The Ecosystem Paradigm and Environmental Risk Management

Human and Ecological Risk Assessment: Vol. 6, No. 3, pp. 369-381 (2000)

The Ecosystem Paradigm and Environmental Risk Management Torgny J. Vigerstad1 and Lynn S. McCarty2 Bio-Response Systems Limited, 6171 Jubilee Road, Halifax, NS, Canada B3H2E9 E-mail: [email protected]; website: www.bioresponse.com;2 L.S. McCarty Scientific Research and Consulting, 94 Oakhaven Drive, Markham, ON, Canada L6C 1X8, Tel.: (905) 887-0772; Fax: (905) 887-0766; E-mail: [email protected]

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ABSTRACT Modern approaches to environmental evaluation and management decisionmaking derive from ecological theories developed largely in the 1960s and earlier. Widespread use of such practices warrants a review of the status of theoretical ecology and its relationship to practical risk management decision making. Two paradigms of ecology, the Ecosystem Paradigm and Fry’s Paradigm, can be summarized in three principles: (1) in the biological levels of organization scheme there is a level of organization called “the ecosystem”; (2) to study an ecosystem, observations must be made at the ecosystem level of organization; (3) observations should be quantitative measurements. The literature shows that these principles have largely been ignored by ecologists when examining aquatic systems. Many theoretical concepts for describing the ecosystem have been proposed, but quantification is often poor or unworkable. It is evident that the “ecosystem” or “levels of organization” ecological paradigm has not produced a mature theory or hypothesis of ecology as there is no generally accepted, technical, quantitative description of an ecosystem, of the other levels of organization in the scheme, or of their interrelationships. Instead, managers, who need practical tools with reasonable predictive and explanatory power, routinely use quantitative descriptors based directly or indirectly on economics or environmental engineering in their environmental decision making. Key Words: ecosystem, environmental management, ecology, ecological theory INTRODUCTION There has been much discussion about environmental risk assessment/analysis, its use and development, and its future in addressing environmental management issues. Suter (1993a) has reviewed earlier work and has provided a new baseline to work from. In short, it can be said that environmental methodologies have moved 1080-7039/00/$.50 © 2000 by ASP

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Vigerstad and McCarty

from the “environmental assessment” approach, used largely in the 1970s, to the “environmental” or “ecological risk assessment” approach, used in the 1990s. Both, however, are derived from ecological theories developed largely in the 1960s and earlier. Since modern approaches to environmental evaluation and management ultimately depend on these ecological theories, it is important periodically to reexamine such theories both for suitability of use and validity in theory and practice. Science proceeds by the rising and falling of paradigms. A paradigm is a scientific practice that is . . . sufficiently unprecedented to attract an enduring group of adherents away from competing modes of scientific activity. Simultaneously, it is sufficiently open-ended to leave all sorts of problems for the redefined group of practitioners to resolve (Kuhn, 1970).

Paradigms are not necessarily scientific hypotheses or theories, which are more robust intellectual constructs that must be rigorously defined—usually mathematically—and are at least theoretically testable by experimentation. As elements of a general philosophical framework, paradigms define how scientists collect and work with data to produce further understanding. The working paradigm is thus a critical influence on the development of specific hypotheses or theories in a field. The environmental risk assessment/analysis approach is a part of a risk-based management paradigm. It is heavily influenced by and dependent on the theory and practice of ecology. To understand the scientific validity and applicability of modern risk assessment with regard to environmental issues, it is necessary to understand the ecological paradigms on which risk assessment relies. A commonly employed paradigm for the ecological sciences was articulated by Odum (1971): Perhaps the best way to delimit modern ecology is to consider it in terms of the concept of levels of organization. Ecology is concerned largely with systems levels beyond that of organism.

This statement was accompanied by a figure showing the spectrum of levels of organization he had in mind (genetic systems, cell systems, organ systems, organismic systems, population systems, and ecosystems), in which the ecosystem is the highest level of organization. Populations of species and communities of populations represent the biotic subcomponents of this ultimate level of organization. The eminent Canadian biologist F. E. J. Fry gave succinct direction on how to approach the study of a level of organization. One must begin by making an observation—preferably a measurement of a property or properties of the level of organization one wishes to understand—then, You take the properties of a level of organization and use those observations to analyze the next level of organization below it. If you take the properties too many steps down, you’re being stupid; and you cannot go the other direction (Kerr, 1976).

