The emergence of ecology from natural history by Keith R. Benson

The modern discipline of biology was formed in the 20th century from roots deep in the natural-history tradition, which dates from Aristotle. Not surprisingly, therefore, ecology can also be traced to natural history, especially its 19th-century tradition emphasizing the adaptive nature of organisms to their environment. During the 20th century, ecology has developed and matured from pioneering work on successional stages to mathematically rich work on ecosystem energetics. By the end of the century,
ecology has made a return to its natural-history heritage, emphasizing the importance of the integrity of ecosystems in considering human interactions with the environment.

Today, the field of biology includes a vast array of diver-gent and unique subdisciplines, ranging from molecular biology to comparative endocrinology. With very few exceptions, most of these specialty areas were created by biologists during the 20th century, giving modern biology its distinctive and exciting character 1 . However, before 1900, the field was much different because even the term biology was seldom used 2 . Indeed, most of those who studied the plants and animals scattered over the earth’s surface referred to themselves as naturalists: students of natural history 3 . Perhaps the most popular form of contemporary biology is the subdiscipline most closely related to the natural-history roots of biology: ecology.

As with many things currently enjoying popularity, however, the term ‘ecology’ is often poorly understood and even more inaccurately used. Considered by convention to be synonymous with ‘natural’, ‘environmental’ or ‘conservation’, it is frequently used to refer to a personal perspective on the natural world or to a political position concerning the use of nature. In fact, many of those who describe themselves as ecologically oriented, as having an ecological perspective or as being interested in ‘saving the ecology of the land’ have never bothered to take a university-level course in ecology or to have examined in any depth a classic eco-logical text. As a result, the exact nature and definition of ‘ecology’ remains obscured by its popular usage.
In part, some of the definitional misunderstanding comes from ecology’s biological lineage. Certainly, its subject matter (the planet’s ecosystems) has a much greater reso-nance with the general public than, say, the arcane and esoteric subject that is molecular biology. Nevertheless, like molecular biology, ecology emerged as a distinct area in biology only at the turn of the century but very quickly developed its own conventions of biological discourse. Unlike molecular biology and several other
biological subsciplines, ecology’s roots are buried deep within natural history, the descriptive and often romantic tradition of studying the productions of nature.
Perspectives on the natural world before the 20th century Aristotle, the western world’s greatest philosopher who included the natural world in his philosophical treatments, was the first to record observations about the natural his-tory of the earth’s plants and animals 4 . However, his teleo-logical world of designed and invariable types hardly placed a stress upon the reciprocal and dynamic relationships that exist between the biotic world and the earth’s physi-cal environment. Not surprisingly, given his assumption of the eternal nature of species, Aristotle did not stress the adaptive character of fauna and flora, which is perhaps ecology’s cornerstone. In fact, adaptation did not appear as a biological notion until nature was reinterpreted as the product of a historical and developmental process at the end of the enlightenment (18th century). Thus, for almost 2000 years, naturalists considered the earth to have been created originally much as it was observed. As part of the scientific revolution capped by Isaac
Newton at the beginning of the 18th century, natural philosophers opted to examine the natural world for mechanical explanations of natural phenomena, often in terms of mechanisms they could either observe in nature or infer from nature. These explanations, best exem-plified by the law-like behavior of Newton’s universal gravitation, promised to provide precise and knowable information about nature, usually in mathematical form.No longer bound to accept the natural world as a created
given, the philosophes of the enlightenment soon began to apply the Newtonian method to the biotic world. The limitations of this application became apparent almost immediately. Bernard de Fontenelle expressed the futility of the age’s mechanistic orientation when he proclaimed that two mechanical watches will sit side by
side forever without producing a third but, if two dog ‘machines’ are placed side by side, more dogs would soon appear!

