Oxford Handbooks Online

On the Nature of Species and the Moral Significance of their Extinction

On the Nature of Species and the Moral Significance of their Extinction Russell Powell The Oxford Handbook of Animal Ethics Edited by Tom L. Beauchamp and R. G. Frey

Print Publication Date: Oct 2011 Subject: Philosophy, Moral Philosophy, Philosophy of Science Online Publication Date: May DOI: 10.1093/oxfordhb/9780195371963.013.0022 2012

Abstract and Keywords

This article begins by noting that in the history of life, every species up to presently existing species has become extinct. Complex life itself has been on the brink of annihilation at various points in the evolutionary process. A problem, given this history, is whether we should regard the causing or the permitting of the extinction of species as a bad outcome to be avoided. It notes that so-called common-sense intuitions about these matters are not trustworthy and often do not hold up to theoretical scrutiny. Using the evolutionary and ecological sciences, the discussion takes the currently received view that species should be analyzed in terms of individual lineages and not as a temporal natural kinds.

Keywords: extinction, life history, evolution, ecological sciences

WE owe our existence to an unbroken chain of reproduction that began with the inception of life some 3.5 billion years ago. Rejoicing in the fortuity of our genealogy, however, can obscure an equally salient but far less auspicious pattern in the history of life—namely, the extinction of nearly every species that has ever existed. There have been geological moments, and one in particular about 250 million years ago, when complex life itself teetered on the brink of annihilation. Yet the fragility of animal life per se pales in comparison to that of individual taxa.1 The mean duration of species is around four million years—an incomprehensibly vast interval to the human mind, but a mere pittance geologically speaking. And as we will see, species do not seem to get any better over time at not going extinct. What is more, if it were not for the most recent mass extinction, mammals might still be relegated to a small, nocturnal existence in the ecological shadow of dinosauria. Why, then, should we think that causing or permitting the extinction of species is a bad thing?

In claiming that it is prima facie wrong for humans to contribute to or fail to prevent the extinction of species, environmental ethicists have often relied on the intuition that species qua species have moral value. This intuitively attractive idea has been notoriously difficult to justify, however. And unlike moral judgments about fairness, lying, and torturing the innocent, intuitions about the value of species are not sufficiently robust across persons and cultures to serve as the lynchpin (p. 604) for an ethical framework, especially one that aims to influence public policy. Another reason to avoid hanging an ethical theory of species conservation on untutored moral intuitions is that folk judgments about biological entities have a less-than-stellar track record. As recently as the eighteenth century, it was still commonly believed that organisms are composed of various ratios of the four elements identified by Aristotle, that living things are driven by vital forces, and that species reflect eternal, immutable essences around which biological variation gravitates.

While commonsense intuitions have an important role to play in philosophical ethics, many folk judgments in the biological realm, such as our attitudes toward genetically modified organisms or invasive species, are often premised on certain presuppositions about the causal structure of the living world that may or may not hold up to theoretical scrutiny.2 Just as our considered moral-status judgments about comatose patients should be informed

Page 1 of 19

PRINTED FROM OXFORD HANDBOOKS ONLINE (www.oxfordhandbooks.com). (c) Oxford University Press, 2015. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a title in Oxford Handbooks Online for personal use (for details see Privacy Policy). Subscriber: Harvard University Library; date: 24 August 2015 On the Nature of Species and the Moral Significance of their Extinction

by neuroscientific findings regarding the functional specialization of different regions of the human brain,3 so too should environmental ethics be constrained by the ontological landscape that is sketched by the evolutionary and ecological sciences. This is not to imply that the relationship between descriptive biology and normative environmental ethics is a unilateral one; ethicists can draw the attention of scientists to the types of entities or causal relations that are deemed to be of moral significance, and scientists in turn can go out and look for these objects or properties in the blooming, buzzing confusion of the biological world.

In this chapter I will consider several moral justifications for the conservation of species in light of what we know about the ontology and evolution of species and their interrelations.4 The discussion will be structured as follows. In section 1, I consider the nature of species and their role in evolutionary theory. Although there are many species concepts available in contemporary evolutionary biology, I believe that for the purposes of ethical analysis there is sufficient overlap between these to avoid systemic conflicts in our individuation of species. The dominant view in biology and the philosophy of science, and the one that I support, is that species should be thought of as individual lineages, rather than as atemporal, natural kind classes. That we regard species as concrete individuals that evolve in space and time has important ramifications for the value that we might ascribe to them.

Nevertheless, in section 2 I show that a species is not the sort of individual that exhibits properties thought to create morally relevant interests, such as sentience or goal-directedness, and I conclude therefore that species are not promising candidates for intrinsic moral value. I move on to consider theories that regard species as valuable not as moral patients, but because of their relation to morally considerable beings. I suggest a number of ways that species and even higher taxa could have both final and instrumental value that is not reducible to their constituent parts, focusing on informational, evolutionary, and ecological properties and the organizational levels at which they are manifest.

In section 3, I examine metaphysical and epistemic arguments against prioritizing species for conservation, including those grounded in the “seamless web” and “delicate balance of nature” metaphors that often motivate environmental law and policy. I find these arguments unpersuasive on both theoretical and empirical grounds.

(p. 605) Finally, in the conclusion, I consider whether there is a morally important difference between human- caused extinctions and those that result from “natural” evolutionary processes. I suggest that the degree of “badness” that is added to some state of affairs because a culpable moral agent is implicated is minimal, and thus should not significantly affect our conservation priorities.

1. The Ontology of Species

What Is a Species?

The aim of this essay is to determine whether species are proper objects of moral concern. To make this determination, we first need to be clear on the ontological status of species, which in turn requires that we examine the theoretical role that the species concept plays in contemporary evolutionary science.

As far as we can tell, all life on Earth shares a common ancestor. Despite this evolutionary continuity, biological variation is not smoothly distributed in space and time. There are fairly discrete clusters of variation at all levels of the nested biological hierarchy, a clumping of form that generally reflects evolutionary relationships and which taxonomic classification intends to capture. Among taxonomic categories (see note 1), the most theoretically fundamental is the species.

Nearly all biologists and philosophers of science agree that species are comprised of geographically distributed populations of organisms with varying levels of gene exchange. Yet there is no single, widely accepted definition of the term “species.” Probably the most influential formulation is the “biological species concept,” according to which a species is the maximally inclusive set of potentially interbreeding organisms that are reproductively isolated from other such groups.5 This definition is far from canonical, however, and the species concept remains highly contested in biology and philosophy.6

Indeed, the last few decades have witnessed a proliferation of species concepts, sometimes complementary but often conflicting, with different groups of biologists attuned to properties that are of particular relevance to their

Page 2 of 19

subfield of study, such as evolutionary history, morphology, inter-fertility, or ecological role, to name a few. This conceptual and methodological discord has led many authors to embrace some form of theoretical pluralism regarding the species concept.7 This poses a problem: if biologists and philosophers of science cannot agree on what the term “species” refers to, or which groupings of organisms or populations it picks out, then how can ethicists talk meaningfully about preserving such entities?

Fortunately, the space of disagreement between alternative accounts of species is small enough to avoid prejudicing ethical discussions concerning the moral value of species. The reason for this optimism is that regardless of which properties they deem relevant to or necessary for species membership, all contemporary species concepts (p. 606) agree on the following key point: species are separately evolving metapopulations. That is, they are sets of spatially distinct subpopulations of sexually reproducing organisms that extend over time to form lineages (ancestor-descendent sequences of breeding populations) whose boundaries are determined in part by patterns of interbreeding.8

Conflicting species judgments, to the extent they arise, usually occur in relation to attempts to taxonomically partition “evolutionary gray zones.” These are situations in which potentially speciating lineages have yet to exhibit total reproductive isolation or significant genetic, morphological or ecological divergence.9 A potentially speciating lineage that has begun to diverge from its parent population can be reabsorbed by the latter if there is sufficient gene flow (interbreeding) between them. The upshot is that judgments as to whether speciation has occurred are inherently retrospective, and in hindsight there will be nearly unanimous agreement as to whether a speciation event has taken place. So apart from these relatively rare and evolutionarily short-lived “gray zone” cases, scientists and environmental philosophers should encounter little practical disagreement over how to partition species for the purposes of biological and ethical analysis, respectively.10

