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The assessment and documentation of plant diversity can be traced back through many ancient cultures and certainly the use of plants has varied across time and across continents. In Western cultures museums, botanical gardens, and herbaria have traditionally been the academic centers for the study of plant life. Many of the early botanical institutions began and flourished in 18th and 19th century Europe and North America when new plant discoveries were being made as exploratory expeditions returned from far away lands. The age of discovery of Nature in turn gave way to the development of new schemes of classifying plants and eventually an understanding of the evolutionary principles responsible for the process of speciation and their origin. Natural history museums and botanical gardens today continue to be at the center of modern plant research. Yet as the threat to Nature increases these institutions are expanding their efforts in the conservation of biodiversity while at the same time continuing the challenge to discover, describe, and inventory the remaining unknown plant species on Earth. How will they complete this inventory, what will they find, and how long will it take to complete?

At the start of the great age of exploration by European naturalists in the 18th and 19th centuries, Nature seemed mysterious, immense, and infinite. Expeditions to explore uncharted regions of the world were sent out by governments, monarchies, and wealthy patrons to survey and acquire new lands, to bring back new plant products, such as spices and medicines, and to collect natural history specimens for newly established national museums as well as private collections. Most of the preserved and living specimens of plants that were brought back from Africa, South America, and Asia to museums and botanic gardens by such explorers as Alexander von Humboldt, James Cook, Charles Darwin, Ernest Henry Wilson, and Frank Kingdon Ward, to name only a few, were new to science and to horticulture. Discovery and description of biodiversity proceeded at a pace as if the natural world was limitless, enduring, and permanent. Botanists at botanic gardens at Kew, Edinburgh, Madrid, Berlin, St. Petersburg, Singapore, and Bogor, at natural history museums in Paris, London, Leiden, and later Washington, as well as universities at Uppsala, Oxford, and Harvard preceded at a frenzied pace in describing new species of plants, especially from the tropical regions of the world. The great age of exploration starting in the 18th century resulted in an explosion of discovery and documentation of biodiversity in the 19th and early 20th centuries.

Compared to the great natural history expeditions of the Europeans the exploration efforts of the young United States of America in the 19th Century have been largely ignored. In the early 1800’s American scientists in the newly established capitol of Washington desperately wanted to enter the international scientific arena and formed the Columbia Institute for the Promotion of Arts and Sciences. Chartered by Congress in 1818, the Institute started the first botanical garden on the Nation’s Mall and established the beginnings of a National Herbarium with specimens from local naturalists William Darlington and Alexander McWilliams. Although the Institute went defunct in 1837, it provided the impetus for the first US international exploring expedition.

In 1828 Congress approved the United States South Seas Exploring Expedition, especially through the efforts of John Cleves Symmes of Ohio, who believed in the “Holes in the Poles” theory that the Earth was hollow and could be entered through cavities at the two poles. Part of the mission of this expedition, which had commercial, diplomatic, and scientific objectives, was to find these entrances to the center of the Earth and claim their rights for the newly developing country. Ten years later in 1838 the expedition actually began when Ltn. Charles Wilkes set sail from Virginia in the flagship Vincennes with a fleet of six vessels. The Wilkes Expedition or US Ex Ex, as it was to be called, cost $928,000, lasted four years, covered nearly 87,000 miles, and visited most of the continents of the world, including a significant effort in the exploration of the coast of Antarctica.

Nine “scientifics” were on board representing all of the major natural history disciplines. William Brackenridge and William Rich were the botanists. Asa Gray, America’s foremost botanist at the time, was originally slated to go on the voyage, but declined at the last minute to take a position as professor of Botany at the University of Michigan. He eventually assisted in preparation of the Expedition volumes on plants.

When the Expedition finally returned at the end of four years, over four thousand animals specimens, fifty thousand plant specimens (both living and preserved), thousands of anthropological artifacts, and thousands of minerals, gems, and fossils had been amassed. These collections comprised the largest number of natural history objects that young America had accumulated and represented specimens native to our own country as well as regions throughout the world. These collections were the basis for the beginning of two great botanical institutions now based in Washington: the Smithsonian Institution’s United States National Herbarium and the United States Botanic Garden.

After the demise of the Columbia Institute, the remainder of that establishment merged with the Historical Society of Washington in 1841 to form the National Institute for the Promotion of Science. The natural history collections as well as the garden plants were placed under custody of the National Institute. With the return of the Wilkes Expedition in 1842 with its thousands of specimens, Congress authorized the formation of the Smithsonian Institution to serve as a National Museum for the advancement and diffusion of knowledge.