Animal generation, along with a host of other biotic operations, seemed to resist the simplicity of the mathematical treatment of invariable mechanical laws 5 . Nevertheless, the mechanical philosophy opened the door for fresh investigations of plants and animals, their relationships to each other, and their relationships to the natural world. By the beginning of the 19th century, the notions of structural analogy (transformism) and func-tional integrity (biogeographical distribution) that investigators re-corded from their observations be-gan to lead them to examine the his-torical record of the earth’s fauna and flora 6 . This was particularly true as naturalists observed that different landscapes of the earth’s surface with almost identical physical conditions had remarkably different resident populations of plants and animals. This was quite a surprise because, according to the prevailing view of natural law, the same environ mental conditions should produce nearly identical species. Yet, for example, Australia had endemic forms of life seen nowhere else on the globe. The new stress on the uniqueness of the forms of life along with the uniqueness of the landforms served as the fertile soil for what became ecological insights. But those who made these observations were not, per se, ecologists.Instead, they were among the 19th century’s most accom-plished naturalists. At the beginning of the 19th century, the German adventurer Alexander von Humboldt waxed eloquent about the characteristic physiognomic features of the landscapes in South America, stressing how these
visible features (hence his reference to physiognomy) depended in large part upon the environmental character-istics that controlled the flora. Four decades later, Joseph
Dalton Hooker was to make similar observations in his travels to the Himalayas, New Zealand, Tasmania and Australia itself. Hooker’s more famous compatriot and colleague Charles Darwin observed similar features during his famous voy-age aboard the ‘Beagle’, completed about a decade before Hooker’s voyages but receiving their most influential reading after the publication of On the Origin of Species 7 . In fact, the importance of Darwin’s influential work on the development of ecology cannot be emphasized enough. After all, Darwin was the first to stress forcefully that ani-mals and plants were not perfectly adapted to their natural environments, as earlier naturalists had once believed. Instead, they represented only the best-adapted forms pro-duced at a particular place and time by selective forces, which, in turn, chose the adaptation that was optimal for the conditions that then existed. When conditions (including both biotic and abiotic factors) changed, so the adaptive needs also changed. Those plants and animals that in-cluded an adaptive characteristic favorable to the new
conditions would survive; those not so favorably equipped would perish. The ‘Darwin of Germany’, Ernst Haeckel, devoured On the Origin of Species almost as soon as it was published, becoming an immediate convert to the theory of descent by modification, as evolution theory was originally known. In his influential book Generelle Morphologie 8 , Haeckel stressed the Darwinian notion of change over time pro-duced by the dynamic relationship of organisms and their natural environments. As a measure of the importance of this relationship, Haeckel, who was fond of neologisms, coined the word oecologie, referring to the study of the re-lationship of organisms to their surroundings. In his popu-lar 1876 English edition of his ideas, History of Creation, he noted that Darwin’s doctrine of adaptation provided the law-like nature to explain ecological relationships 9 . Haeckel was not, however, the first ecologist, nor did he immediately spawn an ecological program in Germany. Instead, he served as one of the seminal figures in the 19th century to stress the growing appreciation that the relationship of plants and animals to their natural en-vironments was historical and dynamic. Two other Euro-pean naturalists, Oscar Drude and Eugenius Warming, who were influenced by these same ideas, soon began to stress the study of pflanzengeographie (plant geography), noting the community structure of plant groupings that character-ized specific landforms with specific environmental con-ditions 10 . Remarkably, for there was not an equivalent scien-tific community in the USA to match that in Europe, these
ideas were picked up by American naturalists at the end of the 19th century: Charles E. Bessey at the University of Nebraska and John Coulter at the University of Chicago. Ecology’s early-20th-century roots Neither Bessey or Coulter, however, is well known as an ecologist. Both were natural historians at their respective institutions, trained in the traditional methods of naturalhistory, emphasizing the naming, description and classifi-cation of plants and animals. However, both were also well read in the new trends of the emerging field of biology and they knew of the implications that evolution theory had on their own studies. Encouraging their students to pursue new research opportunities that stressed the new biological perspectives at the end of the 19th century, Bessey led Frederic Clements to the work of Drude, and Coulter directed Henry Chandler Cowles to Warming 11 . Certainly, there may be other national claims to the origins of ecology, including the German one, but the role of the USA in the development of ecology through these two midwestern schools cannot be diminished. Coulter’s star pupil, Cowles, was soon working on the plant-community structure of the sand dunes along Lake Michigan, referring to his work as physiographic plant ecology. That is, he was interested in studying the relationship of plant communities to the underlying geological formation, a relationship that he thought explained why the physiology of the plant responded to the geological features of the land, leading to characteristic geographical groupings of plants.

