What environmental duties and obligations does human membership in biotic communities generate? To preserve the integrity, stability, and beauty of the biotic community? These cardinal values of the Leopold land ethic may have to be revised--dynamized, to coin a word--if they are to be ecologically credible. Leopold was aware of and sensitive to environmental change. He knew that conservation must aim at a moving target. How can we conserve a biota that is dynamic, ever changing, when the very words "conserve" and "preserve"--especially when linked to integrity and stability--connote arresting change? The key to solving that conundrum is the concept of scale. Scale is a general ecological concept that includes rates as well as scope--that is, the concept of scale is both temporal and spatial. A review of Leopold's "The Land Ethic" section of A Sand County Almanac reveals that he had the key, although he may not have been aware of just how multiscalar change in nature actually is.

      In "The Land Pyramid" section of "The Land Ethic" Leopold writes, "Evolutionary changes . . . are usually slow and local. Man's invention of tools has enabled him to make changes of unprecedented violence, rapidity, and scope." As noted, Leopold was keenly aware that nature is dynamic, but, under the sway of mid-century equilibrium ecology, he conceived of natural change primarily in evolutionary, not in ecological terms. Nevertheless, scale is equally normative when ecological change is added to evolutionary change, that is, when normal climatic oscillations and patch dynamics are added to normal rates of extinction, hybridization, and speciation.

      The scale notion is currently being employed to refine the ecosystem concept in ecology. As also noted, a major problem with the ecosystem concept in ecology is the problem of bounding ecosystems. Lindeman's field-defining paper reported his study of Cedar Bog Lake. The influential work of Gene Likens and Herbert Bormann focused on Hubbard Brook. Thus, one way that ecosystems came to be defined was to regard them as coextensive with watersheds. But such a method of defining ecosystems is crude at best and inapplicable at worst to marine ecosystems and to other study areas that are not easily divisible into watersheds. The watershed method of defining ecosystems is also inapplicable to transwatershed problems such as demarcatin g the Greater Yellowstone Ecosystem or determining the ecosystemic needs and functions of wide-ranging species like bears and wolves. However, with the development of hierarchy theory in ecology, ecosystems may be defined quite precisely--albeit both abs tractly and relativistically--in reference to temporally scaled processes. According to Tim Allen and Tom Hoekstra,

      Ecosystems are not readily defined by spatial criteria. Ecosystems are more easily conceived as a set of interlinked, differently scaled processes that may be diffuse in space, but easily defined in turnover time. . . . Thus a single ecosystem is itself a hierarchy of differently scaled processes. . . . There are differently scaled processes inside a single ecosystem, as well as sets of differently scaled, more inclusive and less inclusive ecosystems. . . . The degree to which processes of different types express themselves and the length of time they do so, are both ways of describing the uniqueness of particular ecosystems. Much of what we observe in ecosystems, is better set in time rather than space. . . . The ecosystem is a much richer concept than just some meteorology, soil, and animals, tacked onto patches of vegetation. ... Ecosystems can be seen more powerfully as sequences of events rather than things in a place. These events are transformations of matter and energy that occur as the ecosystem does its work. Ecosystems are process-oriented and more easily seen as temporally rather than spatially ordered. [Toward A Unified Ecology, 1992, pp. 94, 98-100].

      Homo sapiens is a part of nature, "a plain member and citizen" of the "land-community," as Leopold puts this evolutionary-ecological point. Hence, anthropogenic changes imposed on nature are no less natural than any other. However, since Homo sapiens is a moral species, capable of ethical deliberation and conscientious choice, and evolutionary kinship and biotic community membership add a land ethic to our familiar social ethics, anthropogenic changes may be land-ethically evaluat ed. But by what norm? The norm of appropriate scale . . . .

      Biotic communities may be ever changing assemblages of organisms of various species that happen to be adapted to the same edaphic and climatic gradients. However, that makes them even more analogous to human communities than the old static-holistic representation. Ever-changing, imprecisely bounded communities of human individualists are robust enough to be identifiable entities and to generate special obligations to fellow members and to such communities per se. Why should a communitarian environmental ethic such as Leopold's have to meet any higher standard of community robustness?

      The summary moral maxim of the land ethic, nevertheless, must be dynamized in the light of developments in ecology since the mid-twentieth century. Although Leopold acknowledged the existence and land-ethical significance of natural environmental change, he seems to have thought of it primarily on a very slow evolutionary temporal scale. But even so, he thereby incorporates the concept of inherent environmental change and the crucial norm of scale into the land ethic. In light of more recent developments in ecology, we can add norms of scale to the land ethic for both climatic and ecological dynamics in land-ethically evaluating anthropogenic changes in nature. One hesitates to edit Leopold's elegant prose, but as a stab at form ulating a dynamized summary moral maxim for the land ethic, I hazard the following: "A thing is right when it tends to disturb the biotic community only at normal spatial and temporal scales. It is wrong when it tends otherwise."

      J. Baird Callicott is professor of philosophy at University of North Texas and the author of In Defense of the Land Ethic (1989), and editor of Companion to A Sand County Almanac (1987). The above is adapted from an essay by Callicott, "Do Deconstructive Ecology and Sociobiology Undermine Leopold's Land Ethic?" Environmental Ethics, Winter 96, at 369-372, and is reprinted with permission of Environmental Ethics and the author.

To comment or raise questions about Baird Callicott's article, go to the Discussion Area for this article.