ODUM, HOWARD THOMAS

(b. Durham, North Carolina, 1 September 1924; d. Gainesville, Florida, 16 September 2002)

ecology, ecosystem studies, biogeochemistry, thermodynamics, ecological engineering, ecological economics.

More than any other scientist, Odum shaped the way ecologists think about energy. He pioneered large-scale experimental studies of energy flow in natural ecosystems. His theoretical writings, although often esoteric, strongly influenced the development of the field. Howard wrote the chapters on energy for the early editions of the highly influential textbook, Fundamentals of Ecology, authored by his brother Eugene. Howard’s early energy-flow diagrams continue to be widely used both in textbooks of ecology and general biology. Together, the Odum brothers helped to established ecosystems as an important focus of ecology during the 1950s and 1960s. Although the concept never quite attained the centrality that they envisioned, ecosystem ecology has become a recognized and well-established field within ecology. During his long career, Howard Odum trained nearly one hundred students. His ideas continue to be developed by these scientists, who are quick to acknowledge his influence and sometimes proudly identify themselves as “Odumites.”

Education and Intellectual Influences Odum’s father was the sociologist Howard W. Odum, a leading advocate of regionalism. Regionalism, as opposed to sectionalism, favored active government involvement in fostering cooperation and coordination among the various regions of the nation. The elder Odum encouraged his son to pursue a scientific career, and Odum adopted his father’s holistic perspective on human societies. Throughout his career, Odum took a lively interest in topics on the interface between science and society, and he dedicated his most famous book, Environment, Power, and Society, to his father.

Odum was also strongly influenced by his brother Eugene, who was eleven years his senior. As a child he learned about biology, particularly bird watching, from Eugene. Following his brother’s example, Howard Odum’s earliest research was in ornithology, conducted while he was still an undergraduate at the University of North Carolina. This research led to two articles on bird migration and navigation published in the Auk. In his later studies of energy flow in ecosystems, organisms and species virtually disappeared from view. Nonetheless, Odum apparently maintained an informal interest in natural history. According to his student John Ewel, Odum was able to identify all of the songbirds of the eastern United States and every North American seashell.

Odum’s undergraduate studies were interrupted for three years when he joined the Army Air Corps as a meteorologist during by World War II. His work on predicting hurricanes gained considerable recognition, and he later recalled that it stimulated his interest in studying large, complex systems. After the war, he studied under G. Evelyn Hutchinson at Yale University. During the 1940s Hutchinson was deeply involved with research on biogeo-chemical cycles. Together with one of his protégés, the postdoctoral fellow Raymond Lindeman, Hutchinson began discussing biogeochemical cycles and energy flow in terms of the new ecosystem concept. He also explored the field of cybernetics to discuss feedback controls in natural systems, including populations and ecosystems.

Arriving in Hutchinson’s lab in 1947, five years after Lindeman published a seminal paper on energy flow and biogeochemical cycling in aquatic ecosystems, Odum began a dissertation on the biogeochemistry of strontium. Apparently neither Odum nor Hutchinson anticipated the significance that strontium would later have in the atomic age, but Odum’s research was listed in Life magazine as one of the fifteen most noteworthy presentations at the 1950 meeting of the American Association for the Advancement of Science. Later published in Science, Odum’s dissertation research on the strontium content in fossils supported his claim that biogeochemical cycles were maintained in a stable steady state over long periods of geological time. In Odum’s view these biogeochemical cycles driven by solar energy could be described as ecosystems.

Large-Scale Experiments After completing his PhD in 1951, Odum was appointed assistant professor in the Biology Department at the University of Florida. There he began two ambitious experimental studies to measure the overall “metabolism” of ecosystems: one in a freshwater spring in central Florida and the other on a coral reef in the Pacific. For Odum, Silver Springs provided an ideal natural laboratory for studying productivity and the movement of energy through a community of organisms. The flow rate of water from the springs, its temperature, and its chemical content remained relatively constant throughout the year. Therefore, Odum claimed that the system was in a stable state equivalent to what could be artificially produced by a chemostat in a laboratory.

By measuring dissolved oxygen and carbon dioxide upstream and downstream, Odum was able to construct an energy budget comparing photosynthetic productivity of aquatic plants and the respiration of various trophic levels of producers, consumers, and decomposers. He found that most of photosynthetic productivity was consumed by plants themselves, through their own respiration, but that about 12 percent was passed on to herbivores. At each step in the food chain similar respiratory losses were recorded. Odum’s diagram of energy flow

through the aquatic system became famous and was widely reproduced in textbooks of ecology and general biology.