Noting that the plant community and the environment were in constant flux, Cowles was led to view natural systems as being characterized by change: processes that
were evident in the succession of floral community struc-ture observed in the sand dunes 12 . Early in the 20th century, Cowles transported his new ideas to a marine setting at the University of Washington’s new laboratory at Friday Harbor (on the San Juan Islands in the Gulf of Georgia), where he taught the first course in marine ecology in the USA. His most famous student, Victor Shelford, was to continue his work on the West Coast, working on eco-logical nvestigations at Friday Harbor through the early
1930s.
In Nebraska, Bessey’s protégé was Frederic E. Clements, a student who came to understand the Drude version of community structure through his own survey of native vegetation in that State. First in the Phytogeography of Nebraska (1900), then in Research Methods of Ecology (1905) and finally in Plant Succession (1916), Clements laid out his influential ideas of plant-community struc-ture, succession stages of community development and the climax community, the ultimate goal of mature natural
habitats 13 . But Clements did much more than just provide a programmatic design for the new field of biology. Supported by the Carnegie Institution of Washington, he
was able to develop laboratory facilities in ecology in Colorado and California, where he provided empirical and experi-mental demonstrations of his newideas, thus helping to popularize the new field of ecology. Most of these biological investi-gators
were also well aware that they were breaking new ground in the understanding of the dynamical relationship between plants and animals and their environments, thus contribut-ing to a new field of ecology. Clements rferred to the ecologist as an outdoor physiologist, a reference to the ex-citing laboratory-based area of physiology just emerging in institutes throughout Germany and England and begin-ning to appear in the new scientific universities in the USA. Shelford referred to the new field as scientific natural history, again a reference to the experimental and labora-tory (field-laboratory) approaches developed at Nebraska and Chicago that acted to move natural history in a different direction from its traditional museum heritage 14 . However, limitations to the new field cropped up almost immediately. One problem was that it was difficult to investigate animals with the same approaches used for plants, as the fauna did not remain fixed to the environ-mental substrate in the same way that the flora was fixed. Thus, the physical factors that provided the causal deter-minates
of community structure were more difficult to establish. Second, some ecologists soon began to question the goal-directed nature of Clements’ climax communi-ties, preferring to view the natural world as being in constant flux.

Many of these ecologists were influenced by the re-publication of an article by Stephen Forbes from 1887, which received its greatest reception in the 1920s 15 . Forbes’ emphasis on the dynamic equilibrium of all the components of the lake seemed to offer a different way to appreciate nature, one that stressed the natural world as a system. Instead of succession stages, Forbes pointed ecologists toward seeing the world as a vast array of inter-dependent environments through which materials and en-ergy
were constantly being cycled. Charles Elton adopted this position in his influential book, Animal Ecology (1927), freeing ecologists from merely examining the physical
factors of environments but also obligating them to search for methods to evaluate the immense constellation of factors that determine community structure 16 .
The maturation of modern ecology Although Clements’ work continued to be enormously influential, its stress on deterministic climax communities drew increasing criticism from ecologists in the 1930s, especially from those who were interested in adding the study of animals to ecology. The English ecologist A.G. Tansley provided the most cogent attack in an article in the new journal Ecology in 1935, challenging his col-leagues to adopt the term ecosystem, a reference stressing the dynamic nature of community structure rather than Clements’ goal-directed climax stage 17 . When G. Evelyn Hutchinson and his student Raymond Lindeman provided clear, albeit highly complicated, mathematical models to depict the various interacting com-ponent parts of the ecosystem, ecol-ogy promised to become a fully mathematized and experimental discipline. Lindeman, in particular, contri-buted
to this important change when he published a paper in 1942 that synthesized the work of Clements, Elton, Tansley and his mentor Hutchinson by speaking of biogeochemical
cycling, energy flow through trophic levels and dynami succession 18 . Even more importantly, he saw the con-tinuous cycling of material through the ecosystem as an energy-driven process that included producers (organisms that fixed the energy from the sun), consumers and de-composers, which cycled material back to the producers as energy from the sun continued its one-way flow through the ecosystem.

