A new life for centuries-old herbaria

Evolution of herbaria: from hortus siccus in ancient books to virtual collections worldwide

The birth of the herbarium (i.e., collection of dried plants classified by family, genus and species) can be traced back to the Renaissance when the Italian botanist Luca Ghini set up a technique to collect, preserve and catalogue plant specimens. Precisely, he pressed and preserved medicinal plants in books, thus creating the first hortus siccus – a dry garden stored in bookshelves. Two centuries later, Carl Linnaeus  – known as the “Father of Taxonomy” – optimized this method by fixing one specimen into a single sheet of paper and produced a repository of plant cards organized in groups of closely related species. Strikingly, this format has been used for trading and exchange for centuries, and it’s still considered a standard!

Six hundred years after, 3000 herbaria worldwide are experiencing a real revolution: digitization of old plant cards, extensive use of machine learning for species identification and description, and online mobilization of big data are accelerating the generation of the herbarium of the future, a global inventory of plant biodiversity containing comprehensive information about thousands of species (e.g., images, georeferencing, uses and preparations, genetic and phenotypic data). Besides their well-established use in systematic botany, new applications of old herbaria have been proposed by Charles C. Davis – Professor of Organismic and Evolutionary Biology and Curator of Vascular Plants in the Harvard University Herbaria – in a recent review published in Trends in Ecology and Evolution, with a particular focus on plant conservation. 

Colonial Legacy of Plant Collections

Since the first botanical explorations in the XVI and XVII centuries, naturalists have been “hunting plants” in regions with high biological diversity – typically tropical areas of the Global South – and preserving specimens for further studies in botanical gardens and private collections – typically in temperate regions of the Global North. 

Although great advances have been made in regulating specimen exchange and plant discovery, more work is still needed to firmly acknowledge the origin of plant biodiversity and recognize the value of local knowledge handed down by indigenous communities. 

Value of Digital Biodiversity Resources for Plant Conservation

In addition to the historical and cultural values of these amazing artworks, herbaria offer an extraordinary opportunity to tackle the biodiversity crisis. Indeed, innumerable records of plant specimens facilitate the study of plant evolution across time and space since they provide valuable information about a species’ origin and geographical distribution, as well as its diversification pattern and present-day preservation. Thus, herbaria can greatly help plant conservation programmes aimed at better protecting biodiversity hotspots and monitoring the status of biodiversity loss. According to the IUCN red list, some plant species have already undergone extinction, others are at serious risk in their current habitat, and several species are becoming extremely vulnerable in the anthropogenic epoch due to the adverse effects of climate change. 

Towards a Global Plant Inventory: Open Access and “Herbariomics”

The author suggested that international institutions should strengthen their collaborations to put together digital resources, track data with Digital Object Identifiers (DOIs), and globally provide Open Access to valuable information not only to amateur naturalists and non-specialists involved in Citizen Science projects but also to the scientific community.

Improvements in extraction protocols of ancient DNA, optimized and cheap sequencing of degraded genomes, and availability of bioinformatics tools to process large data sets are making the DNA barcoding of plant collections a reality. Genomic data and accurate data on the morphological and phenotypic characterization of plant species included in the scientific database should be linked to existing plant inventories to create a global metaherbarium.

READ THE ARTICLE

Davis, C.C. (2023) “The herbarium of the future,” Trends in Ecology & Evolution, 38(5), pp. 412–423. Available at: https://doi.org/10.1016/j.tree.2022.11.015.