Folks, I believe that is possible to define the term, invasive, without reference to origin or assumption of harm. Invasive could be viewed simply as an adjective that describes a species in the process of invasion, which then requires a definition of the term, invasion. Valéry et al 2008 (Biological Invasions) provide a definition that seems reasonable to me. I've adopted and adapted their definition of the phenomenon of invasion (removing, in my opinion, some loaded and unnecessary terms such as "conquer" and "natural") to generate a working definition of an invasive species.
Invasive species: A species that has acquired a competitive advantage following the disappearance of obstacles to its proliferation, which allows it to spread rapidly within recipient ecosystems and become a dominant population. Although "competitive advantage" portends the potential for harmful effects, that is something to be tested, rather than to be assumed. Note also, as claimed by Valéry et al, this definition makes no assumption about the native/non-native origin of the species, as nativeness is a matter of degree in both time and space. Examples of the disappearance of obstacles to proliferation could include obvious ones such as human-mediated transport of species from another biogeographical realm or continent or less obvious and perhaps more controversial ones such as fire suppression that allows expansion of fire-sensitive "native" species from habitats historically protected from fire or climate change that allows pole-ward range extension within a biogeographical realm. Unfortunately, there is no general agreement among ecologists on the definitions of invasive or invasion, and I suspect that the definition provided here won't satisfy many. This is a pity because I think that continuing to argue over what we mean by invasive or invasion gets in the way of actually learning about the impact of these species, what to do about them, and what ecological and evolutionary insights we could gain by studying them. Cheers, Steve cheers, Steve ________________________________________ From: Ecological Society of America: grants, jobs, news [[email protected]] on behalf of Richard [[email protected]] Sent: Monday, May 28, 2012 11:57 AM To: [email protected] Subject: Re: [ECOLOG-L] invasive truffles 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 >
