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Re: Biodiversity and Humans (was Brashears on Hansen)



Fred McGalliard wrote:
> 
> Jim wrote:
> 
> > I would submit that environmental problems are not sufficiently
> > described by "some animals being inconvienced". Although knowledge of
> > global biodiversity is sketchy, virtually all biologists are in
> > agreement that mankind is causing what would be the sixth mass
> > extinction the earth has experienced, and may cause a majority of the
> > world's species to go extinct.
> 
> Most of the rest of Jim's post I entirely agree with, but this part cannot go unchallenged. We may be
> an important predator, and responsible for some of the changes that wipe out species, but we are by no
> means the only game in town. I think we are clearly in the middle of a die off of large proportions,
> but I do not think we are the prime cause. The question should be, why have the species stopped
> adapting to the changes that we and other factors are making in the environment? If a major species
> bloom were to happen, would we be able to survive? Perhaps we should be thankful that we are in an
> extinction period.

I can answer that question-because specices are not genetically equipped
to tolerate such rapid change. Evoloution does not proceed at anywhere
near the pace you are thinking of. Speciation occurs when a niche opens
in a new habitat, and a population of an existing species colonizes by
making the necessary genetic changes. When it becomes so genetically
different from the parent species to be incompatible, an new species is
born. But if you wipe out an existing species completely in a matter of
years (in the falling rainforests, often days), there is no time for
adaptaion, especially with highly specialized and demanding species with
small populations. Also, there really isn't any sort of life that can
make itself at home in the wastelands we are creating. When a landscpae
is physically mutilated by humans, there are forms of life that could
live in it, so adaptation is not an option. The primary cause of this
mass extinction is the clearcutting of rainforests. The loss of species
here is quite apparent, as is the cause, so it really isn't a matter of
"are we the primary factor?" By the way, a "species bloom" is called a
radiation. This has happened several times in the earth's history over
millions of years, for reasons that are partially understood. If it were
to happen again (a possibility humans have eliminated by wiping out the
breeding grounds for new species), the earth and humanity would be
immeasurably enriched.



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