also creates large numbers of relatively independent local authorities such as towns, counties, states, and the national government, all neatly arranged in a spatially nested hierarchy. The U.S. Constitution, similar constitutions at the state level, and law govern interactions within this well-defined hierarchy. But they also govern many other specialized units and agreements whose purpose is to address interactions whose patterns of occurrence do not conform to the “normal” nested hierarchy. For example, states are part of the federal union but also members of various associations or agreements among states organized for particular purposes, such as the Atlantic States Marine Fisheries Commission. In all these systems the connections between units are generally loose but, on the whole, lead to coordinated activities (Ostrom, 1991).

An important benefit of this form of organization is that the scale of operation of each component of the organization can always be chosen (for efficiency or other reasons) so that it matches the scale of the activity in question, that is, the scale at which the impacts from an activity generate consequences (costs and benefits). So local activities are assigned to local authority, regional to regional, and so on. The other side of that same coin is that the governance of activities at a local scale that might generate costs for neighbors can always be shifted to a higher scale, where wider than local impacts can be handled. When activities do not interact along the neat lines of a spatially nested hierarchy, arrangements can be made for ad hoc components tailored to the structure of that particular problem. In economic terms this kind of polycentric organization is equivalent to the internalization of spatially related externalities, or if one prefers, to the minimization of the transaction costs necessary to resolve spatially relevant externalities.

These ideas apply to natural as well as social systems (O’Neill et al., 1986; Pattee, 1973; Walker, 1992, 1995). Simon and other authors describe ecosystems, the human body, and living organisms in general in terms of nearly decomposable subsystems. From this perspective a straightforward (i.e., simple hierarchical) view of an ocean ecosystem translates into a world of spatially discrete but not completely independent subsystems connected horizontally and aggregated into larger, nested subsystems.

This is consistent with the modern treatment of scale and space in ecology (e.g., MacArthur and Wilson, 1967; O’Neill et al., 1986; Levin, 1992, 1999; Hanski and Gilpin, 1997) and, as I’ll describe, with our ability to organize a collective learning process. It is not consistent with the species-centered approach of conventional management. One of the principal reasons for suggesting this alternative conceptual approach is that the conventional approach does not lend itself to a practical way to manage ecosystems. In other words, when the complexity of the ocean is simplified by looking at individual species, we may blind ourselves to much of the feedback in the system. Just as important, an ecosystem conception based on a species-centered approach only makes sense if one could conceive of “modeling” all the biotic and abiotic interactions in the system. The massive impracticality of such an undertaking leaves one with, at best, ad hoc



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