Thinking of species as separately evolving meta-populations, rather than as classes in which membership is determined by a set of essential properties, is one of the central insights of the Modern Evolutionary Synthesis.11 The shift in biology away from essentialism and toward “population thinking” built on the Darwinian reinterpretation of variation as a central, irreducible cause in evolution rather than indicative of some unseen but ontologically primary essence.12 As David Hull puts it, the inability to differentiate species by sets of necessary and sufficient conditions “follows from evolutionary theory just as surely as quantum indeterminacy follows from quantum theory.”13 Rarely will there be traits that are both universal and unique to a given species, and even if there were such traits, they would be short-lived because the very evolutionary processes that are responsible for their fixation will inevitably produce exceptions to the rule.14

Consequently, the received view in biology and the philosophy of science is that species and other taxa are more productively thought of as individual lineages, rather than immutable natural kinds.15 That is to say, species are individuals located in space and time with organisms as their constituent parts, rather than atemporal sets with organisms as their members. Because species are not natural kind classes, they originate, change, and go extinct much like individual organisms do. While natural kind classes may figure into laws of nature, they are not causal in the sense that they cannot make anything happen. By contrast, species as independently evolving meta- populations are not “mere” theoretical constructs. They are the furniture of the biological universe—real, causal entities whose ontological status in evolutionary biology is on par with other fundamental units of organization, such as organisms, cells and genes.16

If species are individuals with component parts, rather than abstract categories with concrete instances, this opens the metaphysical door to ethical value attaching to species over and above their constituent organisms, just as it does to organisms over (p. 607) and above their constituent cells. On the other hand, if species are atemporal classes, then their existence would not be predicated on the existence of any physical object, and consequently they could not go extinct or be harmed. Moral duties as typically conceived are owed not to abstract properties such as “pleasure” or “sentience” (or even their concrete instances), but rather to the individuals that possess those properties. What makes something a candidate for ethical conservation is not that it is a category, such as “castle,” which can only be preserved in the mind, but rather that it is an individual that we deem valuable, such as “Edinburgh Castle.” If species were classes, the relevant moral question would be whether we have an obligation to maintain non-empty sets rather than to preserve species themselves. Unlike species-as-individuals, species-as- classes do not exist in space and time and hence cannot be preserved—at least not in the way that conservation biologists typically go about preserving them (such as by protecting or restoring habitats or breeding populations).

Page 3 of 19

Another reason to think that species are individuals, particularly for the purposes of ethical preservation, is that arguments in favor of conservation often hinge on the contingent generalization that extinction is irreversible. To the extent that the permanence of extinction serves as a central motivation for preservation efforts, this casts further doubt on the species-as-classes view. Since classes can be empty at one time and non-empty at another, it is difficult to see how the concept of extinction would apply to them. Consider the quintessential natural kind class gold. Gold is a class of heavy element with a particular atomic structure; this class was empty in the early stages of the universe, because the production of gold atoms had to await the formation of high-mass stars where they would be produced by nuclear fusion and dispersed by super novae. As an atemporal class, gold cannot go extinct, even if at any given moment there are no token gold atoms in the universe. Given the right conditions, gold atoms will emerge again and again with the same physical signature and intrinsic properties that determine membership in the class. The question, then, is whether we have any reason to believe that species resemble the heavy elements in this respect. Given the right ecological conditions, will token instances of a species type emerge predictably and repeatedly, just like individual atoms of gold?

The standard view in the philosophy of biology is that due to the nature of the evolutionary process, there are no invariant or even robust generalizations about the kinds of organisms and adaptive features that will evolve—that is to say, there are no laws of fitness.17 Indeed, part of the supposed tragedy of species extinction is that some unique and historically contingent thing has vanished, presumably forever.18 It would seem, then, that the only viable way to consider species as atemporal sets for the purposes of conservation would be to think of them as classes that are unlikely to ever be repopulated once they are emptied. The trouble with this approach is that the inherent contingency of the evolutionary process would lead us to posit an unmanageable disjunction of potential species-as-classes; and given that we expect natural kind classes to do theoretical work by figuring into laws of nature (which, among other things, are supposed to exhibit a wide range of invariance and support counterfactuals), such a result would be methodologically dubious.

(p. 608) Species as Pseudo-Individuals

Even if species are better thought of as individuals rather than classes, this does not imply that they are the kind of individual that might be amenable to moral consideration. Although individuals are never classes, an entity need not be a true individual in the biological sense—or in the sense relevant to moral analysis—simply because it is not a class. In order to constitute a biological individual, an entity must possess some or all of the following properties: internal homeostatic mechanisms, differentiated parts, functional autonomy, developmental life cycle, reproduction, and metabolism.19 Even more broadly, to be an individual in the biologically relevant sense, an entity must maintain some degree of integration among its parts and it should respond as a single unit to environmental perturbations.20 There are certainly possible worlds in which species exhibit some or all of these characteristics, but in the actual evolutionary world, species rarely if ever exhibit properties like functional integration and differentiation, cohesion, homeostatic mechanisms, goal-direction, reproductive life cycle, and so forth.

First, species do not replicate or reproduce like other complex living things that go through a unicellular bottleneck (or single-celled stage) in each generation. Instead, their “parts” (sub-populations) will occasionally give rise to new species in a manner that is analogous to “budding” in asexual organisms. Even if species may be said to reproduce in some rudimentary sense, unlike organisms they do not exhibit a “life cycle,” or an intergenerationally replicable series of stages through which they pass, beginning and ending with same event.21 Individual organisms are born, grow, reproduce, and die. Species originate, fluctuate in number and character traits, and go extinct. The history of individual species is not a linear story of developmental transformation, any more than the history of life is a ladder of progress climbing from protozoa to people.22 Because species do not progress through stages of ontogeny in the way that organisms do, they do not form true reproductive lineages.

The analogy between organisms and species further breaks down because the latter do not clearly exhibit characteristics that befit the categories of health and disease, and hence it is not clear that they are capable of being harmed. Species qua species are not obviously goal-directed, they do not respond as a coordinated whole to perturbations, and they exhibit few if any biological functions. There are two dominant approaches to function in biology and the philosophy of science: “selected effects” and “causal role.” The former refers to traits with a history of selection for their effects, while the latter describes features that play a current causal role in a highly integrated biological system.23 Organisms are paradigmatic individuals because they exhibit functions in both

Page 4 of 19

senses of the term: they are functionally autonomous wholes that respond as a single, integrated unit to environmental perturbations, and they are comprised of a complex suite of phenotypic traits that have been constructed by the cumulative operation of selection for their effects. Not so with species. Species rarely exhibit irreducible species-level adaptations24; the few traits that have been proposed, such as those relating to population structure or geographic range,25 are not complex, cumulative adaptations, and do not entail the (p. 609) homeostatic, goal-directed functions that give concepts like disease and harm their normative content.

Furthermore, the constituent parts of species (populations, groups, organisms etc.) are only loosely coordinated by gene exchange. Not only are conspecifics not physically connected to one another in the way that cells are adhesively joined, but neither are they behaviorally coordinated at the population level in the way that caste members of certain insect colonies (such as those of ants, bees, and wasps) tend to be. Individual members of species are not differentiated according to their functional role, unlike cells, tissues, and organs within the organism, or polymorphic castes within the insect colony. Finally, species members are often functionally opposed to one another. In fact, the competition within species is usually more intense than that between them—a degree of antagonism between parts that is not present between cells of the organism and other entities that have evolved mechanisms for enforcing cooperation and blocking conflict among their subcomponents. These mechanisms enable cell lines within organisms, and caste members within insect colonies, to sacrifice their own immediate reproductive fitness in order to partake in a coordinated, collaborative endeavor at a higher level of biological organization. Such mechanisms do not obtain at the species level.

To sum up the discussion thus far: species are neither abstract classes nor full-blown biological individuals. Instead, they may be roughly characterized as follows: independently evolving, spatiotemporally restricted meta- population lineages that are poorly integrated, weakly cohesive, non-goal-directed, nondevelopmental, and composed of largely nondifferentiated, nonfunctional, and noncooperative parts. Let us now consider the moral value that such an entity might reasonably be said to possess.

2. The Value of Species

Do Species Have Intrinsic Value?

For an entity to be “morally considerable,” it must have interests that it would be prima facie wrong to impede, where this wrongness stems from the intrinsic value of the being in question and not from any indirect effects that being may have on other beings.26 Much of the discussion concerning moral considerability has centered around identifying the crucial property or set of properties that make a being the kind of being that can not only be harmed, but also wronged. Many candidate capacities have been advanced, such as personhood,27 intentionality (of the first or second order), being the “subject of a life,”28 sentience,29 and goal-directedness,30 to name a few.

