Tuesday, June 19, 2012

On Balance, a Battle: Simberloff (vs. Grene) vs. Odum on the Greek Roots of Ecosystem Ecology’s Enduring Appeal

[Recently I wrote about Eugene Odum’s ecosystem concept.  Its motto is that “the whole is greater than the sum of its parts.”  Odum’s view that natural ecosystems were integrated wholes which developed in a manner that parallels the development of an individual organism or human societies (a harkening back to the largely discredited views of Frederic Clements) was regarded with great suspicion by ecologists who saw the Balance of Nature view as obsolete and unhelpful.  I discuss one especially influential critique of Odum’s ecology in this post.  Since this is a rough draft of what will be a more comprehensive essay please feel free to comment if you think I stand in need of correction: no doubt I do!)]

Daniel Simberloff (1942 - ), an iconoclastic American ecologist, visited a variety of Irish zoological institutions in the early 1990s to examine collections of mustelid skulls (weasels, martens, stoats and so on).  He was doing so in order to test ideas about a phenomenon called ecological release – that is, changes in the anatomical characteristics of animals predicted to emerge in circumstances of reduced competition.  Ireland, a relatively small moist rock off the European coastline, has 20 terrestrial mammal species, compared to 42 in relatively larger island of Britain, and 134 on the European continental mainland.[1]  Therefore, one might expect that some anatomical characteristics of these mammals would differ between the Irish populations and their British and European counterparts, since in Ireland there are fewer species competing for resources in the same place at the same time. The size and shape of predators’ skulls, an aspect of these animals associated with that most ecological of characteristics, feeding, seemed an excellent feature to examine.  Consistent with the expectations of theory Simberloff confirmed that in many important respects these Irish mammals differed significantly from their British counterparts.[2]  I remember his visit well, not only because my friend John Lynch, then a brash young evolutionary biologists, now at Arizona State University (not quite as youthful, but still, thankfully, brash!) hosted him.  Simberloff had a comprehensive knowledge of the Irish fauna, and indeed was very familiar the work of most contemporary Irish naturalists; though some of them did not know him!

It should not have been a surprise to find Simberloff in Ireland since from the earliest days of his career he had been embroiled in an important controversy about the composition of island biotas.  In particular, Simberloff had been one of the first to experimentally test hypotheses about the so-called equilibrium theory of island biogeography which made predictions about the number of species likely to be found on islands of different sizes and located at increasingly distances from the continental mainland.

The theory of island biogeography is an equilibrium theory – a theory of balance, though balance meant here in a milder sense than in the holistic ecosystem concept of Gene Odum.  In 1967 in one of ecology’s more famous monographs, Simberloff’s mentor at Harvard, E O Wilson speculated along with mathematical ecologist Robert McArthur, that the number of species on an island was related to the geographical extent of the island, and emerged as a dynamic equilibrium between immigration and extinction rates.  Large islands and those closer to a continental shore enjoyed higher immigration rates – they are easier to find and colonize by species from the mainland, and in turn, by virtue of the larger populations which they can support, larger island experience lower extinction rates.  The equilibrium between these rates therefore predicted higher species richness on such large and/or close islands. 

To test this theory Simberloff and Wilson censused invertebrates on five mangrove islands off the Florida coast and then controversially chopped them up to create archipelagos of smaller islands.  They also defaunated some of them using methyl bromide (CH3Br) and observed the recolonization of insects in the years that followed.  In all cases they expected that the islands would re-equilibrate in a manner predicted by the theory.  Although the results of this audacious project confirmed many aspects of theory, nevertheless Simberloff urged caution both in interpreting these results as tests of the equilibrium theory and in extending these insights into conservation practice in mainland situations.[3]

There is much to be said about this work, its implications and the controversies that surround it, but let me just make the following remark: Simberloff’s commentary on the research showed a willingness to exercise caution in the interpretation of his own work, a commendable scholarly trait.  His prudence regarding the extrapolation of island biogeography to make general conservation prescriptions was noticeable[4].  Simberloff did not propose a “strategy of island faunal development”, and did not enter into discussion of whole faunas being in any way greater than the sum of its parts, that is, there is simply no attempt in his work at a holistic ecology of islands. 