While he was completing the study of Silver Springs, Odum joined his brother Eugene in a similar research project supported by the Atomic Energy Commission at Enewetak Atoll. Enewetak was an important site of nuclear weapons testing, and the Odums’ ecological study was part of a broader move by the commission to understand the biology, geology, and oceanography of the Marshall Islands and to investigate the effects of radiation on the environment.

During a six-week period in 1954, the Odums applied the techniques that Howard had perfected at Silver Springs to study the metabolism of coral reef community. They discovered that the water passing over the reef was nutrient poor, and did not contain enough plankton to support the coral polyps. However, the coral animals housed photosynthetic algae inside their bodies. Other biologists had claimed that the algae were parasites that weakened the coral skeleton by burrowing into it. In contrast, the Odums concluded that the algae were symbiotic partners with the coral animals forming a mutually beneficial relationship. By measuring dissolved oxygen during the day and night on either side of the reef, the Odums were able to calculate the overall “metabolism” of the complete ecosystem, balancing the photosynthetic productivity of the symbiotic algae with the respiration of the living community as a whole.

They described the reef as a highly cooperative system. The coral polyps provided protection for photosynthetic algae that lived inside the small marine animals. In exchange, the algae provided food for the coral. For the Odums, Enewetak became a paradigm case of an ancient ecosystem that had developed a high degree of stability through the obligate mutualism of its constituent populations. The study, published in Ecological Monographs, won the Mercer Award from the Ecological Society of America in 1956.

Throughout his career, Odum pursued daunting experimental studies that would have deterred a less imaginative ecologist. Supported by large grants from the Atomic Energy Commission, he led a team of nearly one hundred scientists in a four-year study (1963–1967) of a tropical rain forest in Puerto Rico. A circular area of the forest approximately 160 meters in diameter was irradiated with radioactive cesium for three months to study the ecological effects of radiation and the ability of the ecosystem to recover from these effects. Odum and his coworkers also constructed a huge plastic cylinder 17 meters tall and about 15 meters in diameter to measure metabolism and transpiration of a section of the forest.

Odum conceived this large-scale study on the model of a military task force, with himself as commander. Individual scientists had to agree not to publish their results before the final report appeared. A Tropical Rain Forest was a massive book, some 1,600 pages long and divided into 111 chapters. Although some critics complained about the book’s lack of cohesiveness, the study served as the study was a precursor to later “big ecology” projects associated with the International Biological Program and Long Term Ecological Research Program.

Ecological Theory From the beginning of his career, Odum took a serious interest in ecological theory, particularly the application of thermodynamics to ecosystem processes. As Peter Taylor noted, Odum reduced all of the complexity of ecological systems to energy relationships. Following an idea first proposed by Alfred Lotka during the 1920s, Odum and the chemist Richard Pinkerton formulated their “maximum power principle,” which Odum considered to be a new law of thermodynamics. According to this principle, all natural systems sacrifice efficiency to maximize power output. Odum and Pinkerton claimed that this maximum power output occurred when the efficiency of energy production was about half of what was theoretically possible. Turning to another early suggestion by Lotka, Odum argued that natural selection favored the persistence of those biological systems that maximized power output. Thus the maximum power principle provided the basis for understanding the stable state that Odum claimed to find in mature ecosystems including Silver Springs, the coral reef at Enewetak, and the El Verde rain forest in Puerto Rico. Formulated early in his career, this idea unified all of Odum’s later work.

One is easily impressed by the mechanistic perspective underlying Odum’s theoretical ecology. He and Pinkerton used numerous simple mechanical models such as waterwheels and systems of weights and pulleys to illustrate the maximum power principle. These were more than simple analogies, because Odum viewed the principle as a law of thermodynamics that applied to all open systems.

Even more than mechanical models, Odum was drawn to electrical circuits. During the late 1950s he began to simulate ecosystem dynamics using simple analog computers. Trophic levels and other ecological units were simulated by electronic components such as resistors and capacitors, and energy flow by the current moving

through the circuits. Later, he replaced these physical models with a more abstract set of symbols that retained the look of traditional electronic symbols, but which Odum hoped would provide a more general way of representing energy relationships. He explored this new energy circuit language, which he called “energese,” in his best-known book, Environment, Power, and Society. The 1971 book effectively encapsulated Odum’s diverse interests, and concisely presented the ideas that impressed his admirers and alarmed his critics. The circuit diagrams were an important contribution to ecosystem modeling, and some admirers later claimed that they marked the birth of a more general discipline of systems ecology. The diagrams also provided an approach to modeling human interactions with natural systems, laying the conceptual foundation for Odum’s forays into ecological engineering and ecological economics.

