Newsgroups: sci.environment

/ hpindda:sci.environment / gil@Gilsys.DIALix.oz.au (Gil Hardwick) / 10:23 pm  Nov  5, 1992 /

In article <149180017@hpindda.cup.hp.com> alanm@hpindda.cup.hp.com writes:
>
> > >Humans are at least as much a keystone species as owls . . .
> >  
> > If you are thinking of the northern spotted owl, it is *not* a keystone
> > species. It is an indicator species, which is something entirely different:
> > an indicator species is one whose presence indicates that certain functions
> > are occurring. Removing it need not alter those functions. A keystone species
> > is one whose removal has repercussions and causes extinctions throughout a 
> > subcommunity. Humans are ecological dominants to be sure, but that is not 
> > synonomous with keystone species. Even when humans maintain what Rappoport
> > calls an "anthropocentric ecosystem" with a species inventory that would change
> > if the humans were removed -- letting the ecosystem "revert" -- this is not a 
> > result of the coevolution of humans and the other species involved.
>
>Alan, you have not disputed what I said; it just becomes a word game
>with all these endless variations on a theme. 

I'm not engaging in neologism, just presenting terms as they are commonly
used in the literature. I admit to the pedantry of liking to use terms 
precisely. Humans are not "keystone species" as that term is properly
used.

>I remain very acutely
>uncomfortable with your abstract model of ecosystem functions, 

My "abstract model" of ecosystem functions is just the idea of a hierarchy
of levels of biological organization, each level of which has emergent 
properties but is *constituitively* reducible to the level below it. There 
is little doubt that removing population-level functions very often degrades 
ecosystem level functions. E.g. removing species from a decomposer chain 
is likely to slow the rate at which nutrients are cycled, and also likely 
to increase nutrient losses from the system: those nutrients are liberated 
from detritus by the growth of *populations* of decomposer organisms. 
Likewise, the behavior of a population arises from the properties of the
organisms that make it up -- their individual tolerances and their chance 
encounters with varying conditions that are the day-to-day working of
natural selection.

>although
>I am also aware that Americans adhere far more strongly to a Darwinian
>evolutionary hypothesis than we do here, 

Are you saying that Australian ecologists and evolutionary biologists
are *not* (at least neo-) Darwinians? This is news to me. It would be news 
to everyone in the Ecological Society of America, I think. Will too many 
oil-can-sized Fosters do that to you? :-) :-) [Or does Gil's "we" refer 
to ethnologists and his "Darwinian evolutionary hypothesis" to something 
like (human) sociobiology, especially when (mis)read as right-wing
political apology?] 

I also don't see what it has to do with ecosystem functions per se, except 
insofar as these arise from the niches or tolerence envelopes that govern
population growth, which in turn are products of natural selection. 

>none of which enlightens us
>in any way as to how various impacts might be examined for their
>actual effect on what environments.

True enough, but we weren't discussing any specific cases. This subthread
arose in response to a person who asked what biologists mean by "degradation"
as the term applies to ecosystems, and I answered him. 

>In this particular case I do not want to enter debate with you on how
>you define your own words, 

That's good, as it gets tiresome to repeat textbook definitions after
a while. 

>I simply keep wondering when your field data
>is to be presented, that any other of us could have a look at it to get
>a line on the substance of your arguments.

Are you saying that you think that ecosystem degradation is an original
discovery of mine, which I ought to defend with my own field observations?

Giving detailed examples would be very educational, to be sure. But 
there is a limit to what this medium can be used for. It is not a
substitute for one's own study. My purpose here is mainly to stimulate
readers to learn more on their own. To that end it's very important to 
present *concepts*, especially in a crowd that is apt to assume that if
none of *them* can answer the question "what does x mean", that *must* 
imply that x doesn't mean anything at and that only idiots would talk 
about x. 

This same basic question -- what is a "fragile" ecosystem, what is ecosystem
"degradation" or "disturbance" etc. has been bobbing up in this group 
repeatedly for the past couple of years at least, alway asked in a tone which
suggests that the questioner is sure that there can be no answer. Two years
ago McCarthy was opining that this is an "emotive" concept. The answer I've
been giving repeatedly strives to correct the mistaken impression that
there is something subjective or aesthetic about this concept -- that it 
is all a matter of taste whether a clearcut is "degraded" or "improved". 

This thread itself -- the criterion for ecocentrism -- was about giving
a non-subjective definition of how much reduction of disturbance is 
"enough". The answer is -- enough to halt the extinction crisis. That
most certainly does not preclude human life, as some who are long on
ideology but short on biology like to claim. It does preclude endlessly
expanding, endlessly consumptive human life.

> > >What *type* (not level) of disturbance are you referring to here?
> > >Disturbance by, say, a major volcanic eruption is quite of a different
> > >order to that by a keystone species, such as humans. The problem,
> > >again, is in determining what impact of a species represents a plague
> > >of that species.
> >  
> > The key point is that ecosystems respond to some extent in the same way 
> > (e.g. moving back towards earlier successional states) to a wide range of 
> > *different* types of disturbance (short of total obliteration, e.g. under 
> > lava flows). By "extreme disturbance" I was thinking of disturbances which
> > disrupt the soil community -- e.g. clearcut logging can be an extreme
> > disturbance, particularly on slopes.
>
>Well, sure. We are referring here to disturbance and all I was fishing
>for was some clarification from you about what you meant by it. Would
>it not be better to get some surveys done, that actual cases can be
>studied instead of us having to rely on the arguments of somebody who
>speaks for management in favour of the environment against others in
>favour of human "needs"?

Now perhaps we are getting somewhere. Management "in favor of the environment"
--i.e. in favor of preserving the workings of the natural world -- has to
be management to preserve its biological diversity. Often this requires a
shift of management from the short-sighted anthropocentrism which historically
typifies management for "human needs". It requires choosing and maintaining
reserves which are large enough to support healthy populations of the 
species in them. It requires maintaining variety at the ecosystem level by
protecting ecosystem types including *rare* ecosystem types -- even if very 
small [this was the issue over Mt. Graham, at least as far as biologists are 
concerned]. And it requires restoring damaged, degraded, or converted areas
to something like their original state in order to expand habitat areas
(and hence the sizes and numbers of populations) of many species which are
either threatened or declining. These are the research areas of the new 
science of conservation biology.

		*	*	*	*	*	*

Dean Alaska suggests that it's "time for more ECOCENTRALs". Maybe so. I'd
like to start the series up again, this time focusing initially on population
genetics. What does that have to do with conservation biology? Well,
ecosystem functions (or "services") arise from "healthy" populations of many
different kinds of species -- and a "healthy" population is one which can
maintain its adaptedness in the face of continuous environmental changes 
such as the appearance of new disease strains or a climatic fluctation. That
in turn takes genetic diversity at the population level. But to maintain 
population genetic diversity you can't let a population become too small
-- nor the number of populations of the species become too small. A population
which is too small loses alleles by *genetic drift*, and a metapopulation
which is too small is unable to reestablish small populations which go extinct.

I would also like to do some ECOCENTRALs on the subject of speciation, to
show how the effects which humans are having on the planet work to reduce 
the chances of speciation for vastly more species than have their chances
improved. This results as well from the loss or reduction in size
of ecosystem *types* -- from loss of diversity on a geographical scale:
speciation potential is a product of biological diversity at all levels.

Maybe I should recycle the old ECOCENTRALs, too.

------------
Alan McGowen