As meta-populations only loosely integrated via patterns of gene exchange, it is difficult to imagine how species might instantiate any of the aforementioned properties, even the most zoologically inclusive ones such as goal- directness. Goal-directedness is one of the defining features of life. It refers to the ability to (p. 610) maintain physiological, morphological, or behavioral homeostasis across a wide range of environmental perturbations.31 Although some ethicists maintain that goal-directedness is sufficient to create interests that bring a being within the ambit of moral consideration,32 most moral philosophers hold that a more substantial cognitive property, such as sentience or personhood, is necessary and sufficient to create morally relevant interests—interests that demand equal consideration. For the present purposes, however, we will simply assume that goal-directedness is sufficient to create interests that make a being the kind of being that can not only be harmed in the biological sense, but also wronged in the moral sense.

Goal-directedness is such a fundamental property of organisms that it brings invertebrate animals, plants, protozoa, bacteria, and all other non-sentient but incontrovertibly living things into the moral fold. Yet it does little to make the case for species, which lack the coordination, cohesion, differentiation, and cumulative adaptations necessary for goal-directed behavior. If species qua species do not even exhibit goal-direction, let alone more complex functional properties like sentience, it is difficult to see how they might have morally relevant interests.33

Nevertheless, merely because an entity is not a classical individual does not mean that it lacks moral status. There is a growing tradition in political philosophy to recognize group rights, or rights possessed by a group as a group 34

Page 5 of 19

rather than by its members severally.34 Because these rights are those of the group, they engender duties to the group entity, rather than or in addition to obligations owed to its members severally. Can the moral patient-hood of species be derived from theories of group rights? The argument for group rights proceeds as follows: if individuals have rights because they possess certain emergent properties (such as intentionality or sentience), then groups may have the same rights insofar as they too possess those emergent properties. Mere aggregates of individuals, such as crowds, do not have irreducible moral worth, because they do not exhibit any of the relevant properties at the level of the ensemble, even though the individuals that comprise them do possess those properties. By contrast, groups that have an integrated internal structure and division of labor, and which act pursuant to a collective purpose, may be said to have interests in themselves.35 Yet this merely brings us back to where we started: namely, to the conclusion that species are not integrated, differentiated, purposeful, goal-directed entities, and hence that they are more like crowds of conspecifics than business firms or insect colonies.

There is an uncontroversial sense in which damage done to a species could entail a wrong to individual organisms of that species, assuming these individuals possess morally relevant characteristics. For example, habitat destruction could cause greater total suffering to individual organisms through starvation and exposure than would be the case if habitats were preserved. However, if the value of species simply reduces to that of their constituent organisms, then species have no normative value as such, and hence they are not proper objects of moral concern.

One common move at this point is to shift the locus of moral analysis away from species, and toward the entities forged by the complex interrelations between them, such as communities and ecosystems. A discussion of the ontological (p. 611) properties of ecosystems and their moral significance is beyond the scope of this essay. In section 3, however, I will consider the physical properties of communities insofar as they speak to the implications of species extinction. Suffice it to say that higher-level ecological entities have been notoriously difficult to delimit, leading many researchers to question their ontological and theoretical status.36 And to the extent that ecosystems and communities can be individuated as organized systems, they have been shown to lack even the most basic properties of living things, such as goal-directedness.37

The Extrinsic Noninstrumental Value of Natural History

Some authors have argued that species have intrinsic value by virtue of the fact that humans value them for their own sake and not for any instrumental role they play in bringing about other valuable ends.38 Others have rejected the notion that anthropocentric value can be “intrinsic.”39 Contrasting intrinsic value with instrumental value is misleading, however, for, as Christine Korsgaard points out, some values are both “extrinsic” (grounded in relational properties) and “final” in the sense that they are valuable as ends in themselves.40 Whether we choose to call it intrinsic or extrinsic final value, if species qua species are valuable in the same way that historical artifacts are valuable, then this would provide a non-instrumental, normative basis for species conservation that does not rely on them being morally considerable.

Artifacts, architecture, and other objects of historical significance are commonly thought to have extrinsic final value, to which the proliferation of tourism-generating UNESCO World Heritage sites can attest. If human history has final value to both historians and people generally, it is not much of a stretch to conclude that natural history might have final value as well. Many protected World Heritage sites are in fact “natural” sites, such as mountain ranges, barrier reefs, and fossil deposits. Artifacts and other objects of material culture are considered valuable in part because of the information they contain about the past. Perhaps we can draw the more general conclusion that an object may be valuable simply by virtue of its possessing information.

Advancing a strong version of this argument, Luciano Floridi concludes that all natural objects, whether living or nonliving, have moral value qua “information objects,” and from this he derives negative duties not to cause, and positive duties to prevent, the entropy of information.41 One problem with this view is that the information object (the set of properties and characteristics of an entity) is an abstract category, and thus it cannot ground moral status or generate duties in others.42 As we saw above in the context of species, because atemporal classes do not have interests, they cannot have intrinsic moral value and thus they cannot be wronged. A more plausible version of Floridi's thesis would be to claim that information is of enormous value to humans for both extrinsic final and instrumental reasons, and hence that objects containing information are valuable, even if they are not morally considerable.

Page 6 of 19

(p. 612) What sorts of information do species possess? Information contained in a species includes all of its physical, anatomical, genetic, developmental, physiological, cognitive, behavioral, populational, ecological, evolutionary, and historical properties. Species as evolving lineages are inherently historical entities, accumulating vast amounts of information (in the “correlational” sense of the term) about their environment over evolutionary time, leading to exquisite adaptive solutions to countless ecological design problems. This epistemic feat is accomplished not with the benefit of foresight and intentionality, but through the cumulative operation of natural selection acting on a genetic channel of inheritance. Because natural selection tends to modify complex organisms by building incrementally “on top of” more primitive (evolutionarily older) structures, lineages will tend to accumulate or exhibit a net gain in information over generational time.

This would seem to be true for all levels of the nested taxonomic hierarchy. Higher taxa,43 such as phyla, classes, and orders, will tend to accumulate information as their constituent species diversify into a wide range of morphologies and ecological roles. Some of this natural historical information will be valuable because of its immediate use to humans44; some of it will be valuable because of its potential but currently unforeseeable use to humans in the future; while still other bits will have no present or future utility, but will nonetheless be interesting and hence valuable in their own right. For many people, coming to appreciate the extraordinary evolutionary journey of a species is meaningful in and of itself, even if it does not lead to other valuable information or ends. A deeper understanding of natural history can lead to important self-knowledge by situating the human species in the vastness of evolutionary space and time, and illuminating the connections of humankind to other beings and its “embeddedness” in the great tree of life.

The Instrumental Ecological Value of Species

Many philosophers and policy makers are rightfully uncomfortable with the idea of resting a broader environmental ethic on final-value judgments that are not deeply rooted in human moral psychology and which might be held hostage to the ebb and flow of culture. Thus, the dominant approach to species conservation, especially in the arena of public policy, is a form of anthropocentric instrumentalism that links the extinction of species (and other indicators of biodiversity) to identifiable ecological harms that might befall morally considerable creatures, including and especially human beings.

Species have instrumental value insofar as they provide various resources such as food, medicine, fuel, energy, raw materials, and tourism.45 Species also offer so-called “ecosystem services,” such as the regulation of atmospheric oxygen, carbon dioxide and moisture levels, pollination, seed dispersal, waste decomposition, nutrient cycling, and so forth, the economic value of which is estimated to exceed the world's total gross domestic product.46 In addition, speciel diversity provides what have been termed “evosystem services,”47 which include the capacity for adaptive evolutionary change in the face of changing environments, as well as the ability to produce novel (p. 613) beneficial variations. Evosystem services may grow increasingly important as climate change and other anthropogenic alterations of the environment impose higher levels of stress on communities and ecosystems. Together, ecosystem and evosystem services forge a strong link between biodiversity and human wellbeing.

Knowledge of the ecological interactions and energy flow between species enables biologists to predict different harms from the extinction of different lineages. This, in turn, offers a basis for prioritization or “triage” in the distribution of limited conservation resources.48 Species may be ranked based on their expected value or the disvalue of their extinction, and this can then be weighed against conflicting moral interests such as economic development and the alleviation of poverty. One implication of adopting a wholly instrumentalist approach to species value is that critically endangered species will often be assigned a low preservation priority, because lineages on the brink of extinction are typically small in number and will rarely be major ecological players let alone the lynchpins of global ecosystems. Assuming comparable extrinsic final values, we will usually get more moral bang for the buck by allocating resources to “threatened” rather than “critically endangered” species.49

Furthermore, measuring the success of preservation efforts in terms of the total number of species preserved can obscure important ecological differences between species, and hence the harms that are likely to flow from their extinction. Identical magnitudes of species loss can have profoundly different ecological and evolutionary consequences, depending on their trophic distribution, or their position in a food web. The elimination of primary producers, for instance, can have far more significant ramifications for global ecology than the extinction of

Page 7 of 19

lineages at higher trophic levels—not only with respect to its immediate consequences, but also with regard to the pace and pattern of faunal recovery in its aftermath.50 Thus, it makes little sense to speak of the instrumental value of species in the abstract. In order to assess the disvalue that is likely to flow from the extinction of any given species, we need to advert to a detailed map of the causal ecological structure in which the species is embedded, and its relation to other things that we independently value.

