The translocation of species around the world can, and do, have dramatic
effects on the world's ecosystems. Well known and respected ecologists rank
these biological exchanges as one of leading threats to ecosystem integrity
in marine, freshwater, and terrestrial ecosystems over the next 100 years
(see Sala et al. 2000, Simberloff 1996, and others). These rankings are in
part a matter of conjecture, but we also have a great body of quantitative
knowledge on the effects of biological exchanges. When we ask the question
'Are non-native species ecologically different from native species?' we must
be careful not to lose ourselves in semantics. This said, there is
legitimate concern among ecologists regarding the development of a sub-field
of invasion biology that operates in isolation from other ecological
disciplines such as community ecology. Simply put, non-native species may
have very similar ecological functions from native species and lessons
learned in community ecology should help drive our understanding of
biological invasions. Does this mean there is not a meaningful ecological
distinction? Absolutely not. When species are moved around and between
continents by human activities (at increasingly high rates) they often leave
behind natural predators, competitors, parasites, and diseases. In some
cases these non-native species become troublesome, and in a small proportion
of cases very troublesome. Thus, from a community ecology perspective
non-native species that may be functionally similar to native species may
still induce changes in food webs, nutrient cycling, etc that have far
reaching implications. So, are exotic and native species ecologically
different...they certainly can be. Is the distinction ecologically
meaningful...absolutely.
Scott Higgins
-Original Message-
From: Ecological Society of America: grants, jobs, news
[mailto:ecolo...@listserv.umd.edu] On Behalf Of James Crants
Sent: Monday, May 10, 2010 5:23 PM
To: ECOLOG-L@LISTSERV.UMD.EDU
Subject: Re: [ECOLOG-L] Ecology Terminology and associated phenomena
Colonizing species etc
Jim,
Actually, you answered the question of whether exotic and native species can
be distinguished at all, while the question we could not agree on is whether
the distinction is ecologically meaningful. Does an exotic species behave
differently from a native one? If not, then why should it matter to an
ecologist whether a species is native or not? I say exotic species do
behave differently, for reasons I gave in my post, and I think it does
matter whether a species is native. Dr. Chew (as I understand it) says
exotic species do not behave differently, as a group, that the distinction
is ecologically meaningless, and that it therefore does not matter whether a
species is native. We define native and exotic based on geographic
history, and I think he says that that's the only distinction that can
objectively be made between the two categories.
I would agree with William Silvert that we are getting wrapped up in
irrelevant rigor, except that I think important things might hang in the
balance here. Invasive species biology loses most of its social relevance
if native and exotic species are not ecologically distinguishable. Also,
while I agree that we have to accept fuzzy definitions for fuzzy concepts
(i.e., most concepts), a tendency emerged in the off-forum discussion to
fuzz everything together to the point where humans are just another
organism, nothing we do is exceptional, and we have no moral obligation to
modify our ecological impact, one way or another, even if doing so is well
within our power. That's a matter of using such fuzzy definitions that they
cease to be definitions at all, which is different from what Silvert is
advocating, but I guess I'm just saying that it's important not to throw out
a categorization just because the categories have fuzzy boundaries.
Jim Crants
On Mon, May 10, 2010 at 4:52 PM, James J. Roper jjro...@gmail.com wrote:
Ah Jim,
But that question is easy to answer. If humans put the species in a place
or it arrived in a place that it would not have gotten to on its own, then
it is introduced, otherwise it is native or natural. Clearly this is a
mere
consequence of the short history of humans as dispersal agents on the
planet, but it is a good enough definition for 99% of the cases - just
check
the classic by Elton.
We already have the term naturalized which basically means it's here to
stay and there is nothing we can do about it.
I personally think that for almost all intents and purposes, those
definitions work. When they don't work, we are either splitting hairs or
don't have clear objectives.
I think a clear consequence of this, is that humans should avoid
introducing and we should often actively eliminate introductions. But,
that
idea is based on the premise that we want nature to run its course without
human help - but that is not a universally accepted premise
