WT and Ecolog,
Since the CBD definition of ecosystem calls it "a dynamic complex," not
"the
dynamic complex," it implies that there is more than one ecosystem on
earth
(assuming the authors of this definition didn't define it this way to make
room for any extraterrestrial life we might one day discover).
The definition also says that the components of the ecosystem interact "as
a
functional unit." I think that part of the definition of a functional
unit
must be that the biotic and abiotic environment inside the unit differs
from
that outside it, and that the shift in environment from inside to outside
corresponds with the borders of the unit. (Minnesota would have a
different
species list from Iowa, but there's no perceptible shift in biology at the
border between the two states, so they are not discrete functional units.)
A deer's rumen is a functional unit. If you tried to define the borders
of
the rumen based purely on community composition and abiotic factors, I
think
you'd end up with very similar borders to what you'd see if you defined
them
based on the shape of the rumen. Similarly, a kettlehole bog would be a
functional unit, and an outcrop of serpentine soil in California might be,
too. However, an arbitrarily-defined hectare of prairie in the Nebraska
Sandhills would not qualify, since organisms and nutrients would flow
across
the borders of that hectare plot just as freely as they would cross any
random line drawn through the middle of it, and a sampling transect
running
across any border of that plot would find no great shift in species
composition or abiotic factors corresponding with the location of the
border
(except by chance).
There are also functional units that only exist because of what I called
"ecological discontinuities we've imposed on the landscape." An arbitrary
hectare of prairie surrounded by many other hectares of prairie is not a
functional unit, but the same hectare, surrounded by many hectares of
cornfields, is a functional unit. It has different species of plants,
animals, and microbes, different nutrient inputs, maybe a different annual
rainfall total (if the cornfields are irrigated), more leaf litter, and a
different soil composition (probably more organic matter, and much more
clearly defined soil horizons in the top foot or so of soil). It likely
has
a different fire regime, especially if it's managed to maintain the
pre-settlement vegetation.
Concepts like "community" and "ecosystem" might not seem so natural to us
if
we did not live in a world where "nature" was largely relegated to islands
in a sea of anthropogenic landscapes, which themselves are cut into
sharp-edged patches of different land uses. When I wrote about ecosystems
as "artifacts of the ecological discontinuities we've imposed on the
landscape," I was thinking of cases like that hypothetical hectare of
prairie, where little bits of natural habitat were turned into isolated
units sometime before scientists started trying to find useful labels for
ecological systems.
Jim Crants
On Thu, Jul 1, 2010 at 6:30 PM, Wayne Tyson <landr...@cox.net> wrote:
JC and Ecolog:
(Note to Jim: I finally found it.)
"'*Ecosystem*' means a dynamic complex of plant, animal and
micro-organism
communities and their non-living environment interacting as a functional
unit." https://www.cbd.int/recommendation/sbstta/?id=7027
I don't see that this definition excludes humans either; perhaps DeClerck
will ask her mystery colleague how he/she came to that conclusion?
I don't interpret the definition as necessarily relating to a plurality
of
units, but rather to the entire ecosystem. I've always had a bit of
trouble
referring to subsets of the earth's ecosystem as discrete units, even
though
I recognize the utility of doing so. I would like to understand what
Crants
means by "functional units" as well as "artifacts of ecological
discontinuities."
As I have said elsewhere, I see culture as a psychological phenomenon
that
served a utilitarian purpose--that of permitting humans to manipulate
their
environment far more than any other any other species--almost without
limit.
All animal make mistakes--mountain sheep fall off cliffs, but humans seem
to
grow better and better at making mistakes and institutionalizing them
than
other species. Insanity is not limited to Homo sapiens--sick and injured
bears fly into rages and sometimes attack even humans and kill "without
reason." But humans, even apparently healthy ones, have instutionalized
not
only killing but have found ways to rationalize almost any
murder--particularly mass murder committed in the name of the culture,
aka,
"cult." Whereas Nature has been able to quickly take out deviants as part
of
ecosystem function, humans have found ways to beat that rap in countless
ways. But, as my wife is fond of saying, "Nature bats last." I suspect
we're
past the first inning.
WT
