The Ecosystem Concept &
its Application to Agricultural Systems

Table of Contents

• The Ecosystem Concept
• Agroecosystems
• Related Concepts
• Useful Links
• Cited Literature

The term 'ecosystem" was first applied by Sir Arthur Tansley in 1935; he defined it as follows:

the whole system (in the sense of physics) including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment of the biome-the habitat factors in the widest sense. Though the organisms may claim our primary interest, when we are trying to think fundamentally we cannot separate them from their special environment, with which they form one physical system. It is the systems so formed which, from the point of view of the ecologist, are the basic units of nature on the face of the Earth.

R. Lindeman's work on a pond ecosystem, reported in the early 1940s is cited as the first to apply the ecosystem concept quantitatively (McIntosh, 1980; Golley, 1993). He introduced or formalized the concepts that

• nature is organized into systems which are recognizable objects (such as a lake)
• ecosystems have a definable structure, (a network of feeding relationships among the species populations; description of this structure can be simplified by grouping the populations into food chains or trophic levels)
• ecosystems have a behavior involving processing of energy and chemicals imported to the system: it can be described by rates of primary productivity, the length of food chains, the amount of chemical energy stored at different levels, the efficiency of trophic transfers and losses due to respiration, predation and decomposition
• in the processing of organic matter, energy is made useless by respiration, however inorganic constituents of organic matter are released and made available again for plant growth
• microbes cycle energy and chemicals from dead organic matter back into food chains;
• cycling of energy and materials couples the living organisms to the non-living parts of the systems, and couples one ecosystem to another;
• ecosystems have an origin and development through an ecological succession to an equilibrium or steady state.

From his study of the history of the "ecosystem concept" in ecology 50 years later, Golley (1993) concluded there have been three ways in which the concept has been applied scientifically. The first is as a theoretical paradigm is the sense of Kuhn (1962) .. an overarching and organizing idea; second, ecosystems have been defined as objects which have definable structures and behavior (such as a the pond with structures and processes as described by Lindeman); in its third usage, it has served as a bridge between a scientific paradigm, a physical object, and a holistic point of view. Finally, Golley comments on the popularization of the concept of ecology and ecosystems, noting that while "popular ecosystem science simplified and thereby in a sense, misrepresented the technical science" it has contributed to a new dialogue about how humans value nature, and correspondingly the new disciplines of environmental ethics or ecological philosophy. "It is not clear to me where ecology ends and the study of ethics of nature begins, nor is it clear to me where biological ecology ends and human ecology begins, the ecosystem for some at least, has provided a basis for moving beyond strictly scientific questions to deeper questions of how humans should lie with each other and the environments. "

Jorgensen (1992) put forward 27 propositions concerning the properties of ecosystems.

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Definitions and discussions of agroecosystems quoted below illustrate the three usage's cited by Golley (above).

Loucks (1977): "For the purposes of this review, ecosystems are defined as functioning units of the biosphere, usually self-maintaining (often with perturbations), and deriving distinctive properties from their structural components as well as from interactions among those components. For functioning of agro-ecosystems, the concept must be elaborated to include the agents of the expanded inputs and exports, and to provide for quantifiable boundary conditions such that exchange of materials with adjacent systems is minimized and in any case is measurable."

Odum (1984): " Agroecosystems are domesticated ecosystems that are in many basic ways intermediate between natural ecosystems, such as grasslands and forests on the one hand, and fabricated ecosystems, such as cities on the other hand;. They are solar powered as are natural ecosystems, but differ in that (1) the auxiliary energy sources that enhance productivity are processed fuels (along with animal and human labor) rather than natural energies; (2) diversity is greatly reduced by human management in order to maximize yield of specific food or other products; (3) the dominant plants and animals are under artificial rather than natural selection; and (4) control is external and goal oriented rather than internal via subsystem feedback as in natural ecosystems."

