scarce vs local

Thu Aug 24 12:51:43 EDT 2000

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"Kondla, Norbert FOR:EX" wrote:

> My take on this issue of scarce vs local butterflies is that it is a real
> and fundamentally important distinction when discussing degrees of
> endangerment or non-endangerment of butterflies.  Scale is especially
> important when reflecting on local vs widespread.  for example a species may
> occupy a substantial absolute area of several hundred square
> miles/kilometres with very healthy populations that are not under any kind
> of threat.  But if you 'assess' this species within the context of a large
> country that occupies millions of square miles/kilometres then it would be
> deemed to be 'local' and hence some people may be deceived into
> automatically thinking that it is a subject of conservation concern.

I agree.  Another way to put it that might be better understood by some is to
look at it in terms of how many there are per unit of area.  If a given species
is common (let's say 500 indiciduals per swaure mile) in a given area (let's say
the Kern River drainge in Sequoia National Forest) and pressure is at a minimum,
that population may well not be endangered (or Endangered), but if it occurs
elsewhere and its average total numbers per year are declining, then the
situation changes.  Also, if a species occurs over a large area but is common ro
varying degrees in different parts of its range, that changes the situation as
well.  Something it needs in order to survive can be common in one area and
almost totally absent in another, causing to follow a parallel population curve,
and be common where it can -- and totally absent from areas where it cannot
survive.  A good example occurs among sphinx moths here in southern California:
several species (the ello sphinx and the rustic sphinx, for example) cannot
survive along the coast for more than a few life cycles due to climatic factors,
but are locally common inland where climate and other factors are more
favorable.  Does this mean that Manduca rustica and Erinnyis ello are common
throughout the Colorado Desert?  No.  Their foodplants are not in sufficient
supply throughout the area, and their flexibility in choosing a foodplant is not
anywhere near that of the white-lined sphinx (Hyles lineata).  Even if it were,
total food supply in the deserts is not very plentiful, nor is what is out there
always edible at all, even for insects.

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"Kondla, Norbert FOR:EX" wrote:
<blockquote TYPE=CITE>My take on this issue of scarce vs local butterflies
is that it is a real
 and fundamentally important distinction when discussing degrees of
 endangerment or non-endangerment of butterflies.&nbsp; Scale is especially
 important when reflecting on local vs widespread.&nbsp; for example
a species may
 occupy a substantial absolute area of several hundred square
 miles/kilometres with very healthy populations that are not under any
kind
 of threat.&nbsp; But if you 'assess' this species within the context
of a large
 country that occupies millions of square miles/kilometres then it would
be
 deemed to be 'local' and hence some people may be deceived into
 automatically thinking that it is a subject of conservation concern.</blockquote>
I agree.&nbsp; Another way to put it that might be better understood by
some is to look at it in terms of how many there are per unit of area.&nbsp;
If a given species is common (let's say 500 indiciduals per swaure mile)
in a given area (let's say the Kern River drainge in Sequoia National Forest)
and pressure is at a minimum, that population may well not be endangered
(or Endangered), but if it occurs elsewhere and its average total numbers
per year are declining, then the situation changes.&nbsp; Also, if a species
occurs over a large area but is common ro varying degrees in different
parts of its range, that changes the situation as well.&nbsp; Something
it needs in order to survive can be common in one area and almost totally
absent in another, causing to follow a parallel population curve, and be
common where it can -- and totally absent from areas where it cannot survive.&nbsp;
A good example occurs among sphinx moths here in southern California: several
species (the ello sphinx and the rustic sphinx, for example) cannot survive
along the coast for more than a few life cycles due to climatic factors,
but are locally common inland where climate and other factors are more
favorable.&nbsp; Does this mean that Manduca rustica and Erinnyis
ello are common throughout the Colorado Desert?&nbsp; No.&nbsp; Their
foodplants are not in sufficient supply throughout the area, and their
flexibility in choosing a foodplant is not anywhere near that of the white-lined
sphinx (Hyles lineata).&nbsp; Even if it were, total food supply
in the deserts is not very plentiful, nor is what is out there always edible
at all, even for insects.
 &nbsp;</html>

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