By the end of World War II, ecology had become thoroughly transformed from scientific natural history to ecosystem ecology. Nowhere was this more evident than
in the publication of the ecologists’ Bible, Principles of Animal Ecology, written by W.C. Alee and his colleagues at the University of Chicago during the War but only published in 1949 19 . Although community structure and succession still remained basic ecological principles, the climax community was now treated as virtually syn-onymous with mature community and most of the book dealt with the dynamic inter-relationships of ecological investigations. Even more important, the last chapter of the book featured a long discussion of the evolution of interspecies integration and ecosystems, emphasizing the influence of the Hutchinson and Lindeman approach
(both authors are heavily cited in the book). ecology and its professional practitioners are often greeted as advocates for the conservation or preservation of the natural world By the end of World War II, ecology had become thoroughly transformed from scientific natural history to ecosystem ecology
Even more dramatic for the new direction in ecology was the publication of Eugene Odum’s new text, Fundamentals of Ecology (1953), with its overt recognition of systems theory. In addition to the mathematical modeling from Hutchinson and Lindeman, Odum also benefited from his experience with the Atomic Energy Commission and its Atoms for Peace project 20 . Using radioactive materials, he was able to
observe and to measure the recycling of inorganic materials throughout the ecosystem, leading him to borrow from physiology and to refer to the metabolism of the ecosystem. By the time the second edition of the book appeared (1959), it was full of energy-flow diagrams, with arrows pointingin all directions to emphasize the inter-relatedness of the myriad factors within an ecosystem. Soon, Odum became convinced that it was the complex interactions within the ecosystem that provided its stability, protecting it from perturbations in much the same way as homeostasis in organisms regulates the physiology of those systems. Ecology and environmentalism There were other perturbations that soon attracted Odum’s attention. Rachel Carson published Silent Spring in 1961, a damning exposé of the pesticide industry in general and the use of DDT in particular. President Kennedy convened the first presidential commission on the environment, a commis-sion that almost immediately recommended the prohibition of DDT. However, there were other issues within the en-vironment, ranging from suffocating air pollution in Los Angeles to fiery water pollution on the Cayuhuga River in Cleveland. Odum soon saw his role not just as an ecological researcher but as an advocate to preserve the earth’s fragile ecosystems. In the third edition of his text (1971), he added a chapter on the environment and conservation, also explaining how ecological principles, such as the food pyramid, could be used to explain how non-biodegradable pesticides (e.g. DDT) take their toll on the ecosystem by accumulating at the top of the pyramid. Thus, ecology now claimed a new niche, that of informing the populace about environmental issues. Ironically, ecology’s contributions to the environmental crisis may have caused it to become much more popular with the public and to return it, at least in the eyes of the general public, back to natural history. That is, the stress in ecology on the integrity of natural systems has led many to consider the word ‘ecology’ to be synonymous with ‘environmental’, conservationist’ or even ‘natural’. Certainly, ecology and its professional practitioners are often greeted as advocates for the conservation or preservation of the natural world. And this characterization is often correct, for many ecologists and their professional organizations (e.g. the Ecological Society of America) have been quick to criticize societal practices that harm the environment and have also been among the forefront of citizens arguing for the need to set aside vast
areas of the environment for study and for preservation. However, in large part, in addition to scientific support, these positions are taken for the same esthetic reasons that lead non-ecologists to protect the natural world. That is, our experiences in nature seem to have a salutory influence on us as humans. Ecologists are those fortunate enough to have adopted a profession that keeps them closely attached to their historical roots in natural history.