In regard to (4) Odum remarked that the goal of the traditional independent farmer was not only to make a living but also to maintain the farm from one generation to another..."to some extent, at least, such a farmer is an "internal controller" since he operates within the farming system. Unfortunately in the past decade or so control has more and more passed from the farmer to more distant controllers...the goal of the remote controllers is primarily directed to obtain the largest possible yield of a cash crop, not to maintain long term productivity." He suggests "it may be feasible to design agroecosystems so that internal controls such as operate in natural ecosystems can contribute to overall efficiency, homeostasis, and stability. the theory here is that any services we can get from natural internal self-organizing and self-maintaining processes will reduce the need to spend money and energy to provide theses services by artificial, external means."

Conway (1985): "A system is defined here as an assemblage of elements contained within a boundary such that the elements within the boundary have strong functional relationships with each other, but limited, weak or non-existent relationships with elements in other assemblages; the combined outcome of the strong functional relationship within the boundary is to produce a distinctive behavior of he assemblage such that it tends to respond to stimuli as a whole, even if the stimulus is only applied to one part .

"We can conceive of the natural living world as a nested hierarchy of such systems (organisms-population-community-ecosystem-biome-biosphere) each with a more or less well defined boundary and a distinctive system behavior. In agricultural development, ecosystems are transformed into hybrid agroecosystems for the purpose of goods or fibre production. these too can be arranged in a hierarchical scheme (e.g. field-farm-village-watershed-region). A basic feature of such hierarchies is that the behavior of higher systems in the hierarchy is not readily discerned simply from a study of the behavior of lower systems. Each level of the hierarchy has to be analyzed in its own right.

"For the purpose of analysis I make the further assumption that the behavior of agroecosystems can be described by four system properties: productivity, stability, sustainability and equitability."

Coleman and Hendrix (1988): "an agroecosystem is an ecosystem manipulated by frequent, marked anthropogenic modifications of is biotic and abiotic environments"

Tivy (1990): "Agroecoystems vary in the extent to which they deviate in form and function from the unmanaged ecosystem, depending on the type, level of management and number and amount of inputs and outputs. Smith and Hill (1975) identify four main parameters by which these systems can be defined: biological diversity; intensity of human management; net energy balance; and management responsibility; and they stress that there is a continuum between the wild or unmanaged and most intensively managed ecosystem. At one end of the spectrum, when the management is low and input other than human labor is negligible, the existing semi-natural ecosystem may be directly exploited for livestock production, as in open range grazing, with little management for either its organic components or the physical environment. In this case, inputs and outputs are small and agricultural productivity is clearly related to that of the uncultivated vegetation resource. Similarly in one of the simplest forms of cropping, that of shifting agriculture in the humid tropical rainforest environment, management is limited and the particular agro-ecosystems is closely adapted to the existing ecological conditions... At the other end of the spectrum are the agroecosystems in which there is a very high level of management involving often drastic modification of the environment, crops and livestock. The high number and volume of capital, rather than labour, inputs is reflected in high productivity. indeed it has been suggested that, in this type of agroecosystem, man's technical expertise is such that the physical environment is no longer a significant variable either determining or influencing the type of agroecosystem."

Swift et al. (1996): "In the last decade concerns for sustainability have replaced the maximization of productivity as the target for agricultural development. This has generated increased interest in agroecosystem design, a more holistic concept than the "commodity-led technology development" paradigm which has dominated the post-world-war period of agricultural development. The fundamental features of this sustainability agenda, are that productivity should meet the aspirations of the farmers and society, whilst at he same time conserving resources and environments for the future. It has been hypothesized that the inclusion of biodiversity is a key feature of such sustainable agriculture ... Agroecosystems design should thus draw in scientific information derived from study of "complex agroecosystems" rather than simply on reductionist information drawn form the study of crop plants in isolation."

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Agroecology

Altieri (1987) defined this term as follows: "The scientific discipline that approaches the study of agriculture from an ecological perspective is herein defined as "agroecology" or "agricultural ecology" and is defined as a theoretical framework aimed at understanding agricultural processes in the broadest manner. the agroecological approach regards farm systems as the fundamental units of study, and in these systems, mineral cycles, energy transformations, biological processes and socioeconomic relationships are investigated and analyzed as a whole. Thus, agroecological research is concerned not with maximizing production of a particular commodity, but rather with optimizing the agroecosystem as a whole. This approach shifts the emphasis in agricultural research away from disciplinary and commodity concerns and toward complex interactions among and between people, crops, soil and livestock."

