My understanding is that "exotic" refers basically to a species that has been transported by humans some time after the "Columbian Exchange" -which is a phrase coined by Alfred Crosby that refers to rapid, and radical, alteration of patterns of global commerce following the time of Columbus. As a thought experiment, if we imagine the rate/range of species dispersal as a global phenomenon I imagine the curve would make the "hockey stick" we see with CO2 look like a teensy blip, and that species transport has been massively altered by humans, particularly following the industrial revolution, and this continues to intensify. The bend in the species dispersal curve, I imagine, is anthropogenic and very obvious.
It seems that some would call this arbitrary, but it does not seem so to me. In fact, this alteration in commerce changed human societies across much of the world. It is real. And, to me at least, it makes sense that ecologists use this as a demarcation for whether something is native or exotic. (Exotic, of course, does not mean evil, and it does not even mean "invasive" which describes population biology, not origin) Second, I see why the term "invasive" seems an anthropomorphic mess, but in practice, it does a pretty good job communicating an idea. Land managers and ecologists (who spend time in the field) here in Ohio readily agree on what are the most important invasive species in the region. It is plain to see very strong negative effects on biodiversity of some invasive species. Take a walk through the forest, it is obvious which species are "not playing by the rules." What are those rules, how do some species get to ignore them, and what happens to the ecosystem when a species acts like this? Those seem like good questions to me, or at least questions of practical usefulness... One might argue that ecological communities that have been invaded will arrive at some kind of new equilibrium- insects will figure out how to eat kudzu, etc. If so, why bother? To me, the answer basically comes back to how much do you value biodiversity? Are we willing to let the diversity of ecosystems crash and wait it out? In fact, this is what is happening over much of the landscape. Managers who have their eyes on invasive species control less than a tiny speck of the total land area...if we want to manage those specks for biodiversity (intelligent tinkerers keeping the parts) then it seems to me pertinent to understand and manage "invasions". Ryan -- Ryan W. McEwan, PhD Assistant Professor Department of Biology University of Dayton 300 College Park, Dayton, OH 45469-2320 On Mon, May 28, 2012 at 12:57 PM, Richard <[email protected]> wrote: > I find this discussion very interesting, perhaps as I am in the majority > Matt describes who hadn't thought about the term "invasive" all that much. > (Perhaps I should point out that my background is in how scientists and > non-scientists think about environmental systems. As such, I hope I might > have something of value to offer on the linguistic/philosophical aspects of > the discussion.) > > Matt's arguments here have made me at least a partial convert. He makes a > strong case that a negative judgment is inherent in the term "invasive" and > that as a result it would likely color any further discussion about the > species and ecosystems involved. > > However, Matt's description of "a process consisting of unintended arrival, > survival and successful reproduction of organisms" doesn't seem to tell the > whole story about what people are typically referring to when they talk > about an invasive species. > > Jane describes invasive as referring "to either an exotic that's spread > rapidly > and/or widely, or an exotic that causes effects we don't like (i.e. harm)." > Matt's arguments make sense to me in their rejection of the second part of > this definition. Since what constitutes harm is a matter of perspective > and opinion, the inclusion of harm in the definition makes the concept less > scientifically useful. (The term "succession" comes to mind as an > alternate example. It describes a process of change toward a different > ecological state that could either be desirable or undesirable, depending > on one's preferences, but there is no inherent judgment in the term > itself.) > > Still, the first part of Jane's definition, about an exotic species > spreading rapidly and/or widely does seem to me different enough from > Matt's definition (at least in degree) to warrant its own term--one that > might be applied both to crops and what we call invasives. > > Would you still object to a more neutral term, Matt? > > Thanks to both of you for the interesting discussion. > > -Richard > > > > > > On Mon, May 28, 2012 at 1:59 AM, Matt Chew <[email protected]> wrote: > > > We don’t need to have a linguistic discussion, because labeling a process > > consisting of unintended arrival, survival and successful reproduction of > > organisms an “invasion” is a conceptual, categorical error. That makes > it > > a philosophical discussion, but hardly an arcane one. I'll only use a > few > > terms borrowed from philosophy, and then only because they precisely > > represent the necessary concepts. > > > > Whether deliberately or reflexively applied to biota, “invasion” denotes > > biogeographical anomaly and connotes reprehensible, willful misbehavior. > > More > > importantly, it always elides description or explanation and rushes to > > judgment. There are understandable reasons for doing that; either we > feel > > threatened, or we sympathize with someone else who feels threatened, or > we > > project those feelings onto things that can’t feel threatened and feel > > threatened on their behalf. All very human. The trouble, for present > > purposes, is the space where the science of ecology can add anything > unique > > or valuable to the discussion is limited to the descriptive, explanatory > > steps we skip over in the rush to judgment. > > > > > > > > Returning to cases, nobody who suddenly finds they can’t depend on all > > locally procured truffles to be equally valuable needs an ecologist to > > explain commercial value or truffle sorting. Folk taxonomy and practical > > business acumen is sufficient to the task. Nor can an ecologist improve > > the situation by simply echoing and reifying the truffle > > hunter/dealer/buyer’s lament. Worse yet, claiming from a stance of > > (supposed) scientific authority, “Chinese truffles are invading Europe” > > makes that statement out to be a scientific assessment. It isn’t > > scientific at all. It neither describes nor explains any actual > > phenomenon. > > > > > > > > It does, however, vaguely (and yes, pejoratively) lump the European > advent > > of Chinese truffles together with a broad range of reputedly deplorable > > cases likewise labeled “invasive species.” It also incidentally serves > to > > distinguish the "bad" invaders from useful species celebrated for > > economically or aesthetically comporting with proximate human objectives. > > That's pretty ironic, because field crops are the only plants that > > effectively occupy and hold territory while completely excluding all > > others. Our mutualists are not called invasive, even when cultivating > them > > arguably meets defensible criteria for description as a biological > > invasion. Nobody needs ecologists, ecology or an ecological education to > > draw such categories. That's why the basic ideas involved were already > > worked out in the 1830s. Explaining why they are still current among > > ecologists is more of a puzzle. It all could have ended with Darwin, and > > certainly should have ended with the "modern synthesis." > > > > > > > > No so-called “invasive” species is doing anything anomalous. None has > any > > capability to persist where it is unfit. None has any responsibility to > > perish where it is fit simply because it is novel there by human > standards. > > None is responsible for issues of time or distance. Ecologists may, > > retrospectively, be able to work out the details of why particular cases > > proceeded in particular ways in particular places at particular times. > > What > > we cannot say, in our roles as ecologists, is whether the dispersal > events > > leading to those cases should have occurred. > > > > > > > > We can, of course, apply personal preferences to cases and announce > whether > > we like them or not. But (contra the implications of Aldo Leopold’s > ‘world > > of wounds’) our preferences do not arise from an ecological education. > > Neither does any privilege of holding or expressing them. If you prefer > to > > maximize beta diversity, fine; you may know what that shorthand means > > because of an ecological education, but preferring it doesn’t follow from > > knowing precisely how ecologists describe it. All you need to know is > that > > you like different “places” to be as different as possible. As an > > ecologist, you should realize that the amounts and types of rapid traffic > > bringing formerly isolated locations into practical contact renders such > a > > preference increasingly unrepresentative of the real world real plants > and > > animals live in. > > > > > > > > Beta diversity means nothing until you learn its definition. Lacking > that > > knowledge, you might envision something, but there is a low possibility > > that anyone would randomly hit upon its accepted ecological meaning. > > Unlike beta diversity, “invasion” is not a legitimate ecological term, or > > even a useful shorthand. Invasion is a common concept with a > longstanding > > military meaning. It is useful as a metaphor because its meaning is > > stable. > > Ecologists who protest that “invasion” has a specific, ecological meaning > > wholly divested of its common metaphorical associations are mistaken. > > Perhaps they are rationalizing our inability or unwillingness to (a) > > construct a coherent, defensible ecological category or (b) abandon the > > advantages of investing their personal valorization preferences with > > scientific authority. > > > > > > Several times I have been warned by thoughtful, well-intentioned > ecologists > > who acknowledge the categories native, alien and invasive are > theoretically > > weak (even empty) that repudiating them would be too costly--in terms of > > lost societal and political influence--to contemplate. In my view, > failing > > to repudiate them will be costlier still. I suspect most of us still > > haven't really thought about it much. > > > > > > Matthew K Chew > > Assistant Research Professor > > Arizona State University School of Life Sciences > > > > ASU Center for Biology & Society > > PO Box 873301 > > Tempe, AZ 85287-3301 USA > > Tel 480.965.8422 > > Fax 480.965.8330 > > [email protected] or [email protected] > > http://cbs.asu.edu/people/profiles/chew.php > > http://asu.academia.edu/MattChew > > >
