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 On Nov 19, 2007 4:54 PM, Kelly Stettner <[EMAIL PROTECTED]> wrote= : > Bill (and all): interestingly, it has been proven that ecosystems with a > large degree of biodiversity (read: "healthy ecosystems") have more > varieties of invasives present than those ecosystems that have less > biodiversity. I can dig up the studies, if anyone is interested. > > There is always the question of what good do invasive species > (particularly plants) do in an ecosystem? Yes, here I go again, playing > Devil's Advocate...but consider for a moment how some of these rampant, > densely-populated plant colonies effectively fix carbon from the atmosphe= re, > alter the soil chemistry and hence the soil zoology and biology (potentia= lly > for the better?), and some even filter toxic chemicals from the soil. Fo= r > example, Japanese knotweed (Fallopia japonica, Polygonum cuspidatum) appe= ars > to thrive in old mines, being quite adept at leaching out copper from the > soil. I think that a lot of ecological thought can be turned on its ear = by > thinking outside one's paradigm, looking at the bigger picture. But Bill= is > right in that so very many people make abolishing invasives their life's > work...their sole raison d'etre. Invasive =3D Evil, no ifs, ands or buts= . > That is simply not a scientific approach, not is it realistic or pragmat= ic. > Other scenarios and > paradigms must be recognized and considered in order for respectful and > honest discussion can take place. > > Working with knotweed in Vermont, > > Kelly Stettner, Director > Black River Action Team > Springfield, VT > www.blackriveractionteam.org > > > ---------------------------------------------------------------------- > > Date: Fri, 16 Nov 2007 10:18:47 -0000 > From: William Silvert > Subject: Re: ECOSYSTEM Health Alien invasions persistence decline limits > control Re: semi-silly question from John Nielsen > > I'll pick up on two of Wayne's points. One is that "some aliens that do > little harm" -- this is true, and some aliens are introduced deliberately= . > Mustangs are alien to N. America, and are widely appreciated. Many > ornamental plants are deliberately introduced. My mother was a member of > the > Florida Native Plants Society, and felt that they were fighting a losing > battle against the imports. An interesting downside is that often > introduced > plants in dry areas require lots of water and this creates problems. > > As for the comment that healthy ecosystems resist invasion, this depends > on > whether they have had a chance to immunise themselves by past experience. > Because mammals were unknown in Australia, their introduction was > impossible > to resist. The same is often true when snakes or mosquitos arrive in > regions > where nothing similar has every been present. Often the best defence > against > an invading species is a predator that can control it, but if such > predators > are not already present, it may take a few million years for them to > evolve. > > Sometimes man has tried to counter one alien invasion by introducing > another > alien species to control it -- which brings into action the Law of > Unintended Consequences. It's a tricky game to play. > > Bill Silvert > > --------------------------------- > Be a better sports nut! Let your teams follow you with Yahoo Mobile. Try > it now. > --=20 James J. Roper, Ph.D. Ecologia e Din=E2micas Populacionais de Vertebrados Terrestres Caixa Postal 19034 81531-990 Curitiba, Paran=E1, Brasil E-mail: [EMAIL PROTECTED] Telefone: 55 41 33857249 Mobile: 55 41 99870543 http://www.bio.ufpr.br/ecologia/ Ecologia e Conserva=E7=E3o na UFPR http://jjroper.googlespages.com Personal Pages
