[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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