There is no way to avoid a value judgement in the whole IAS issue, a certain amount of objectivity is useful but really it is a management orientated discipline, you are not interested in whether a species is alien per se but whether it is having a negative impact on values you hold dear. Usually I focus on valued native biodiversity. That is the point! In the same way extinctions are "natural" at some level you could say that a human mediated extinctions are no less natural, but for me I can say it doesn't seem the same, even if there were a functionally equivalent alien species to take its place? I could explain why it seems important to save species and ecosystems but you would have heard it all before. I would say we don't know enough to define functional equivalence with confidence. Dr Chew is known for his critcisms of the invasive species concept, issue and science and he puts up some solid arguments.
Somehow after having worked in NZ, Galapagos and Hawaii it really does seem to be an issue of importance and a scientific approach adds value, and is therefore valid whether or not the semantics and terms are agreed. Define your question, terms and your assumptions and go for it, probably most fields of science are heavily value driven. Avoiding bias will only take you so far, its a worthy goal that we strive for probably without ever quite reaching it. PS: There is no evidence that the proportion of aliens that naturalize or become widespread will not increase for the forseeable future as long as we continue to move spp to new site, after all if it grows in a location (outside) the real question is why wouldn't it reproduce, establish and spread? On 5/10/10, James Crants <jcra...@gmail.com> wrote: > Jim and others, > > In the discussion off-forum, we were unable to come to any conclusions > because we could not agree on answer to even the most fundamental question: > is the distinction between exotic and native species ecologically > meaningful? If you can't agree on that, there's no point in going on to ask > whether there's such a thing as an invasive exotic species, whethere > invasive exotics are a problem, and what, if anything, we should do about > it. > > In our conversation, Matthew Chew argued that the distinction between native > and exotic species is ecologically meaningless. A species does not have > higher fitness because it is dispersed by humans instead of other agents. > Most species dispersed by humans fail utterly in the new environment to > which they were dispersed. Very few species are evolutionarily specialized > for human-mediated dispersal (I think exceptions would be some of those > species we use as crops, pets, and livestock, and some agricultural weeds > that have evolved such that their seeds are difficult to separate from crop > seeds). An "invasive" exotic species shows the population dynamics you > would expect for any species that is rapidly expanding its range, regardless > of its origin. If exotic and native species are not biologically > distinguishable, then the distinction is merely "historically incidental." > The categories are not ecologically meaningful, and they are only useful for > marshalling support for one group of plants (natives) and opposition to > another (exotics). > > Actually, Dr. Chew adhered strictly to the term "alien." Many people write > and talk about "alien" species, and this term, as well as the term > "invasive," provoke hostility. They do not serve us well if we want to > discuss these things rationally. On the other hand, since Dr. Chew > considers these terms to be ecologically meaningless, he is not obliged to > suggest alternatives, and he does not. I use "exotic" instead of "alien" > because it seems less inflammatory, but Dr. Chew and I agree (I think) that > there is no way to discuss exotic and native species without ending up > favoring one category over the other, regardless of what labels we put on > them. > > That's my summary of Dr. Chew's arguments, as I understand them. As he > amply demonstrated in the off-forum discussion, he can make his case much > better than I can. I have CC'ed him because I don't think he's on this > forum, and he might want to make his point in his own words. > > Initially, my argument was on moral grounds: whatever negative effects > invasive species have on native species are the fault of our species (unless > a non-human disperser was responsible for the intial long-distance-dispersal > event, which very rarely happens), and, as moral agents, we are obligated to > try to undo or mitigate the harm we cause to others. That's my Catholic > upbringing speaking, I guess, and it's apparently not a compelling argument > to someone who hasn't already reached the same moral conclusion on exotic > invasives. > > I was working on a factual argument against the assertion that exotic > species are not ecologically different from native species, but I have not > had time to check what I believe to be true against the evidence. Maybe > others can help on the evidence, but I'll keep working on it. For now, > here's what I think is true: > > (1) Exotic species, on