Ecology, History of

Historians have debated the origins of ecology for decades. But there is no particular person or precise date or definite occurrence that marks the beginning of the science. Ecology gradually emerged as a distinct discipline during the latter part of the nineteenth century from a diverse array of different areas, including plant geography, plant physiology , taxonomy, and Charles Darwin's theory of evolution.

Linnaeus and Humboldt

One of the most important individuals in the early development of an ecological view of nature was Swedish botanist Carolus Linnaeus (1707-1778). Linnaeus was the father of modern taxonomy, the science of identifying and naming species. His great goal was to describe and catalog all known organisms. In 1749 Linnaeus published a book called The Oeconomy of Nature. In this book Linnaeus presented his view that nature, while seemingly chaotic and unpredictable, actually existed in a balanced state of order as designed by the creator. Linnaeus felt that if one looks closely at nature it is clear that even the simplest organisms have an important role to play in this natural economy; that no living thing is useless.

By the end of the eighteenth century, many scientists began to question Linnaeus's views. They felt that he had been far too descriptive in his approach to understanding nature. Rather than the static, harmonious world that Linnaeus envisioned, nature was dynamic and constantly changing. The chief proponent of these views was German explorer and scientist Alexander von Humboldt (1769-1859). Humboldt insisted that the only way to understand nature's complexity was to take accurate measurements in the field and then search for general laws. Influenced by German philosopher Immanuel Kant (1724-1804), von Humboldt believed that nothing in nature could be studied in isolation. All phenomena were connected.

Darwin and Haeckel

While some historians claim that von Humboldt single-handedly created the science of ecology, the true origins of modern ecology are found in English naturalist Charles Darwin's (1809-1882) On the Origin of Species, published in 1859. Darwin's theory of evolution by natural selection provided a mechanism, not only for understanding how species arose, but also for interpreting patterns in the distribution and abundance of species. A central insight of Origin was that plants and animals had the potential to reproduce very quickly and reach huge population densities. Darwin realized that this potential was rarely achieved because each species is subject to a series of natural checks and balances. "Look at a plant in the midst of its range," said Darwin, "Why does it not double in numbers? … To give the plant increasing numbers, we should have to give it some advantage over its competitors or the animals that prey upon it." While Darwin's work laid the foundation for the emergence of ecology thirty years later, there was no term that clearly defined the new area of biology that he had created.

The German biologist Ernst Haeckel (1834-1919) soon provided a name for the science that Darwin founded. Greatly influenced by Darwin, Haeckel published the Morphology of Organisms in 1866 with the aim of interpreting anatomy in the light of evolution. In this book, Haeckel provided the first definition of ecology: "By ecology we mean the body of knowledge concerning the economy of nature—the total relations of the animal to both to its inorganic and organic environment."

Thanks to Haeckel, ecology finally had a name. But for almost two decades no one seemed to notice. In the 1880s and 1890s, however, ecology experienced an explosion of interest. In Germany in 1885, Hans Reiter published the first book with the new term "oekology" in its title. In Denmark, the botanist Johannes Eugenius Warming (1841-1924) began to study plant physiology in relation to the environment and published the first textbook on plant ecology in 1895. In America, ecology gained almost instantaneous recognition amongst botanists and soon attracted a following of bright, young researchers. The first mention of Haeckel's term in the American press occurred on December 1, 1892, in the Boston Globe. A front-page article read "New Science. Mrs. Richards Names It Oekology." (Mrs. Richards was the leading conservationist of her day and the first director of the Water Quality Lab at the Massachusetts Institute of Technology.) In 1893 the first book in English with ecology in its title, Flower Ecology by L.H. Pammel, was published. Also in 1893, the Madison Botanical Congress adopted the term "ecology" as denoting a new branch of botany distinct from physiology and morphology .

The Twentieth Century

By the start of the twentieth century American plant ecologists had taken a leading role in the development of the new science. At the University of Chicago, Henry Chandler Cowles (1869-1939) began a series of classic studies on ecological succession in the dunes around Lake Michigan. At the University of Nebraska, Frederic Clements (1874-1945) developed new dynamic theories of plant associations and vegetational change. Other ecologists soon challenged the ideas of Cowles and Clements. The British ecologist Arthur Tansley (1871-1955) developed the concept of an ecosystem as an alternative to Clements's classification of plant communities. American botanist and plant ecologist Henry Allan Gleason (1882-1975) criticized Clements's idea of the plant community as a superorganism and proposed an alternative individualistic theory of plant associations.

