>
> >Example: What profound consequences could conceivably
> occur because the range and abundance of 4 bumblebee
> species in the USA has declined during the past 25 years?


Not the best example, Paul, since bumblebees are polylectic--pollinating
numerous species, which are in turn pollinated by other pollinators.

A better example would be to consider oligolectic species--especially those
in which the host plant is completely dependent upon a single pollinator to
allow it to reproduce (e.g., yucca and the yucca moth).  In that case, the
loss of the pollinator will likely lead to the extinction of the host plant.
 And in the case of the yucca, the night lizards and other species that are
largely dependent upon yuccas as food and/or habitat.

Another good example would be the fruit bats or  cassowaries that are
critical to the dissemination of seeds of rainforest trees.  Without those
animals, entire ecosystems can be greatly altered by the loss of predominant
plant species.

That is not to say that the ecosystem would turn to desert--other plant
species will likely fill in for the lost species, just as cockroaches and
rats would be glad to populate our cities should humans annihilate
ourselves.  We lost the elms and chestnuts in eastern North America, but the
forests, although now depauperate in those keystone species, are still
forests, but now  very different forests.

Any of us over 50 have seen ecosystem shifts in our lifetimes.  I personally
have watched invasive weeds take over huge areas of California, and then
disappear once biocontrols were introduced.  Life will go on.  The questions
then are (1) what right do humans have to intentionally or inadvertently
cause the extinction of another life form on this planet, and (2) since we
don't know how closely linked some of those life forms are to the ecological
equilibrium that is currently suitable for the survival of Homo sapiens, we
should tread carefully in our own self interest!

Randy Oliver

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