Almost simultaneously Congress authorized the construction of a botanical garden on the Mall and in 1856 it was officially named the “United States Botanic Garden” under the jurisdiction of the Joint Committee on the Library. Thus began the nearly 150 year history of the Department of Botany at the Smithsonian Institution and the US Botanic Garden.

The publication of the discoveries of the Expedition was the responsibility of Wilkes who eventually published 19 volumes over the course of 30 years. For the botanical discoveries Asa Gray and Wilkes argued over the publication of the new plant taxa. Interestingly they first disagreed over the extent of the Latin descriptions of the new taxa. Secondly, Wilkes wanted this work to be an entirely American “enterprise” without any assistance from foreigners while Gray insisted that proper identifications and descriptions of the new species were dependent on making comparisons to specimens found only in European herbaria. Eventually Gray won the day by distributing duplicates of the collections to the major European herbaria and obtaining assistance from foreign plant specialists in making proper determinations. Gray fundamentally established botany as a recognized science in our country and brought American botany into the international arena.

The initial period of global exploration by Europeans and to a lesser extent the Americans was soon followed by an unprecedented pace of colonization of the newly explored regions of the Americas, Africa, and Asia. In Europe the expanding populations, disease epidemics, economic hardships, and religious persecution sent hundreds of thousands of people to these recently opened territories that promised limitless opportunities and riches. The massive, unspoiled landscapes encountered by European settlers to North America, for example, were viewed as an endless, natural garden to be cultivated and exploited, regardless of the native peoples that inhabited these lands (Shabecoff, 1995). Yet at the same time this wilderness was forbidding and frightening to these early colonists. In response to both of these perceptions, limitless bounty but frightening wilderness, the woodlands were felled, crops were planted, towns and cities grew at the great expense of the natural landscapes. The slow but steady threat to the survival of native species in the New World had begun.

As the 19th and 20th century progressed through unbridled expansion of human populations throughout the world biologists began to realize that natural habitats, landscapes, and even species were indeed limited, transitory, and ephemeral. The abundance of discoveries of species that started in the 18th century led to an intense period of descriptions and taxonomic analysis in the 19th and 20th century. The tremendous influx of new species being described required an overhaul of the earlier classification system of Linnaeus (1753). Major new classification systems of plants were proposed to incorporate the new discoveries first by the French botanist de Jussieu (1789), followed by the British taxonomists Bentham and Hooker (1862-1883), and later the Germans Engler and Prantl (1887-1915).

After the turn of the 19th century Darwin’s theory of evolution through natural selection and the developing field of genetics preoccupied a different set of biologists in their investigations of the natural world. In the 1940s and 1950s a significant decrease took place in the description of new species of plants, perhaps as a result of the international effects of World War II. This decrease of new discoveries was coupled with an increase in the reanalysis of the taxonomic hierarchy and relationship of taxa to reflect new ideas on the nature of species resulting from the evolutionary synthesis led by biologists Theodosius Dobzhansky, Ernst Mayr, George Gaylord Simpson, and George Ledyard Stebbins, Jr. (Mayr and Provine 1980). The intense interest by evolutionary biologists in understanding how species are related to each other, termed phylogenetics, has persisted to the present day. New technological advances using DNA sequence data have revolutionized our concepts on the phylogenetic relationships of plants and a new classification of flowering plants is gaining wide acceptance (Angiosperm Phylogeny Group 2003).

At the same time that taxonomists and evolutionists were trying to understand the evolution and classification of plants, ecologists and environmentalists were beginning to assess the relationship of people to natural habitats. Aldo Leopold and others in the 1940s were early advocates who clearly saw the threat of unbridled human expansion to natural environments and the species that inhabited them. It was not until the 1970s that a significant realization was made by most biologists, ecologists and taxonomists that the natural world was under threat and in trouble. In the last three decades of the 20th century the urgent need to understand and protect the Earth’s habitats and organisms has resulted in an explosion of new academic programs aimed at studying the environment, professional societies (e.g., the Society for Conservation Biology) and local activist groups to unite scientists and citizens in taking action, and even legislation (e.g., the Endangered Species Act) to turn concern for the environment into law.