Is the Value of Species Irreducible?

Thus far we have done little to show that the extrinsic value of species does not merely reduce to that of their constituent parts, such as organisms or populations. Our answer to the question of reduction will determine whether species qua species have normative value, or whether “species value” is really just a placeholder for that of organisms or populations. My contention is that the extinction of a species will tend to result in a greater loss of both natural history information and ecological/evolutionary utility than that which flows from the death of any populational subset alone.51

The vast majority of information about a species is accumulated and preserved at the meta-population level, where it remains distributed until the last viable population dies off and the species goes extinct. Although subpopulations and individual organisms contain unique informational signatures and thus may be uniquely (p. 614) valuable, the loss of information that corresponds to the death of all individuals of a species is greater than the loss of information that attends to the death of any non-zero fraction of the total population. Due to gene exchange within and between populations of a species, the informational (including genetic and phenotypic) differences between conspecifics are relatively small; by contrast, the differences between species can be anywhere from substantial to vast, depending on the age of their last common ancestor. As a heuristic, we might say that the greater the evolutionary distance between an extant species and its closest living taxon (for humans, this would be chimpanzees), the more information that will be lost by the extinction of the former. It follows that even a tiny, reproductively viable population can preserve the majority of valuable information contained in a species— information that would be irreversibly lost if the species were to go extinct. In other words, the informational and ecological properties of a species do not decline in linear fashion with the depletion of its constituent populations; instead, they drop off steeply at the species extinction event.

There remains a problem, however. If given their high relative similarity, each organism of a species possesses the overwhelming majority of the information that is contained at the species level, then is it not the case that the information lost due to extinction simply reduces to the loss of the last individual of a species? For that matter, why could not the information of an entire species be retained by preserving the DNA of one of its individuals, storing a formaldehyde-pickled specimen, or by maintaining a captive breeding population? The answer is that in each of these cases, only a fraction of the full informational value of a species would be retained, especially when it comes to complex animals. First, the phenotypes of complex organisms cannot be reconstructed on the basis of DNA information alone, because they are the result of a complex interaction of genetic and non-genetic factors in development. Second, many traits are polymorphic at the meta-population level, sensitive to developmental context, non-genetically inherited (transmitted in a social learning environment), and contingent on the frequency of similar traits in conspecifics. These and other so-called epigenetic factors cannot be “read off” of DNA and are not preserved by maintaining nonliving specimens of the species. For the same reasons, keeping a few solitary living individuals or even a captive breeding population does not preserve the dynamic evolutionary and developmental environment that shapes the distribution of complex traits in the wild. Nor does it preserve the ecological connections that the species has forged over time with other co-evolving lineages in its food web.

Like its informational value, the ecological/evolutionary utility of a species does not reduce to that of its component parts. There is a stark contrast between the irreversible effects of species extinction on the one hand, and the remediable nature of demographic depletion on the other. Species can recover from heavy losses and reassume their ecologically valuable role, so long as they maintain a minimally viable population that has the potential to rebound and take on a more prominent role in global ecology.52 Extinction, by contrast, is irreparable. While it is conceivable that a breeding population of an otherwise extinct species could be “resurrected” from DNA material and reintroduced into the wild, because of the context sensitivity of development (discussed above) and the dynamic nature of ecology, there is no (p. 615) guarantee that the resurrected species would perform the same ecological role and hence possess the same instrumental value as its predecessor. While it is possible that another

Page 8 of 19

species could eventually evolve to fill the empty niche that was vacated by a given extinction (just as birds filled the aerial niches vacated by the extinction of the pterosaurs in the end-Cretaceous), this could take millions of years, during which time much ecological damage may be wreaked.

In sum, extinction is a species-level phenomenon that raises unique ethical issues over and above those that are associated with the depletion of its constituent organisms and populations. If this reasoning is correct, then it implies that talk of species value does not merely serve as a placeholder for the value of organisms and populations. Species are legitimate objects of value in their own right.

The Value of Higher Taxa

I have suggested that the extrinsic final and instrumental value of species is irreducible because information is stored and ecological/evolutionary utility is located uniquely at the meta-population level. These properties and their associated values are permanently lost with the extinction of species. If this analysis is sound, then a further case can be made for the irreducible value of higher taxonomic categories that represent larger swaths of the tree of life.

The effect of extinction on higher taxa is a much-neglected topic in discussions of biological conservation. This is probably due to the fact that in contrast to the general realism about species, higher taxa (such as genera, families, orders, classes, and phyla) are often thought to be carved up arbitrarily rather than at nature's joints. However, recognizing the extrinsic value of large-scale evolutionary history does not require accepting the reality of higher taxa. It only presupposes “tree-thinking,” which is essentially the phylogenetic counterpart of population thinking—that is, the idea that species are not members of a classificatory set, but rather interconnected and diverging segments of an evolutionary branching sequence.53 We can avoid problems associated with the individuation of higher taxa by focusing on the effects of extinction on phylogenetic disparity, or the “width” of the evolutionary tree. In order to show that phylogenetic disparity has unique evolutionary/ecological/informational value, we will have to delve somewhat deeper into large-scale evolutionary pattern and process.

The late paleontologist Stephen Jay Gould famously drew attention to the fact that the major animal body plans (such as those characterizing the vertebrates, arthropods, mollusks, and so forth) have been markedly segregated from one another in “morphological space” ever since their origin around 600 million years ago. Animal body plans are generally reflected under the taxonomic heading of phyla. Based on a particular interpretation of the fossil record of the earliest animals, Gould proposed that animal life began with many more body plans and hence a broader range of “morphospace” occupation, which was irreversibly whittled down over the history of life as many of the early body plans went extinct, leaving permanent gaps between the remaining phyla.54

(p. 616) Although Gould's hypothesis remains controversial, it introduced a theoretically important distinction between diversity on the one hand, and disparity on the other. Diversity is typically measured in terms of species richness, whereas disparity tracks morphological variance—a variable that is independent of speciosity. Since the origin of animals, diversity as measured by species richness has increased steadily over time.55 Notwithstanding some major setbacks in the history of life, such as the end-Permian extinction that eliminated nearly 96% of living species, diversity has always rebounded and increased its outer limit. Not so with disparity, however, which on average has either remained the same56 or else decreased57 over the history of life.58 Thus, in focusing almost exclusively on lower taxonomic categories like species, conservationists have tended to overlook an important aspect of biological variation—disparity—which appears to hold a far less secure place at the high table of macroevolution.

If Gould is right that losses in higher level morphospace will rarely if ever be recouped, then extinctions that prune larger trunks in the tree of life may be more evolutionarily consequential than losses in more “bushy” sections, even when the latter involve greater magnitudes of species loss. So while diversity is highly resilient, the loss of large-scale phylogenetic history—and with it the unique genetic, developmental, and phenotypic strategies that determine the parameters of ecological and evolutionary possibility for a group—is likely to be permanent.59

Fortunately, due to the hierarchical relationship between species and higher taxa, the latter are exceedingly difficult to kill off. The macroevolutionist David Raup demonstrated this in a series of models showing that the phylogenetic distribution of extinction is an important factor in understanding and predicting the effects of

Page 9 of 19

extinction events. Raup showed that if extinctions are random with respect to taxa, then even a species kill ratio approaching 95% can sustain 80% of the underlying phylogenetic disparity (evolutionary history).60

The key point is this: the same magnitude of species loss—that is, the same reduction in diversity—can have differential implications for disparity and hence for the future of life on earth, depending on the phylogenetic distribution of extinction.61 Take, for example, the five living species of rhinoceros, three of which are critically endangered. These are the last remaining species of a once-successful family (Rhinocerotidae), which at one time included more than thirty genera that flourished for over 30 million years. The few rhino populations that have persisted into the twenty-first century do not play a significant role in terrestrial ecology. And yet, if living rhinos are pushed into the evolutionary abyss, not only will five species go extinct, but so too will an entire family of odd-toed ungulates, shrinking our increasingly narrow evolutionary portfolio. It is quite possible that nothing like a rhino will ever evolve again, and even if some independent lineage would eventually hit upon a convergent “rhino-like” solution, this might take millions of years longer than the evolutionary duration of the human species. As a result, losing the few remaining rhino species would have different implications for natural history than losing an equivalent number of species from a much more diverse family, such as (p. 617) Bovidae (a group of cloven- hoofed mammals that includes upwards of 150 species). Moreover, the greater the phylogenetic disparity of a set of taxa, the more known and unknown ecosystem/evosystem services they are likely to provide. For these reasons, conservation triage should also take into account the phylogenetic implications of extinction.