Later, commenting on island biogeography he noted that both species number and species composition emerges as equilibria in several factors operating at the same time.  And these equilibria are frequently disrupted as a result of capricious events such as introductions or geological changes. Thus the equilibria are ultimately what he called “quasiequilibria” and are subject to long-term change. “‘Equilibrium’ in this sense is synonymous with "compromise," he said, “and the realization that island communities represent compromises parallels a Dawinian view that individual species are compromises.” Simberloff was prepared to argue an analogy between the equilibrium in species richness on islands and the optimizing of evolutionary forces, however, he did not succumb to a temptation to extend the analogy of island communities to organisms.  Though islands biotas might be balancing acts they are not superorganisms.  Patterns of species richness on island could be understood based upon the probabilistic outcomes of the comings and goings of individual biological populations.

I have dallied a little on island biogeography not only because it illustrates that ecology can propose theories of balance that do not make a commitment to holism but also because Simberloff  later became the most spirited critic of the Odum conception of the ecosystem.  There may be a balance in nature – ecological patterns emerging as a temporary balancing of forces – but there is no Balance of Nature.

Simberloff’s criticism of Odum’s holistic concept of the ecosystem was delivered in a paper called A succession of Paradigms in Ecology; Essentialism to Materialism and Probabilism.[5]  A defining feature of the Dawinian revolution, Simberloff pointed out, was that it was inconsistent with longstanding philosophical traditions that dated back to the Greeks, namely idealism (in Plato) and essentialism (in Aristotle).  From these metaphysical perspectives variation within a species should be considered “noise”, since individuals of one species belong to the same basic type; the only differences that mattered being that which existed between types. The big problem for evolutionarily inclined thinkers was to hypothesize about how new types emerged.  Darwin and Wallace’s genius was, of course, to take the noise seriously.  The noise, variation between individuals was the very engine that runs the evolutionary machine.  This was, Simberloff said, echoing historian Jacques Martin Barzun’s thesis in Darwin, Marx, Wagner: Critique of a Heritage, a triumph of materialism over essentialism.  In Barzun’s book he had unified those three disparate figures by signaling their contribution to the growth of mechanical materialism; in fact the three together can, Barzun said, be seen as “the crystallization of a whole century’s belief.”  To materialism, Simberloff claimed, gets added a pessimistic dash of probabilism, a tendency “to think statistically about all aspects of our day-to-day existence.  Probabilistic because deterministic materialism became statistical, Heisenbergian not Newtonian; pessimistic because “a true, precise, and readily understood knowledge of the physical world” eludes us. 

Simberloff then identified the succession of philosophical paradigms through which ecology has progressed starting, he says, in 1905 with Frederic Clements notion of the plant community as a superorganism.  The notion of the biological community as superorganism has the distinctive characteristic of Greek idealism, viz. differences within type, a given plant community, is less important that difference between types.  The worst failing of the essentialized plant community was that it failed, according to its critics at least, to provide a mechanistic explanation of natural patterns.  Clementsian ecology was supplanted by views that can be traced back to Henry Gleason, an Illinoisan who proposed "The individualistic concept of the plant association” in 1917.  There Gleason claimed that "the phenomena of vegetation depend completely upon the phenomena of the individual".  Communities according to this view could be seen as probabilistic outcomes based upon the interactions of individual populations.  This viewpoint was largely overshadowed by the Clementsian views that it critiqued but was rehabilitated in the middle 20th century, by which time Gleason had left the field.

