number of structuring processes into a small number of levels, each characterized by a distinct scale of 'architectural' texture and of temporal speed of variables" (Holling, 1992, p. 484). This hypothesis, if verified by further research, may have important consequences for the way we think about environmental values as well. Holling's model suggests (a) that environmental values are shaped, perhaps even genetically, within an architecturally structured natural world; (b) that human valuation may therefore exhibit scientifically describable scalar characteristics; and (c) that an examination of scalar aspects of environmental valuation may illuminate the perplexing problems of intertemporal evaluation.

Further, these theoretical ideas can be developed into a general approach to managing ecological systems as developed in Holling's contribution to this volume. Holling argues that, since systems exhibiting these characteristics can function in more than one equilibrium, and since changes in these structural features can occur abruptly, switching systems into alternative equilibria, it will be necessary to modify traditional engineering approaches to stability. As a system is controlled (to maximize production of a particular species, for example) it becomes more brittle, setting it up for pathologies and "flips" into a new steady state. He concludes that in the face of such flips and pathologies, near-equilibrium behavior and control (engineering resilience) seems irrelevant and the prescriptive goal shifts from questions of maximizing constancy of yield to one of designing interrelations between people and resources that are sustainable in the face of surprises and the unexpected. On this view, management attention "shifts to determining the constructive role of instability in maintaining diversity and persistence and to designs of management that maintain ecosystem function in the face of unexpected disturbances" (in this volume, p. 38). This general approach is sometimes referred to as ''adaptive management" (Holling, 1978; Lee, 1993; Walters, 1986). Holling's ideas, and those of others who are exploring similar approaches, may usher in a new era in thinking about environmental management, an era that is more concerned with processes, functions, and thresholds, and less concerned with system behavior near equilibrium.

And yet (as I think Holling realizes), there is a confounding paradox at the heart of this new and promising approach to management. Where do human values and choices fit into this complex system of analysis? Can humans, by managing their own behaviors, shaping them consciously in response to ecological information, "choose" to forbear from certain actions to protect processes crucial to ecological structure and function. Since most applications of hierarchical organizational structures emphasize that control and constraints flow down spatiotemporal systems, with the larger and slower-changing processes constraining the behavior of individuals at lower levels, hierarchical reasoning is therefore best suited to treat human choices as effects of natural changes. And yet humans are today, without question, important, even dominant, actors in every "natural" hierarchy. Looked at in this way, it is often the accumulation of many individual human choices (based in human "values") that drives changes in ecosystem states.



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