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The Ecosystem Paradigm and Environmental Risk Management

Taken together, current ecosystem theory and practice can be summarized in three “principles”: 1. There is a distinct level of organization in nature, called “the ecosystem”, which is beyond population and community. 2. An ecosystem study, either descriptive or analytical, requires observations obtained at the ecosystem level of organization. 3. Ecosystem-level observations should be quantitative measurements. Application of these principles begins with clear identification of the level of organization under study and its boundaries, followed by a decision on which system properties to study. These should be properties of the system as a whole, and there should be measurements associated with them. The importance of quantification is elaborated by Peters (1991): It is summed up in a phrase attributed to Lord Kelvin: “If you cannot measure, your knowledge is meagre and unsatisfactory.” As a result, quantitative theories prevail over qualitative competitors.

In addition to its scientific value, quantification is also preferred by managers: “If you can’t measure it you can’t manage it.” Quantification, is emphasized in the U.S. EPA’s guidelines for ecological risk assessment (USEPA, 1998): Whenever goals are general, risk assessors must interpret those goals into ecological values that can be measured or estimated and ensure the managers agree with their interpretation.

This scientific process would likely lead to some predictive possibilities, which would be of real value to managers in calculating risk. A predictive, science-based ecosystem management process would then be founded on the above-mentioned types of data. EXAMINATION OF THE USE OF ECOSYSTEM-LEVEL MEASUREMENTS IN ENVIRONMENTAL MANAGEMENT A number of techniques have been used, or proposed, to quantify observations made at the ecosystem level of organization. For example, a measure of energy flow in units of kg/unit time, the Production/Biomass (P/B) Ratio, is calculated by summing the net productivity of all discrete carbon fixing parts of the defined ecosystem and dividing the total by the sum of the biomass for those parts; Effluent Loading describes the amount of a material that enters the ecosystem; Event Frequencies is the number of events (e.g., fires per unit of time) expressed in various statistical descriptors, such as average or variance, or as a probability. These and other putative properties of the ecosystem level of organization and their quantification are reviewed below.

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Tables 1 and 2 list 26 concepts developed by ecologists to describe properties of the ecosystem level of organization. (The list is not exhaustive, but should be considered reasonably comprehensive; the references cited are not necessarily the first occasions on which particular terms were used.) Each of these was examined to determine three things: 1. Is there a method for quantifying this property at the ecosystem level of organization? 2. Is this property commonly quantified and, if so, is there a generally agreedupon method? 3. Is this property generally used in management decision-making? In addition to literature review, the answer to question 3 relies on the authors’ personal experience. Much of the environmental regulatory effort over the last few decades has been focused on aquatic systems, as has much of the ecological research. Our analysis focuses on management of the aquatic environment, although the principles should be generally applicable. Table 1 lists 12 ecosystem properties used by managers to aid in decision-making with regard to the aquatic environment. Eight have well-defined methods for quantification, the results of which are routinely used as a basis for making management decisions; two—Degradation and Damage—are also quantified by association with other quantifiable properties and are primarily risk communication terms; two, Diversity-species and Diversity-genetic, are also rarely quantified and have not been rigorously defined at the ecosystem level (Hammond, 1995). Diversity is useful primarily for communication, as it is of limited value as a scientific concept (Peters, 1991; Schrader-Frechette and McCoy, 1993), but has been used to provide an aura of scientific validation to what are essentially intuitive (philosophical, commercial, or utilitarian) decisions on the importance of preserving species (Heywood, 1995; Ehrlich and Ehrlich, 1981; Ehrlich and Ehrlich, 1996; Abramovitz, 1991). There are few measures of diversity for an entire ecosystem, although Patrick (1985) attempted to determine the relative numbers of species in various functional groupings in an aquatic system. This would be difficult to accomplish today, however, since microbiologists cannot agree on how diversity should be quantified (Hammond, 1995). Aesthetics, Pollution Export and Productive Capability are used for environmental management. They would be more useful if more and better quantification were completed (Mackay, 1991; Suter, 1990). All of the properties may be associated with, and are amenable to, monetary evaluations and/or are directly linked to some human use of the ecosystem. Table 2 lists the 13 remaining properties that are not used by environmental managers to make decisions. Disturbance, Homeostasis, Perturbation, Stress, and Trophic Levels have no known method for quantification on an ecosystem basis. Health and Integrity are quantified by indices, which are not system properties, have debatable merit as predictive tools, and are primarily chosen for their value as tools for communication with the public (Suter, 1993b). Food Web and Stability have quantification methods associated with them, but have only been pursued by a few academic investigators (Webster, Waide, and Patten, 1975; Paine, 1988). The prop-

