Ray,
Eugene Odum wrote a nice little primer on Ecology and published it in 1989.
It's called _Ecology and our endangered life-support systems_. He has a good
discussion on these terms and if you can get a copy of the book, it is worth
it. I'll try to put Odum's ideas into another context for the sake of
brevity.
All these terms (biome, landscape, ecosystem, etc.) are best seen as a
hierarchy. Odum compares them to geographical and political units as a way
to define them.
Biosphere = World
Continent = Biogeographic Region
Nation = Biome
Region = Landscape
State (or Province) = Ecosystem
County = Biotic Community
Town (or township) = Population (or species)
Human Population (ethnic group, etc.) = Organism
INDIVIDUAL
The term "Ecosystem" was coined by the English botanist Sir Arthur Tansley
in 1935 to indicate an assemblage of biotic (living) and abiotic
(non-living) units which were connected to each other in such a way as to be
considered as a whole. He was not using the term to be a all-encompassing
term to indicate all factors affecting vegetation, but as a term to show an
organized unit in the real world. Tansley also believed that ecosystems
showed progress toward a state of equilibrium. This is probably a hold-over
of the pre-Darwinian concept of "Vitalism," an idea that is now more or less
discarded (except by some new-age environmentalists). The term wasn't used
much until well after Tansley's death and has gotten beaten up a good deal
over the years. I've seen in the literature units as small as the cloacae of
a sea cucumber defined as an "ecosystem." I don't know why some biologists
want to confuse the issue with these irrelevancies, but there you go. In
general most "real world" ecologists now use the term to mean a fairly
discrete unit, such as the Colorado Plateau, or the Everglades. And, in
general, most ecologists have abandoned the concepts of "progress," and
"equilibrium." If you want to read a book length, and fairly dense
discussion of this, try _Ecological Communities: Conceptual issues and the
evidence_ edited by Strong, Simberloff, Abele, and Thistle (Princeton Univ.
Press, 1984). They really beat the crap out of most of the old deterministic
ideas in ecology. Another would be _The Ecological Web_ by Andrewartha and
Birch (Univ. Chicago Press, 1984).
The term "landscape" is meant to mean an assemblage of ecosystems, but
systems that are not considered as a whole. Ecosystems are more or less
defined by energy flow, but do not necessarily have defined boundaries.
Landscape has now often replaced the idea of ecosystem in management. It is
a large unit usually defined by geographic terms. For example there are
management plans for the part of the North American grasslands/wetlands from
Alberta clear to northern Colorado.
The term "patch" is relatively new in ecology. It is used in a couple of
ways, but most commonly as a sub-unit of either ecosystem or biotic
community. In most cases it is meant to mean a relatively small unit of
vegetation within some larger group. Like a meadow in a forest.
As to whether or not this discussion has been over terms, I tend to think
not. At one time the idea that ecosystems, biotic communities and such were
governed by certain rules and that those rules were largely deterministic.
In other words, an ecosystem was a highly stable unit, which was undergoing
slow change toward a defined state; the climax state. Given this view, any
change other than the "natural" changes of the ecosystem can be view as
"bad." The other view that ecosystems are largely stochastic, in other words
not progressing toward any certain state, but rather changing in random
ways, allows some induced changes. The first view has some intuitive value
in that you can simply label all human change as "bad." The second view is
more difficult because it allows for change, but means you have to determine
how much change, when, where, all that sort of thing.
Are ecosystems real or conceptual? Well, I suppose in some ways they are
both. You can take the concept of ecosystem in the field and use it to
determine the unit of study, or management, or policy. Once a unit is
labeled an "ecosystem" in policy it does take on a legal reality, which can
be good. For example there was an effort to define a large area around
Yellowstone National Park the "Yellowstone Ecosystem" back during the Bush
the First's reign. It got several top level Federal Government policy people
fired. If it had gone thru, there would have been a "real" ecosystem. I
don't have other examples, but I guess my answer is that ecosystems are not
fully real, but they are not merely conceptual either.
Hope this clarifies my point of view Ray, thanks for asking.
Steven
“Our human ecology is that of a rare species of mammal in a social,
omnivorous niche. Our demography is one of a slow-breeding, large,
intelligent primate. To shatter our population structure, to become abundant
in the way of rodents, not only destroys our ecological relations with the
rest of nature, it sets the stage for our mass insanity.”
Paul Shepard
-----Original Message-----
From: Discussion forum for environmental ethics.
[mailto:[log in to unmask]]On Behalf Of Ray Lanier
Sent: Monday, October 29, 2001 12:21 PM
To: [log in to unmask]
Subject: Re: Ethical implications of environmental change
Folks,
Interesting discussion. Tenatively, I'm inclined to think that you folks
are talking past each other. I may be wrong, but it seems to me that you
folks generally agree about the way the overal system operates but are not
in agreement about what to call the subsets and how they might be defined.
But then, I'm no ecologist etc.
It would be helpful to me if someone would define the several terms that are
being used and the relationships among them. For example: landscape,
ecosystem, patch, and others that you see as relevant, in your professional
views. Or is that too big a question set?
Guidance would be most appreciated. And please continue the discussion.
Sincerely,
Ray
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