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.