3. Metaphysical and Epistemic Objections to Prioritizing Species

The Precautionary Approach

Given that different species have different extrinsic values, and given that our conservation resources are limited, it makes sense that we would prioritize species for conservation. Nevertheless, some radical biocentric environmental philosophies, such as “deep ecology,” reject conservation triage because they maintain that all species have equal intrinsic worth and thus are entitled to equal treatment.62 Not surprisingly, most moral philosophers have rejected such “biocentric egalitarianism.”63 But even some authors who embrace mainstream anthropocentric instrumentalism have rejected the triage approach, arguing that we should try to preserve all species regardless of their expected instrumental value.64 This more precautionary approach to conservation, one that jettisons cost-benefit analysis when harms to human health or the environment are at stake, is motivated in part by the vulnerability of traditional principles of risk management to special-interest manipulation and human myopia.

The triage approach to species conservation could justifiably be rejected on precautionary grounds if two conditions were met: (1) Ontological condition: the causal structure of the biological world is such that communities and ecosystems are composed of highly interconnected webs of species poised in a delicate balance that is wont to unravel in the face of even small perturbations; (2) Epistemic condition: the causal interdependence of species is too complexly configured for humans to adequately map out, and therefore any prioritization decision, no matter how well intentioned, is likely to be erroneous and to produce more harm than good.

If ecosystems are highly integrated webs of species that are extremely sensitive to perturbations, then the extinction of even ostensibly low-value species may have cascading results. In this view, ecosystems are like houses of cards, subject to total collapse given the “wrong” ecological modification or once some unknown threshold of disturbance is realized. If this combination of sensitive ecological dynamics and severe epistemic limitations obtains, then our chances of improving global or even local ecology via selective preservation look bleak, while the risks associated with intervening appear unjustifiably high.

(p. 618) The Benevolent Balance of Nature

Is there a delicate and benevolent balance of nature that human efforts are more likely to disrupt than to improve? Before examining these claims in greater detail, however, it would be good to dispel notions that I am building up a straw man. The idea of a benevolent balance of nature is not simply a playful metaphor that is tossed around by environmental activists or peddled by “new age” energy healers. Delicate interconnectedness has not only been invoked by environmental philosophers in support of conservation efforts,65 but it has also motivated a growing

Page 10 of 19

body of environmental law and policy. For instance, many domestic constitutions contemplate a positive right to a “natural ecological balance” or a “harmony of nature” that may be disrupted by anthropogenic extinctions or additions.66

Because individual organisms are goal-directed and homeostatic, they are by definition robust—not fragile— processes. Nonetheless, it is possible that complex associations of organisms and taxa are governed by a different and more volatile dynamic. Indeed, this has been the working assumption of biologists operating under the so- called “equilibrium paradigm” in ecology.67 The eminent biologist and avid conservationist E. O. Wilson nicely captures this view, stating that “the biosphere [is] a stupendously complex layer of living creatures whose activities are locked together in precise but tenuous global cycles of energy and transformed organic matter …. When we alter the biosphere in any direction, we move the environment away from the delicate dance of biology.”68 Some early ecologists thought that ecosystems were so tightly integrated and internally differentiated that they constituted veritable super-organisms.69 This view has been rebuked by mainstream evolutionary theorists for its failure to identify acceptable scientific mechanisms.70 Nevertheless, many ecologists continue to see stability as following from natural selection and its various auxiliary principles, such as “competitive exclusion,” or the idea that no two species can occupy the same ecological niche in the same community indefinitely.

There are several ways to think about stability in ecology. The first relates to constancy in the numbers of individuals that comprise a population.71 Yet even this simple demographic version of equilibrium is problematic.72 The net rate of change in species population density often fluctuates stochastically, rather than trending toward zero—at least until it hits the ultimate “absorbing boundary” of extinction. The second type of ecological equilibrium relates to the trophic structure of interconnected food webs. The view that ecosystems represent seamless webs of interdependent species hangs on the plausibility of a certain theory of niches (due to Elton73) that has been widely criticized74; in addition, it assumes that the resources within a community are fully allocated —an assumption for which there is little evidence.75 Moreover, the origination and extinction of paleo-ecosystems is not generally coordinated in a way that indicates their long-term evolutionary cohesion. Studies of both living and paleontological communities show that trophic webs are usually maintained despite substantial changes in fundamental parameters, such as extinction, invasion, migration, diversity, and energy pathways.76

In fact, there is evidence to suggest that the more weakly linked the components of a given community are, the more diverse and stable that community will be.77 An (p. 619) allusion to the individual organism helps to make this point. During embryogenesis, organisms make use of a modular construction that creates developmental “firewalls” to ensure that any damage incurred during development is contained in the affected module and does not spread in cascading fashion to collateral areas. It is likely that ecosystems make use of a similar design principle, as highly interconnected communities will not persist for long. A modular construction allows sub- assemblies to buffer the larger community against environmental perturbations, such as demographic changes or fluctuations in the biotic or abiotic environment.78 Ironically, to the extent that ecological balance exists at all, it will depend on the absence of sensitive interactions between species.

Contrary to ecological balance theory, biotic interactions will tend to undermine, rather than reinforce, the stability of faunal associations. Species interact with one another in evolutionary time: sometimes these interactions are cooperative, as in the case of mutualisms, but often they are strategic, resulting in an evolutionary arms race in which one organism's ecological solution is another's design problem, and vice versa. This is common for example in the interactions between predator and prey and between host and parasite. Strategically interacting lineages must continue to evolve merely to maintain their present fitness levels—a dynamic that the biologist Leigh Van Valen has dubbed the “Red Queen effect,” after a character in Lewis Carroll's Through the Looking-Glass who must continually run in place merely to remain where she is.79

The Red Queen effect is one of the chief explanations of Van Valen's famous observation that the probability of extinction for a given lineage does not vary as a function of its taxonomic age. In other words, a lineage's probability of going extinct is independent of its previous evolutionary success. Another way of putting it is that perpetual arms races prevent species from getting progressively better at not going extinct. Whereas biologists had tended to assume that strategic interaction would generally lead to evolutionarily stable solutions, even simple arms races have been shown to create ecological instability that ultimately leads to extinction.80

Page 11 of 19

At the same time, the causal interrelations of species in a community are not entirely opaque. We can make fairly solid predictions about the ecological consequences of the extinction of certain species, given their centrality in a food web and their degree of connectivity to other species.81 For all of these reasons, the metaphysics of ecology and the limitations it places on our ability to understand the causal structure of the biological world do not in my view justify an all-or-nothing or even precautionary alternative to the cost-benefit analysis of triage.

4. Conclusion: Is Anthropogenic Extinction Morally Unique?

In concluding, I will consider a final question: is there something that makes anthropogenic extinctions worse than the ordinary background and occasional mass extinctions that pervade the history of life? Marc Ereshefsky has made the case, (p. 620) persuasively in my view, that there is nothing intrinsically different about the nature of anthropogenic extinctions, apart from the fact that they are caused by human behavior.82 The fossil record is punctuated by five major perturbations, the most recent being the end-Cretaceous mass extinction around 65 million years ago. Some biologists believe that we are currently in the midst of a sixth great mass extinction, one that is driven not by geological or extraterrestrial events, but by a single technological species with a knack for population growth, habitat destruction, pollution, and climate modification on a genuinely global scale.83 Many paleontologists are not convinced that the present rates of extinction rise to the level of the Big Five.84 Virtually all biologists agree, however, that we are witnessing a period in which extinction is substantially outpacing speciation, threatening many lineages that narrowly avoided annihilation in the previous mass extinctions.85 But the extinctions caused by human beings do not differ either in magnitude or distribution from those that have occurred throughout life's history.

