Humans are not part of nature? No wonder the planet is sick..... On Tue, May 11, 2010 at 10:15 PM, Geoffrey Patton <[email protected]>wrote:
> This has been an especially interesting and worthwhile discussion, > particularly on the ethics front. My ethics derive from an ecologist whose > name I can no longer recall but whose mantra was that Nature took millions > of years to sort out the current state and any human-caused change is, by > definition, adverse. Where people have a hand in it, it is bad, regardless > of any perceived shot-term benefit. Pedagogical but true in my view. > > Cordially yours, > Geoff Patton, Ph.D. 2208 Parker Ave., Wheaton, MD 20902 301.221.9536 > > --- On Tue, 5/11/10, James Crants <[email protected]> wrote: > > From: James Crants <[email protected]> > Subject: Re: [ECOLOG-L] Ecology Terminology and associated phenomena > Colonizing species etc > To: [email protected] > Date: Tuesday, May 11, 2010, 10:47 AM > > I think I have not made my arguments clearly enough. I merely intended > to summarize my moral case for suppressing invasives as part of my summary > of the off-forum conversation. My numbered paragraphs were intended to > address the claim that there is no ecological difference between native and > exotic species, and the claim that there is no ecological difference > between > human-mediated dispersal and dispersal by any other agent. My responses to > Matt's responses to those paragraphs are below: > > > JC(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. > > MC(1) Natural selection only produces interactions good enough to persist > > under prevailing conditions; there is no gold standard. By definition, > 50% > > of all species interact with fewer species than average, and 50% of all > > interactions are weaker than average. Preferring stronger, more complex > > interactions means preferring more tightly-coupled (and therefore) > > 'riskier' > > systems with a higher likelihood of failure. > > > JC (1b) The argument about how many species interact with fewer species > than > average misses my point. I'm saying that, if you counted the biological > interactions for each native species and each exotic species in some area > (could be a square meter, could be the world), I believe you would find > that > the average number for exotic species would be significantly lower than the > average for exotic species. Thus, exotic species are ecologically > different > from native species. > > Actually, having more interactions may mean greater stability, on average, > since some of those interactions are functionally redundant. I would have > to brush up on my community ecology to be sure I'm not being overly > simplistic, but I know this is true in pollination systems; pollinators > that > interact with more angiosperm species have greater population stability, on > average, and angiosperms with more pollinator species have greater > reproductive stability, on average (though I don't know if this leads to > greater population stability for long-lived species). > > I'm not sure what you mean by "systems with a higher likelihood of > failure." It seems to me that failure is a matter of human values not > being > realized. If, by "failure," you mean "rapid change," well, that hardly > seems to be a problem for you. I would have to agree that systems managed > to promote natives at the expense of exotics are more prone to failure than > those where any and all ecological outcomes are deemed acceptable, but > that's only because "failure" in the former group means invasion and > domination by exotic species, while there is no such thing as "failure" in > the latter group. > > > > > JC(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). > > MC(2). JC appears to be arguing that once rare occurrences are no longer > > rare. I agree. But I draw the opposite conclusion, because he is > arguing > > that to generate such changes is morally wrong, while I am just saying: > > when > > these conditions prevail, long distance dispersal becomes normal. > > > JC(2b) I'm not saying anything (here) about whether the recent commonness > of > previously-rare dispersal events is morally wrong. I'm countering the > argument that human-mediated dispersal confers no fitness advantage > over dispersal by any other agent. Others may be aware of an invasive > exotic species that was not imported by humans in far greater numbers than > we could reasonably expect from any other agent, even if it had 100,000 > years to work, but I am not. > > Furthermore, most invasive species were carefully planted and tended across > large areas. Others may know of a dispersal agent that takes such care of > the species it disperses AND has any realistic potential of dispersing > something over 1,000 miles, but I do not. Human-mediated dispersal is > unlike dispersal mediated by any other agent. > > > > JC(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. > > MC(3). See MC(2). What was once normal is no longer normal. > 'Ecologically > > consequential' in this context is standing in for 'morally > consequential'. > > Ecologically, change is change. > > > JC(3b) By this logic, ice ages are ecologically inconsequential. I'm not > making a moral judgement (here). I'm only pointing out that humans have > accelerated the frequency of invasion by new species by many orders of > magnitude, and that this is having the sort of dramatic ecological effects > you would, in theory, expect it to have. Again, this goes toward > countering > the claim that there is no ecological difference between human-mediated > dispersal and dispersal by other agents. If we are increasing the > probability of intercontinental dispersal by many orders of magnitude over > what you find for all other agents combined, there is an ecologically > important difference between human-mediated dispersal and dispersal by > other > agents. > > > > > JC(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. > > MC(4). JC undermines his argument here by trying to make the difference > > between natives and aliens morally inconsequential. I think we can > assume > > that he sees no moral imperative emerging from the statistical likelihood > > that men are (and have been) taller than women. But we know he believes > a > > moral imperative emerges from the claims he makes in (1-3). So his > analogy > > isn't really an analogy. A better analogy would be a claim that men > are, > > on average, more politically powerful than women, evaluated in light of a > > moral claim that no such difference should exist. But even that analogy > > would only recommend equalizing average fitness; leveling the playing > > field. > > And it flies in the face of the "past = desired future" formula inherent > in > > anti-alien sentiment. Finally, if Williamson's legendary '10s' rule is > > even > > remotely accurate, the aliens are already disadvantaged by multiple > orders > > of magnitude. Long distance transport is now vastly more likely, but > > establishment at the other end is still a long shot. > > > JC(4b) Again, I'm not making a moral argument at all. You (and others) > have > said that native and exotic species cannot be distinguished ecologically. > One way I've seen other people arrive at this conclusion is by observing > that there are no ecological criteria that can perfectly predict whether a > species is native or exotic (e.g., there are invasive natives, there are > exotic plants with more insect herbivores than related natives, etc.). I'm > saying that this approach is like trying to predict people's sex based > on their height, noting that you often guess wrong this way, and concluding > that sex is not relevant to height. > > > > > -- Jan Ygberg Juan Fanning 380 Lima 18 Peru INT+(511) 446 1099
