From: spears@bobcat.lmc.edu (Gene Spears)
Subject: Re: Ancient Forest Action Alert!
Organization: Lees-McRae College, Banner Elk, NC
Distribution: sci
Date: Tue, 21 Jul 1992 14:56:58 GMT

In article <1992Jul17.224508.23945@news.nd.edu> gsmith@minyatur.next.nd.edu (george smith) writes:

>       Recently, I was in an old forest called Warren Woods in northern  
>Indiana (I know, I laughed too when I heard about old- growth forests in  
>Indiana, but these were big trees, unfortunately the area is small).  Only  
>two tree species, beech and maple, dominated the woods.  Other sorts of  
>trees were found rarely or in places where an older tree had fallen,  
>opening the canopy.  This was remarkably less diverse than my native Smoky  
>Mountains that were logged back in the 30's or so.  I'm fairly sure you  
>have heard of the "intermediate disturbance hypothesis"; the trees in  
>Warren Woods seemed a good example.  Let me reiterate it, anyway: in an  
>ecosystem with a great deal of disturbance (natural or man- made)  
>biodiversity is low since everything is getting killed; a chewed- up coral  
>reef, for instance.  In an ecosystem with very little disturbance,  
>biodiversity is also low since the more competitively superior species are  
>free to dominate (predators may also be thought of as "disturbances" in  
>some cases); a redwood forest, for instance.  At intermediate levels of  
>disturbance, the competitively superior species is of insufficient numbers  
>to entirely outcompete others, so that more species may exist in competion  
>without any one achieving the upper hand.  Creosote- producing bushes in  
>chapparal areas seem to have just this in mind by encouraging fires.   
>Prarie ecosystems were once maintained by fire and bison grazing.  
>       Tree farms are, of course, the epitome of monoculture and differ  
>most importantly, I think, from old forests in that all the trees are of  
>the same age.  Second growth forests, however, are not necessarily tree  
>farms.  The Smokies, as I said, were mostly all logged away, but now there  
>are more plant species there than in any other state or nat'l park in the  
>US.  I don't think that biodiversity in the old- forest ecosystems is a  
>necessary argument for their preservation.  The fact that they're all soon  
>going to be gone should be sufficient.

>peace and trees,

>george
>gsmith@minyatur.next.nd.edu    

This post points out an important distinction that needs making by advocates 
of old growth protection.  

As the author correctly describes, communities with intermediate levels of 
disturbance often show the highest species diversity (remnant pioneer 
species co-existing with shade-tolerant, later successional species).  If 
BIODIVERSITY is the ultimate measure of an ecological community's worth, 
then old growth may not have the greatest value.  The more important 
argument for protection, in my opinion, is that because old growth is now so 
rare, those plant and animal species that require such habitat are 
increasingly endangered.  Calculating a species diversity value for a forest 
tells us nothing about the status of the species in the forest.

There's lots of forests around with high and intermediate levels of 
disturbance, but very few around with low rates of disturbance.


Gene Spears
spears@bobcat.lmc.edu
Newsgroups: sci.environment,sci.physics,sci.energy