In the era following World War II, plant ecologists abandoned many of the central principles developed by Clements, including the idea of the stable climax association. They reexamined the central issue of community ecology: whether communities were simply chance associations of independent species or integrated, holistic entities that could not be understood by studying individual species. In the 1950s American botanist and ecologist Robert Whittaker (1920-1980) created a technique called gradient analysis that helped to resolve this question. Whittaker's pioneering studies indicated that plant species had unique and fairly independent distributions across physical gradients such as moisture and temperature. These studies led ecologists to reject Clements's theory of holistic plant communities composed of predictable associations of species that shared similar environmental constraints.

Under the influence of American ecologist and educator Eugene Odum (1913-), a whole new subdiscipline of ecosystems ecology grew to prominence during the latter half of the twentieth century. Ecosystems ecology emphasized both the biotic and physical aspects of the environment. In particular, ecosystems ecology was concerned with the large-scale flows of energy and nutrients through ecological communities. The International Biological Program, and studies by Gene Likens and E. Herbert Bormann of nutrient budgets in the Hubbard Brook Experimental Forest, helped to bring the ecosystem approach to plant ecology into the mainstream of ecological science. While ecosystems ecology has fostered new methods of understanding the complex dynamics of natural systems, it has remained largely separate from more traditional branches of ecology that emphasize populations and individual adaptations.

In the 1990s plant ecologists became increasingly concerned with issues related to biodiversity and the loss of plant habitats due to human activities. Human beings have destroyed about half of the forests that once covered 40 percent of the planet. Each year over 150,000 km² of tropical rain forest are lost to logging, farming, and fire. At this rate there will be no rain forests left in fifty years or less. Earth's plant communities provide homes for millions of different species. They cleanse the air and water, protect against erosion, and replenish the soil. What are the ecological consequences of the continued destruction of forests and other plant habitats? How can what is left be preserved? These and other questions regarding the management and maintenance of the natural world will be the consuming issues for plant ecologists over the coming decade.

see also Clements, Frederic; Darwin, Charles; Ecology; Ecology, Energy Flow; Ecology, Fire; Humboldt, Alexander von; Linnaeus, Carolus; Odum, Eugene; Plant Community Processes; Warming, Johannes.

Bradford Carlton Lister

Bibliography

Kingsland, Sharon E. Modeling Nature. Episodes in the History of Population Ecology. Chicago: University of Chicago Press, 1985.

McIntosh, Robert P. The Background of Ecology: Concept and Theory. Cambridge, UK: Cambridge University Press, 1985.

Real, Leslie A., and James H. Brown, eds. Foundations of Ecology Classic Papers with Commentaries. Chicago: University of Chicago Press.

Ecology, History of

Ecology descended from a tradition of natural history beginning in antiquity. What has been called protoecology is seen in the writings of Carolus Linnaeus, a Swedish botanist, who, in the eighteenth century, wrote of interactions of plants and animals, which he called The Economy of Nature. In the early nineteenth century a German biogeographer, Alexander von Humboldt, stimulated the study of the distribution of vegetation as communities of plants and their environment that was pursued into the twentieth century by such European botanists as Oscar Drude and Eugene Warming. Edward Forbes, a British marine biologist, studied seashore communities early in the nineteenth century and was among the first to use quantitative methods for measuring water depth and counting individual organisms.

Early Roots

The name ecology, however, was coined in 1866 by German biologist Ernst Haeckel, a prominent proponent of Darwinism. In 1870 Haeckel wrote, "Ecology is the study of all those complex interactions referred to by Darwin as the conditions of the struggle for existence." (Darwin himself figures prominently in protoecology.) Ecology emerged as a recognized science in the 1890s and early 1900s as a mix of oceanography, its freshwater counterpart limnology, and plant and animal ecology. It departed from the late-nineteenth-century emphasis on laboratory studies of physiology and genetics to return to the field emphasis of traditional natural history. Premier British animal ecologist Charles Elton defined ecology as scientific natural history.

In the United States, ecology flourished particularly in the Midwest. S. A. Forbes of the Illinois Laboratory of Natural History initiated studies of lakes and streams in the 1880s. In the 1890s Edward A. Birge pioneered lake studies at the University of Wisconsin. Frederic Clements initiated vegetation studies at the University of Nebraska and formulated ideas of ecological communities in the 1890s that dominated American ecology for fifty years. In the same decade Henry C. Cowles, from the University of Chicago, studied the vegetation of the dunes of Lake Michigan.

