ABSTRACT
The increasing intensity of agricultural production in recent years has resulted in a degradation of natural ecosystems at a range of scales. Soil degradation, groundwater and surface water pollution, destruction of wildlife habitat and biodiversity loss have prompted questions about the sustainability of agroecosystems in recent years (Brown, 1997; World Commission on Environment and Development, 1987). The importance of agroecosystems to social and economic health has driven a demand for policy development and analysis focusing on the long-term sustainability of these systems. Agricultural ecosystems (agroecosystems), distinguished from natural ecosystems by the dominant role of human management for specific marketable products, are an important component of global land use and resource appropriation. Agroecosystems, like natural ecosystems, depend on the fundamental processes, primary production, consumption, and decomposition in combination with abiotic energy flows and nutrient cycling. Within an agroecosystem these processes are inextricably linked with economic and social components through the role of human management. These natural and social processes can be characterized as the flow of goods and services coming from the capital stock of the agroecosystem. The capital stock of an agroecosystem includes man-made, human, and natural capital corresponding to the factors of production, capital, labor, and land (Costanza and Daly, 1992; Prugh, 1995). Man-made capital is the manufactured means of production including machinery, equipment, buildings, technology, etc. (Prugh, 1995). Human capital is the collective knowledge, skills, and culture of the human population. Natural capital is comprised of components that are natural in origin. The maintenance of these capital stocks over time is an important condition for the preservation of the function of these agroecosystems.
