The pioneers of ecology, however, used all sorts of analogies, in order to stress different things. Tansley's use of metaphors is scattered across subjects as disparate as ecology and psychology. I will therefore use Stephen A. Forbes's use as example, because it is exceptionally focused. He went from the organism through the machine to the microcosm metaphor in the space of 16 pages of the Bulletin of the Illinois State Laboratory of Natural History, Volume 1 (no.3).
Using the organism, he emphasized that ecological relations - unlike evolutionary relations - cannot be illustrated by a tree structure, but are more like the interdependent organs of a body.
"While the anatomical characters of the various groups may show that they are all branches of a common stock, from which they have arisen by repeated divisions and continued divergence, the history of their lives will show that they are now much more intimately and variously bound together by mutual interactions than are twigs of the same branch,-- that with respect to their vital activities they occupy rather the relations of organs of the same animal body." (Forbes 1880a, p. 3)The next thing he does, however, is not to draw the analogy too far, but to delimit it. By comparing the ecosystem (that word did not exist then, but I use it for lack of a contemporary term) with a single animal, he points out the difference.
"To cut off the leg of an animal is often sufficient to destroy its life, but one might cut off the head of the animal world, so to speak, without seriously impairing its energy. Suddenly to annihilate every living vertebrate would doubtless set on foot some tremendous revolutions in the life of the earth, but it is certain that in time the wound would heal,-- that Nature would finish by reädjusting her machinery, and would then go on much as before." (Forbes 1880a, p. 4)In delimiting ecosystems from real organisms Forbes arrives at the machine metaphor, because machines do not die when one part is missing, but can be repaired. Of course, this analogy is also limited because there is no repairer doing the job and thus Forbes arrives, as he always does, at yet another metaphor, the balance of nature. He thought this balance to be a common interest of predator and prey or plant and herbivore - a rather Spencerian idea.
Fifteen pages later, Forbes introduces the next article using the microcosm analogy in order to stress that studying a smaller system can teach us something about the larger whole.
"Consequently, one finds in a single body of water a far more complete and independent equilibrium of organic life and activity than in any equal body of land. It forms a little world within itself,--a microcosm within which all the elemental forces are at work and the play of life goes on in full, but on so small a scale as to bring it easily within the mental grasp." (Forbes 1880b, p. 19)Okay, this is actually two metaphors in one. The microcosm and the play of life. Plays or novels are often called microcosms, when the author manages to reflect a whole society in a small set of characters. So there's a connection between microcosm, play of life, and society. Forbes (1887) thought that studying a lake may hold a lesson for human society.
Today, microcosm experiments are still used in ecology courses. This means to take a sample of water from a lake and to study processes in that sample as representative of the whole lake. Forbes took the whole lake as a sample representative of a still larger whole instead.
The harder we look, the more language itself seems to be shot through and through with metaphor. It is therefore highly irritating to read histories that try to narrow the diversity of analogies in a historical account down to one current meaning.
"Forbes's explicitly organismic conception of the lake parallels Clements's organismic concept of plant formation" (McIntosh 1985, p. 59)Nope, Clements's (1905, p. 199 and 1916, p. 3) organism analogy stressed the similarity between plant succession and organism development, whereas Forbes's (1880a) stressed the difference between evolutionary and ecological relations. Later, Forbes (1883, p. 33) also used the organism analogy in order to emphasize the "internal economy of insect life" (yet another metaphor). What he meant was that insects do compete with and destroy each other to such an extent, that the effects of insects upon plants or other animals are mitigated a lot more than they would be without this insect internal economy. This passage also has an interesting implication concerning Forbes's idea of an organism as characterised by interior conflicts not harmony. Looking into a system he saw conflict and strife. Taking a remote perspective, he saw a balance of nature and a common interest of enemies.
Concerning the use of metaphors in proto-ecology Joel Hagen got it right:
"Forbes relied upon a variety of metaphors: mechanical, organic, political, and economic." (Hagen 1992, p. 8)
"Ecologists had a number of metaphors to aid in explaining the complex interactions and interdependencies that they encountered in nature: community, organism, and machine." (Hagen 1992, p. 12)
- Clements FE (1905) Research methods in ecology. Reprinted in 1977 by Arno Press, New York
- Clements FE (1916) Plant succession. Carnegie Institution Washington, publication no. 242
- Forbes SA (1880a) On some interactions of organisms. Bulletin of the Illinois State Laboratory of Natural History 1(3): 3-17
- Forbes SA (1880b) The food of fishes. Bulletin of the Illinois State Laboratory of Natural History 1(3): 19-70
- Forbes SA (1883) The food relations of the Carabidae and Coccinellidae. Bulletin of the Illinois State Laboratory of natural History 1(6): 33-64
- Forbes SA (1887) The lake as a microcosm. Bulletin of the Scientific Association of Peoria, Illinois 1887: 77-87 (reprinted 1925: Bulletin Illinois State Natural History Survey 15: 537-550)
- Hagen JB (1992) An entangled bank. Rutgers University Press, New Brunswick, NJ
- RP McIntosh (1985) The background of ecology. Canbridge University Press, Cambridge