There
was a small bust of Eugene (Gene) Odum in the lobby of the Institute of Ecology
at the University of Georgia which bore the inscription “The whole is greater than the sum of its parts”. It used to entertain me to see Odum, that
spritely giant of ecology, pass by his own bust most days without remarking it
much at all. Lesser men might have
glanced. I showed it to my father once
when he visited me in Georgia while I worked there in the 1990s. His response after he read it was merely a
shrug and he wondered whether the phrase actually meant anything. My father was not the only one to wonder
this.
In
fact, the epigram was central to Odum’s holistic understanding of ecology. In the mid 1960s he wrote that there were two
types response to discussions about ecology as a system’s science. One group of responders would affirm, he
thought, that “any school child knows that the whole is not a sum of the
parts”, but another “remains unconvinced that there is anything really new or
different at ecological levels that can not be ultimately explained either by
the reduction of the whole into even smaller parts…”[1] Identifying the most appropriate unit of
analysis was critical to humanity adequately addressing of its environmental
problems. Odum recognized the ecosystem
as that unit of analysis. As he defined
it, a definition that remains serviceable in contemporary ecology, the
ecosystem was
“made up of all the organisms in a given area (that is, “community”) interacting with the physical environment so that a flow of energy leads to characteristic trophic structure and material cycles within the system.”[2]
Asserting
that the ecosystem whole was greater than the sum of its parts meant that
ecological analysis restricted to another ecological level – individual organisms
or biotic communities, for instance, would fail to capture the dynamics of
nature in a way that permitted us to ameliorate our impacts.
The
attributes of ecosystems, properties which for the most part could not,
according to Odum’s adage, be predicted from an examination of the components
constituting the ecosystemic whole include the following: community energetics
(production, standing biomass, nutrient cycling, and overall metrics of
ecosystem stability). In his list of 24
ecosystem attributes Odum includes metric of biotic community structure, life
history and strategy since lower ecological levels may not add up to the
properties of the whole, nonetheless the whole may constrain the parts.
By
defining the ecosystem in a holistic fashion, one with characteristics such as balance,
integration, the possession of emergent properties, stability, equilibrium, attainment
of a steady-state, and homeostasis, Odum tied his ecology to a venerable
tradition, one that dates to the earliest Greek conceptions of the natural
order known as the Balance of Nature.
The Balance of Nature defined in the most general terms is where the interrelated
components of a system operate in harmony, thereby reflecting a stable
equilibrium of traversing forces. This dynamic
harmony persists unless disturbed by external interventions. Odum’s unit of concern is primarily the
ecosystem, but since his ecosystem is the upper-level entity that constrains
those levels below it in the ecological hierarchy, therefore where he expresses
a Balance of Nature perspective it ramifies throughout the entire system.
Natural
ecosystems, Odum asserted, were integrated wholes, and developed in a manner
that parallels the development of individual organism or human societies.[4] On the one hand the expression of
similarities between ecosystems and organisms, even when expressed somewhat
neutrally as a “parallel”, troubles the contemporary ear, and yet it also
harkens back to some fairly ancient views of the natural world, as we have seen
elsewhere). This development of the
natural systems, succession in other words, is orderly, predictable, and
directional. It is mechanistically directed by the biotic community’s
modification of the physical environment.
Importantly, it leads to a stabilized ecosystem with predictable ratios
of biomass, productivity, respiration and so forth. The “strategy” of ecosystem development, as
he called it, corresponds to the “strategy” for long-term evolutionary
development of the biosphere – “namely, increased control of, or homeostasis
with, the physical environment in the sense of achieving maximum protection
from its perturbations.” Homeostasis
etymologically derives from the Greek standing still and in the sense that Odum
means to imply, indicates a dynamic and regulated stability. So the strategy of successional change is for
the system to achieve a balancing of forces that confers upon it a dynamic
stability.
The
degree of protection that ecosystems have from perturbations comes in part, Odum
claimed, from the increasing complexity of food webs as succession
proceeds. The mechanisms – both
antagonistic and mutualistic – that develop between species confer this
stability. Though the patterns of diversity during succession may be quite
variable – often increasing in early succession, peaking in middle succession
before declining, though Odum makes an interesting point that “organic extrametabolites”
by which one supposes he means exudations into the environment, increase during
succession, and these serve as an indicator of increasing biochemical
complexity. This is important because
such compounds can impose some regulation of populations, “preventing
population from overshooting the equilibrium density” and in this dampens
oscillation and promotes stability.
Though Odum equivocates on the cause-and-effect relations of diversity
and stability, nonetheless, he declares that if the relationship is real then
it means that conservation is justified on “scientific as well as esthetic
grounds”.
Now
the upshot of Odum’s analysis of the development of ecosystem attributes is
that the net result is a development towards “symbiosis, nutrient conservation,
stability, a decrease in entropy, and an increase in information.” In other words as a system develops over time
the elements increasingly operate in harmony and the integration is a reflection
of an equilibrium emerging between opposing forces. These are characteristic of a Balance of
Nature perspective. To illustrate, in
the 1969 paper there is quite extensive use made of terms that code for a Balance
of Nature perspectives. Among the
specific claims are that energy fixed tends to be balanced by the energy cost of maintenance (thus autotrophic and
heterotrophic metabolism are balanced especially in the climax community);
minerals in soils are balanced as
succession proceeds contributing to a “tightening” of nutrient cycling during
development; secondary metabolites may be important in regulation populations
at a equilibrium density; species
with lower growth rates but better competitive abilities are favored under the equilibrium density of late successional
stages; the time required to reach a steady
state may vary not only with different ecosystem attributes in the same
physical environment. These terms are used
extensively - “stability” alone is used 13 times in the paper; balance 10
times.
Of
course, it is not as if Gene Odum stands on trial here of covertly advocating a
Balance of Nature perspective. He made
no bones about it. I am not therefore
claiming as a great investigative coup the discovery that Odum’s ecology, with
it holistic commitments to the developmental emergence of homeostatically-regulated
ecosystems, has conspicuous Balance of Nature commitments. After all in his account of the history of the
ecosystem concept Frank Golley asserts that the Odum conception of the ecosystem
asserts both its self-regulated and it “goal-seeking” properties.[5] However,
I want to highlight the fact that as an inclination towards holism, teleology
(goal-directedness), equilibrium, and balance declined in ecological science
the Odumite conception of the ecosystem was increasingly criticized. Furthermore, and perhaps less remarked upon,
the implications of ecology for the sensible management of human affairs differs
under the assumption of balance than it does in the new non-equilibrium,
disturbance oriented models.
I
will take up the explicit criticism of the Odum ecosystem concept in the next
post, and show that an view of the ecosystem that stresses it holistic
properties will have quite different implications for environmental practice
than one which other, arguably more contemporary (or more fashionable)
conceptions of ecology.
[1]
Odum E P The New Ecology BioScience, Vol. 14, No. 7, Ecology (Jul.,
1964), pp. 14-16
[2]
Odum E. P. The Strategy of Ecosystem Development. Science 164 262-270 1969, 262
[3]
Odum, E P and Barrett, G W Fundamentals of Ecology. 5th Ed. Thompson
2005
[4]
Odum E. P. The Strategy of Ecosystem Development. Science 164 262-270 1969
[5]
Golley, F B Golley A History of The Ecosystem Concept, Yale University Press,
1993
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