78
GERALD L. YOUNQ
definition of a closed system is a feedback system, one “influenced by its
own past behavior”, one with a “closed loop structure that brings
results from past action of the system back to control future action”.
By Forrester’s definition, an ecosystem could not satisfy the conditions
of either an open or a closed system. It cannot be considered open
because overloads within the system operate aa feedback for selfadjustment; inputs are definitely related to outputs, they cannot be
isolated. It is not a closed system in that its structure is not closed; it
exists interdependently not independently. In this sense, the adjustment may be based on a feedback loop within the system but one that
derives its energy from outside the system.
The confusion lies in the inadequacy and restrictiveness of Forrester’s
definition. An ecosystem is a self-adjusting system, but it does not
depend on a closed loop structure to accomplish this. Forrester’s
definition assumes independence and this is non-existent in ecological
terms. Living systems cannot exist independently (including those of
man). At the same time, inputs and outputs are interrelated in an
ecological system as feedback mechanisms for homeostatic adjustment
(cf. Brock, 1967).
The confusion is partly one of absolutes. It is convenient to consider
an ecological system as closed, as absolute, as contained. This is convenient for analytical purposes because it is easier to draw boundaries,
to put a handle on the system. But, problems arise when ecological
systems are treatedfunctionally as closed, e.g. when the effects of a
system’s outputs on other systems are ignored. Of related interest is the
increasing tendency to consider the earth as a closed ecosystem (the
space-ship idea); everyone knows that the earth as an ecological system
cannot be considered closed, but its recognition as an open system has
created the dangerous assumption of an infinite life-support capacity.
Acceptance of the idea of a closed system imposes limits that badly need
to be recognized. Perhaps just as useful is recognition of an open system
but one with channels that have a limited capacity for the transportation of inputs, flow-through, and outputs and one that, as a system, has
limited capacity for absorption of the necessary inputs. This assumes a
recognition of limits without constructing a falsely analogous closed
system.
There is sufficient evidence in the literature to convince me that
systems analysis, the study of ecosystems, is a common method in
human ecology, present in every one of the fields utilizing an ecological
approach. Concern with the ecosystem is almost synonymous with
many of the most recent inquiries in sociology (cf. Duncan, 1961, 1964;
Bailey, 1968; Hawley, 1968). And of course the work of Parsons (1951,
1968), while not specifically ecological in emphasis, presents system
GERALD L. YOUNQ
definition of a closed system is a feedback system, one “influenced by its
own past behavior”, one with a “closed loop structure that brings
results from past action of the system back to control future action”.
By Forrester’s definition, an ecosystem could not satisfy the conditions
of either an open or a closed system. It cannot be considered open
because overloads within the system operate aa feedback for selfadjustment; inputs are definitely related to outputs, they cannot be
isolated. It is not a closed system in that its structure is not closed; it
exists interdependently not independently. In this sense, the adjustment may be based on a feedback loop within the system but one that
derives its energy from outside the system.
The confusion lies in the inadequacy and restrictiveness of Forrester’s
definition. An ecosystem is a self-adjusting system, but it does not
depend on a closed loop structure to accomplish this. Forrester’s
definition assumes independence and this is non-existent in ecological
terms. Living systems cannot exist independently (including those of
man). At the same time, inputs and outputs are interrelated in an
ecological system as feedback mechanisms for homeostatic adjustment
(cf. Brock, 1967).
The confusion is partly one of absolutes. It is convenient to consider
an ecological system as closed, as absolute, as contained. This is convenient for analytical purposes because it is easier to draw boundaries,
to put a handle on the system. But, problems arise when ecological
systems are treatedfunctionally as closed, e.g. when the effects of a
system’s outputs on other systems are ignored. Of related interest is the
increasing tendency to consider the earth as a closed ecosystem (the
space-ship idea); everyone knows that the earth as an ecological system
cannot be considered closed, but its recognition as an open system has
created the dangerous assumption of an infinite life-support capacity.
Acceptance of the idea of a closed system imposes limits that badly need
to be recognized. Perhaps just as useful is recognition of an open system
but one with channels that have a limited capacity for the transportation of inputs, flow-through, and outputs and one that, as a system, has
limited capacity for absorption of the necessary inputs. This assumes a
recognition of limits without constructing a falsely analogous closed
system.
There is sufficient evidence in the literature to convince me that
systems analysis, the study of ecosystems, is a common method in
human ecology, present in every one of the fields utilizing an ecological
approach. Concern with the ecosystem is almost synonymous with
many of the most recent inquiries in sociology (cf. Duncan, 1961, 1964;
Bailey, 1968; Hawley, 1968). And of course the work of Parsons (1951,
1968), while not specifically ecological in emphasis, presents system