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Re: mass extinction



Not to mention the potential impact of human-induced
global warming on extinction events.  It's possible
that living dinosaurs may experience a mass extinction
as great as any of the Mezozoic ones:

http://www.msnbc.msn.com/id/3897120/

Guy Leahy

--- tholtz@geol.umd.edu wrote:

> > There was a major extinction of megafauna at the
> end of the Pleistocene on
> > all major landmasses except Africa that was almost
> certainly caused by
> > humans and affected a few hundred hundred species
> of mostly large mammals
> > and smaller numbers of birds and reptiles.
> >
> > Also there was a *very* large extinction in the
> Pacific when it was
> > colonized by the Polynesians. The size is
> uncertain since most islands
> > haven't been studied yet, but it certainly
> affected many more species than
> > 800. From the number of extinct species found on
> the islands that have
> > been
> > investigated David Steadman estimates >2000
> species *of birds alone*, i e
> > 20% of the extant bird species
> > of the World.
> >
> > Another major extinction occurred on Madagascar
> 500-2,000 years ago. Total
> > number of affected species is not known, since
> there has been very limited
> > research as yet.
> >
> > In short major extinctions have occurred
> essentially everywhere where
> > humans have settled, but particularly on islands.
> However it is not
> > considered polite to mention extinctions that
> occurred before the
> > Europeans
> > arrived, hence that 500-year limit.
> 
> And we are in the midst of (potentially) a massive
> marine extinction due
> to recent (last 50 years) changes in marine
> harvesting techniques
> (including benthic trawlers) and phenomenal
> mismanagement of fisheries.
> 
> Keep in mind: the pre-human mass extinction record
> is only of common,
> easily preservable taxa. We don't have that good a
> direct record of what
> happened to the rare or the poorly-preserved at the
> K/T or P/Tr or what
> have you.
> 
> Oh, and Crichton's science in "State of Fear" is
> laughably bad. But then
> again he thinks that Uri Geller has magical psychic
> powers, too, so his
> grasp of what is real science isn't that good.
> 
>               Thomas R. Holtz, Jr.
>       Senior Lecturer, Vertebrate Paleontology
> Department of Geology         Director, Earth, Life & Time
> Program
> University of Maryland                College Park Scholars
>       Mailing Address:
>               Building 237, Room 1117
>               College Park, MD  20742
> 
> http://www.geol.umd.edu/~tholtz/
> http://www.geol.umd.edu/~jmerck/eltsite
> Phone:        301-405-4084    Email:  tholtz@geol.umd.edu
> Fax (Geol):  301-314-9661     Fax (CPS-ELT):
> 301-405-0796
> 
>