An often repeated statement is that “you must know what you have before you can conserve it” …but how do you know what you have in the first place? Field biologists have been working on this question for literally hundreds of years by conducting inventories, from general natural history inventories to small, highly detailed plot studies of flora and fauna. These inventories result in preserved specimens, which in the case of plants, are placed into herbaria along with their associated original locality information. Herbarium specimens then serve as documented proof of a plant’s occurrence at a specific time and place. Herbaria have the advantage over living collections that if well cared for, can last for hundreds of years if not longer. Although living collections are valuable for many purposes, they are expensive and difficult to maintain in cultivation for long periods of time. It is the vast number of preserved plants and their longevity in storage that make them ideally suited for the purpose of archiving a host of information on plants and their habitats.
Worldwide, herbaria contain approximately 300 million specimens, nearly all with labels that include collection locality information. The labels may also contain a variety of information, such as ecology, flowering time, ethnobotany, geology, pollination, fragrances, and dispersal. Other information can be gleaned from herbarium labels such as which plants grew where over time and when did a particular invasive plant invade a particular region. Herbarium label information is most often summarized and published in floras and monographs, though its real potential of biodiversity mapping is being realized through the accumulation of its data on computers in combination with global information systems. One of the most valuable outcomes of this type of work is the ability to determine which areas are the most species-diverse or rich in endemic-species, allowing them to be given higher conservation priorities. A great challenge for herbaria, though, and the biological sciences in general, is capturing plant label information electronically so that it can be made widely available for conservation purposes.
Perhaps of greatest importance, herbaria are potential repositories of genetic information for every species of plant known to science. Techniques are continually being refined to extract DNA and other chemical information from plants preserved decades or even centuries ago. Newer techniques of DNA extraction, particularly amplification, allow for smaller and smaller pieces of herbarium material to be required for genetic analysis, thus preserving the herbarium specimens for other types of studies. Recognizing that some traditional preservation techniques may hinder the future extraction of DNA, herbaria and botanical gardens are adapting and placing more emphasis on the collection of materials in silica gel and cryopreservation of seeds and tissues.
As a fundamental tool for plant taxonomy, herbaria play other roles in plant conservation efforts. The simple act of correctly identifying a plant species is necessary for conservation, providing the language (Latin names) for biologists of far-flung regions and ethnicities to be able to accurately communicate with each other. Herbaria facilitate taxonomic studies by enabling collections from diverse habitats and localities to be studied in one place. Plant species vary in size and shape across their geographical range, and this variation can be observed and studied easily in a herbarium. Herbaria also serve as a place to deposit voucher specimens from scientific studies where the correct identification of a plant is essential.
Considered as relics of the past by some biologists, there is a renewed appreciation in the vast amount of information stored in herbaria and its potential to help us understand, and conserve life on earth.