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Essay on the Geography of Plants
By ALEXANDER VON HUMBOLDT, AIMÉ BONPLAND, Stephen T. Jackson, Sylvie Romanowski
THE UNIVERSITY OF CHICAGO PRESSCopyright © 2009 The University of Chicago
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Introduction: Humboldt, Ecology, and the Cosmos
Stephen T. Jackson
"I formerly admired Humboldt, I now almost adore him...."
"Humboldt had a direct influence on a wider range of people than any scientist since Newton."
We live in a world shaped intellectually by two nineteenth-century figures, Alexander von Humboldt and Charles Darwin. Humboldt's death in May 1859 came only six months before publication of Darwin's On the Origin of Species. Today, nearly 150 years later, virtually everyone in the western world knows something about Darwin while few know anything about Humboldt. Most laypeople know that Darwin had something to do with evolution, and most biologists and environmental scientists are familiar with Darwin's theory of evolution by means of natural selection, his voyage aboard H.M.S. Beagle, his fascination with variation and selection in domesticated pigeons and other animals, his disputes with Agassiz and Owen, his principled conduct in sharing credit with Alfred Russel Wallace, and his friendship with Huxley, Hooker, and Lyell. Dozens of Darwinian legends permeate the culture of modern biology, multiple biographies of Darwin and his contemporaries have been published, and most of his works remain in print. Humboldt, in contrast, is hardly a household name today, although a few geographic features—a river in Nevada, a current in the Pacific, some townships and counties scattered about the United States—bear his name. Most of his works are long out of print, no biographies have been published since the 1970s, and most scientists have at best a vague idea of the breadth and depth of his accomplishments.
The situation was inverted in 1859. Charles Darwin was well known among natural historians for his work on the systematics of cirripedes, his theories of coral-reef formation, and his observations and collections on the Beagle voyage. Although held in high repute by naturalists in England and abroad, his work was largely unknown to the public except for his travel narrative, which had been a minor bestseller in Britain in the 1840s. Humboldt, on the other hand, was an international figure, whose Cosmos had been published in eleven languages and was a standard fixture in lay libraries, along with his Views of Nature and his Personal Narrative of a Voyage to the Equinoctial Regions. Humboldt was the leading scientist and scholar of his day. It is difficult today to comprehend his popular stature—there has been no comparable figure in my lifetime (perhaps a blend of Carl Sagan, Stephen Jay Gould, and Stephen Hawking with some Neil Armstrong, Noam Chomsky, and Edmund Hilary thrown in for good measure). Laypeople and scientists alike read his works and knew of his contributions, and multiple biographies and hagiographies were published in his lifetime. His adventures in South America and elsewhere were widely known; his climbing record on the Chimborazo volcano was not to be broken for another twenty-one years. Humboldt inspired countless individuals to take up the pursuit of science and natural history; had Darwin not read Humboldt's Personal Narrative as a Cambridge undergraduate, he would not have embarked shortly thereafter on H.M.S. Beagle and would today be considered at most a minor figure in Victorian natural history.
Even the scientists who are most indebted today to Humboldt know relatively little of his work. Ecologists and biogeographers may know that he worked out some general principles of plant geography and drew an analogy between latitudinal and altitudinal zonation of vegetation. Climatologists may be aware that he fostered development of the first international net works of meteorological observations and that he invented the isotherm as a means of describing temperature variation in space. Geologists may know that he advocated the volcanic origin of basalt, and geophysicists may know that he pioneered the field of geomagnetism. Physiologists may know of his experimental work on electricity and muscle function. Tropical botanists may know of the thousands of plant species he described with Bonpland and Kunth. Social and economic geographers may credit Humboldt with developing their field and doing exemplary work on the political economy of Mexico and Cuba. But few geographers will know of Humboldt's contributions to physiology, few geophysicists will know of his work in economic geography, few physiologists will know of his work in atmospheric physics, and few ecologists will know of his work in systematic botany.
Humboldt's voyage to the Americas with Aimé Bonpland between 1799 and 1804 was the defining event of his scientific career. At the time of their departure, Humboldt was a well-established scientist of thirty, with publications in botany, physiology, and mineralogy to his credit. However, his five years in the Canary Islands, Venezuela, Cuba, Mexico, the United States, and the Andes of Colombia, Peru, and Ecuador led to his most important and influential scientific works, and his popular writings and lectures on his travels (which overlapped with the technical ones) established his public renown.