The extrinsic final and instrumental values that we might attach to species, which range from the ecosystem/evosystem services they provide to their value as living evolutionary history, are equally implicated in species loss whether it is caused by human agency or non-agential processes. It is sometimes claimed that anthropogenic extinction is “unnatural,” or that somehow the element of human causation makes it morally distinct. Grounding moral judgments in the distinction between “natural” and “unnatural” is conceptually and normatively problematic for well-known reasons that I will not rehearse here.86 Instead, I will consider whether there are any other plausible bases to treat anthropogenic harms differently from “natural” harms, even when they are equivalent in terms of their likelihood and expected consequences for people and the environment.

Should we not expend the same resources guarding against a rogue asteroid impact as we would in dealing with a rogue nuclear regime, assuming the risks and magnitudes of nuclear fallout were identical? From a consequentialist perspective, the answer would seem to be yes. Yet there is a tendency, all things being equal, for people to be more concerned about anthropogenic harms than “natural” harms. Compare, for instance, the motivation in the United States to guard against terrorism after 9/11, with the inclination to shore up domestic infrastructure after Hurricane Katrina (as measured, for example, by the amount of resources allocated and the alacrity of national response). For historical ecological reasons related to the demands of living in a complex social group, harm-by- hurricane is simply not as salient and does not evoke such powerful moral emotions as harm-by-hominid. I would venture to guess that this non-consequentialist asymmetry in moral judgment would also be borne out in the context of species extinction and climate change.

Is there any theoretical basis for this asymmetry? One possibility is that it stems from the considered intuition that it is a greater wrong to cause harm than to allow the same harm to occur “naturally.” This idea is premised on there being a defensible distinction between positive and negative duties, which of course many philosophers deny. In any case, the degree of “badness” that is added to some state of affairs because of its “wrongness,” that is, because it implicates a culpable moral agent, (p. 621) seems minimal and should not significantly affect our conservation priorities. Our duty to contain a preventable outbreak of infectious disease is equally weighty whether it is caused by bioterrorism or “natural” microbiological evolution. To conclude otherwise would be to confuse the culpability of the actor with the badness of the consequences that he or she brings about. If a species is extrinsically valuable, then (ceteris paribus) its extinction is morally undesirable, regardless of whether it is caused directly, indirectly, or not at all by human action.

Given the upward diversity trend of the last 600 million years, it is reasonable to believe that the biota will ultimately recover from the present spasm of extinction, and that it will do so spectacularly. Unfortunately, it is unlikely that

Page 12 of 19

there will be any humans around to witness life's new and magnificent evolutionary directions. Homo sapiens is substantially less than one million years old—a “pre-adolescent” from the standpoint of mean species duration, with hopefully millions of years to go before it is reduced to interesting bits of biostratigraphy. I have argued that species are valuable not only for the basic pleasures and utilities they provide, but also for the meaningful self- knowledge they bring about in contextualizing the human species as simply one twig on a vast branching lineage that extends back to the dawn of life on Earth. If this is so, then our time on this planet will go best if we experience it as stewards of a full house of biodiversity, rather than as overlords of an impoverished lot of a once-arborescent tree of life.87

Suggested Reading

On the ontological and theoretical status of biological species, see M. GHISELIN, “A Radical Solution to the Species Problem,” Systematic Zoology 23 (1974): 536–44; D. Hull, “A Matter of Individuality,” Philosophy of Science 45 (1978): 335–60; P. Kitcher, “Species,” Philosophy of Science 51 (1984): 308–33; R. L. Mayden, “On Biological Species, Species Concepts and Individuation in the Natural World,” Fish and Fisheries 3 (2002): 171–96; K. de Queiroz, “Ernst Mayr and the Modern Concept of Species,” Proceedings of the National Academy of Sciences USA 102 (2005): 6600–7; M. Ereshefsky, The Poverty of the Linnaean Hierarchy: A Philosophical Study of Biological Taxonomy (Cambridge: Cambridge University Press, 2001).

For a discussion of the history of essentialism and the shift toward population thinking in evolutionary biology, see E. SOBER, “Evolution, Population Thinking and Essentialism,” Philosophy of Science 47 (1980): 350–83.

(p. 627) For a conceptual analysis of the property of goal-directedness and its implications for environmental ethics, see (respectively) E. NAGEL, “Teleology Revisited: Goal-Directed Processes in Biology,” Journal of Philosophy 74 (1977): 261–301; P. W. Taylor, “The Ethics of Respect for Nature,” Environmental Ethics 3 (1981): 197–218; H. Cahen, “Against the Moral Considerability of Ecosystems,” Environmental Ethics 10 (1988): 195–216; and the rebuttal by S. Salthe and B. Salthe, “Ecosystem Moral Considerability: A Reply to Cahen,” Environmental Ethics 11 (1989): 355–61.

On the conceptual and moral dimensions of anthropogenic extinction, see M. ERESHEFSKY, “Where the Wild Things Are: Environmental Preservation and Human Nature,” Biology and Philosophy 22 (2007): 57–72. On mass extinction more generally, see D. Raup, Extinction: Bad Genes or Bad Luck? (New York: W. W. Norton, 1991); D. H. Erwin, Extinction: How Life on Earth Nearly Ended 250 Million Years Ago (Princeton, N.J.: Princeton University Press, 2006). For a comparison of modern-day extinction rates with those of past mass extinctions, see D. Jablonksi, “Lessons from the Past: Evolutionary Impacts of Mass Extinctions,” Proceedings of the National Academy of Sciences USA 98 (10) (2001): 5393–98.

For discussions of the balance-of-nature paradigm in ecology, see K. CUDDINGTON, “The ‘Balance of Nature’ Metaphor and Equilibrium in Population Ecology,” Biology and Philosophy 16 (2001): 463–79; F. Doolittle, “Is Nature Really Motherly?” CoEvolution Quarterly 29 (1981): 58–63. For an accessible introduction to the philosophy of ecology and problems in the philosophy of biology more broadly, see K. Sterelny and P. Griffiths, Sex and Death: An Introduction to the Philosophy of Biology (Chicago: University of Chicago Press, 1999).

For overviews of the concept of biodiversity and its role in conservation biology, see J. MACLAURIN and K. STERELNY, What Is Biodiversity? (Chicago: University of Chicago Press); S. Sarkar, Biodiversity and Environmental Philosophy: An Introduction (New York: Cambridge University Press, 2005).

On the nature of values and the sources of normativity, see K. GOODPASTER, “On Being Morally Considerable,” Journal of Philosophy 75 (1978): 308–25; E. Hargrove, “Weak Anthropocentric Intrinsic Value,” The Monist 75 (1992): 119–37; C. Korsgaard, The Sources of Normativity (Cambridge: Cambridge University Press, 1996).

Notes:

(1.) A “taxon” (plural: “taxa”) refers to a taxonomic category or grouping used in biological classification, typically reflecting phylogenetic (evolutionary) relationships and character traits that distinguish it from other such units. A

Page 13 of 19

taxon may or may not be given a formal rank in the nested biological hierarchy, which includes populations of organisms, species, genera, families, orders, classes, phyla, and kingdoms, in ascending order of inclusiveness.

(2.) For a discussion, see R. Powell and A. Buchanan, “Breaking Evolution's Chains: The Prospect of Deliberate Genetic Modification in Humans,” Journal of Medicine and Philosophy 36 (2011): 6–27; R. Powell, “What's the Harm? An Evolutionary Theoretical Critique of the Precautionary Principle,” Kennedy Institute of Ethics Journal 20 (2010): 181–206.

(3.) J. McMahan, “The Metaphysics of Brain Death,” Bioethics 9 (1995): 91–126.

(4.) Throughout this essay, I will use the terms “preservation” and “conservation” interchangeably, although I recognize that some authors prefer to distinguish them in order to connote different approaches to the management of land and biota.

(5.) E. Mayr, Systematics and the Origin of Species (New York: Columbia University Press, 1942).

(6.) For a review, see R. L. Mayden, “On Biological Species, Species Concepts and Individuation in The Natural World,” Fish and Fisheries 3 (2002): 171–96; M. Ereshefsky, The Poverty of the Linnaean Hierarchy: A Philosophical Study of Biological Taxonomy (Cambridge: Cambridge University Press, 2001).

(7.) See e.g., P. Kitcher, “Species,” Philosophy of Science 51 (1984): 308–33.

(8.) K. de Queiroz, “Ernst Mayr and the Modern Concept of Species,” Proceedings of the National Academy of Sciences USA 102 (2005): 6600–7.

(9.) Evolutionary gray zones exist because subpopulations of a meta-population can attain substantial degrees of genetic, morphological, functional, or behavioral divergence before they become reproductively isolated; and conversely, they can become reproductively isolated without diverging significantly along any of the above parameters.