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Table 1. Ecosystem properties used in aquatic environmental management


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Ehrlich and Ehrlich (1981)

Patrick (1985)

h

Turner and Gardner (1991)

f

g

Murdock and Clair (1985)

Wagner and Hart (1986)

Allen and Kramer (1972)

c

e

Health and Welfare Canada (1992)

b

d

Chapra and Reckhow (1983)

a

Table 1. Continued



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Table 2. Ecosystem properties not used in aquatic environmental management

a

Odum, Finn, and Franz (1979)

b

Odum (1971)

c

Odum et al. (1977)

d

Odum (1985)

e

Waide (1988)

f

Paine (1988)

g

USEPA (1989)

h

Rapport (1990)

i

Suter (1993a)

j

Karr (1991)

k

Suter (1990)

l

Webster, Waide, and Patten (1975)

m

Peters (1991)

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erties of Food web and Stability are usually defined operationally, as there is no agreement on a philosophical definition at the ecosystem level (Peters, 1991). Stability, in particular, persists as a property in the ecology literature despite vigorous and convincing arguments demonstrating the numerous problems with it (Peters, 1991; Goodman, 1975). Only one, Energy Flow, is associated with quantification, and despite efforts to explain its usefulness to managers (Odum, 1971), it remains primarily a property used by the academic community. Based on this examination, half of the properties (13 of 26) listed in Tables 1 and 2 are not used by managers. All 13 arose from the scientific/ecological research community. Of the 13 properties in Table 1 used by managers, two arose from the scientific/ecological research community (Diversity-species and Diversity-genetic) and six were developed in schools of environmental engineering. The remaining five were developed by the natural resource utilization community. DISCUSSION Why are there so many aquatic ecosystem properties that are not associated with quantification? Why are the quantified properties often associated with environmental engineering or natural resource utilization rather than ecology? Ecologists have not been able to agree on a theoretical basis for how to approach the study of ecosystems and have long debated these questions (Schrader-Frechette and McCoy, 1993; McIntosh, 1985). Ecology lacks a working relationship between theorists and experimentalists, which leads to a lack of a working relationship between applied ecology and ecological theory (Allen and O’Neill, 1991). While there may be an objective basis for defining the boundaries of an ecosystem (e.g., by examination of the rate of energy transfer [Margalef, 1968]), according to some authors the system boundary cannot be objectively defined. Neither point of view is supported by quantitative data. The relevant hierarchical structure may change from situation to situation, which suggests that the term “ecosystem” may be inadequate (O’Neill et al., 1986). The field of Landscape Ecology has addressed this issue specifically, and divides ecosystems into pragmatic and subjective units. For example, the “ecotope” is described as the smallest mapped, observed, studied, and managed unit within a natural system. The unit described must be more than the organisms of a population or a community (Naveh and Lieberman, 1984). Environmental managers in the United States appear to be moving in this direction; for example, a discussion of the U.S. EPA approach to watershed protection (Wyland, 1998) states: For certain living resources of ecological concern (e.g., migratory bird flight paths), other boundaries are more appropriate. In some cases an ecosystem may be a large geographical area (e.g., the Great Plains, the Mississippi Delta) within which smaller watershed management projects may contribute to broader ecosystem goals. Overall environmental objectives will determine the most appropriate “place” on which to focus.