After his return from the New World, Humboldt spent the next twenty-two years in Paris, exhausting his considerable inherited wealth in preparing and publishing the results of his explorations. These included sixteen volumes on botany (including descriptions of some 8,000 plant species, 4,000 of them new), two volumes of zoology and anatomy (primarily descriptions of new animal species), four volumes of astronomical and geophysical observations, two volumes each of geographical and pictorial atlases, three volumes on the history of exploration and nautical astronomy of the New World, four volumes on the political economy of New Spain (Mexico), seven volumes of the never-finished Personal Narrative of Travels to the Equinoctial Regions of the New Continent, a volume of popular essays—and one small volume on the geography of plants.
Although the Essay on the Geography of Plants was among the shortest works Humboldt produced, it may have been the most influential, at least scientifically. The Essay, together with its pictorial representation of physical, ecological, and societal properties arrayed along an elevational gradient, changed the way western culture viewed the world. Science was provided a new lens—a geographic lens in which diverse phenomena could be seen to covary systematically across the face of the earth. In previous centuries, Galileo's telescope and Leeuwenhoek's microscope made people aware of worlds beyond previous imagining. Humboldt's more abstract lens made people aware of a world that already lay before their eyes, a world in which the local details of climate, flora, fauna, soil, and culture could all be seen as parts of broader regional and global patterns, just as individual tiles in a mosaic form patterns when viewed in the context of surrounding tiles.
Humboldt's Personal Narrative stimulated people to dream of the tropics, and it motivated a few of them—notably Darwin and Wallace—to go there. Humboldt's Essay provoked people to think about the globe in fundamentally new ways—as a single entity with interlinked biological, physical, and cultural properties varying latitudinally and altitudinally in a systematic and comprehensible fashion. It was the most synthetic and widely influential of the many technical works he published following his voyage. In the Essay, Humboldt integrated a wide array of disparate measures—not only vegetation composition and form, but temperature, geology, atmospheric pressure, atmospheric chemistry, the blueness of the sky, humidity, agricultural practices—into a single view, showing how they varied systematically with altitude and how they were interlinked. Humboldt was aiming for a unitary vision of the world and its phenomena. This was a lifelong pursuit, beginning as early as 1793 and culminating in Cosmos, his five-volume magnum opus, which he was still working on at the time of his death at the age of 90. The Essay constitutes the first full articulation of Humboldt's broad, unitary scientific vision. It was the first substantial work Humboldt published after his return to Europe.
The central ecological and geographical ideas in Humboldt's Essay are not original, in the same sense that little of scientific progress is truly original—to paraphrase Newton, we see further by standing on the shoulders of giants. Botanical, biogeographical, and geographic ideas in the work derive in large part from Humboldt's friends, Karl Willdenow and George Forster. Humboldt's accomplishments were in synthesizing these ideas, portraying them graphically using the concrete example of Chimborazo, and integrating them into a broader vision of science—a vision encompassing space, time, the physical and biotic elements of the earth, and human culture and perception. Even the synthesis, though unique, was not completely original; it built on ideas concerning science, form, and geography derived from two other towering figures of the time, the romantic poet (and scientist) Johann Wolfgang von Goethe and the Enlightenment philosopher Immanuel Kant. Details of the synthesis, and its specific application to Chimborazo, owe much to Humboldt's experience in the Andes and his discussions and tours with local naturalists, particularly Francisco José Caldas of Popayán and José Celestino Mutis of Bogotá. Humboldt combined all of these elements into a unique—and original—synthesis that set the stage for the rapid development of biogeography, ecology, and physical geography during the nineteenth century.
Humboldt's passion for botany was launched at age nineteen, when he met Karl Ludwig Willdenow during a visit to Berlin. Willdenow, only four years senior to Humboldt, had just published a flora of the Berlin region and was fascinated by the problems of plant distributions. He discussed plant geography and physiology with Humboldt, who was deeply influenced by Willdenow's ideas concerning the influence of climate on vegetation. Willdenow, in his 1792 Grundriss der Kräuterkunde, articulated several of the central ideas Humboldt discussed in the Essay. Though Humboldt is often credited with these ideas, Willdenow recognized the dominant role of climate in governing plant geography and vegetation zonation, observed that latitudinal zonation is displaced northward in Europe relative to North America, noted that plants of polar regions grow on mountaintops at lower latitudes, demonstrated that plant diversity increases from pole to equator, and argued that vegetation is zoned latitudinally and not longitudinally. Humboldt later expanded these ideas, confirmed them with collections and observations, and devised effective graphical displays to convey the information to diverse audiences.