(10.) One reason why evolutionary “gray zones” are rare and short-lived relates to the general tempo and mode of speciation. In the earlier part of the twentieth century, many biologists argued that the species designation was arbitrary or conventional because there was no objective way of demarcating the point along the gradual continuum through which one species incrementally transforms into another (a process called “anagenesis”). However, it appears that speciation does not typically occur in this manner. Species tend to arise in geologically rapid bouts of evolution in small, geographically isolated populations, which then re-invade the mainland and appear in the fossil record as a new species. Once they have arisen, species tend to exhibit relative morphological stasis until they go extinct. This pattern, dubbed “punctuated equilibrium” by Niles Eldredge and Stephen Jay Gould, makes it easier for paleobiologists to objectively individuate species in space and time. N. Eldredge and S. J. Gould, “Punctuated Equilibria: An Alternative to Phyletic Gradualism,” in Models in Paleobiology, ed. T. J. M. Schopf (San Francisco: Freeman Cooper, 1972), pp. 82–115; see also S. J. Gould, The Structure of Evolutionary Theory (Cambridge, Mass.: Harvard University Press, 2002), chapter 9.

(11.) E. Mayr and W. B. Provine, eds., The Evolutionary Synthesis: Perspectives on the Unification of Biology (Cambridge, Mass.: Harvard University Press, 1980).

(12.) E. Sober, “Evolution, Population Thinking and Essentialism,” Philosophy of Science 47 (1980): 350–83.

(13.) D. Hull, “Are Species Really Individuals?” Systematic Zoology 25 (1976): 174–91.

(14.) J. Beatty, “The Evolutionary Contingency Thesis,” in Concepts, Theories, and Rationality in the Biological Sciences, ed. G. Wolters and J. G. Lennox (Pittsburgh, Pa.: University of Pittsburgh Press, 1995).

(15.) The now-canonical distinction between classes and individuals in the context of biological taxa was introduced by M. Ghiselin, “A Radical Solution to the Species Problem,” Systematic Zoology 23 (1974): 536–44, and was subsequently endorsed by D. Hull, “A Matter of Individuality,” Philosophy of Science 45 (1978): 335–60.

(16.) K. de Queiroz, “The General Lineage Concept of Species, Species Criteria, and the Process of Speciation: A Conceptual Unification and Terminological Recommendations,” in Endless Forms: Species and Speciation, ed. D. J.

Page 14 of 19

Howard and S. H. Berlocher (Oxford: Oxford University Press, 1998).

(17.) For a discussion of lawlessness in biology, see Beatty, “Evolutionary Contingency Thesis.” See also E. Sober, The Nature of Selection (Cambridge, Mass.: MIT Press, 1984). There are a few authors who view “convergent evolution,” or the independent origination of similar biological forms, as indicative of natural-kind-like replicability in the history of life. See, e.g., S. C. Morris, Life's Solution: Inevitable Humans in a Lonely Universe (Cambridge: Cambridge University Press, 2003); D. C. Dennett, Darwin's Dangerous Idea (New York: Simon & Schuster, 1995), p. 307. This view is decidedly in the minority, however, and I critique it elsewhere. See R. Powell, “Is Convergence More than an Analogy? Homoplasy and its Implications for Macroevolutionary Predictability,” Biology and Philosophy 22 (2007): 565–78.

(18.) Consistent with thinking of species as historical individuals, some environmental philosophers have argued that even if we could restore a destroyed ecosystem molecule for molecule, the product would be metaphysically and morally distinct from the original, because it would have a different history. See, e.g., R. Elliott, Faking Nature: The Ethics of Environmental Restoration (New York: Routledge, 1997).

(19.) R. A. Wilson, “The Biological Notion of Individual,” Stanford Encyclopedia of Philosophy, ed. Edward N. Zalta (Winter 2010), available at http://plato.stanford.edu/entries/species/ (accessed February 1, 2010).

(20.) B. Mishler and R. Brandon, “Individuality, Pluralism, and the Phylogenetic Species Concept,” Biology and Philosophy 2 (1987): 397–414.

(21.) Wilson, “Biological Notion of Individual.”

(22.) On metaphors of progress in macroevolutionary theory and in popular conceptions of evolution, see S. J. Gould, Full House (New York: Three Rivers Press).

(23.) R. Amundson and G. V. Lauder, “Function Without Purpose: The Uses of Causal Role Function In Evolutionary Biology,” Biology and Philosophy 9 (1994): 443–69.

(24.) Although it is widely accepted that species-level selection can occur in principle, it is probably rare in fact for two reasons: first, the lack of integration and specialization among species’ parts, and second, the vast spans of time necessary for species-level selection to occur and the tendency for lower (e.g., organismic) level selection to undermine it in the interim. See T. Grantham, “Hierarchical Approaches to Macroevolution: Recent Work on Species Selection and the ‘Effect Hypo-Thesis,’ ” Annual Review of Ecology and Systematics 26 (1995): 301–22.

(25.) D. Jablonksi, “Species Selection: Theory and Data,” Annual Review of Ecology, Evolution, and Systematics 39 (2009): 501–24.

(26.) K. Goodpaster, “On Being Morally Considerable,” Journal of Philosophy 75 (1978): 308–25.

(27.) C. Korsgaard, The Sources of Normativity (Cambridge: Cambridge University Press, 1996).

(28.) T. Regan, “The Case for Animal Rights,” in In Defence of Animals, ed. P. Singer (Oxford: Basil Blackwell, 1985).

(29.) P. Singer, Practical Ethics (Cambridge: Cambridge University Press, 1993).

(30.) P. W. Taylor, “The Ethics of Respect for Nature,” Environmental Ethics 3 (1981): 197–218.

(31.) E. Nagel, “Teleology Revisited: Goal-Directed Processes in Biology,” Journal of Philosophy 74 (1977): 261– 301. Nagel argued that in order for a system to be goal-directed, it must possess homeostatic mechanisms that coordinate parameter values that are “orthogonal” to or nomically independent of one another, such as glucose and water levels in the blood. The criterion of orthogonality effectively disqualifies certain physical processes (such as tornados) from exhibiting goal-directed behavior, even though they have a dynamic internal structure that is otherwise quite robust against perturbations.

(32.) Taylor, “Ethics of Respect for Nature.”

(33.) Note that simply having adaptive features does not make an entity goal-directed. Earlier I discussed some

Page 15 of 19

potential species-level adaptations, such as geographic range or population density. Even if these traits are the product of between-species selection, they do not seem to constitute homeostatic mechanisms that coordinate nomically independent variables in the face of perturbation in order to produce some fitness-enhancing effect.

(34.) For a review, see P. Jones, “Group Rights,” Stanford Encyclopedia of Philosophy, ed. Edward N. Zalta (Fall 2008), available at http://plato.stanford.edu/entries/rights-group/ (accessed February 1, 2010).

(35.) P. A. French, Collective and Corporate Responsibility (New York: Columbia University Press, 1984).

(36.) D. Simberloff, “A Succession of Paradigms in Ecology: Essentialism to Materialism and Probabilism,” Synthese 43 (1980): 3–39; K. Sterelny and P. Griffiths, Sex and Death: An Introduction to the Philosophy of Biology (Chicago: University of Chicago Press, 1999).

(37.) H. Cahen, “Against the Moral Considerability of Ecosystems,” Environmental Ethics 10 (1988): 195–216. For a reply, see S. Salthe and B. Salthe, “Ecosystem Moral Considerability: A Reply to Cahen,” Environmental Ethics 11 (1989): 355–61.

(38.) E. Hargrove, “Weak Anthropocentric Intrinsic Value,” The Monist 75 (1992): 119–37.

(39.) P. Singer, “Not for Humans Only: The Place of Nonhumans in Environmental Issues,” in Ethics and Problems of the 21st Century, ed. K. E. Goodpaster and K. M. Sayre (Notre Dame, Ind.: University of Notre Dame Press, 1979).

(40.) Korsgaard, Sources of Normativity.

(41.) L. Floridi, “On the Intrinsic Value of Information Objects and the Infosphere,” Ethics and Information Technology 4 (2002): 287–304.

(42.) See, e.g., Kenneth E. Himma, “There's Something about Mary: The Moral Value of Things Qua Information Objects,” Ethics and Information Technology 6 (2004): 145–59.

(43.) Ordinarily, the phrase “higher taxon” refers to any taxonomic rank above species, including genera, families, orders, classes, and phyla.

