Jim,
I hope my (perhaps) subtle tongue in cheek comments about invasives has
not confused the issue. I completely agree that human caused
introductions are to be avoided at all costs, and active eradication of
exotics should be undertaken as a default position until a
well-developed argument suggests otherwise.
As Elton documented long ago, invasives are problems, both ecologically
and financially. States and countries spends billions of dollars each
year trying to control many exotics. While I think that we can find
examples for both, innocuous exotics and maladapted natives, those
examples do not support any position taken on exotics.
I would also venture to state that even if statistical tests could not
identify an exotic, that does NOT mean the exotic is inconsequential. I
think in this case, we should assume guilty until proven innocent.
After all, nature took millions of years to come up with what we have
today, while we can screw that up in less than a decade. We do not have
the information required to decide whether an exotic "matters" in some
philosophical moral sense. We should assume that it is a problem,
however, as the best default position - avoid introductions at all
costs, eradicate when possible. If we use a moral position, that
position can be argued endlessly. If we use a pragmatic position -
introductions are uncontrolled experiments and uncontrolled experiments
should always be avoided because we cannot know how to predict the
outcome (and much less control it) - then until someone can really show
how great uncontolled experiments are, no argument will be effective
against it.
Sincerely,
Jim
James Crants wrote on 12-May-10 13:02:
Jim and others,
Your last sentence converges on the point I was trying to make: if
you compared native species, as a group, against exotic species, as a
group, you would find statistically significant ecological differences
(ie, trends), even though you would also find numerous exceptions to
those trends. A statistically significant trend is not negated by the
existence of outliers, any more than the tendency for men to be taller
than women is negated by the fact that many women are taller than many
men.