It should be pretty clear from this what objection Simberloff has to Odum’s ecology.  Despite the best efforts of ecologists in the late 20th C to materialize and probabilize ecology, nonetheless, Simberloff claimed that Clements’ superorganism is “transmogrified into a belief that holistic study of ecosystems is the proper course for ecology.”  Surviving alongside the maturing ecological science, and in some ways superseding it, was the Greek metaphysical fossil of ecosystem ecology.   Along with Odum, Bernard Patten and C S Holling are noted as advocates of essentialist and holistic ecology.  A main objection is that these holistic accounts of ecology simple don’t work.  Variation is discounted; abruption fluctuations in populations are ignored. 

Simberloff wondered why ecosystem ecology has been so seductive.  Is it, he wondered, because it legitimated the notion of a self-regulating market in “unfettered capitalism”?  Noting the impeccable Marxist credentials of many ecologists, he conceded that this may not be the reason.  No, a more likely reason, Simberloff said, is that the ecosystem is where the money is.  At the time he was writing (1980) the budget for ecosystem ecology at the National Science Foundation was twice that of other ecology programs.  Ecologists, like sensible economic actors, were following the money.  Adding to the appeal of dough was the panache associated with doing voguish science.  Ecosystem ecologists were employing cybernetic analysis which was supposedly alluring and added to the “glamor of turning ecology into space-age science.”  But chief among the reasons for the continued appeal of ecosystem ecology was that “it accords with Greek metaphysics.”  This, Simberloff implied, is the myth of the balance of nature.  Because Odumite ecosystem ecology is rooted so profoundly in ancient world views it will not, predicts Simberloff vanish easily.

That Odum’s concept of the ecosystem is holistic is undeniable, certainly Odum did not deny it.  That it is so for the love of money, unfettered capitalism, or that ecosystem ecology aspired to transform ecology into a space-age science is harder to assess (as Simberloff seemed to acknowledge.)  That its enduring appeal derives from its weddedness to Greek metaphysics is, perhaps, untestable but there may be something to it.  To be true it would require that scientists identify as holists or reductionists based upon a set of intuitions rather than a cool appraisal of the philosophical arguments in favor of either of these positions since they are Greek metaphysicians unbeknownst to themselves.  [As an aside: relations between scientists and philosophers are somewhat surly these days.  And it is rare, certainly, for ecologists to receive a philosophical training.  In turn philosophers by and large have a limited grasp on the nuances of ecological sciences.  In fact several of the more interesting ecologically-inclined philosophical thinkers that I know are in some senses outsiders to both camps.  This might be relevant from an interdisciplinary perspective.  For instance, Tim Morton, now at Rice University, trained in literature though is now a figure in the object-oriented philosophy movement and a leading environmental thinker, and Anthony Paul Smith, trained in philosophical theology, has written comprehensively on restoration ecology; his dissertation was on ‘Ecologies of Thought: Thinking Nature in Philosophy, Theology, and Ecology’!]

Ironically, a case may be made that Simberloff himself had not exhaustively examined the complexities of Greek idealism and essentialism and was therefore making too much of Odum’s idealism.  This is the case made by philosopher Marjorie Grene in her response to Simberloff’s paper.[6]  I note in passing that Marjorie Green, in addition to her matchlessness as a philosopher of biology, also spent time running a family farm in Ireland (when she was married to classicist David Grene, a Dubliner).  She starts her critique of Simberloff’s paper somewhat famously (in some circles, at least) with the following:
“Many biologists, when they turn to philosophical  (epistemological or ontological)  questions, abandon  the  standards  of  accuracy  that,  at least in the layman's  view,  ought to govern their discourse as scientists.  Simberloff's argument forms an unusually flagrant example of this practice.”
Admitting that she was not fully versed in all the relevant ecological literature, Grene focused instead on his philosophical missteps, accusing Simberloff of inaccuracy in his treatment of “the villain of [his] piece”, Greek idealism.  Agreeing that Simberloff’s characterization of idealism represented that of Plato “in the middle period of his career”, she nevertheless chastised him for bringing Aristotle’s essentialism into the discussion of idealism.  Further, she finds fault with an equating of idealism with holism and determinism.  Closer to the ecological case in hand though, Grene questions whether probabilistic accounts of nature really did close the door on cause-and-effect determinism, a claim she attributes to Simberloff (though he rebuffed this claim in a written reply).  

