Perhaps more than any other philosopher J. Baird Callicott has worked to extend the frontiers of environmental ethics by grounding it in the thought of Aldo Leopold. [See J. Baird Callicott, In Defense of The Lan d Ethic: Essays in Environmental Philosophy, 1989]. Callicott follows Leopold in providing not "only 'respect' for individual members of the biotic community, but 'biotic rights' for species"; further, he says, "in the last analysis, 'the integrity, beauty, and stability of the biotic community' is the measure of right and wrong actions affecting the environment." Once we see land as Leopold's "biotic community," says Callicott, the land or environmental ethic emerges. The "conceptional and logical foundations of the land ethic," he says, are evolutionary and ecological biology.

      Although Leopold's (and Callicott's) land ethic rests on "the ecological concept of a biotic community," Callicott deserves high praise because he goes to some length to defend the intrinsic value of nonhuman species . At least part of his motivation is the widespread species extinctions occurring all over the planet. Many writers, myself included, believe that it makes sense to argue for the intrinsic value of natural entities and nature as a whole. It makes sense because this intrinsic value can be grounded in some properties of the entities, such as being living.

      Leopold's (and Callicott's) views, however, run into several difficulties. (1) There is no scientifically/biologically coherent notion of "community" robust enough to ground either contemporary community ecology or environmental ethics. (2) Because of (1), it is not always clear how to safeguard the interests of these communities. There is, for example, no clear sense in which one can claim that natural ecosystems proceed toward homeostasis, stability, or some balance. Likewise there is no consensus among ecologists on the ecosystemic view of balance or stability, and almost no support for the diversity-stability view held by MacArthur, Hutchinson, and Commoner. [See M. Sagoff, Environmental Ethics 7 (Summer 1985) 107-110.] The reasons for the disfavor attributed to the view of MacArthur et al. are both empirical and theoretical. Salt marshes and the rocky intertidal are two of the many counterexamples to the diversity-stability view, and empirically based counterexamples have multiplied over the last two decades. Even though some laypersons and policymakers appeal to the hypothesis, most scientists either have repudiated it or have cast strong doubt on it.

      Doubts about balance and stability have arisen, in part, because ecologists cannot say what it would be, in a non-question-begging way, to hinder some balance, stability, or integrity. This is because communities an d ecosystems regularly change and regularly eliminate species. Indeed, change is the norm, and most scientists now believe that biotic "communities" cannot be identified by any specific properties or species that give predictive power over them. Nature doesn't merely extirpate species or cause them to move elsewhere because their niches are gone. And if not, then there are no noncontroversial scientific grounds for defining and preserving some notion of balance or stability. Hence it is not clear that Leopold's (and Callicott's) appeals to ecology can help environmental ethics in any precise, scientific way. It will not do to say that what happens naturally is good, whereas what happens through human intervention is bad; this would be to solve the problem of defining "balance" or "stability" in a purely stipulative or ad hoc way.

      Another conceptual problem besetting environmental appeals to scientific/ecological balance, wholeness, or integrity is that ecologists must take into account thousands of different communities, species, and individu als, as well as the health or balance of ecosystems or the biosphere. It is unclear both (1) how to define (scientifically) the health of a system (as opposed to an individual), since system health is relative to some specific goal, and (2) how to define the system at issue. The ecological problem of defining the system at issue is analogous to the economic problem of defining a theory of social choice and choosing some "whole" that aggregates or represents numerous individual choices.

      Defining an ecological "whole" to which Leopold can refer is especially problematic for at least two reasons. One reason is that contemporary scientists do not accept the views of the biologists (e.g., Clements, Elt on, Forbes) cited by Callicott to explicate his Leopoldian views. The other reason is that most ecologists have rejected the contemporary variant of Clements' position, the GAIA hypothesis, as unproved metaphor or mere speculation. They admit the scient ific facts of interconnectedness and coevolution on a small scale, but they point out that ecosystems and communities, as intact systems, do not persist through time. Hence there is no clear referent for the alleged "dynamic stability" of an ecosystem or community.

      Moreover, it is not clear which (of many) alleged ecological communities whose stability one ought to seek. One could seek to stabilize (whatever that means) the ecosystem, or the association, or the trophic level, for example. Or, if one is a holist, then why should not the collection of communities and ecosystems be optimized, namely, the biosphere? One can make a human value judgment to optimize the well being of a particular community, the biosphere, or some ecosystem, but this is just that, a human value judgment. It is not science. And if not, it cannot be part of an ecological foundation for environmental ethics.

      Admittedly, once one makes a human value judgment about which particular whole one wants to stabilize or balance, it is obvious that particular ecological conclusions are valid within certain spatial and temporal sca les. Nevertheless, ecologists cannot optimize the welfare of all the different wholes (each having a different spatial and temporal scale) at the same time. Because they cannot, there is no general level at which ecological problem solving takes place. Hence there is no general temporal or spatial scale within which scientists can currently define a stable "whole."

      Because there is no universal scientific/ecological theory to which ethicists can appeal in defining the "whole" about which Leopold (and Callicott) speak, ecologists are forced to work on a case-by-case basis. Also, many ecosystemic or holistic explanations are neither falsifiable nor even testable. This is why at least one scientist, R. P. MacIntosh, called ecosystems ecology "theological ecology." [See The Background of Ecology, 1985]. There is neither a clear definition of what it is to be balanced or stable, nor of the whole that is allegedly balanced or stable. Indeed, there is no universal scientific account of balance or stability because ecologists do not agree on the underlying processes that allegedly structure communities and ecosystems.

      One biological problem with Leopold's views here is that nature does not respect communities. There is strong biological evidence (e.g., fossilized pollens) of radical changes in community composition and structure throughout history. These changes, in turn, suggest that there is no such thing as a stable or balanced community "type" existing through time. Rather the types only appear stable because our time frame of examination is relatively short. Even if climate and environment remained the same, communities could not be classified into balanced or stable "types" on the basis of climate. Both spatial and temporal fluctuations undercut any universal notion of a stable or balanced community. As a result, it is difficult to avoid stipulative and question-begging arguments that humans ought to respect biotic communities. Ethicists need to avoid such pitfalls.

      Where do these considerations leave us? Just as scientific progress comes from a plurality of theories, so also progress in environmental ethics likely will come from a plurality of philosophical approaches -- such as Leopold's and Callicott's work, rooted in a profound grasp of moral theory, and my own work, grounded in biology and philosophy of science. Ernst Mayr said that the "spectacular recent progress" in evolutionary theory was not due to improvements in measurement but due to improvements in the clarification of concepts. The same can be said for much of environmental ethics. Let us clarify and improve Leopold's concepts so that we can use them to promote environmental protection.

      Kristin Shrader-Frechette is professor in the Philosophy Department, Biology Department, and the Center for Environmental Sciences, University of Notre Dame, and is the co-author of Method in Ecology, Strategies for Conservation, 1993. Portions of this essay were supported by NSF grant BOS - 8619533. The opinions expressed are those of the author and not the National Science Foundation.

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