Whether or not introduced species are bad in every case is something that we really can't predict. We can, however, say for sure that introducing a non-native species into a new ecosystem does introduce much uncertainty. More often than not, this often results in competition with native species.
with them can also come introduced diseases and many other unpredictable problems. When faced with the choice of introducing a non-native these considerations must be weighed. Unfortunately, the complexity of the biosphere are far more difficult to dissect than it superficially appears. On Wed, November 21, 2007 8:50 am, Kelly Stettner wrote: > Jim, > > I must in turn respectfully disagree that "introduced species are bad, > no ifs, ands or buts." Here in Vermont, our lilacs and our red clover > are both non-native (if you want to look at 1492 as the 'cut-off' for > determining "native-ness"). The red clover is our state flower, and the > lilac is a perennial favorite. They became naturalized...red clover is > a preferred food for deer in our area. I think "bad" is a value-laden > term, and a very relative one at that. If an exotic is negatively > impacting something we value, then the creature or plant or algae is > "bad, no ifs, ands or buts." If it naturalizes or something eats it or > it has an obvious ecological benefit, then it is viewed with neutrality > tempered with skepticism. > > Too many ecological terms are become over-used and hence meaningless, or > at least vague. "Invasive" should pertain to a particular species' > behavior, not neccessarily its origins. After all, how far back does > one go to determine place of origin? If you go back far enough, humans > aren't even indigenous to North America; "we" came over across the > Bering Strait, if you go by the fossil record. Since so many creatures > are classified based on behavior, "invasive" should indicate a set of > behaviors that are exhibited by a species -- and it usually does. Yet > this also begs some questions: to some extent, every plant exudes > allelopathic compounds into the surrounding soil to protect itself from > pathogens and from encroaching neighbors. So how much "invasive" > behavior is simply good strategic defense or adaptive behavior? How > about poison ivy? Some states list it on their lists of invasive > plants, yet it is considered "native" to North America. > > There is a species of Daphnia in Lake Constance (between Germany and > Switzerland) that has adapted over the past thirty years or so to > actually eat toxic cyanobacteria. > (http://www.cnn.com/NATURE/9910/01/pollution.eaters.enn/index.html) Who > is to say that ecosystems can't adapt to a noxious invader or that all > non-natives must be eradiacted in order for an ecosystem to be > "healthy"? > > In addition (and in closing, so as not to bore everyone to tears!), why > are "invasions" seen as bad and never as part of the evolutionary > process? Rather than make the plant or animal the "bad guy", why not > recognize that species hitch-hike-- it is what they do, it is how they > travel, and it is how the planet has operated for millenia. When land > bridges arose, animals and plants moved in vast quantities and at great > speed. Landscapes changed forever. The fossil pollen record proves > that. I realize that human activity is responsible for lots of > introductions, but they don't all end in disaster. First, there is the > Rule of Tens: 10% of introduced species can survive in their new > habitat; 10% percent OF THOSE actually escape and survive outside of > cultivation; 10% OF THOSE become "invasive." Second, the Panama Canal > was one example of a sudden, major introduction of two riverine habitats > -- "all of the original species found in each stream in a 1916 survey > are still > there." (http://usinfo.state.gov/gi/Archive/2004/Aug/23-973558.html) > > Anyway, it's some food for thought. To paraphrase Willy Wonka, a little > paradigm shift now and then is treasured by the wisest men. > > Cheers, > Kelly Stettner > > Date: Tue, 20 Nov 2007 10:32:12 -0200 > From: "James J. Roper" <[EMAIL PROTECTED]> > Subject: Re: ECOLOG-L Digest - 15 Nov 2007 to 16 Nov 2007 (#2007-310) > > Kelly, > > I respectively disagree. Introduced species are bad, no ifs ands or > buts.... Some of them are naturalized and so there is probably > absolutely > nothing we can do about them. The others often have potential for > causing > catastrophe, and it is hubris to think that we can just USE them to > suit OU= > R > purposes (of what, fixing something that we already messed up?) with no > repercussions. > > Also, your argument below is circular. An ecosystem that is very > diverse > has the exotics as part of the calculation of diversity, so less > diverse > will have fewer species overall. Also, healthy does not equal diverse > - > else deserts and alpine systems are all unhealthy. If you say that > within > any biome, the most healthy are the most diverse, I bet you do not have > the > data to support that stand. > > Is leaching copper good? What does "filter" toxics mean? The take > toxins > from the soil and do what with them? And, what do they do in areas > that > have no toxins when they escape cultivation? > > Complicated issues, and I think the best answer is never introduce, > plant > natives, eliminate exotics. > > Cheers, > > Jim > > > Black River Action Team (BRAT) > 45 Coolidge Road > Springfield, VT 05156 > [EMAIL PROTECTED] > > http://www.blackriveractionteam.org > > ~Making ripples on the Black River since 2000! ~ > > > --------------------------------- > Be a better sports nut! Let your teams follow you with Yahoo Mobile. Try > it now. > Malcolm L. McCallum Assistant Professor of Biology Editor Herpetological Conservation and Biology http://www.herpconbio.org [EMAIL PROTECTED] [EMAIL PROTECTED]
