From: mcgrath@cs.uiuc.edu (Robert McGrath)
Subject: Re: does this sound right?
Reply-To: mcgrath@cs.uiuc.edu
Organization: University of Illinois, Dept of Computer Science
Distribution: sci
Date: Tue, 26 Jan 1993 15:37:02 GMT

In article <1993Jan25.222902.6230@newshost.lanl.gov>, jlg@cochiti.lanl.gov (J. Giles) writes:
|> In article <C1F8Dq.5KE@cs.uiuc.edu>, mcgrath@cs.uiuc.edu (Robert McGrath) writes:
|> |> In article <1993Jan23.4286.31987@dosgate>, "dan mckinnon" <dan.mckinnon@canrem.com> writes in part:
|> |> |>    The "gone forever" part gives me more trouble, unless every acre is
|> |> |> on a mountainside and quickly devastated by erosion, or unless third
|> |> |> world countries are erecting shopping malls at an alarming rate.
|> |> 
|> |> Got it on the second try (at least in the Amazon basin).  The soil
|> |> of the forest pretty much turns to useless muck in about two years
|> |> after the trees are cleared.  The forests do not grow back.  Nothing
|> |> much grows at all, especially if cattle are grazed on it.
|> |> 
|> |> And in the case of ANY primary growth forest, clearing it out
|> |> is permanent. Even if a secondary growth forest develops (after
|> |> decades) it is NOT the same kind of forest, and much of the life
|> |> that lives there is gone forever.  Lots of trees is not the same
|> |> thing as a climax forest ecology.  Compare, for instance, the
|> |> unlogged forests of Oregon with the secondary growth in, say,
|> |> Michigan, which was logged out about 1910.
|> 
|> It's a little misleading to compare the Amazon basin to, say, Oregon.
|> In Oregon, many of the "old growth" forests are on the sites of recent
|> (less than a thousand years) complete devastation by volcanic activity.
|> Yes, the forests regrew.  

Hmm.  I hadn't realized that the entire forest on the West Coast was
something like 1000 years old.   That must have been one heck of a volcano
to wipe out enough forest to be compared to large scale human clearing.

And, of course, 1000 years is effectively forever in terms of human
lifetimes.  Somehow, the idea that, if we mow down a forest, a new
one might grow back just as good a few hundred years after I'm dead
(assuming nobody messes it up) is pretty much the same as being
gone forever.

|> And, only 90 years is 
|> a little too short an interval (in forest terms) make any firm conclusions
|> about whether the Michigan forests can or will regrow.

The forest that is regrowing in Michigan is a completely different forest
that was there originally.  There is almost no chance at all that it
will ever grow back the way it was.  In that sense, the original forest
is definitely gone forever.

|> How much forest can be cut and what policies should be in place to best
|> encourage recovery and renewal of the resource are questions about which
|> a lot is known, but not nearly enough to make absolute positive claims.
|> The present state of knowledge leaves a lot of room for wildly different
|> opinions between equally well-informed scientists.  You could argue that 
|> cutting down "old growth" forests before the above questions (and others) 
|> have been answered is irresponsible.  On the other hand, depriving people 
|> of an important source of income during a recession because of problems 
|> that only *may* occur could also be characteized as irresponsible.  Welcome 
|> to the wonderful world of politics.

I agree that management policy is a political question, and that 
deforestation is driven by pretty raw economic forces.  (You forgot
to note the economic interest of the tourist industry, which requires
un-logged forests.)

I should note that the Amazon deforestation has often been done by
a relatively few, who level a large area (basically wasting the lumber), 
use it for a couple of years to grow cash crops for export (rather
than food or improving the domestic economy) and then abandon it.  
This kind of activity is not great policy in anybody's book.

-- 
  Robert E. McGrath
  Urbana Illinois
  mcgrath@cs.uiuc.edu