average, interact with fewer species than native > species, and their interactions are weaker, on average. In particular, > they have fewer parasites, pathogens, and predators, counted in either > individuals or species. This is especially true of plants, and especially > non-crop plants. I suspect, but have not heard, that exotic plants also > have fewer mycorrhizal associates than native ones, but I doubt that they > have significantly fewer pollinators or dispersers. Meanwhile, back in > their native ranges, the same species have the same number of associations > as any other native species. > > (2) Very-long-distance dispersal by humans confers a fitness advantage over > very-long-distance dispersal by other agents, on average, for two reasons. > First, humans often disperse organisms in groups, such as containers of > seeds, shipments of mature plants and animals, or large populations > contained in ballast water, allowing them to overcome the Allee effects > (lack of mates, inbreeding depression) their populations would face if > introduced as one or a few individuals. We also often take pains to > maximize the establishment success of organisms we disperse, by shipping > healthy, mature plants and animals and propogating them when they arrive, > while non-human dispersal agents usually introduce small numbers of > organisms, often nowhere near their peak fitness potential (e.g., seeds, > spores, starving and dehydrated animals). > > (3) Although the population dynamics of invasive species do not differ by > what agent introduced them (whether humans brought them, some other agent > did, or they evolved in situ), it is ecologically consequential that human > activities are generating so many more invasive species than natural > processes usually do. Aside from maybe continents or oceans merging through > plate tectonics, nothing non-human introduces such a flood of new species to > new environments as we humans have in the last several centuries. > > (4) To arrive at the conclusion that the terms "native" and "exotic" (or > "alien") are ecologically meaningless, you must approach the issue this > way: if there is no set of criteria by which one can reliably categorize an > organism as native or exotic in the absence of historical evidence, the > distinction is meaningless. I think the valid approach is this: if there > is no set of criteria by which one can reliably distinguish the category > "native species" from the category "exotic species" (*after* the > categorization is done based on geographic history), the distinction is > meaningless. By analogy, the first approach is like saying that there is no > difference in height between men and women because one cannot reliably > identify the height of a person by their sex, while the second approach is > like saying that there is a difference in height between men and women > because men are, on average, significantly taller than women. > > That's all. If you've read this far, I salute you. > > Jim Crants > > > On Sun, May 9, 2010 at 8:38 AM, James J. Roper <jjro...@gmail.com> wrote: > >> Wayne, and others, >> >> This email was nebulous enough to where it appears to me that several >> concepts are being bantered around to the detriment of resolving any. >> >> Of course all terms are relative - we humans made up language to put names >> on things to help us. >> >> The problem of invasive species is important or not, depending on your >> particular philosophy, so you would have to come to some common grounds >> first to resolve what invasive is second. >> >> The problem of invasives is just like the problem of endangered species. >> 99% of all species that ever lived are extinct, so we know that it is a >> consistent evolutionary process. Probably 99% of all species that exist >> started out somewhere else. However, the glitch is that in our >> generation, >> we are causing the extinction of many species at a much more rapid rate >> than >> nature ever did, and we are causing the introduction of species in new >> places at a rate much more rapid than nature ever did. >> >> As Elton in his classic book on introduced species stated (here >> paraphrased), Because of introductions and their consequences, we will be >> left with a world much simpler, much less diverse, and much less >> interesting. >> >> Sincerely, >> >> Jim >> >> Wayne Tyson wrote on 07-May-10 16:47: >> >> Ecolog: >>> >>> Back on April 12, 2010, I posted an enquiry along these lines that >>> resulted in an off-list discussion between three Ecolog-l subscribers and >>> three others. A lot of interesting points were made, but this side >>> discussion did not, in my view, settle the matter of what terminology, if >>> any, should be used to describe the ecological phenomena associated with >>> plants (and other organisms) that "colonize" or "invade" parts of the >>> earth >>> upon which they did not appear/evolve before dispersal by human culture >>> (including various artifacts and impacts and domesticated plants and >>> animals >>> and their cohorts). >>> >>> Since the off-line discussion did not seem to resolve the issue beyond >>> opinions, I am