(44.) The emerging field of “biomemetics” demonstrates the immediate utility of natural historical information. For example, researchers are creating microfiber adhesives by studying gecko toe hairs, designing energy-efficient buildings by consulting the thermo-regulatory properties of termite mounds, and mining the rainforest for plants and fungi with resistance-free antibacterial properties.

(45.) A. Randall, “Human Preferences, Economics, and the Preservation of Species,” in The Preservation of Species: The Value of Biological Diversity (Princeton, N.J.: Princeton University Press, 1986).

(46.) IUCN, UNEP, and WWF, World Conservation Strategy: Living Resource Conservation for Sustainable Development (Gland, Switzerland: International Union for Conservation of Nature and Natural Resources, 1980).

(47.) D.P Faith, S. Magallo, A.P. Hendry, E. Conti, T. Yahara and M.J. Donoghue, “Evosystem Services: An Evolutionary Perspective on the Links Between Biodiversity and Human Well-Being,” Current Opinion in Environmental Sustainability 2 (2010): 66–74.

(48.) S. Sarkar, Biodiversity and Environmental Philosophy: An Introduction (New York: Cambridge University Press, 2005).

(49.) M. Colyvan, S. Linquist, W. Grey, P. Griffiths, J. Odenbaugh, and H. P. Possingham, “Philosophical Issues in Ecology: Recent Trends and Future Directions,” Ecology and Society 14 (2009): 22–34.

(50.) R. V. Solé, J. M. Montoya, and D. H. Erwin, “Recovery from Mass Extinction: Evolutionary Assembly in Large- Scale Biosphere Dynamics,” Philosophical Transaction of the Royal Society 357 (2002): 697–707. Some of the greatest extinctions in the history of life appear to have been triggered by the destruction of foundational species, as was likely the case for planktonic foraminifera during the end-Cretaceous perturbation in which the dinosaurs (and many other groups) perished. The same is true of “reef-builders” throughout the history of life, and the extinction of modern-day corals would likely have similar cascading consequences for extant marine diversity.

Page 16 of 19

(51.) Note that even if the informational or ecological properties of species supervene on that of their constituent organisms—that is, even if all species with the same organism-level properties must have the same emergent, species-level properties—this does not imply that a species’ value reduces to that of its constituents. A supervenience relation does not entail a reduction relation: emergent moral (or mental) properties cannot be explained as and do not reduce to the sum value of the properties of the individual cells or atoms on which they supervene. J. Kim, Supervenience and Mind: Selected Philosophical Essays (Oxford: Oxford University Press, 1993).

(52.) R. H. MacArthur and E. O. Wilson, The Theory of Island Biogeography (Princeton, N.J.: Princeton University Press, 1967).

(53.) Phylogeny refers broadly to evolutionary history, in particular to the spatiotemporal distribution of ancestor- descendent populations; it is typically represented by a branching diagram reflecting patterns of common descent.

(54.) S. J. Gould, Wonderful Life: The Burgess Shale and the Nature of History (New York: W. W. Norton, 1989).

(55.) J. Sepkoski, Jr., “A Kinetic Model of Phanerozoic Taxonomic Diversity,” Paleobiology 10 (1984): 246–67.

(56.) D. E. G. Briggs, R. A. Fortey, and M. A. Wills, “Morphological Disparity in the Cambrian,” Science 256 (1992): 1670–73.

(57.) M. Foote and S. J. Gould, “Cambrian and Recent Morphological Disparity,” Science 258 (1992): 1816–18.

(58.) For a review of the methodological challenges confronting measures of disparity, see J. Maclaurin and K. Sterelny, What Is Biodiversity? (Chicago: University of Chicago Press), especially chapters 3–4.

(59.) D. H. Erwin, Extinction: How Life on Earth Nearly Ended 250 Million Years Ago (Princeton, N.J.: Princeton University Press, 2006).

(60.) D. Raup, Extinction: Bad Genes or Bad Luck? (New York: W. W. Norton, 1991).

(61.) D. Jablonksi, “Extinction: Past and Present,” Nature 475 (2004): 589; see also Erwin, Extinction.

(62.) A. Naess, “The Shallow and the Deep, Long-Range Ecology Movement,” Inquiry 16 (1973): 95–100.

(63.) For a critique, see W. Grey, “Anthropocentrism and Deep Ecology,” Australasian Journal of Philosophy 71 (1993): 463–75.

(64.) See, e.g., D. Takacs, The Idea of Biodiversity: Philosophies of Paradise (Baltimore, Md.: Johns Hopkins University Press, 1996); B. Norton, The Preservation of Species: The Value of Biological Diversity (Princeton, N.J.: Princeton University Press, 1986).

(65.) See, e.g., Norton, Preservation of Species.

(66.) For a discussion, see Powell, “What's the Harm?”

(67.) S. E. Kingsland, Modeling Nature: Episodes in the History of Population Ecology (Chicago: University of Chicago Press, 1985).

(68.) E. O. Wilson, The Future of Life (New York: Knopf, 2002), p. 39.

(69.) E.g., J. Lovelock, Gaia: A New Look at Life on Earth (Oxford: Oxford University Press, 1979).

(70.) S. J. Gould, “Kropotkin Was No Crackpot,” Natural History 106 (1997): 12–21; W. F. Doolittle, “Is Nature Really Motherly?” CoEvolution Quarterly 29 (1981): 58–63.

(71.) K. Cuddington, “The ‘Balance of Nature’ Metaphor and Equilibrium in Population Ecology,” Biology and Philosophy 16 (2001): 463–79.

(72.) S. P. Hubbell, The Unified Neutral Theory of Biodiversity and Biogeography (Princeton, N.J.: Princeton University Press, 2001); S. L. Pimm, The Balance of Nature? (Chicago: Chicago University Press, 1991).

Page 17 of 19

(73.) C. S. Elton, The Ecology of Invasions by Animals and Plants (London: Chapman and Hall, 1958).

(74.) For the classic critique of “lock-and-key” models of the organism-environment relationship, see R. C. Lewontin, “Gene, Organism, and Environment,” in Evolution from Molecules to Men, ed. D. S. Bendall (Cambridge: Cambridge University Press, 1983); see also Sterelny and Griffiths, Sex and Death, chapter 11.

(75.) S. R. Reice, “Nonequilibrium Determinants of Biological Community Structure,” American Scientist 82 (1994): 424–35.

(76.) An exception may be island invasions. See J. W. Valentine and D. Jablonksi, “Fossil Communities: Compositional Variation at Many Time Scales,” in Species Diversity in Ecological Communities: Historical and Geographical Perspectives, ed. R. E. Ricklefs and D. Schluter (Chicago: University of Chicago Press, 1993).

(77.) K. McCann, “The Diversity-Stability Debate,” Nature 405 (2000): 228–33; G. D. Kokkoris, V. A. A. Jansen, M. Loreau, and A. Y. Troumbis, “Variability in Interaction Strength and Implications for Biodiversity,” Journal of Animal Ecology 71 (2002): 362–71.

(78.) K. Sterelny, “The Reality of Ecological Assemblages: A Palaeo-Ecological Puzzle,” Biology and Philosophy 16 (2001): 437–61.

(79.) L. Van Valen, “A New Evolutionary Law,” Evolutionary Theory 1 (1973): 1–30.

(80.) B. E. Beisner, B. E. E. McCauley, and F. J. Wrona, “Predator-Prey Instability: Individual-Level Mechanisms for Population-Level Results,” Functional Ecology 11 (1997): 112–20.

(81.) See discussion in note 50 and accompanying text. See also J. Montoya, S. L. Pimm, and R. V. Sole, “Ecological Networks and Their Fragility,” Nature 442 (2006): 259–64.

(82.) M. Ereshefsky, “Where the Wild Things Are: Environmental Preservation and Human Nature,” Biology and Philosophy 22 (2007): 57–72.

(83.) M. Novacek, Terra: Our 100-Million-Year-Old Ecosystem—and the Threats That Now Put It at Risk (New York: Farrar, Straus and Giroux, 2008).

(84.) See, e.g., D. Jablonksi, “Lessons from the Past: Evolutionary Impacts of Mass Extinctions,” Proceedings of the National Academy of Sciences USA 98 (2001): 5393–98; Erwin, Extinction.

(85.) D. B. Wake and V.T. Vredenburg, “Are We in the Midst of the Sixth Mass Extinction? A View from the World of Amphibians,” PNAS 105 (2008): 11466–73.

(87.) I would like to thank Nick Shea, Sanem Soyarslan, and the editors of this volume for helpful comments on an earlier draft of this manuscript.

Russell Powell Russell Powell, Uehiro Centre for Practical Ethics, Oxford University, UK

Page 18 of 19

Page 19 of 19