At the turn of the 21st century it has become clear to biologists, conservationists, and a significant segment of the general public that a major extinction of plants, animals, and microorganisms caused by human activities is not only possible but probable unless immediate action is taken. This threat has resulted in the creation of many local, regional, and national government and non-government organizations devoted to halting and reversing these activities. One international response to this imminent extinction as a result of increasing degradation of the environment was the Convention on Biological Diversity authorized at the Earth Summit in Rio de Janeiro, Brazil, in 1992. This treaty initiated a revolution in the value placed on biodiversity and the intellectual property rights attached to Nature. According to the Convention biodiversity should be conserved, sustainably used, and its benefits shared among all parties. Since the Rio Summit 188 countries have signed the treaty and a host of additional resolutions, national strategies, and work plans have been developed and implemented (see Chapter 13). Although not the initial intent, one result of the CBD was that Nature, like other commercial commodities, has now become internationalized. The ownership of Nature, whether it be for natural product development through “bioprospecting,” establishing logging concessions on indigenous people’s land or collecting plant specimens for scientific study, is now a matter of worldwide concern and law.

The globalization of Nature and biodiversity coupled with increased species extinction has significantly changed the way that modern-day plant explorers and taxonomists pursue their activities. As habitat destruction accelerates, the pace of discovery, identification, and description of new species of plants has also speeded up. The number of newly described species of plants significantly increased in the 1980s and 1990s over the previous four decades. Unlike the predominant perceptions of the 17th and 18th centuries that Nature and species were infinite and limitless, we now know this is not true. Estimates of the number of plant species currently present on Earth range from 220,000 to over 420,000 (Govaerts 2001; Scotland and Wortley 2003). By extrapolation from what we have already described and what we estimate to be present it is possible that at least 10 percent of all vascular plants are still to be discovered and described (J. Kress and E. Farr, unpubl.). This number suggests that a considerable amount of work still needs to be done by botanists to find them.

The recent marriage of biology and advanced technology is leading to the development of novel tools with the potential to transform current methods of plant collecting, such as image recognition software to be employed in electronic field guides and on-the-spot, rapid DNA sequencing, termed DNA bar coding, for species identification. We envision that 21st century naturalists will be equipped with palm-top and wearable computers, global positioning system receivers, and web-based satellite communication. These explorers will more swiftly comb the remaining unexplored habitats of the earth, identifying and recording the characters and habitats of plant species not yet known to science. For example, through remote wireless communication, field botanists will be able to immediately compare their newly collected plants with type specimens and reference collections archived and digitized in museums thousands of miles away. The information gathered by these botanists will be sent with the speed of the Internet to their colleagues back in the lab where the genetic composition and phylogenetic position of each new species will be rapidly determined. The habitat data will be modeled with unparalleled speed and accuracy by ever more powerful computers to determine the place of each species in its respective ecosystem. Moreover, the biochemical constituents of each species will be automatically screened and analyzed for any compounds that may be of benefit to society.

These technological dreams are already being converted into reality by designing new plant explorers of the future. The documentation of the remaining species of plants with the aid of these new tools will provide a solid basis for the precise identification of the species-rich areas of the world for immediate assessment, conservation, and protection. The social, economic, political, and technological changes of the last few decades have ushered in the final age of plant exploration and conservation in the 21st century. We predict that the last new species of plants on the Earth will be discovered and described by the year 2040. Natural history museums will continue to play a central role in the discovery, documentation, and conservation of biodiversity.

Literature Cited

Angiosperm Phylogeny Group [APG]. 2003. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG II. Botanical Journal of Linneae Society 141:399-436.

Bentham, G. and Hooker, J.D. 1862–1883. Genera Plantarum. A. Black (v.1, pt. 1); Reeve and Co. (v.1, pt. 2-v. 3), London.

Engler, A. and Prantl, K. 1887–1915. Die Naturlichen Pflanzenfamilien. Wilhelm Engelmann, Leipzig, Germany.

Govaerts, R. 2001. How many species of seed plants are there? Taxon 50(4):1085-1090.

de Jussieu, A.L. 1789. Genera Plantarum Secundum Ordines Naturales Disposita. Paris.

Linnaeus, C. 1753. Species Plantarum. Stockholm.

Mayr, E. and Provine, W.B. 1980. The Evolutionary Synthesis: Perspectives on the Unification of Biology. Harvard University Press, Cambridge, Massachusetts and London, England.

Scotland, R.W. and Wortley, A.H. 2003. How many species of seed plants are there? Taxon 52:101-104.

Shabecoff, P. 1993. A fierce green fire: the American environmental movement. Hill and Wang, New York.

Note: This essay was adapted from the final chapter of “Plant conservation: a natural history approach” edited by G. A. Krupnick and W. J. Kress being published by the University of Chicago Press, 2005.

W. John Kress
Research Scientist and Curator
Department of Botany, MRC-166
United States National Herbarium
National Museum of Natural History
Smithsonian Institution, P.O. Box 37012
Washington, D.C. 20013-7012
Tel: (202) 63-0920
Fax: (202) 786-2563