Notes and references
1 Rainger, R. et al., eds (1988) The Development of American
Biology, University of Pennsylvania Press
2 The Frenchman Lamarck and the German Treviranus are generally credited as being the first to originate the word biologie at the beginning of the 19th century, which they used to separate the living world from the world of the inert. Joseph Caron has written about the origin of the word biology in its modern context: Caron, J. (1988) ‘Biology’ in the life sciences: a historiographical contribution. Hist. Sci. 26, 223–268
3 The term ‘natural history’ is the time-honored way to describe the investigation of the natural world, including plants, animals and geological specimens. This was the tradition pioneered by Aristotle, given its modern guise by Georges Buffon in
his Histoire Naturelle (1749–1789) and memorialized in the famous Museum d’Histoire Naturelle in Paris
4 One of Aristotle’s most widely cited works is Historia Animalium, which is the text upon which many later works in natural history were based. His student Theophrastus
wrote an Aristotelian botanical work, Historia Plantarum, which provided the botanical analog for later naturalists. The best work on Aristotle as a biologist is Grene, M. (1963) A Portrait of Aristotle, University of Chicago Press
5 Roger, J. (1963) Les Sciences de la Vie dans la Pensee Francaise du XVIII Siecle, Armond Colin
6 Larson, J.L. (1994) Interpreting Nature, Johns Hopkins University Press
7 Darwin, C. (1859) On the Origin of Species, John Murray
8 Haeckel, E. (1866) Generelle Morphologie der Organismen, G. Reimer
9 Haeckel, E. (1876) History of Creation, Appleton
10 Drude, O. (1896) Deutschlands Pflanzengeographie (1896);
Warming, E. (1896) Lehrbuch der Okologischen Pflanzen-geographie eine Einfuhrung in die Kenntniss der Pflanzenvereine
11 Tobey, R. (1981) Saving the Prairies: The Life Cycle of the
Founding School of American Plant Ecology, University of California Press
12 Cowles, H.C. (1899) The ecological relations of the
vegetation of the sand dunes of Lake Michigan. Bot. Gazette
27, 95–117; Cowles, H.C. (1899) The ecological relations of
the vegetation of the sand dunes of Lake Michigan. Bot.
Gazette 27, 167–202; Cowles, H.C. (1899) The ecological relations of the vegetation of the sand dunes of Lake Michigan. Bot. Gazette 27, 281–308; Cowles, H.C. (1899)
The ecological relations of the vegetation of the sand dunes of Lake Michigan. Bot. Gazette 27, 361–391
13 Pound, R. and Clements, F.E. (1900) The Phytogeography of Nebraska, Botanical Seminar; Clements, F.E. (1905) Research Methods in Ecology, University Publishing Company; Clements, F.E. (1916) Plant Succession, Carnegie Institute of Washington
14 The rhetorical power of the words ‘laboratory’ and ‘experiment’ needs to be stressed within this context. Natural history’s traditional methods were often seen to be somewhat dated, especially in comparison to the methods of experimentation, a major component of physiology. Thus, the closer the ecologists could come to experimental or laboratory-based methods, the closer they imagined themselves to be to the cutting-edge aspects of modern 20th-century biology.
15 Forbes, S.A. (1887) The lake as microcosm. Bull. South Africa Peoria 77–87
16 Elton, C. (1927) Animal Ecology, Macmillan
17 Tansley, A.G. (1935) The use and abuse of vegetational concepts and terms. Ecology 16, 284–307
18 G. Evelyn Hutchinson was enormously influential in the development of modeling in ecology, but the seminal article was written by his student Raymond Lindeman. The paper was published posthumously as Lindeman, R.L. (1942) The trophic–dynamic aspect of ecology. Ecology 23, 399–418
19 Allee, W.C. et. al. (1949) Principles of Ecology, W.B. Saunders
20 Odum’s father was a sociologist who borrowed heavily from the work of sociologists at Chicago, the same individuals who were so influential on the Chicago school of ecology. In addition, his brother Howard studied with Hutchinson at Yale, providing Eugene Odum with direct access to the new dynamical model of ecology. Odum, E.P. (1953) Fundamentals of Ecology, W.B. Saunders
Note: See Slobodkin, L.B. and Slack, N. (1999) George Evelyn Hutchinson: 20th-century ecologist. Endeavour 23, 24–30 62 Endeavour Vol. 24(2) 200
Is currently a professor of medical history and ethics at the Uni- versity of Washington, where he serves as Director of the Program
in the History of Science, Technology and Medicine. He is coeditor of two books on the history of American biology and has written
numerous articles on the development of the biological sciences in the USA. He is also a past Executive Secretary of the History of
Science Society. At present, he is completing a book on the history of marine biology in the USA. krbenson@u.washington.edu