260ECOSYSTEM THEORY
The concept of the ecosystem is not only the center of
professional ecology today, but it is also the most relevant
concept in terms of man’s environmental problems. During
the mid 70s, the public seized on the root meaning of ecology,
namely “oikos” or “house,” to broaden the subject beyond its
previously rather narrow academic confines to include the
“totality of man and environment,” or the whole environ-
mental house, as it were. We are witnessing what is called
a historic “attitude revolution” (Odum, 1969, 1970c) in the
way people look at their environment for the very simple
reason that for the first time in his short history man is faced
with ultimate rather than merely local limitations. It will be
well for all of us to keep this overriding simplicity in mind as
we face the controversies, false starts and backlashes that are
bound to accompany man’s attempts to put some negative
feedback into the vicious spiral of uncontrolled growth and
resource exploitation that has characterized the past several
decades.
Man has been interested in ecology in a practical sort
of way since early in his history. In primitive society every
individual, to survive, needed to have definite knowledge
of his environment, i.e., of the forces of nature and of the
plants and animals around him. Civilization, in fact, began
when man learned to use fire and other tools to modify his
environment. It is even more necessary than ever for man-
kind, as a whole, to have an intelligent knowledge of the
environment if our complex civilization is to survive, since
the basic “laws of nature” have not been repealed; only their
complexion and quantitative relations have changed, as the
world’s human population has increased and as man’s power
to alter the environment has expanded.
Like all phases of learning, the science of ecology has
had a gradual, if spasmodic, development during recorded
history. The writings of Hippocrates, Aristotle, and other
philosophers of the Greek period contain material which is
clearly ecological in nature. However, the Greeks literally
did not have a word for it. The word “ecology” is of recent
coinage, having been first proposed by the German biologist
Ernst Haeckel in 1869. Before this, many of the great men of
the biological renaissance of the eighteenth and nineteenth
centuries had contributed to the subject even though the
label “ecology” was not in use. For example, Anton von
Leeuwenhoek, best known as a pioneer microscopist of the
early 1700s, also pioneered the study of “food chains” and
“population regulation” (see Egerton, 1968), two impor-
tant areas of modern ecology. As a recognized distinct fieldof biology, the science of ecology dates from about 1900,
and only in the past decade has the word become part of
the general vocabulary. Today, everyone is acutely aware of
the environmental sciences as indispensable tools for cre-
ating and maintaining the quality of human civilization.
Consequently, ecology is rapidly becoming the branch of
science that is most relevant to the everyday life of every
man, woman, and child.
As recently as 1960 the theory of the ecosystem was
rather well understood but not in any way applied. The
applied ecology of the 1960s consisted of managing compo-
nents as more or less independent units. Thus we had forest
management, wildlife management, water management,
soil conservation, pest control, etc., but no ecosystem man-
agement and no applied human ecology. Practice has now
caught up with theory. Controlled management of the human
population together with the resources and the life support
system on which it depends as a single, integrated unit now
becomes the greatest, and certainly the most difficult, chal-
lenge ever faced by human society.
As we have seen, an “anthropocentric” definition of
the ecosystem might read something as follows: Man as a
part of, not apart from, a life support system composed of
the atmosphere, water, minerals, soil, plants, animals, and
microorganisms that function together to keep the whole
viable.
Any unit including all of the organisms (i.e., the “com-
munity”) in a given area interacting with the physical envi-
ronment so that a flow of energy leads to a clearly defined
trophic structure, biotic diversity and material cycles (i.e.
exchange of materials between living and nonliving parts)
within the system is an ecological system or ecosystem.
The following formal definition is the one used in the
third edition of Fundamentals of Ecology (E.P. Odum, 1971)The word ecology is derived from the Greek oikos, meaning
“house” or “place to live.” Literally, ecology is the study of
organisms “at home.” Usually ecology is defined as the study
of the relation of organisms or groups of organisms to their
environment, or the science of the interrelations between living
organisms and their environment. Because ecology is con-
cerned especially with the biology of groups of organisms and
with functional processes on the lands, in the oceans, and in
fresh waters, it is more in keeping with the modern emphasis
to define ecology as the study of the structure and function of
nature, it being understood that mankind is a part of nature.C005_003_r03.indd 260C005_003_r03.indd 260 11/18/2005 10:21:02 AM11/18/2005 10:21:02 AM