Tartly, Simberloff begins by his rebuttal of Grene’s critique by reformulating her opening sentences (quoted above). 
“Many philosophers, when they turn to biological questions, abandon in  favor  of captious logomachy the  quest for epistemological or ontological  enlightenment  that,  at  least  in  the layman's  view,  ought to govern their  discourse. Grene's argument (1979) forms an unusually flagrant example of this practice.” 
He makes light work of some aspects of Grene’s criticisms suggesting that her admitted deficit in ecological expertise prevents her from seeing the full context of his remarks.  Without this context she supposedly missed the ways in which essentialist thinking in ecology has “produced deterministic models of population and community structure and function.”  This is all well and good, and if all Grene’s paper was doing was schooling Simberloff in the minutiae of Greek metaphysics her paper might indeed read a little schoolmarmishly.  However, her core complaint: that the links between idealism, essentialism, holism and determinism are simplistically presented by Simberloff, seems powerful to me, especially when it comes to Simberloff’s dismissal of Odum’s conception of the ecosystem.  Simberloff’s claim, that the ecosystem is idealistic, and a revival of the Clementsian superorganism and thus the myth of the Balance of Nature is, as we have seen, founded on relatively few criticisms made by Simberloff: the relatively unsupported claim that its proponents gloss over nonlinearity, allegations that abrupt population fluctuations are ignored by ecosystem ecologists, and ultimately on its “failure to add substantially to our understandings of the workings of nature.”  The appeal of ecosystem ecology is precisely because of its resonance with Greek metaphysics.  But if Grene, the philosopher, is correct and that Simberloff’s confusion regarding these Greek metaphysical ideas is in places “simply astonishing”, then her criticism is powerful.  This is because the ecological context in which Simberloff uses these ideas cannot really matter, since he claims that the appeal of ecosystem science to ecologists (other than money and the appeal of sexy space-agey ideas) is their accordance with Greek metaphysics, the appeal, that is, of a world view the preceded an ecological and evolutionary one.  Put another way, if the Greek metaphysical worldview was more heterogeneous than Simberloff claims it to be; if that worldview hosts constellations of ideas – determinism, holism etc – that are not as tightly correlated as he claims them to be, if, in fact, that there was a lot of philosophical “noise” in the Greek worldview, then it seems as if Simberloff is employing a type of idealism of his own where variation, fluctuation, and heterogeneity are ignored. 

If the strong version of Simberloff’s argument – that a holistic concept of the ecosystem persists, despite its poor empirical performance, because it smuggles in the tenacious metaphysical worldview of the Greeks, cannot be defended, or at least not without more work, then I wonder if a weaker form is tenable.  Something like this: in an evolutionary and ecological context a “Greek-like framework” that includes a dash of idealism, a smidge of essentialism, a soupçon of holism, and a dollop of non-probabilistic determinism has proved to be appealing to contemporary ecologists.  This worldview, as an integrated Weltanschauung at least, cannot, of course, be dated back two millennia, and is therefore a chronological-hybrid, accreting over an unknown period of time. Could be, could be!  But frankly, Simberloff’s argument is not as persuasive without him being correct in proposing that the ecosystem is but the latest flowering of a meme long living in western culture. 

If the idealistic component is disentangled from mechanical determinism and from holism and if the origins are sought from different sources then the weak form of Simberloff’s these may give us something to work with.  Idealism and the appeal of the Balance of Nature then may be traced to Plato, but cause and effect determinism and the notion of holism, “wholes being greater than the sum of their parts” may have roots in different philosophical traditions.  Of course, it may be that some of this worldview comes not from pre-conceived paradigms but may have been adopted by ecosystem ecologists either because of their methodological appeal (does one really need to study decomposition or production – typical emergent properties studied by ecosystem ecologists – by aggregating the influences of every species that contributes to these processes), or it may indeed be based upon empirical insights drawn from close observation of the natural world.  Certainly there are few who would doubt that Odum (and Clements before him) were skilled natural historians.