The units ecologists choose to identify as ecosystems may represent systems (middle number systems) about which it is impossible to make predictions, since the

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level at which the prediction is to be made lacks unambiguous constraint over all the parts (Allen and O’Neill, 1991). In other words, one must know what is the whole and what are its parts. In middle number systems the individual parts can make a difference to the outcome of what is predicted for the whole system. This describes all aquatic ecosystems, as the term is currently understood. If all observational data suggest that such entities are middle number systems, and if middle number systems are inherently unpredictable, then management of an aquatic environment by using the specification of “ecosystem” will be an inherently unpredictable approach. There are many other examples of confusion about ecosystem theory. Koonce (1990) argues that “ecosystem health” is a useful metaphor for managing the environment, indicating that natural environmental forces interact and on balance act as homeostatic regulators of communities and ecosystems. Suter (1993b) argues forcefully that health is not a useful metaphor: Ecological theory does not address the health of an ecosystem any more than celestial mechanics addresses the health of planetary orbits;

and Engelberg and Boyarsky (1979) argue that ecosystems do not have homeostatic mechanisms because they are not cybernetic systems: Ecosystems lack (1) global information networks to integrate their parts, (2) lowenergy cause and high-energy effect interactions to make the regulation of highenergy events possible, and (3) global informational feedback cycles to stabilize and regulate. Ecosystems are not cybernetic systems.

Botkin (1990) explains this as the tendency for humans to impose familiar archetypes on new problems; thus, some view ecosystems as simple mechanical devices which are managed to continue a natural steady-state output. Alternative views include the ecosystem as a super organism or as a manifestation of a divine being. Botkin demonstrates that none of these images of ecosystems are supported by ecologists’ observations. Suter (1993b), citing several sources, states: “(T)here is currently no acceptable ecosystem paradigm.” This conclusion had been previously made quite thoroughly and rigorously by O’Neil et al. (1986). Stated more generously: the previously discussed prevailing ecological paradigm has not produced a mature, broad, generally accepted theory or hypothesis of ecology. This is supported by the lack of even a generally accepted technical description of what constitutes an ecosystem. There is also no generally accepted technical description of the relationships between the levels of organization. In some cases this problem extends even to the definition of the levels themselves. According to the three principles outlined earlier, a suitable and clear technical definition of “ecosystem” must be agreed upon. If the “levels of organization” framework is to move beyond the status of a conceptual paradigm, technical definitions of the various levels and their relationships must also be agreed upon. Some levels, such as organism and population, are generally accepted and readily defined in many circumstances; however, since alternative relationships have been proposed (O’Neill et al., 1986; Munkittrick and McCarty, 1995), even general acceptance of the nature and degree of the hierarchical relationships between levels is in question. Despite the apparent lack of theory, there is much published litera-

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ture with the term “ecosystem” in the title. How is ecosystem research usually carried out? “Ecosystem studies” are usually based on measurements of components—usually populations or communities—within a given environmental system. This reductionist approach is not consistent with the Fry paradigm. While it may be good science and may provide good information for making management decisions about important populations and communities, it is not a study of the ecosystem level of organization. To call this approach “ecosystem analysis” may be to mislead the reader as to what level of organization is being assessed and as to what use can be made of the data. Many “ecosystem” models suffer from the same confusion, which may lead to inappropriate conclusions about the usefulness of any given model. Kersting (1988) and Landis et al. (1994) have attempted to define several quantitative measurements of system-level behaviour. Their papers are examples of researchers who have attempted to apply the three principles we have identified to an artificially created system that has defined boundaries (the aquatic microcosm). CONCLUSION AND RECOMMENDATIONS Since much of what has so far arisen out of the “ecosystem” or “levels of organization” paradigm is of little practical use in environmental decision making, it is imperative that a viable alternative be developed and adopted. Although some field studies (Schindler et al., 1985) and some microcosm studies (Landis et al., 1994) have been serious in their attempts to focus on the “ecosystem” level, there is a need for more empirical studies of ecosystems. O’Neill et al. (1986) have attempted to define a theoretical context for this review. Peters (1991) argues that, given the large amounts of existing ecological information already published, very cost-effective and scientifically sound advances in ecology could be made by using existing data in developing and testing newer theoretical concepts. There is a pressing need for just this type of review. Such a review should focus on the three principles noted earlier, to develop a viable, technically oriented expression of the “ecosystem” paradigm. At a minimum it should provide environmental managers with the information needed to determine an appropriate metaphor or concept that will support science-based management strategies. It should also produce specific guidance on how observations made about levels of organization can be factored into such strategies. For example, “sustainability” may be a more suitable conceptual underpinning for a strategic environmental management system, because it will lead to management questions that can be answered by the existing body of knowledge in ecology or by the collection of new data (Suter, 1993b). Cairns (1994) suggests that the many properties of ecological systems he refers to as “services” may also do the same and be useful for communication with the public, an approach adopted by the Ecological Society of America (Daily et al., 1997). The lack of an effective paradigm implies a profound state of instability in a scientific field (Kuhn, 1970). This must be addressed if ecological science is to be truly and thoroughly incorporated into environmental management. Currently, an environmental risk management framework can be considered to be science-based if the properties being managed are selected from those listed in Table 1. The properties listed in Table 2 are ecologically based,

