At the core of RBGE’s scientific mission is to “explore” the world of plants and on the 350^th anniversary of our foundation, the herbarium’s 3 million specimens from 157 countries is testament to the success of our research documenting the world’s flora. In order to pinpoint centres of high species diversity that should be priorities for conservation at a time when habitat is being lost faster than ever before, such data on what plant species are, and where they grow, are absolutely essential. However, in times of climate crisis, when conditions across the planet are changing so fast, can RBGE’s science also contribute to understanding the future fate of vegetation even when it is protected from habitat conversion?

The answer to that question is “yes” because RBGE’s tropical science has, over the past decade, increasingly aligned itself with ecological research networks that are monitoring how tropical forests are responding as climate changes. Central to these networks are areas of forest where all individual trees are monitored at intervals to measure how fast they are growing, if they are dying, and if new individuals are growing up to replace lost trees. In a sense, such science is easy – it just requires numbering every tree in an area (often one hectare) of tropical forest with a permanent aluminium tag, and measuring how the diameter of its trunk changes over time. However, given that tropical forests are tough places to work in terms of access, hot temperatures and biting insects, establishing and re-measuring such ecological monitoring plots can be back-breaking work – especially considering that an ‘average’ hectare of tropical rain forest can contain 600 individual trees greater than 10cm diameter, which is generally the threshold for measurement.

The sheer number of trees, however, is only part of the problem. A massive issue is how to name all the species when a single hectare in Amazonia can contain 300 tree species. For comparison, only 32 tree species are found across the entire United Kingdom. This problem of identification is compounded by the fact that tropical floras are poorly known and in most places there are no easy-to-use identification guides. Knowing what all the species are is important because their individual fates in these times of change may be distinct – each species has different ways of growing, attracting pollinators and being dispersed, plus different tolerances to drought and higher temperatures. Species that today are rare could be the very species that will thrive in future forests, whereas as today’s most common species might be highly vulnerable. But if we cannot identify each species, we will not be able to know who will win and who will lose, and this is vital information if we are to manage, plant and restore forests in future.

RBGE has been lending its expertise in tropical plant identification to ecological plot networks in Africa (Dr David Harris, Dr Antje Ahrends), Asia (Dr Colin Pendry, Dr Peter Wilkie) and especially in Latin America, where over the past decade, we have helped to expand monitoring from rain forests, where it has been concentrated, into the neglected, but highly threatened tropical dry forests in projects funded by NERC and the Newton Fund in partnership with the regional research councils FAPERJ (Rio de Janeiro) and FAPESP (Sao Paulo) in Brazil.

More recently, we have just completed an exciting project in Colombia, supported by the British Council that has made major steps in monitoring Colombian forests and in particular, in developing resources and tools to allow ecologists there to identify the trees in their monitoring plots with greater accuracy. BRAVO – Botanical Resources Available Online for the Colombian Flora – was a project with components at RBG Kew and RBGE.

RBGE’s work in the BRAVO project, in collaboration with ColTree (Red de Monitoreo del Bosque en Colombia; “Monitoring network of Colombian forests”), helped to establish and re-census 47 inventory plots across the tropical rain forests, dry forests and Andean montane forests of Colombia, taking measurements from more than 23,000 individual trees. Critically, it facilitated the collection and photography of more than 5000 herbarium specimens of trees from these plots, which, with the help of taxonomic experts from RBGE and Kew, have been accurately named. The images of these voucher specimens are now freely available online, including via the ForestPlots.net database, which is hosted by our project partners at the University of Leeds, and is the leading global repository for forest plot inventory data.

In addition, as part of the BRAVO project, RBGE informatics staff, Dr Roger Hyam and Rob Cubey have developed software that can allow the onscreen comparison of multiple plot voucher specimen images with images of specimens that have been accurately identified in herbarium collections from across Europe. This is a vital step forward to allow ecologists to not only identify trees in single plots, but critically, to make sure that identifications are uniform across multiple, geographically dispersed plots. The importance of the new software is that such cross-plot specimen comparisons were not previously feasible because the physical specimens are dispersed across numerous herbarium collections, or are not deposited in herbaria at all.

RBGE is also a centre of expertise in DNA barcoding, the process by which individual plants may be identified through sequencing of a small region of DNA. In Colombia, BRAVO has extracted DNA from 5000 individual trees from monitoring plots for which DNA barcode sequences will be generated and made available through online repositories such as GenBank. In the future, the same DNA region can be sequenced from un-named trees and compared with existing sequences in online databases for identification purposes.

More accurate species identifications will be central to the 21^st Century science that determines the long-term effects of disturbance and climate change on the species composition and function of tropical forests. We hope that our recent project will therefore help to secure the future of Colombian forests, upon which the entire Colombian population depends, especially poor and vulnerable people in rural areas.

Dr Toby Pennington – February 2020. Toby is a tropical botanist and biogeographer working at the Royal Botanic Garden Edinburgh and University of Exeter.