Early in 1789, Humboldt joined his older brother Wilhelm at the University at Göttingen, where he studied an array of subjects ranging from archeology and philology to physics and chemistry. At Göttingen, Humboldt met George Forster who, at eighteen, had set out with his father (Johann Reinhold Forster) aboard H.M.S. Resolution on Captain James Cook's second voyage of exploration around the world (1772–75). Forster and Humboldt became fast friends. In the spring of 1790, they traveled together down the Rhine, across Belgium to the French coast, and crossed the Channel to England. They returned by way of Paris, arriving there just in time for the first-anniversary celebrations of the fall of the Bastille. This trip, which was written up by Forster in a three-volume account, had a tremendous influence on Humboldt. He sympathized with the French Revolution, was exposed to a variety of landscapes, languages, and cultures, and most importantly, spent countless hours listening to Forster's accounts of his South Sea voyages and discussing geography and science. Forster's father had recognized the role of climate in shaping plant form and distribution, and viewed vegetation pattern as the most important signature of the environment. George Forster adopted this view as well, expanding it to a unitary vision of geography, whereby all natural phenomena showed interlinked patterns in space. Forster's views grounded the next seven decades of Humboldt's thinking.
After the trip with Forster and a boring interlude in business school in Hamburg, Humboldt traveled to Saxony for a stint at the Freiberg Academy of Mines—at the time the foremost academy of its kind in the world. Abraham Gottlob Werner directed an intensive and rigorous curriculum of geology, engineering, mathematics, chemistry, and surveying. In his daily trips to the pits and shafts of the local mines, Humboldt observed mosses, fungi, algae, and vascular plants growing in seemingly unfavorable and lightless environments, and he studied them with what time he could spare. He spent the next five years as a mining inspector in Prussia, where he improved mining and extraction efficiency, opened a free training school for the unlettered miners (paid for out of his own pocket), and devised a number of mine-safety improvements, including portable breathing devices and safety lamps. At the same time, he completed and published his second scientific monograph, Florae Fribergensis (1793). This work is principally concerned with the physiology of the subterranean plants, algae, and fungi that Humboldt found in the mines. However, it includes a discussion of the general approach to plant geography that Humboldt was developing in his mind, influenced by Willdenow and Forster, as well as by Immanuel Kant's essays on physical geography.
Humboldt's earliest scientific work was largely observational and synthetic. However, he soon demonstrated an aptitude for careful and systematic experimentation. Humboldt became interested in the recently discovered principle of galvanism, whereby muscles are stimulated by the application of electrical current. Between 1792 and 1797, he did extensive experiments on the subject, many on himself. In the course of these studies, he came very close to stumbling on the principle of the battery, discovered a short time later by Volta. Humboldt described some 4,000 individual experiments, involving some 300 different kinds of animals and plants—mice and mimosas, leeches and tapeworms. He concluded that animals share the general potential for electrical stimulation (which is lacking in plants), and that the electrical stimulation is transmitted through nerves. The lasting significance of these studies, summarized in a two-volume monograph (1797), lies in Humboldt's rigorous, systematic application of reductionist, experimental science.
Humboldt's reductionist empiricism confronted its holistic, intuitive antipode when he met Johann Wolfgang von Goethe in 1795. Humboldt and Goethe shared interests in the sciences and visual arts, and it is a credit to their powerful and nimble intellects that instead of colliding they became close friends and mutual admirers. Goethe had already established himself as a premier writer with The Sorrows of Young Werther and numerous poems, and he had for some time also been preoccupied with the morphology of plants and the physics of color. He had published his Metamorphose der Pflanzen (Metamorphosis of Plants) five years earlier, in which he made a series of arguments that were to influence Humboldt's perception of nature and vegetation. Goethe's concept of organic morphology (a word he coined) was central to his thinking. He emphasized the features that all plants held in common (rather than those which differentiated them, which Linnaeus and his followers focused on), and viewed plant genera, species, and individuals as variations of archetypal forms. Goethe also observed that the outer forms of plants and animals reflected their environments, noting, for instance, that the submersed leaves of Ranunculus aquatilis differed morphologically from the aerial leaves, and that individuals of the same species varied morphologically when grown in different habitats. Finally, he viewed form as an index to underlying processes—by understanding surface features, fundamental insights would emerge. These notions were to play important roles in Humboldt's ecological thinking.
Excerpted from Essay on the Geography of Plants by ALEXANDER VON HUMBOLDT, AIMÉ BONPLAND, Stephen T. Jackson, Sylvie Romanowski. Copyright © 2009 The University of Chicago. Excerpted by permission of THE UNIVERSITY OF CHICAGO PRESS.
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