ALL SYSTEMS ARE BASED ON COMPOSITION, STRUCTURE, AND FUNCTION
We perceive objects by means of their obvious structures or functions. Structure is the configuration of elements, parts, or constituents of something, be it simple or complex. The structure can be thought of as the organization, arrangement, or make up of a thing. Function, on the other hand, is what a particular structure either can do or allows to be done to it or with it.
Let’s examine a common object, a chair. A chair is a chair because its structure gives it a particular shape. A chair can be characterized as a piece of furniture consisting of a seat, four legs, and a back; it is an object designed to accommodate a sitting person. If we add two arms, we have an armchair wherein we can sit and rest our arms. Should we now decide to add two rockers to the bottom of the chair’s legs, we have a rocking chair in which we can sit, rest our arms, and rock back and forth while doing so. Nevertheless, it is the seat that allows us to sit in the chair, and it is the act of sitting, the functional component allowed by the structure, that makes a chair, a chair.
Suppose we remove the seat so the structure that supports our sitting no longer exists. Now to sit, we must sit on the ground between the legs of the once-chair. By definition, when we remove a chair’s seat, we no longer have a chair, because we have altered the structure and therefore also altered its function. Thus, the structure of an object defines its function, and the function of an object defines its necessary structure. How might the interrelationship of structure and function work in Nature?
To maintain ecological functions means that one must maintain the characteristics of the ecosystem in such a way that its processes are sustainable. The characteristics one must be concerned with are (1) composition, (2) structure, (3) function, and (4) Nature’s disturbance regimes that periodically alter an ecosystem’s composition, structure, and function.
We can, for example, change the composition of an ecosystem, such as the kinds and arrangement of plants in a forest or grassland; this alteration means that composition is malleable to human desire and thus negotiable within the context of cause and effect. In this case, composition is the determiner of the structure and function in that composition is the cause, rather than the effect, of the structure and function.
Composition determines the structure, and structure determines the function. Thus, by negotiating the composition, we simultaneously negotiate both the structure and function. On the other hand, once the composition is in place the structure and function are set—unless, of course, the composition is altered, at which time both the structure and function are altered accordingly.
Returning momentarily to the chair analogy, suppose you have an armchair in which you can sit comfortably. What would happen if you either gained a lot of weight or lost a lot of weight but the size of the chair remained the same? If, on the one hand, you gained a lot of weight, you might no longer fit into your chair. On the other hand, if you lost much weight, the chair might be uncomfortably large. In the first case, you could alter the composition by removing the arms, and thus be able to sit on the chair. In the second case, you might dismantle the chair, replace the large seat with a smaller one, and reassemble the chair.
In a similar but more complex fashion, the composition or kinds of plants and their age classes within a plant community create a certain structure that is characteristic of the plant community at any given age. It is the structure of the plant community that in turn creates and maintains certain functions. In addition, it is the composition, structure, and function of a plant community that determine what kinds animals can live there, how many, and for how long.
Hence, if one changes the composition of a forest, one changes the structure, hence the function, and thus affects the animals. The animals in general are not just a reflection of the composition but ultimately constrained by it.
If townspeople want a particular animal or group of animals within its urban growth boundary, let’s say a rich diversity of summering birds and colorful butterflies to attract tourist dollars from bird-watchers and tourists in general, members of the community would have to work backward by determining what kind of function to create. To do so, they would have to know what kind of structure to create, which means knowing what type of composition is necessary to produce the required habitat(s) for the animal(s) the community wants. Thus, once the composition is ensconced, the structure and its attendant functions operate as an interactive unit in terms of the habitat required for the animal(s).
People and Nature are continually changing the structure and function of this ecosystem or that ecosystem by manipulating the composition of its plants, an act that subsequently changes the composition of the animals dependent on the structure and function of the resultant habitat. By altering the composition of plants within an ecosystem, people and Nature alter its structure and, in turn, affect how it functions that, in turn, determines not only what kinds of individuals and how many can live there but also what uses humans can make out of the ecosystem.
Text © by Chris Maser 2010. All rights reserved.
This series of blogs is excerpted from my 2009 book, Social-Environmental Planning: The Design Interface Between Everyforest and Everycity, CRC Press, Boca Raton, FL. 321 pp.