Balance of nature

DEFINITION: Ecological concept that nature, in its undisturbed state, achieves constant equilibrium

The concept of the balance of nature has never been legitimated in science as either a hypothesis or a theory, but it persists as a designation for a healthy environment.

Greek natural philosophers in the fifth and sixth centuries BCE attempted to explain naturalistically how nature works rather than depending upon myths. The atomistic theory of Leucippus and Democritus stated that matter can be transformed but is never created or destroyed. The Pythagoreans heard musical harmony in the universe. Hippocratic medicine taught that the balance of humors within the body produces health and an imbalance produces disease, and Greek physicians believed in the healing power of nature. Within this worldview, ecological balance would have been a compelling expectation.

Herodotus, the father of history, wrote about not only the human histories of Greece, Persia, and Egypt but also their geographies and natural histories. He was influenced by ideas in natural philosophy, and he was concerned with concrete examples that might illustrate generalities. In organizing his information on the lions, snakes, and hares of Arabia, he asked why predatory species do not eat up all of their prey. His answer was that a superintending “Providence” had created the different species with different capacities for reproduction. Predatory species, such as lions and snakes, produce fewer offspring than species that they eat, such as hares. From Egypt, Herodotus obtained a report about a mutually beneficial relationship between Nile crocodiles and plovers: Crocodiles allow plovers to sit on their teeth and eat the leeches that infest their mouths.

Plato lived after the natural philosophers and Herodotus, but he lacked their trust in sensory data, and therefore he explained nature with naturalistic myths. In a dialogue called Prōtagoras (c. 390 BCE; English translation, 1804), Plato asked Herodotus’s question about why some species do not eat up the others, but he asked it more abstractly and not for its own sake. The point of this creation myth was to explain why humans do not have specialized traits such as wings or claws. The gods assigned to Epimetheus the task of creating each species with traits that would enable it to survive. He had given out all the specialized traits before he got around to creating humans, and his brother Prometheus had to save humanity by giving it reason and fire. The secondary point of the myth supplements what Herodotus had concluded about differences in reproduction with a conclusion about differential traits that ensure survival.

In the writings of Aristotle and his colleagues in Athens, full-fledged science emerged. These scholars realized the importance of both collecting data and ordering it so as to allow the drawing of conclusions. These scholars, however, focused on physiology and anatomy and neglected to look for what modern-day persons call ecological explanations of how nature works. For example, they explained that the greater number of offspring in hares than in lions is because of their size. Since hares are smaller, it is easier for more of them to grow within a female than for multiple larger lion cubs to grow in their mother. The balance-of-nature concept was not distinct enough to require either defending or refuting.

Scientific Revolution

The ancient Romans excelled in engineering, not science. They were mostly content with abbreviated Latin versions of Greek science. Roman writings are still worth mentioning, however, because of their influence on later European naturalists. Aelianus compiled a popular natural history book that, among other things, explained that jackdaws are friends to the farmer because jackdaws eat the eggs and young of locusts that would eat the farmer’s produce. The philosopher Cicero wrote an influential book, De natura deorum (44 BCE; On the Nature of the Gods, 1683), in which he saw the work of Providence in endowing plants with the capacity to feed humans and animals and still be able to have seeds left over to ensure their own reproduction. Another philosopher, Plotinus, pondered the evil of suffering when predators kill animals for food. He decided that the existence of predation allows a greater diversity of life to exist than would be possible if all animals ate plants. These miscellaneous observations were insufficient for a theory, but they kept alive the notion of a balance of nature.

During the scientific revolution, fresh observations and conclusions appeared. Most significant, John Graunt, a merchant, analyzed London’s baptismal and death records in 1662 and discovered the balance in the sex ratio and the regularity of most causes of death (excluding epidemics). England’s chief justice, Sir Matthew Hale, was interested in Graunt’s discoveries, but he nevertheless decided that the human population, in contrast to animal populations, must have steadily increased throughout history. He surveyed the known causes of animal and in 1677 published the earliest explicit account of the balance of nature.

English scientist Robert Hooke studied fossils and in 1665 concluded that they represented the remains of plants and animals, some of which were probably extinct. John Ray, a clergyman and naturalist, argued in response that the extinction of species would contradict the wisdom of the ages, by which he seems to have meant the balance of nature. Ray also studied the hydrologic cycle, which is a kind of environmental balance of water. In the late seventeenth century, Antoni van Leeuwenhoek, one of the first investigators to make biological studies with a microscope, discovered that parasites are more prevalent than anyone had suspected and that they are often detrimental or even fatal to their hosts. Before that, it was commonly assumed that the relationship between host and parasite was mutually beneficial.

Richard Bradley, a botanist and popularizer of natural history, pointed out in 1718 that each species of plant has its own kind of insect and that there are even different insects that eat the leaves and bark of a tree. His book A Philosophical Account of the Works of Nature (1721) explored aspects of the balance of nature more thoroughly than had been done before. Ray’s and Bradley’s books may have inspired the comment in Alexander Pope’s An Essay on Man (1733-1734) that all the species are so closely interdependent that the extinction of one would lead to the destruction of all living nature.

