Rare species

Don McAllister mcall at SUPERAJE.COM
Wed Jul 30 07:53:48 CDT 1997

Geoff Read wrote:
> > IUCN has recently revised the species at risk categories. They can be
> > through the IUCN home page. ...
> > ... So its not necessary to re-invent what is meant by rare. ...
> I see something at:
> http://www.iucn.org/themes/ssc/redlist/categor.htm
> Is that the page? It appears to be about endangeredness rather than
> rarity as such.
Yes that's it, and vulnerable is the equivalent of rare. Amongst other
criteria are:
Declining rate of 20% in 10 years or 3 generations
Extent of occurrence less than 20,000 square km
Extent of occupancy (species occupy only a part of the area
   within their range) of less than 2,000 square km
and other potential criteria involve: small population size, very small
number of mature individuals or extinction calculaltions.

So there is more than one way to classify a species as vulnerable. The
same goes for other higher or lower states of risk for a species. So the
system is flexible. It has also been tested out on hundreds of species.


Don E. McAllister             /& Canadian Centre for Biodiversity
Ocean Voice International          /Canadian Museum of Nature
Box 37026, 3332 McCarthy Rd. /Box 3443, Station D
Ottawa, ON K1V 0W0, Canada    /Ottawa, ON K1P 6P4
URL: http://www.ovi.ca  E-mail: mcall at superaje.com
 (or: ah194 at freenet.carleton.ca) Tel: (613) 264-8986, Fax: (613)

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