submitting my version of the results for consideration by >>> the >>> Ecolog community. >>> >>> Among the points (you can ignore these, but they give SOME idea of where >>> the discussion wandered) made by various correspondents were: >>> >>> 1. Persistence is an interesting problem, since it requires an arbitrary >>> stipulation. Fitness is demonstrated (or not) generation by generation. >>> >>> 2. . . .why ARE so-called "natives" of a higher value than so-called >>> "exotics"? How far back are we supposed to go before something is >>> considered "native?" >>> >>> 3. . . . humans should learn how the land works, make minimal changes and >>> only necessary ones, and try to adapt to the landscape as best as >>> possible, >>> using history's lessons to create our future. Trying to make zero >>> "footprint" or impact or change as we live our lives is like trying to >>> swim >>> without getting wet or making ripples. >>> >>> 4. Eventually Albert Thellung split 'aliens' into 7 distinct categories >>> in >>> 1912: ergasiophytes, ergasiolipophytes, ergasiophygophytes, >>> archaeophytes, >>> neophytes, epecophytes, and ephemerophytes; plus two more denoting 'wild' >>> plants growing in modified habitats. Search any of them and they'll pop >>> up >>> in recent central European literature, but they're dead letters in the >>> Anglophone world. >>> >>> 5. Alien and invasive are both relative. The labels are relevant only in >>> areas where new populations have (respectively) appeared, and spread in >>> some >>> discomfiting manner. They provide no information about any biological >>> essence of any species . . . >>> >>> 6. What matters is fitness under prevailing conditions. >>> >>> 7. . . . the whole question of what response to invasive species is >>> morally best is beside the point. >>> >>> 8. For now, I still believe that each of these terms reflects an >>> objective >>> reality, but that each has nebulous boundaries. >>> >>> 9. The danger of separating natural from artificial mentally might be >>> that >>> we think we have to exclude nature wherever we go. The danger of not >>> separating them is that it can help us rationalize an anything-goes >>> approach >>> to natural systems. >>> >>> 10. Have we decided on any definitions, or are there still differences >>> about terminology? Are we ready to list them yet, even if with a >>> multiplicity of definitions? Either way, it looks like we're making >>> entertaining progress in the realm of associated phenomena. Maybe that's >>> the >>> first, if indirect, hurdle in gaining a workable set of terms? >>> >>> 11. My question is, what belongs there, and why? >>> >>> 12. . . . the important thing is to keep the lines of communication >>> open--ESPECIALLY with those who have "alien" ideas. >>> >>> 13. Once an idea catches on, it's next to impossible to replace it with >>> another one--something like the tenacity of an alien species--or, one >>> might >>> also say with equal "validity" or "spin," that, like the popular pastime >>> of >>> reasoning by analogy, that it is an example of resistance to invasion. >>> >>> 14. I am interested in the question of whether we ought to "subsidize the >>> unfit, and suppress the fit." >>> >>> >>> My own summary interpretation of some of the various conclusions are: >>> >>> 1. All organisms move from place to place by some means. >>> >>> 2. Some don't survive in some places. >>> >>> 3. Some survive and reproduce in "new" places better than some of the >>> organisms that apparently evolved adaptations in accordance with site >>> conditions. >>> >>> 4. Because of various semantic alliances, word meanings and etymology, >>> and >>> interpretations thereof, terms like "colonizer," "invader," and "alien" >>> are >>> deemed unsatisfatory to some for the purposes of disciplined enquiry into >>> ecological phenomena. >>> >>> 5. Testable hypotheses seem to be lacking. >>> >>> >>> This is all very incomplete; I hope that contributions from Ecolog >>> subscribers will help to make it more so, if not resolve the issue(s). >>> >>> WT >>> >>> >> >> -- >> >> >> James J. Roper, Ph.D. >> >> Ecologia, Evolução e Dinâmicas Populacionais >> de Vertebrados Terrestres >> ------------------------------------------------------------------------ >> Caixa Postal 19034 >> 81531-990 Curitiba, Paraná, Brasil >> ------------------------------------------------------------------------ >> E-mail: jjro...@gmail.com <mailto:jjro...@gmail.com> >> Telefone: 55 41 36730409 >> Celular: 55 41 98182559 >> Skype-in (USA):+1 706 5501064 >> Skype-in (Brazil):+55 41 39415715 >> ------------------------------------------------------------------------ >> Ecologia e Conservação na UFPR <http://www.bio.ufpr.br/ecologia/> >> Home Page <http://jjroper.googlespages.com> >> Ars Artium Consulting <http://arsartium.googlespages.com> >> In Google Earth, copy and paste -> 25 31'18.14" S, 49 05'32.98" W >> ------------------------------------------------------------------------ >> > > > > -- > James Crants, PhD > Scientist, University of Minnesota > Agronomy and Plant Genetics > Cell: (734) 474-7478 > -- Sent from my mobile device Chris Buddenhagen
