimens.

Interestingly, we’re also discovering new species in the Herbarium, some of which may already be extinct. Keeping a collection up-to-date with the latest concepts of names and relationships is like keeping the Forth Rail Bridge painted - as soon as you think you've caught up somebody has proposed a new arrangement. But without taxonomists and curators to do this, the collection soon begins to lose value. At Kew we’re approaching the end of complete reorganisation of the Herbarium, based on new understanding of plant families made possible by molecular systematics (genetic research). Kew scientists were instrumental in the development of the new system, which is based on the evolutionary relationships between plant families and is now in its third revision (Angiosperm Phylogeny Group III, 2009; Chase & Reveal, 2009).