Toward a Science of

Swedish naturalist Carolus Linnaeus was an important protoecologist. In his essay Oeconomia Naturae (1749; The Economy of Nature, 1749) he attempted to organize the aspect of natural history dealing with the balance of nature, but he realized that one must study not only ways that plants and animals interact but also their habitats. He knew that while balance had to exist, there occurred over time a succession of plants, beginning with a bare field and ending with a forest. In Politia Naturae (1760; Governing Nature, 1760) he discussed the checks on populations that prevent some species from becoming so numerous that they eliminate others. He noticed the competition among different species of plants in a meadow and concluded that feeding insects kept them in check. French naturalist Comte de Buffon developed a dynamical perspective on the balance of nature from his studies of rodents and their predators. Rodents can increase in numbers to plague proportions, but then predators and climate reduce their numbers. Buffon also suspected that humans had exterminated some large mammals, such as mammoths and mastodons.

However, a later Frenchman, Jean-Baptiste Lamarck, published a book on evolution called Philosophie zoologique (1809; Zoological Philosophy, 1914), which cast doubt on extinction by arguing that fossils represent only early forms of living species: Mammoths and mastodons evolved into African and Indian elephants. In developing this idea, he minimized the importance of competition in nature. An English opponent, the geologist Charles Lyell, argued in 1833 that species do become extinct, primarily because of competition among species. Charles Darwin was inspired by his own investigations during a long voyage around the world and by his reading of the works of Linnaeus and Lyell. In his revolutionary book On the Origin of Species by Means of Natural Selection: Or, The Preservation of Favoured Races in the Struggle for Life (1859), Darwin argued an intermediate position between those of Lamarck and Lyell: Species do evolve into different species, but in the process, some species do indeed become extinct.

Darwin’s theory of evolution might have brought an end to the balance-of-nature concept, but it did not. Instead, American zoologist Stephen A. Forbes developed an evolutionary concept of the balance of nature in his essay “The Lake as a Microcosm” (1887), in which he observes that although the reproductive rate of aquatic species is enormous and the struggle for existence among them is severe, “the little secluded here is as prosperous as if its state were one of profound and perpetual peace.” Forbes emphasized the stabilizing effects of natural selection.

Ecology

The science of became formally organized in the period from the 1890’s through the 1910’s. One of its important organizing concepts was that of “biotic communities.” Frederic E. Clements, an American plant ecologist, wrote a large monograph titled Plant Succession (1916), in which he drew a morphological and developmental analogy between organisms and plant communities. Both the individual and the community have a life history during which each changes its anatomy and physiology. This superorganismic concept was an extreme version of the balance of nature that seemed plausible as long as one believed that a was a real entity rather than a convenient approximation of what one sees in a pond, a meadow, or a forest. However, the studies of Henry A. Gleason in 1917 and later indicated that plant species merely compete with one another in similar environments; he concluded that Clements’s superorganism was poetry, not science.

While the balance-of-nature concept was giving way to ecological hypotheses and theories, Rachel Carson decided that she could not argue her case in Silent Spring (1962) without it. She admitted, “The balance of nature is not a status quo; it is fluid, ever shifting, in a constant state of adjustment.” Nevertheless, for Carson the concept represented a healthy environment, which humans could upset. Her usage of the phrase has persisted within the environmental movement.

In 1972 English medical chemist James Lovelock developed a new balance-of-nature idea, which he called Gaia, named for a Greek earth goddess. His reasoning owed virtually nothing to previous balance-of-nature notions, which focused on the interactions of plants and animals. His concept emphasized the chemical cycles that flow from the earth to the waters, atmosphere, and living organisms. Lovelock soon had the assistance of a zoologist named Lynn Margulis, and the studies they conducted together convinced them that biogeochemical cycles are not random; rather, they exhibit homeostasis, just as some animals exhibit homeostasis in body heat and blood concentrations of various substances. Lovelock and Margulis argued that living beings, rather than inanimate forces, mainly control the earth’s environment. In 1988 three scientific organizations sponsored a conference to evaluate their ideas; the conference was attended by 150 scientists from all over the world. Although science more or less understands how homeostasis works when a brain within an animal controls it, no one succeeded in satisfactorily explaining how homeostasis can work in a world “system” that lacks a brain. As was the case with other balance-of-nature concepts, the Gaia hypothesis remained an untestable theory well into the twenty-first century. Despite acceptance in some environmental circles, the idea of a fundamental balance in nature remained speculative and unproven by science.  

Bibliography

Egerton, Frank N. “Changing Concepts of the Balance of Nature.” Quarterly Review of Biology 48 (June, 1973): 322-350.

‗‗‗‗‗‗‗. “The History and Present Entanglements of Some General Ecological Perspectives.” In Humans as Components of Ecosystems, edited by Mark J. McDonnell and S. T. A. Pickett. New York: Springer, 1993.

Judd, Richard W. The Untilled Garden: Natural History and the Spirit of Conservation in America, 1740-1840. New York: Cambridge University Press, 2009.

Justus, James. "The Balance of Nature." The Philosophy of Ecology. Cambridge University Press, 2021, pp. 58–73.

Kirchner, James W. “The Gaia Hypotheses: Are They Testable? Are They Useful?” In Scientists on Gaia, edited by Stephen H. Schneider and Penelope J. Boston. Cambridge, Mass.: MIT Press, 1991.

Kricher, John C. The Balance of Nature: Ecology’s Enduring Myth. Princeton, N.J.: Princeton University Press, 2009.

Milne, Lorus J., and Margery Milne. The Balance of Nature. 1960. Reprint. New York: Alfred A. Knopf, 1970.