Ecosystem Health; Agroecosystem Health

"The growing field of ecosystem health applies a medical health paradigm to ecosystem analysis with the aim of yielding a framework which is both comprehensive and evaluative...An extension of the health paradigm to agroecosystems has been proposed as a way to comprehensively diagnose and remedy the impacts of modern agriculture..For example it provides a measuring stick for assessing the health of agriculture...[they] are sufficiently general so as to encompass ecological, social and economic processes in agriculture" (Bradshaw and Smit, 1997). Calow (1992) considers the advantages and difficulties of applying the concept to ecosystems. See Rapport et al. (1998) for a recent review on assessment of ecosystem health.

Integrated Agriculture; Integrated Farming Systems

" IFS is "an holistic pattern of land use, which integrates natural regulation processes into farming activities to achieve a maximum replacement of off-farm inputs and to sustain farm income." IFS attempts to make maximum use of on-farm resources in order to minimize the qualities of purchased inputs such as fertilize and pesticides required for maintenance of high yields or for adequate financial returns; the objective is to reduce costs and pollution, but not necessarily to eliminate use of agrochemicals (El Titi, 1992)

Organic Agriculture

Organic agriculture has been broadly described as "a system that attempts to provide a balanced environment, in which the maintenance of soil fertility and the control of pests and diseases are achieved by the enhancement of natural processes and cycles, with only moderate inputs of energy and resources, while maintaining an optimum productivity. " (Hodges, 1982). This description applies to most traditional farming systems, and to modern systems referred to as biological, ecological, alternative, regenerative, LISA (Low Input Sustainable Agriculture) etc. Since the early 1980s, the term has taken on a more specialized or legalistic meaning as a result of the widespread introduction of "organic certification codes" to ensure consumers that produce labelled as "organic" is in fact produced according to certain procedures. These codes define what practices or materials may and may not be used; use of synthetic chemicals (e.g. ammonium nitrate, many pesticides) or secondarily processed chemicals (e.g. superphosphate) and biochemicals (e.g. antibiotics) is prohibited (URL), as is the use of transgenic organisms (*NOVA SCOTIA ORGANIC GROWERS ASSOCIATION). Otherwise, the practices of organic agriculture are largely the same as those now considered to be part of "sustainable agriculture", e.g. cover cropping, composting, conservation tillage, use of legumes to provide nitrogen.

Sustainable Agriculture; Sustainable Development

Sustainable development is the management and conservation of the natural resource base and the orientation of technological and institutional change in such a manner as to ensure the attainment and continued satisfaction of human needs for the present and future generations. Such sustainable development (in the agriculture, forestry and fisheries sectors) conserves land water, plant and animal genetic resources, is environmentally non-degrading, technically appropriate, economically viable and socially acceptable. (FAO definition cited in Ongley, 1996)

Permaculture

"Permaculture principles focus on thoughtful designs for small-scale intensive systems which are labor efficient and which use biological resources instead of fossil fuels. Designs stress ecological connections and closed energy and material loops. The core of permaculture is design and the working relationships and connections between all things. Each component in a system performs multiple functions, and each function is supported by many elements. Key to efficient design is observation and replication of natural ecosystems, where designers maximize diversity with polycultures, stress efficient energy planning for houses and settlement, using and accelerating natural plant succession, and increasing the highly productive "edge-zones" within the system." Source of quote: http://www.peg.apc.org/~pgan/#permaculture Permaculture Global Assistance Network

Precision managed agriculture (Site Specific Farming)

"The use of local soil and crop parameters to make precise applications of production inputs to small areas with similar characteristics" (Sadler et al., 1998). It is a high-technology farming that requires use of geo-referencing devices and mapping techniques, sensors to detect variability, variable rate technology for applications or soil manipulations, and formulation and use of treatment decision rules (*PRECISION FARMING AND INTEGRATED PEST MANAGEMENT).