Clements and Cowles, among the first to earn advanced degrees in ecology, examined the changes of plant species populations, communities, and environments over time, a process they called succession , adapting the term from poet-naturalist Henry D. Thoreau. Clements's concept of succession, which dominated ecology until the 1950s, was of communities developing progressively to a relatively stable state, or climax, that he said had properties of a superorganism. Ecology became institutionalized in British and American ecological societies in 1913 and 1915, respectively.

Integration and Quantification

Charles Elton wrote the first book on animal ecology in 1927 and provided organizing ideas that served to integrate population and community ecology and remain as key concepts. These were:

1. Food chain or cycle (later called food web or trophic structure): the sequence by which nutrients and energy passed from plants to herbivores to predators then to various forms of decomposers and back to the inorganic environment.
2. Niche: Each species had adaptations that fitted it to a particular status in a community.
3. Pyramid of numbers: More small animals are required to support fewer large organisms in a food chain because some nutrients and energy are lost from the food chain.

The 1920s and 1930s also produced early developments in quantitative ecology and mathematical theory. Ecological studies increasingly used quantitative samples of populations and communities to assess the numbers and kinds of organisms in a habitat and to measure the physical environment. Theoretical, mathematical, population ecology was an attempt, particularly by a physicist, Alfred Lotka, and a mathematical biologist, Vito Volterra, to extend principles of physical chemistry into ecology in the form of a differential equation, the logistic, that describes the growth of a population over time.

Ecological theory flourished in the 1950s in the work of George Evelyn Hutchinson and Robert MacArthur, who formulated a niche theory of animal communities predicated on competition among species. Also in the 1950s, the long-ignored, individualistic concept of community of Henry A. Gleason, which held that organisms responded individualistically to the physical environment and other organisms, was resurrected and became widely accepted as alternative to the superorganism theory of Clements. Ecologists became increasingly aware of the significance of historical and chance events for developing ecological theory.

Ecosystems and Human Influences

British ecologist Sir Arthur Tansley recognized that it was not possible to consider organisms apart from their physical environment, as ecologists conventionally did, and in 1935 coined the term "ecosystem." Ecosystems are integrated systems of living organisms (biotic) and inorganic (abiotic) conditions. The ecosystem concept was integrated with the trophic concept and succession in 1942 by a young American limnologist, Raymond Lindeman. Ecosystem ecology focused on the movements of matter and energy through the food web. Partly through the influence of American ecologist Eugene Odum, ecosystem ecology became one of the principal forces in ecology in the 1960s and 1970s and the basis of a new theoretical ecology termed "systems ecology."

As ecology developed as a science it became evident that its concepts of population, community, environment, and ecosystem must incorporate human beings and their effects on Earth. This, too, had antecedents in nineteenth-century natural history. In 1864 George Perkins Marsh argued that human actions have profound, reciprocal, and commonly destructive effects on the earth on which humanity depends. Early ecologists were acutely aware of the implications of ecology for human environments and worked on agricultural, fisheries, wildlife, disease, and conservation problems. This insight became widely evident to the American public and politicians with the recognition in the 1970s of the environmental crisis. In 1962 marine biologist Rachel Carson provided an early warning of the threat of herbicides and pesticides to the environment, a warning for which she was castigated by the chemical industry that produced them and the agricultural industry that used them injudiciously.

Aldo Leopold, an American forester turned animal ecologist, published the Sand County Almanac in 1949 as a plea for an ecological view of the earth and of humanity. Leopold wrote: "That land is a community is the basic concept of ecology, but that land is to be loved and respected is an extension of ethics." Leopold's ideas influenced conservationists and philosophers, especially ethicists, and extended ecological ideas to a concerned public.

see also Biogeochemical Cycles; Biogeography; Carson, Rachel; Community; Ecology; Ecosystem; Linnaeus, Carolus; Theoretical Ecology; von Humboldt, Alexander

Robert P. McIntosh

Bibliography

Carson, Rachel. Silent Spring. Boston: Houghton Mifflin, 1962.

Kingland, Sharon E. Modeling Nature: Episodes in the History of Population Ecology. Chicago: The University of Chicago Press, 1985.

Leopold, Aldo. Sand County Almanac. Oxford: Oxford University Press, 1949.

McIntosh, Robert P. The Background of Ecology: Concept and Theory. Cambridge: Cambridge University Press, 1985.

Worster, Donald. The Wealth of Nature: Environmental History and the Ecological Imagination. Oxford: Oxford University Press, 1993.