Table

Comparison of Emerging Ideas on Self-Organization

Proponent Conceptual Basis

Stuart Kauffman (1995)

Per Bak (1996)

Mitchel Resnick (1994)

Manfred Eigen

(Eigen and Schuster, 1979)

Ilya Prigogine (1980)

Systems evolve to the "edge of chaos," which allows the most flexibility; studied with adaptive "landscapes"

Self-organized criticality; studied with sand pile models

Emergence of order from decentralized processes; studied with an individualbased computer program called STAR LOGO

Hypercycles or networks of autocatalyzed reactions; studied with chemistry

Dissipative structures; studied with nonequilibrium thermodynamics

System of Study

General systems with emphasis on biochemical systems

General systems with emphasis on physical systems

General systems

Origin of life; biochemical systems

General systems with emphasis on chemical systems

Francisco Varela (Varela et al., 1974)

Autopoiesis; studied with chemistry

Origin of life; biochemical systems described this phenomenon: "Ecosystems are the workshops of evolution; any ecosystem is a selection machine working continuously on a set of populations."

H. T. Odum has gone beyond this explanation to build an energy theory of self-organization from the ideas of Alfred Lotka (1925). He suggests that selection is based on the relative contribution of the species to the overall energetics of the ecosystem. Successful species, therefore, are those that establish feedback pathways which reinforce processes contributing to the overall energy flow. H. T. Odum's theory is not limited to traditional ecological energetics since it allows all species contributions, such as primary production, nutrient cycling, and population regulation of predators on prey, to be converted into energy equivalent units. This is called the maximum power principle or Lotka's principle, and H. T. Odum has even suggested that it might ultimately come to be known as another law of thermodynamics if it stands the test of time as the first and second laws have. The maximum power principle is a general systems theory indicating forms of organization that will develop to dissipate energy, such as the autocatalytic structures of storages and interactions, hierarchies, and pulsing programs, which characterize all kinds of systems (H. T. Odum, 1975, 1982, 1995; H. T. Odum and Pinkerton, 1955). Belief in this theory is not necessary for acceptance of the importance of self-organization

FIGURE 1.7 Maxwell's demon controls the movement of gas molecules in a closed chamber. (From Morowitz, H. J. 1970. Entropy for Biologists, An Introduction to Thermodynamics. Academic Press, New York. With permission.)

in ecosystems, and the new systems designed, built, and operated in ecological engineering will be tests of the theory.

According to H. T. Odum (1989a) "the essence of ecological engineering is managing self-organization" which takes advantage of natural energies processed by ecosystems. Mitsch (1992, 1996, 1998a, 2000) has focused on this idea by referring to self-organization as self-design (see also H.T. Odum, 1994a). With this emphasis he draws attention to the design element that is so important in engineering. Utilizing ecosystems, which self-design themselves, the ecological engineer helps to guide design but allows natural selection to organize the systems. This is a way to harness the biodiversity available to a design. For some purposes the best species may be known and they can be preferentially seeded into a particular design. However, in other situations self-organization may be used to let nature choose the appropriate species. In this case the ecological engineer provides excess seeding of many species and self-design occurs automatically. For example, if the goal is to create a wetland for treatment of a waste stream, the ecological engineer would design a traditional containment structure with appropriate inflow and outflow plumbing and then seed the structure with populations from other systems to facilitate self-organization of the living part of the overall design. Interaction of the waste stream with the species pool provides conditions for the selection of species best able to process and transform the waste flow.

The selection force in ecological self-organization may be analogous to an old paradox from thermodynamics (Figure 1.7). Maxwell's demon was the central actor of an imaginary experiment devised by J. Clerk Maxwell in the early days of the development of the field of thermodynamics (Harman, 1998; Klein, 1970). The tiny demon could sense the energy level of gas molecules around him in a closed chamber and operate a door between two partitions. He allowed fast-moving gas molecules to pass through the door and accumulate on one side of the chamber while keeping slow-moving molecules on the other side by closing the door whenever they came nearby. In this way he created order (the final gradient in fast and slow molecules) from disorder (the initial even distribution of fast and slow molecules) and cheated the second law of thermodynamics. In an analogous fashion, the force causing selection of species in self-organization may be thought to be the ecological equivalent of Maxwell's demon (H. T. Odum 1983). The ecological demon operates a metaphorical door through which species pass during succession, creating the orderly networks of ecosystems from the disorderly mass of species that reach a site through dispersal.

Self-organization is a remarkable property of ecosystems that is well known to ecologists (J0rgensen et al., 1998; Kay, 2000; Perry, 1995; Straskraba, 1999), but it is a new tool for engineers to use along with the other, more familiar tools of traditional technology. It will be very interesting to observe how engineers react to and come to assimilate the self-designing property of ecosystems into the engineering method as the discipline of ecological engineering develops over time. Control over designs is fundamental in traditional engineering as noted by Petroski (1995): "... the objective of engineering is control — getting things to function as we want them to in a particular situation or use." However, control over nature is not always possible or desirable (Ehrenfeld, 1981; McPhee, 1989). As noted by Orr (2002): "A rising tide of unanticipated consequences and 'normal accidents' mock the idea that experts are in control or that technologies do only what they are intended to do." Ecological engineering requires that some control over design be given up to nature's self-organization and this will require a new mind-set among engineers. Some positive aspects of systems that are "out of control" are discussed in Chapter 7.

Preadaptation

Self-organization can be accelerated by seeding with species that are preadapted to the special conditions of the intended system. This requires knowledge of both the design conditions of the ecosystem to be constructed and the adaptations of species. As an example, when designing an aquatic ecosystem to treat acid drainage from coal mines, seeding from a naturally acidic bog ecosystem should speed up self-design since the bog species are already adapted to acid conditions. Thus, the bog species can be said to be preadapted to fit into the design for acid mine drainage treatment because of their adaptations for acidity. Adaptation by species occurs through Darwinian evolution along environmental gradients (Figure 1.8) and in relation to interactions with other species (i.e., competition and predation). The adaptation curve in Figure 1.8 is bell-shaped since performance can only be optimized over a small portion of an environmental gradient. The biological mechanisms of adaptation include physiological, morphological, and behavioral features. One sense of a species' ecological niche is as the sum total of its adaptations. Hutchinson (1957, 1965, 1978) envisioned this concept as a hypervolume of space along environmental gradients on which a species can exist and reproduce. The niche is an important concept in ecology and reviews are given by MacArthur (1968), Schoener (1988), Vandermeer (1972), and Whittaker and Levin (1975). The concept covers all of the resources required by a species including food, cover, and space (see also the related concept of habitat discussed in Chapter 5). Each species has its own niche and only one species can occupy a niche according to the competitive exclusion principle (Hardin, 1960). As an aside, Pianka (1983) suggested that ecologists might

High A

Lower Limit of Tolerance Upper Limit of Tolerance Range of Optimum

Lower Limit of Tolerance Upper Limit of Tolerance Range of Optimum a o p-

Zone of Intolerance

Zone of Stress

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