Thursday, November 17, 2005

Biological models

I am very pleased to have been part of a conference-workshop of biologists and oceanographers centering around a biophysical ocean-fisheries model, called NEMURO. Somehow I got invited to it by virtue of my attendance last year in a conference on "Economics of Small Pelagics", where I presented a paper on the economic implications of climate change impacting on fisheries of small pelagics. ("Pelagics" are fish that dwell at upper levels of the water column, hence they tend to be mobile fish; their bottom-dwelling counterpart are the "demersals".) This was pretty hardcore stuff, based on the physics and chemistry of the ocean (currents, nutrient flows, etc.) as well as fish ecology (growth dynamics, food web interactions, etc.) Needless to say, I contributed trivially to that part of the discussion. I did learn something (as in, not nothing) in an osmotic sort of way - in the sense that, hearing "bioenergetics" would evoke in me some faint glimmer of recognition.

I knew enough though to see that in their model, fishing mortality (% of fish that die from being caught by humans) is constant - a black box, as it were. Of course it can be adjusted by the modeler to examine impact on the fish abundance and behavior, but it in itself it is left unexplained. I argued that a complete model needs to account for adjustments in fishing pressure, which is largely explained by economics. In short, the amount caught depends not only on the available fish (biophysical component), but also on the fishing effort (economic component). More to the point, the two affect each other - the fish catch depends partly on effort, and partly on the quantity of available fish, and vice-versa, the quantity of fish depends on fishing mortality. To be fair, economists in the market forecasting business likewise treat available fish populations as a black box, or at most adjusted by modeler's discretion. I presented a paper sketching a practical way in which a grand synthesis of economics and biology (and, in principle, oceanography) can be done, in practical terms.

I think they were definitely interested in such a disciplinary interface. As a modeler, I caught on their sentiment that incorporating added complexity (economics) was far past their immediate interest - which was combining biological and physical systems. It turns out that such biophysical models are on the research frontier. My value added I believe was my assurance that for now, economic behavior can be left well enough alone. (Knowing what not to do can sometimes be as important as knowing what to do!)

Modelers proceed by an accretion of complexity, rather than attacking all the important problems at the same time. So at least economics is on this group's radar screen, perhaps as a future agendum for collaboration. I do believe that interdisciplinary work is crucial; contrary to common belief however, scientists appreciate this. They are after all people whose job is to think, which they do very well - the group I was with is a fine exemplar of that. Cross-disciplinary work is however very difficult; even scientists in allied fields have a hard time collaborating, let alone specialists in entirely different fields. Scientist-bashers tend to be very critical, mainly because of their lack of appreciation of the constraints and complexities involved (charges of "comparmentalization!" "reductionism"! "Not holistic"! can get tiresome). Trust me, we're groping towards that interdisciplinary ideal.

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