Cultural And Historical Perspectives Of The Present Agrolandscape

The Roman writer Cicero termed what is currently considered the cultural landscape "a second nature" (alteram naturam). This cultural landscape, or second nature, comprised all the elements introduced into the physical world by humankind to make it more habitable. Hunt (1992) interprets Cicero's phrase, a second nature, as implying a first, or primal nature before humans invaded, altered, or augmented the unmediated world.

Various ideologies resulting from this second nature, especially how nature should be managed or controlled, have contributed to the present fragmented landscape. The evolutionary significance of the mature (model) system, including how natural selection has resulted in the evolution of efficient mechanisms for insect pest control, nutrient recycling, and mutualistic behavior, is often poorly understood. A hallmark of these mature and sustainable ecological systems is also maximum biological diversity (Moffat, 1996; Tilman et al., 1996; Tilman, 1997). Environmental literacy must increase if societies are to develop sustainable agriculture and sustainable agrolandscapes (Barrett, 1992; Orr, 1992). For example, natural processes and concepts such as pulsing, carrying capacity, natural pest control, nutrient cycling, positive and negative feedback (cybernetics), and net primary productivity must be understood by ecologically literate societies in order to provide a quality environment for future generations. There exists an urgent need to understand these processes and concepts better, and to manage agroecosystems at the agrolandscape level (Barrett, 1992). It is now imperative to couple the heterotrophic urban environment with the autotrophic agricultural environment if societies are to establish or manage sustainable landscapes on a meaningful regional or global scale.

Environmental literacy also includes the aesthetic languages of diverse cultures and histories that determine what a people traditionally considers essential and nonessential resources within cultures. Shifting economic, social, political, or artistic perspectives, for example, affect the definition of what is considered a resource and what is perceived as a nonresource. The encoded messages endemic to these cultures influence human thought in the determination of what is of value in the life of a human being.

The cultural landscape is an integral part of the holistic agro-urban landscape perspective. Nassauer (1995), for example, recognized the need to investigate the relationship between cultural landscape patterns and ecological landscape processes. The aesthetics that are intrinsic to various cultures have influenced the present agrolandscapes. Acknowledging these relationships, including their present and future influences, will increase dialogue among biological, physical, and social scientists; among resource managers, landscape engineers, and urban planners; and among scholars investigating the role of sustainability at the landscape and global levels (Huntley et al., 1991; Lubchenco et al., 1991). The resulting interfaces among fields of study will lead to a deeper understanding of why and of how landscape elements (patches, corridors, and the agromatrices or urban matrices) are related to present regional/global patterns of belief systems, an understanding necessary to conserve biological diversity.

THE CREATION OF AN "OXBOW" URBAN AREA

Figure 2 depicts an urban environment, including the relationship of the inner urban landscape to the outer agricultural landscape. Although much has been written regarding the pattern and shaping of the landscape from prehistory to present day (see review by Jellicoe and Jellicoe, 1987, for details), there exists the need to address and quantify the concept of landscape sustainability from an energetic (solar energy and energy subsidy) perspective. One objective of this chapter is to increase trans-disciplinary dialogue concerning this need. Although we recognize that markets have become increasingly global in structure and function (Brady, 1990), it appears that management practices, for example, integrated pest management and information processing, will be conducted on a regional basis (Elliott and Cole, 1989).

Traditionally, towns and cities were integrated in a sustainable manner (Figure 3). The town served as the marketplace for farmers to sell their goods and products (Mumford, 1961; Hough, 1995); goods and services radiated from the city to support the agricultural landscape, including providing cultural, educational, and social benefits (Le Corbusier, 1987). During the early part of this century in the agricultural Midwest, crop diversity was high (Barrett et al., 1990), as was species and habitat diversity (Barrett and Peles, 1994). The shift from a biologically diversified and, perhaps, a sustainable landscape to monoculture or diculture crops (especially corn and soybean) in the rural landscape was accompanied by the development of suburban areas that reduced not only the amount of arable land, but also the diversity of wildlife habitats and cultural linkages between the inner city and the agricultural landscape. This created what we term an oxbow city, analogous to the creation of

SUBURBAN LANDSCAPE (E.G., HOMES / FOOD CROPS)

EXURBAN / AGRICULTURAL LANDSCAPE

SOLAR-POWERED PATCHES (E.G., PARKS/GARDENS)

URBAN LANDSCAPE (E.G., TOWNS/CITIES)

Figure 2 Diagram depicting urban, suburban, and exurban/agricultural systems. Solar-powered (autotrophic) patches are shown within urban and suburban (heterotrophic) systems.

SUBURBAN LANDSCAPE (E.G., HOMES / FOOD CROPS)

EXURBAN / AGRICULTURAL LANDSCAPE

SOLAR-POWERED PATCHES (E.G., PARKS/GARDENS)

URBAN LANDSCAPE (E.G., TOWNS/CITIES)

Figure 2 Diagram depicting urban, suburban, and exurban/agricultural systems. Solar-powered (autotrophic) patches are shown within urban and suburban (heterotrophic) systems.

an oxbow lake when it becomes separated (physically and functionally) from a flowing meandering stream once the stream changes its course. This isolated city develops different functional processes (i.e., provides different services), resulting in changes in niche and biodiversity (i.e., the inner city creates different occupations and provides habitats for different species of flora and fauna). The integrity of the city frequently becomes less closely related to the total watershed from which it evolved. This developmental process is depicted in Figure 4.

Odum (1997) classified ecosystems based on the proportions of solar and fossil fuel energy used to drive the system. Most natural ecological systems are driven entirely by solar energy. Subsidized systems depend, to varying degrees, on the input of subsidies such as fossil fuel energy, fertilizers, and/or pesticides. Agroecosystems, for example, are driven by both solar energy and subsidies; urban systems depend mainly on enormous inputs of fossil fuel subsidies (Odum, 1989).

These ecosystems may also be classified based on the ratio of energy produced by primary productivity (P) to energy used for respiration or system maintenance (R). Natural and agricultural ecosystems, especially during ecosystem growth and development, represent autotrophic systems where P/R > 1. In contrast, urban areas have increasingly become heterotrophic (P/R < 1). We define sustainable systems as those systems or landscapes where long-term P/R ratios equal 1. During the growth and development of autotrophic systems (i.e., during ecological succession),

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