Roberta Millstein’s The Land Is Our Community reinvigorates the environmental philosophy of Aldo Leopold, the esteemed American conservationist who worked with the US Forest Service in Arizona and New Mexico and at the University of Wisconsin–Madison. Leopold is now most well known for The Sand County Almanac and, in particular, his essay ‘The Land Ethic’, first published in 1949. Millstein’s overall project is to more charitably interpret and apply Leopold’s environmental philosophy, including notions of his such as ‘land community’ and ‘land health’, and to suggest some applications of his views in the present day. To bring this project to fruition, she first provides a reinterpretation of Leopold’s land ethic, including dispelling several common misinterpretations. Along the way, Millstein develops in detail the Leopoldian concepts of ‘interdependence’, ‘land health’, and ‘land communities’. The book ends by presenting and defending an argument for the adoption of the Leopoldian land ethic and discussing the policy implications thereof.

Of particular interest to philosophers of science is Millstein’s analysis of the Leopoldian concept of ‘interdependence’. One of Leopold’s contributions to ecological theory and practice was to notice that interdependency relations between biotic and abiotic components of ecosystems are not (always or usually) unidirectional; for example, predators do not just rely on prey as a source of food, but prey also rely on predators as a source of population control and therefore resource distribution among surviving members of the prey taxon. Leopold writes about the ‘interdependence of the forest and its constituent tree species’ ([1966], p. 249) and the ‘tendency of interdependent individuals or groups to evolve modes of co-operation’ ([1966], p. 238). Of course, nowadays a focus on interdependence seems rather trivial, as ecologists have documented cases of mutual interaction within the complex systems they study for decades. But at the time this idea was revolutionary for conservation biology and provided the impetus for programmes such as the reintroduction of wolves to the American West.

Millstein presents a proposal for how to understand interdependence: ‘namely’, she says, ‘Leopoldian interdependence consists of direct and indirect “negative” and “positive” causal interactions between organisms (including humans), populations, and abiotic components (“interactors”) that yield a variety of needs and vulnerabilities in organisms, populations, and abiotic components (as well as land communities more holistically), with interactions that vary in strength and direction in time and in place, often forming a web or network of such interactions’ (pp. 47–48).

Let’s unpack the key features of this account of interdependence. First, the directness, strength, and direction (negative or positive) of the interaction can vary; importantly, interdependence can involve a positive, beneficial influence as well as a negative, harmful one. The direction of the interaction lines up roughly with whether one component ‘needs’ the other (the latter could have a positive effect on the former by fulfilling that need) or is ‘vulnerable’ to the other (the latter could have a negative effect on the former via the vulnerability; p. 44). Predation, for instance, is typically thought of as positive for the predator and negative for the prey. Second, Millstein’s account specifies that the interaction should be causal. Third, the relata of the interdependence relation are ‘organisms (including humans), populations, and abiotic components (“interactors”)’ (p. 48)—in short, components of ecosystems at any level up to and including the whole land community. Jointly, these interactions serve to form a ‘web’ or ‘network’ that tracks relationships among various component parts.

Millstein is optimistic that Leopoldian interdependence or ‘network thinking’ is useful for ecological theory and practice, compared to more simplified understandings of ecological relationships, and she cites some contemporary ecological work that is consistent with a Leopoldian framework (p. 47). We performed a cursory and non-exhaustive search for recent uses of the word ‘interdependence’ in two ecology journals, Nature Ecology and Evolution and Ecology, and we found several instances for which the ecologists’ use of ‘interdependence’ accords with Millstein’s proposal (for example, Marcarelli et al. [2020]; Opedal et al. [2020]; Manlick et al. [2023]; Sampaio et al. [2024]), including some instances where ecologists speak of interdependence between whole ecosystems or landscape patches (Peng et al. [2022]; Shoemaker et al. [2022]). Of course, these researchers don’t usually spell out in great detail what they mean by ‘interdependence’, but they do typically use a conception of it that shares key features of Millstein’s, such as interdependence being a causal relation that holds between ecosystem components, and can vary in strength and direction.

However, not all uses of ‘interdependence’ that we found share these features. First, not all ecologists have a causal notion of interdependence in mind. For example, some research identifies mere correlative relationships as interdependencies (for example, Cao et al. [2021]). Second, some ecologists equate interdependence with symbiosis, thereby only recognizing positive interactions as constitutive of interdependence, contrary to a Leopoldian view (for example, Cornwallis et al. [2023]).