Traditional agriculture

"Farming based wholly upon the kinds of factors of production that have been used by farmers for generations" (Schultz, quoted in Loomis, 1984)

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Useful Links

• ECOSYSTEMS ON THE MOVE
  (http://www.nafi.com.au/issues/ecosys.html) W. Lang, Auth. (1997, October; Viewed 30 Jan. 2001)
  This paper written by Warren Lang explores the ecosystem definition in relation to forestry. He provides a variety of definitions from different sources and discusses each of them.

Contents

• Altieri, M. 1987. Agroecology. The Scientific Basis of Alternative Agriculture. Westview Press, Boulder; IT Publications, London.
• Bradshaw, B and B.Smit. 1997. Subsidy removal and agroecosystem health. Agriculture, Ecosystems and Environment 64: 245-260.
• Calow, P. 1992. Can ecosystems be healthy? Critical consideration of concepts. Journal of Aquatic Ecosystem Health 1: 1-5.
• Coleman, D.C. and P.F. Hendrix. 1988. Agroecosystem processes. In: L.R. Pomeroy and J.J. Alberts (eds.) Concepts of Ecosystem Ecology: A Comparative View . Springer-Verlag, New York, pp 149-170.
• Conway, G.R. 1985.Agroecosystem analysis. Agricultural Administration 20: 31-55.
• El Titi, A. 1992. Integrated farming: an ecological farming approach in European agriculture. Outlook on Agriculture 21(1): 33-39
• Golley, F.B. 1993. A History of the Ecosystem Concept in Ecology. Yale University Press, New Haven and London. Dal Lib QH 540.8 G64
• Hodges, R.D. 1982. Agriculture and horticulture; the need for a more biological approach. Biological Agriculture and Horticulture 1: 1-13.
• Kuhn, T.S. 1970. The Structure of Scientific revolutions, 2nd edn. University of Chicago Press, Chicago.
• Loomis, R.S. 1984. Traditional agriculture in America. Annual Review of Ecology and Systematics 15: 449-478.
• Loucks, O.L. 1977. Emergence of research on agro-ecocsytems. Annual Review of Ecology and Systematics 8: 173-192.
• McIntosh, R.P. 1980. The background and some current problems of theoretical ecology. Synthesis 43: 195-255.
• NOVA SCOTIA ORGANIC GROWERS ASSOCIATION
  (http://www.gks.com/NSOGA/) Nova Scotia Organic Growers Association, Spons. (2001, January 18, Viewed 30 Jan. 2001)
• Odum, E.P. 1984. Properties of Agroecosystems. In: R. Lowrance, B.R. Stinner & G.J. House (eds.) Agricultural Ecosystems. Unifying Concepts . John Wiley, New York, pp. 5-11. (Dal. Lib. S 589.7 A36)
• Ongley, E.D. 1996. Control of Water Pollution from Agriculture. FAO irrigation and drainage paper # 55, FAO, Rome.
• Rapport, D.J., R. Costanza. and A.J. McMichel. 1998. Assessing ecosystem health. Trends in Ecology and Evolution . 13: 397-402.
• Sadler, E.J., W.J. Busscher, P.J. Bauer, and D.L. Karlen. 1998. Spatial scale requirements for Precision Farming: a case study in the southern USA. Agronomy Journal 90: 191-197.
• Smith, D.F., and D.M. Hill. 1975. Natural agricultural ecosystems. Journal of Environmental Quality 4: 143-5.
• Swift, M.J., J. Vandermeer, P.S. Ramakrishnan, J.M. Anderson, C.K. Ong,  and B.A. Hawkins. 1996. Biodiversity and agroecosystem function. In: H.A. Mooney, J.H. Cushman, E. Medina, O.E. Sala and E.-D. Schulze (eds).Functional Roles of Biodiversity: A Global Perspective , John Wiley and Sons Ltd., New York, pp 261-298.
• Tansley, A.G. 1935. The use and abuse of vegetational concepts and terms. Ecology 16: 284-307.
• Tivy, J. 1990. Agricultural Ecology. Addison Wesley Longman Ltd., Harlow, England.

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