From: tobis@meteor.wisc.edu (Michael Tobis)
Newsgroups: sci.environment
Subject: Re: hurricanes and conservation
Date: 7 Oct 92 17:53:32 GMT
Article-I.D.: meteor.1992Oct7.175332.1553
Organization: University of Wisconsin, Meteorology and Space Science

In article <1992Oct05.193149.100511@watson.ibm.com> andrewt@watson.ibm.com (Andrew Taylor) writes:
>In article <1992Oct5.163645.16211@meteor.wisc.edu> tobis@meteor.wisc.edu (Michael Tobis) writes:
>>While much accelerated by human impacts, introduction of exotics is also a
>>perfectly natural process. ... Should our objective in cases like this be to
>>preserve the most diverse population, or the most nearly natural processes?

>In this case there is no conflict in these objectives.  We do not increase
>global diversity by introducing exotic plants into Florida.  Instead we may
>reduce it, globally many extinctions have been caused by introductions.

You miss my point. I am not saying that policy should encourage or
even tolerate introduction of exotics. However, the exotics are now
introduced, and my question is whether it is more appropriate for
rangers to tromp around the park plucking seedlings that are recently
introduced, or whether it is better just to let nature take its modified
course. While the first approach may lead to larger species diversity, it
eventually leads to an unnatural disequilibrium, which may catastrophically 
collapse, as Yellowstone did. 

I think the philosophical question that needs to be addressed is whether 
nature is delicate or robust. Feeling that it is robust and yet feeling that
the situation is out of control, as I do, is to feel that the human incursions
on nature are enormous and bizarre, and that relatively modest changes
in our behavior will lead to a reasonable balance. Feeling that nature is
so delicate, which I call the "every precious duck" approach, that it needs
constant intervention by trained and brilliant biologists, is not only
contrary to all the evidence, it also leads to situations that are out
of equilibrium, sort of like government micromanagement of the marketplace.

>>Isn't this a version of the Smokey the Bear mistake, suppressing natural
>>catastrophes to the short term advantage and long term detriment of
>>the ecosystem?

>No, the reverse.  We should attempt to maintain species introductions at
>natural levels just we should attempt to maintain the natural fire regime
>in conservation areas.

Granted. But in most cases, we cannot unintroduce species that are already
introduced. Given that, I wonder how much effort ought to be put into
controlling the exotics once released. 

>Its interesting to compare natural and artificial extinction rates.

You mean introduction rates, right?

>In the 50 million years before man reached Australia, there were perhaps
>as few as 3 successful colonisations by land mammals (ignoring bats). In
>the last 200 years, 20 species mammals have been introduced successfully
>(in the short-term) and many more unsuccessfully.  The artificial introduction
>rate is six orders of magnitude higher than the natural one.

That's rather a special case: there aren't that many land mammals to be
introduced, and there's an ocean to traverse. Here at the edge of the
glacial max, the last 10,000 years have seen a progression of ecosystems
from tundra to boreal forest to midlatitude forest to prairie and finally
back to forest due to anthropogenic fire suppression. Yet the diversity
and richness of the untilled and unpaved parts of the landscape is still
quite impressive, while the ranges of the various flora have changed 
continually.

mt