Third, although in many cases ecologists do use ‘interdependence’ to capture a relation between explicit ‘organisms, populations, and abiotic components (as well as land communities more holistically)’, in other cases the relata of interdependence are neither the component parts of land communities nor the land communities themselves. Instead, some ecologists talk of interdependence as a relation between other features of ecosystems or ecosystem parts, such as functions or patterns in which the ecosystem components play a role. For instance, Wootton et al. ([2023]) refer to the interdependence of ecosystem functions (such as the storage of carbon). In this case, the relata of interdependence (the ‘interactors’) are of a higher order than those initially suggested by Millstein’s characterization. For example, functions are performed due to interactions between component parts of land communities, and some ecologists take the interaction between the functions themselves to constitute the relevant interdependency relation. Likewise, Fletcher et al. ([2023]) cite the interdependence of habitat patterns across scales and Manlick et al. ([2023]) the interdependence of food webs, while Blowes et al. ([2022]) and Cao et al. ([2021]) describe the interdependence of various dimensions of biodiversity (abundance, evenness, richness, and beta and gamma diversity). As with functions, the relata in these examples are all of a higher order: patterns, webs, and dimensions of biodiversity each describe interactions between, or in some way refer to aspects of, the Leopoldian interactors (organisms, populations, abiotic components, land communities).

In response to the recognition that contemporary ecologists’ use of ‘interdependence’ is perhaps more permissive than Millstein’s initial proposal for Leopoldian interdependence would allow, there are at least three ways to proceed, each of which is friendly to Millstein’s original proposal. First, one might adopt a pluralist attitude toward the concept of interdependence; perhaps there are multiple kinds of interdependence operating at different scales or between different types of relata, not all of which are properly Leopoldian. Second, a philosopher of science might voice concern about ecologists’ use of interdependence and try to correct their usage, perhaps to be more in line with a Leopoldian conception. Third, one might expand the range of interactors accommodated by Leopoldian interdependence to include higher-order relata (for example, functions, patterns, webs, and so forth). Leopold himself does occasionally refer to the interdependence of such interactors: in A Sand County Almanac, for instance, Leopold writes of the ‘interdependence between the complex structure of the land and its smooth functioning as an energy unit’ ([1966], pp. 253–54) and of the interdependence between the ‘stability and diversity’ ([1966], p. 193) of an ecosystem. An expanded notion of Leopoldian interdependence may have the added benefit of guiding ecologists’ thinking about what sorts of interactions to consider in their models of complex systems. Overall, a view of interdependence that explicitly includes the interactions between abstract higher-order relata such as the structure, functioning, stability, and diversity of ecosystems is plausibly Leopoldian in spirit.

Other than its analysis of the concept of interdependence, The Land Is Our Community introduces a wealth of conceptual resources for philosophers of ecology and environmental ethicists alike. In particular, the latter third of the book is dedicated to advancing Leopold’s view that our ethical obligations extend to land communities. Millstein introduces eight policy-relevant principles of conservation, according to which we should: (i) ‘Include and attempt to integrate all pertinent interests and values’, (ii) ‘Seek cooperation rather than competition between the different interests and values to try to find a harmonious, balanced system of land use’, (iii) ‘Deploy a variety of techniques’, (iv) ‘Recognize that there will be failures’, (v) ‘Recognize and act on obligations to the land over and above self-interest’, (vi) ‘Take the long view of conservation problems’, (vii) ‘Gather applicable scientific information from relevant scientific disciplines’, and (viii) ‘Engender public understanding of the relevant science and its impacts’ (pp. 139–40, 142). These principles focus on an inclusive, cooperative, and pluralistic approach to ethics. Millstein thereby works to develop a more plausible interpretation of the Leopoldian ethical vision; for example, by dispelling existing interpretations of Leopold as an ‘environmental fascist’ who believes that humans ought to sacrifice themselves for the good of the land (p. 12). Instead, she argues that the land ethic simply encourages humans to view obligations to the land as an extension of obligations to one another. To further this claim, Millstein uses specific examples in contemporary ecology that already implement the Leopoldian ethical vision, such as the Ashland Forest Resiliency Project, to show cooperation among multiple interests and one farm’s successful implementation of biodiversity promotion. Principles (vii) and (viii) specifically advocate for a multidisciplinary approach that is transparent and accessible to the general public, an issue that is particularly relevant when considering current policy suggestions regarding conservation and climate change.

Taken in its entirety, The Land Is Our Community is an informative addition to the body of literature on environmental philosophy, as it gestures toward several potential research questions in philosophy, ecology, and environmental policy. As three Wisconsin-based philosophers, we welcomed the opportunity to engage with Leopold’s work while being part of one of the very land communities about which Leopold wrote.

Julia Pelletier
University of Wisconsin-Madison
jcpelletier@wisc.edu

Aja Watkins
University of Wisconsin-Madison
aja.watkins@wisc.edu

Andrew Zeppa
University of Wisconsin-Madison
zeppa@wisc.edu

References

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