Less Specific Thoughts

It is going to take a while for this to come together. I'm currently reading Kauffman's "Reinventign the Sacred" which is a frustrating, annoying, and challenging book. I'll leave the book review for another time. The section I'm reading now talks about "non-ergodic" systems -- systems that have so many possible states that they will not repeat themselves in the history of the universe. He also talks about systems that develop novel features that then affect the future state of the system. His example is swim bladders in fish. By his telling, swim bladders originated as a primitive lung for surviving in low oxygen water. They subsequently became adapted to controlling buoyancy, and once that function was established it permitted a new radiation of fishes. He distinguishes the behavior of these systems from systems with dynamical chaos, because in principle the chaotic system is predictable if its initial state is perfectly known. The appearance of novel features makes the system unpredictable because we can't anticipate which novelties will become adopted, and in what new form (how can you know, in advance, that a lung sac will become a swim bladder, or how the emergence of a swim bladder will alter the trajectory of the system?)

Another feature of complex systems Kauffman describes is criticality. In his models, systems can be chaotic or ordered. The area of transition between the two he terms critical. It is this kind of dynamic system that seems to behave much as biololgical and other complex systems behave. I don't entirely trust this result, and especially not the parameters he finds produce critical systems, because his models are oversimplified in an important way -- the nature of interactions between system components are fixed, and George Mpitsos observes that, in simple nervous systems, the nerves are constantly adjusting their interactions. this seems like a more realistic scenario for systems based on organisms (as opposed to chemicals or genes).

I'm trying to apply this to near-shore ocean ecosystems. We have the idea of non-repeatability and criticality. The first is based on the number of possible interactions being much greater than the number of interacting components, and on the time available for interactions to occur. Criticality (in Kauffman's models) is a property dependent on the number of elements each system component interacts with, and the total number of components. Can we predict future states of an ocean ecosystem? The quick answer is no.We may be able to predict future abundances of individual components with some, short-term, skill. But we can't describe how the components interact, much less predict future interactions. John Field has spent a lot of time building trophic models of the near-shore Pacific, and he will tell you how speculative they are. Can we predict the effects of fishing removals on the ecosystem? No. Changes in wind patterns? No. Benthic disturbance by trawls? No. Marine reserves? No. I submit that the ecosystem is inherently unpredictable in this sense.

What we may be able to do is describe the kind of dynamics we expect the system to show. We can do this if we can define the system in relation to Kauffman's criticality. If the system is near the criticality threshold it should have a predictable set of behaviors (number of stable states, time scales of response ...). If it is ordered or chaotic these behaviors will be different. Extrapolating from Kauffman's models is risky, but it is a place to start, and it provides a context for a more applicable set of theoretical models.

That's enough for now!