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but do not have sufficient technical and quantification information presently available to be considered science-based at the ecosystem level of biological organization. Thus, from an environmental risk management decision-making perspective, it is questionable whether ecosystem research beyond the Table 1 properties should be pursued until a generally accepted ecological system paradigm is developed. At a minimum, the term “ecosystem” must be clearly and rigorously defined at a philosophical and technical level or be at risk of being dropped from the lexicon of environmental science. ACKNOWLEDGMENT The authors wish to thank Ray Cote of Dalhousie University for discussions, comments, and suggestions which faciliated development of this paper. REFERENCES Abramovitz, J. N. 1991. Biodiversity: inheritance from the past, investment in the future. Environ. Sci. Technol. 25, 1817–1818. Allen, H. E. and Kramer, J. R. 1972. Nutrients in Natural Waters. New York, NY, John Wiley and Sons. Allen, T. F. H. and O’Neill, R. V. 1991. Improving predictability in networks: system specification through hierarchy theory. In: Theoretical Studies of Ecosystems: The Network Perspective, pp. 101–114. (Higashi, M. and Burns, T. P., Eds.). New York, Cambridge Univ. Press. Botkin, D. B. 1990. Discordant Harmonies: A New Ecology for the Twenty-first Century. New York, Oxford Univ. Press. Cairns, J., Jr. 1994. Estimating the effects of toxicants on ecosystem services. Environ. Health Perspect. 11, 936–939. Chapra, S. C. and Reckhow, K. H. 1983. Engineering Approaches for Lake Management. Volume 2: Mechanistic Modeling. Toronto, ON, Butterworth Publishers. Daily, G. C., Alexander, S., Ehrlich, P. R., Goulder, L., Lubchenco, J., Matson, P. A., Mooney, H. A., Postel, S., Schneider, S. H., Tilman, D., and Woodwell, G. M. 1997. Ecosystem Services: Benefits Supplied to Human Societies by Natural Ecosystems. Issues in Ecol. 2, 1– 16. Ehrlich, P. and Ehrlich, A. 1981. Extinction: The Causes and Consequences of the Disappearance of Species. New York, Ballantine Books. Ehrlich, P. and Ehrlich, A. 1996. Betrayal of Science and Reason: How Anti-Environmental Rhetoric Threatens Our Future. Washington, DC, Island Press. Engelberg, J. and Boyarsky, L. L. 1979. The noncybernetic nature of ecosystems. Am. Naturalist 114, 317–324. Goodman, D. 1975. The theory of diversity-stability relationships in ecology. Quart. Rev. Biol. 50, 237–266. Hammond, P. M. 1995. The current magnitude of biodiversity. In: Global Biodiversity Assessment, pp. 113–138. (Hawksworth, D. and Kalin-Arroyo, M. T., Chap. 3. Eds.; Heywood, V. H., Exec. Ed.). United Nations Environment Programme. New York, Cambridge Univ. Press. Health and Welfare Canada. 1992. A Vital Link. Health and the Environment in Canada. Minister of National Health and Welfare. Ottawa, ON. Herrick, C. J., Goodman, E. D., Guthrie, C. A., Blythe, R. H., Hendrix, G. A., and Smith, R. L. 1982. Ecol. Model. 15, 1–28. Heywood, V. H. 1995. Global Biodiversity Assessment. United Nations Environment Program. New York, Cambridge Univ. Press.

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