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