It is hard to imagine any ecological theory that does not employ a notion of balance.  After the last Ice Age Irish mammals found themselves separated from their British and continental cousins and, as Simberloff found, they anatomically re-equilibrated to the new ecological circumstances in which these populations found themselves.  Another minimal version of the ecological equilibrium view is seen in island biogeographic theory where nothing other than balance between the opposing tendencies of extinction and recruitment are posited; this theory arguably comes with little additional metaphysical baggage.  Clements’ version of the community as superorganism posits significantly more – the community is an integrated whole which follows a developmental sequence dictated by the local climate.  As Clements said, “The formation arises, grows, matures and dies.” Other ecological attributes of the balance of nature worldview, ones that are at least implied in Clementsian ecology, include homeostasis: a propensity of a system to return to a given state after a disturbance; teleology: a tendency of systems to be directed towards a predetermined goal; and a harmony of parts (where the parts of nature can be seen as akin to the parts of a body, whence superorganism).  The degree to which Odum’s ecology imports the full mythological carnival of the balance of nature is a matter for debate, though that being said, it is rarely debated.  Certainly holistic ecosystem ecology fits between the minimal equilibrium theory of island biogeography and the full blown balance of nature views that are supposedly expressed in Clements views. 

Simberloff’s critique of Odum’s ecosystem approach is of great value since it forcefully articulates the view that the Balance of Nature idea retains a shadowy presence in present-day ecology.  However, his attempt illustrates a frustrating aspect in trying to dispel this shadow: there is no agreement about what exactly the Balance of Nature view is, how to identify it, what its components are, or what the genealogy of the myth is.  All contemporary commentators, nevertheless, seem to be staunchly ‘agin it’.  If it is compound let’s be clear about what parts are useful, what parts insidious, and what parts are harmless parasites.  Believing that the whole is greater than the sum of the parts, Odum’s holistic motto, may be no worse than believing in love: hard to define, perennially frustrating, ultimately unknowable, but it directs the ways in which some of us approach the world, and are perhaps none the worse for it. 

In the end the best arbiter of Odum’s ecology might be precisely this – how does one approach the world when girded with the various aspects of the Balance of Nature perspective.  What does it mean practicality? Though Simberloff claims that this paradigm was a failure, this evaluation seems harsh, or at the very least worth re-interrogating.  I will pursue this in a future post, where I ask if the employment of a conceptual framework that includes elements of the Balance of Nature view (either as a metaphysical assumption, or as an empirical finding) can be shown to have been useful in creating new knowledge about the world, and in prescribing a course of action for the humans facing contemporary environmental problems.

[1] Lynch, J Postglacial colonization of Ireland by mustelids, with particular reference to the badger (Meles meles L.) Journal of Biogeography Volume 23, Issue 2, pages 179–185, March 1996
[2] Dayan, Tamar, and Daniel Simberloff. Character Displacement, Sexual Dimprphism, and Morphological Variation among British and Irish Mustelids. ... Ecology 91:8, 2428-2436. 1994
[3] Simberloff, D S Theory of Island Biogeography and Ecology. Annual Review of Ecology and Systematics, Vol. 5 (1974), pp. 161-182
[4] Simberloff, D S and Lawrence G. Abele Island Biogeography Theory and Conservation Practice Science, New Series, Vol. 191, No. 4224 (Jan. 23, 1976), pp. 285-286
[5] Simberloff Daniel. A Succession of Paradigms in Ecology: Essentialism to Materialism and Probabilism
Synthese Vol. 43, No. 1, (Jan., 1980), pp. 3-39
[6] A Note on Simberloff's 'Succession of Paradigms in Ecology' Marjorie Grene Synthese , Vol. 43, No. 1, Conceptual Issues in Ecology, Part I (Jan., 1980), pp. 41-45

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