Critics decried the circuit diagrams as a misleading analogy that ran counter to well-accepted ecological theories, and perhaps violated common sense. Odum’s claim that ecologists should abandon the idea of predators eating their prey and think instead of food being forced through trophic levels by a kind of “ecopotential” struck traditional ecologists as bizarre. Later chapters in Odum’s book, which attempted to use energese to explain complex social activities such as politics and religion were idiosyncratic, and were ignored by ecologists.

Ecological Engineering and Ecological Economics While he was writing Environment, Power, and Society, Odum was pioneering the interdisciplinary field of ecological engineering. Together with his graduate students

he explored the use of wetlands as natural purification systems for human waste. He designed a number of prototypes where partially treated waste was pumped into swamps or other wetlands. These projects, involving over fifty graduate students and numerous faculty members, became a major training ground for ecological engineers. In this context, Odum’s idea of a “partnership with nature” appeared to make sense.

During the final thirty years of his career, Odum focused considerable attention on developing an ecological economics. He attempted to derive a set of energy terms that could be used to discuss energy transformations in systems that were both ecological and economic. At a basic level this was a mechanism for bringing ecosystem processes that have no dollar value into economic discourse. He developed the term emergy (spelled with an m) or “embodied energy” to denote the quantity of energy of one kind required directly or indirectly to produce a service or product. At a more abstract level, his emergy analysis was a continuation of his earlier quest for a universal energy language. Although used by some other ecological economists, it is unclear whether emergy analysis will influence mainstream ecology or economics.

Honors and Awards Howard and Eugene Odum were jointly awarded the Mercer Prize by the Ecological Society of America (1956), the Prix de l’Institute de la Vie by the French government (1975), and the Crafoord Prize from the Royal Swedish Academy of Science (1987). Howard Odum spent most of his career at the University of Florida (1950–1954, 1970–2002), but at various times also held faculty positions at the University of Texas, University of North Carolina, University of Puerto Rico, and Duke University. He published some fifteen books and three hundred articles.

BIBLIOGRAPHY

WORKS BY ODUM

“The Possible Effect of Cloud Cover on Bird Migration.” Auk 64 (1947): 316–317.

“The Stability of the World’s Strontium Cycle.” Science 114 (1951): 407–411.

With Eugene P. Odum. “Trophic Structure and Productivity of a Windward Coral Reef at Eniwetok Atoll, Marshall Islands.” Ecological Monographs 25 (1955): 291–320.

With Richard C. Pinkerton. “Time’s Speed Regulator: The Optimum Efficiency for Maximum Power Output in Physical and Biological Systems.” American Scientist 43 (1955): 331–343.

“Trophic Structure and Productivity of Silver Springs, Florida.” Ecological Monographs 27 (1957): 55–122.

With Robert F. Pigeon. A Tropical Rain Forest: A Study of Irradiation and Ecology at El Verde, Puerto Rico. Oak Ridge, TN: Division of Technical Information, U.S. Atomic Energy Commission, 1970.

Environment, Power, and Society. New York: John Wiley, 1971.

Systems Ecology. New York: John Wiley, 1983.

Environmental Accounting: Emergy and Environmental Decision Making. New York: John Wiley, 1996.

OTHER SOURCES

Ewel, John J. “Resolution of Respect: Howard Thomas Odum (1924–2002).” Bulletin of the Ecological Society of America 84 (2003): 13–15.

Golley, Frank Benjamin. A History of the Ecosystem Concept in Ecology: More than the Sum of the Parts. New Haven, CT: Yale University Press, 1993.

Hagen, Joel B. An Entangled Bank: The Origins of Ecosystem Ecology. New Brunswick, NJ: Rutgers University Press, 1992.

Hall, Charles A. S., ed. Maximum Power: The Ideas and Applications of H. T. Odum. Niwot: University of Colorado Press, 1995. Celebrating Odum’s sixty-fifth birthday, this Festschrift includes over thirty essays by former students and colleagues.

Mitsch, William J., ed. “Energy-Flow in a Pulsing System: Howard T. Odum.” Ecological Engineering 3 (1994): 77–105. Mitsch’s editorial to this special issue is accompanied by several photographs and twenty-five letters of appreciation dedicated to Odum by former students and colleagues.

gTaylor, Peter J. “Technocratic Optimism: H. T. Odum and the Partial Transformation of Ecological Metaphor after World War II.” Journal of the History of Biology 21 (1988): 213–244.

Joel B. Hagen