2005 BES Annual Meeting Presentation and Poster Abstracts
The Nature of the Urban Ecosysem: What Would Tansley Do?
Abstract: The Baltimore Ecosystem Study is beginning to be a mature project, but it is appropriate to call renewed attention to one of our most significant unifying ideas – the ecosystem concept. This idea was originally proposed by the British botanist and plant ecologist, Professor Arthur G. Tansley, in 1935. He defined an ecosystem as a biotic complex and a physical environmental complex interacting with each other in some specified area (Tansley 1935). This definition has proven remarkably robust, and has been applied to very small areas, on up to the entire biosphere of the Earth (Pickett & Cadenasso 2002). But is this definition adequate for the human ecosystem of cities, suburbs, and their hinterlands? It is -- if researchers and educators remember to include within the idea of the biotic complex and the physical complex much more than the usual subjects of ecology. For example, ecologists may automatically think of the human features of biotic complexity as consisting of human population density and aspects of demographic structure, such as sex ratio and age structure. However, the human component of the biotic complex also includes the whole range of human institutions, cultural tools, and social resources. The human aspects of Tansley’s biotic complex are familiar to members of the Baltimore Ecosystem Study in the form of the Human Ecosystem Framework (Machlis et al. 1997). An overview can be found at http://www.beslter.org/frame4-page_2_1.html. So we can in fact usefully refine the idea of the complexes that make up the ecosystem by identifying a social complex in addition to the more traditional biotic complex that botanists, zoologists, and biogeochemists might have in mind. Can the physical complex be similarly refined to help understand urban ecosystems in the broadest sense? Here, too, it is possible to improve on what Tansley proposed, based on the growing understanding of inhabited and settled ecosystems. While the term “physical complex” could represent the buildings and infrastructure of cities, suburbs, and exurban development, it is useful to highlight that aspect of urban ecosystems as an identifiable complex of its own. This component of urban ecosystems can be labeled the “built complex.” It would include all aspects of the built capital of metropolitan and settled areas, and reflect the intentional design of cities and the historical legacies of construction and change. Putting all this together clarifies Tansley’s definition, and extends ecology toward human processes, which he in fact recommended. A human ecosystem, therefore, consists of a biotic complex, a physical complex, a social complex, and a built complex, all interacting within a specified area. This definition hews to the spirit of Tansley’s original, but makes clear the nature of the human component of ecosystems. Machlis, G. E., J. E. Force, and W. R. Burch. 1997. The human ecosystem. 1. The human ecosystem as an organizing concept in ecosystem management. Society & Natural Resources 10:347-367. Pickett, S. T. A., and M. L. Cadenasso. 2002. Ecosystem as a multidimensional concept: meaning, model and metaphor. Ecosystems 5:1-10. Tansley, A. G. 1935. The use and abuse of vegetational concepts and terms. Ecology 16:284-307.