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Figure 4.7 Estimated stored exergy among the biota inhabiting Surtsey Island.

might be gauged by the amount of exergy stored among the components of the ecosystem. (Exergy being the net amount of total energy that can be converted directly into work. More to come in Chapter 6.) The working hypothesis is that ecosystems accumulate more stored exergy as they mature. Exergy can be estimated once one knows the biomass densities of the various species, the chemical potentials of components that make up those species and the genetic complexity of those species (Jorgensen et al., 2005, see also Chapter 6). In Figure 4.7, one sees that the stored ecological exergy among the biota of Surtsey Island began to increase markedly after about 1985.

It is perhaps worthwhile at this juncture to recapitulate what has been done: first, we have shifted our focus in ecosystem dynamics away from the normal (symmetrical) field equations of physics and concentrated instead on the origins of asymmetry in any system—the boundary constraints. We then noted how biotic entities often serve as the origins of such constraint on other biota, so that the kernel of ecodynamics is revealed to be the mutual (self-entailing) constraints that occur within the ecosystem itself. We then identified a palpable and measurable entity (the network of material-energy exchanges) on which this myriad of mostly hidden constraints writes its signature. Finally, we described a calculus that could be applied to the network to quantify the effects of auto-catalytic selection. Hence, by following changes in the ascendency and overhead of an ecosystem, we are focusing squarely on that which makes ecodynamics fundamentally different from classical dynamics (Ulanowicz, 2004a,b).

The dynamical roots of much of Darwinian narrative having been de-mystified by the directionality inherent in autocatalysis, it is perhaps a bit anti-climatic to note that several other behaviors observed among developing ecosystems also can trace their origins to autocatalysis and its attendant centripetality. Jorgensen and Mejer (1977), as mentioned above, have concluded that ecosystems always develop in the direction of increasing the

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Figure 4.7 Estimated stored exergy among the biota inhabiting Surtsey Island.

amount of exergy stored in the system. Maximal exergy storage has proved a useful tool with which to estimate unknown parameters and rates (Jorgensen, 1992a; see also growth and development forms in Chapter 6). Schneider and Kay (1994) hypothesize how systems develop so as to degrade available exergy gradients at the fastest rate possible. This is, however, only correct for the first growth form, growth of biomass because more biomass needs more exergy for respiration to maintain the biomass far from thermodynamic equilibrium. Further details see Chapter 6. Thirdly, the inputs of ecosystems engender many-fold system circulations among the full community—a process called network aggradation (Fath and Patten, 2001). All three behaviors can be traced to autocatalysis and its attendant centripetality (Ulanowicz et al., 2006).

It should be noted in passing how autocatalytic selection pressure is exerted in top-down fashion—contingent action by the macroscopic ensemble on its constituent elements. Furthermore, centripetality is best identified as an agency acting at the focal level. Both of these modes of action violate the classical Newtonian stricture called closure, which permits only mechanical actions at smaller levels to elicit changes at higher scales. As noted above, complex behaviors, including directionality, can be more than the ramification of simple events occurring at smaller scales.

Finally, it is worthwhile to note how autocatalytic selection can act to stabilize and regularize behaviors across the hierarchy of scales. Under the Newtonian worldview, all laws are considered to be applicable universally, so that a chance happening anywhere rarely would ramify up and down the hierarchy without attenuation, causing untold destruction. Under the countervailing assumption of ontic-openness, however, the effects of noise at one level are usually subject to autocatalytic selection at higher levels and to energetic culling at lower levels. As a result, nature as a whole takes on habits (Hoffmeyer, 1993) and exhibits regularities; but in place of the universal effectiveness of all natural laws, we discern instead a granularity inherent in the real world. That is, models of events at any one scale can explain matters at another scale only in inverse proportion to the remoteness between them. For example, one would not expect to find any connection between quantum phenomena and gravitation, given that the two phenomena are separated by some 42 orders of magnitude, although physicists have searched ardently, but in vain, to join the two. Obversely, the domain within which irregularities and perturbations can damage a system is usually circumscribed. Chance need not unravel a system. One sees demonstrations of systems "healing" in the higher organisms, and even in large-scale organic systems such as the global ecosystem (Lovelock, 1979).

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