The ecosystem as a multidimensional concept: meaning, model, and metaphor

Ecosystems (2002) 5: 1–10 DOI: 10.1007/s10021-001-0051-y

ECOSYSTEMS
© 2002 Springer-Verlag

COMMENTARY

The Ecosystem as a Multidimensional Concept: Meaning, Model, and Metaphor
S. T. A. Pickett* and M. L. Cadenasso
Institute of Ecosystem Studies, Box AB, Millbrook, New York, 12545 USA

ABSTRACT
The ecosystem is a fundamental ecological concept that is not as simple as it firstappears. We explore three key dimensions of the concept that make it both complex and broadly useful—its basic definition, its application via models to concrete or specific situations, and its metaphorical connotations as used in general communication within the domain of science and with the public at large. Clarity in identifying what the dimensions are and how they are related can help to maintain therigor of the concept for specific scientific uses while also allowing enough flexibility for its use in the integration of scientific principles, as well as in public discourse. This analysis of the ecosystem as a multidimensional concept is likely to be generalizable to other important concepts in ecology. Key words: ecosystem concept; ecosystem definition; metaphor; model; specification; values.INTRODUCTION
The purpose of this paper is to explore the various ways that the contemporary concept of the ecosystem can be used. Why analyze one of ecology’s most familiar and widely used concepts? Because, far from being simple and straightforward, the ecosystem is in fact a subtle and complex concept. The multiple layers of its meaning and use can result in confusion, thereby limiting theutility of the concept. Furthermore, these layers of meaning and use have specific yet often unrecognized theoretical linkages. We intend to explore its complexity in a straightforward way. Several of the insights we draw on have been articulated before. However, to our knowledge, this essay is the first attempt to synthesize a full assessment of the complexity of the ecosystem concept. The analysis istimely because concepts and their use evolve through time as a

Received 28 February 2001; accepted 5 September 2001. *Corresponding author; e-mail: picketts@ecostudies.org

science and its application mature. Furthermore, peeling back the layers of complexity and examining the theoretical implications of the ecosystem concept may serve as a model for the analysis of other multifacetedecological concepts. We will conclude by briefly indicating how our analysis of the ecosystem concept can serve as a paradigm for simplifying the complexity of other ecological concepts. There are at least three linked, yet different, ways that the concept of the ecosystem can be used. Each of these uses can be considered a separate dimension of this complex concept. The three dimensions are meaning,model, and metaphor. The first dimension—meaning—is a technical definition that can be used in a wide variety of situations. However, for the definition to actually be used in a given situation, a domain and a variety of features must be specified (Jax 1998). Therefore, the second dimension is a model that embodies the specifications needed to address the many real or hypothetical situations that thedefinition might apply to. Fi-

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S. T. A. Pickett and M. L. Cadenasso ents and energy (Holling 1973). Similarly, ecosystems may be autotrophic or heterotrophic (Odum 1989). They may be simple, such as those that contain only a few microbes and some detritus exported from elsewhere. Likewise, they may be fleeting, remaining in existence only a short time. Of course, the Earth abounds inpersistent and complex ecosystems as well (Odum 1971). In addition, ecosystems can include humans and their artifacts. Tansley (1935), in his seminal definition, was at pains to emphasize that ecologists should study ecosystems that incorporate humans and human-generated processes and structures (Odum and Odum 1976; Odum 1977; Costanza and others 1993; Christensen and others 1996; Grimm and others...