It seems to me that these exotic gallinaceous birds were really
introduced to have something different to shoot. Using them to occupy
vacant niches appears to just be a convenient excuse foisted on us.
After-all, are there really "vacant" niches? One perspective suggests
that the niche is defined around the species, so 'vacant' niches do
not exist. Another specious triumph for wildlife biology.
=========================================
RK Bangert
=========================================
On Nov 21, 2007, at 12:23 PM, Warren W. Aney wrote:
> Decades ago there was discussion (and action) regarding the concept of
> "unoccupied niches" -- a natural system would have a variety of
> niches that
> species could occupy and function in. If there was an unoccupied
> niche,
> than a species could be deliberately brought in to fill that niche to
> benefit an entire system. Some examples: ring-necked pheasants and
> Hungarian partridge introduced to fill unoccupied niches created by
> agricultural development. Chukar partridge brought in to occupy
> niches
> created by spread of cheatgrass and extirpation of native
> gallinules. Wild
> turkey brought in to occupy woodland niches presumably unoccupied
> or not
> fully utilized by native grouse.
>
> Granted, much of this was done under a rather naive understanding of
> ecosystem dynamics. Some might consider wild turkey outside its
> historic
> range an invasive species, and some such introductions may now seem
> unwise
> in retrospect.
>
> This also seems to tie to Kelly's comments about biodiversity -- a
> very
> diverse ecosystem would have many more niches than a simpler
> ecosystem.
> This could suggest that a diverse ecosystem might provide
> opportunities for
> invasive species without penalizing native species. However, I
> think we can
> find way too many examples of invasives displacing rather than
> supplementing
> native species. For example, take a look at what I call the dirty
> dozen of
> Oregon invasives that have taken over or are taking over native-
> occupied
> niches:
>
> European starling -- competing with and replacing native passerines
> European rock dove ("pigeons") -- replacing native columbids
> Herb robert -- replacing native ground covers in otherwise undisturbed
> Columbia River Gorge forests
> Knotweed (more than one species/subspecies) -- invading and
> simplifying
> riparian corridors
> English ivy -- taking over and simplifying urban and suburban woodland
> ground cover
> Armenian (Himalayan) blackberry -- extensive monocultures in
> riparian areas,
> meadows and uplands
> Cheatgrass brome -- replacing native bunchgrasses in a variety of
> semi-arid
> grass and shrubland systems
> Bullfrog -- replacing native amphibians
> Reed canarygrass -- creating extensive riparian and wetland
> monocultures
> (may be a native species)
> Nutria -- replaced native beaver and muskrat in many habitats
> Carp -- replaced native warmwater fishes and degraded their water
> habitats
> Starthistle (more than one species) -- replacing native rangeland
> vegetation
>
>
> The basic questions become: should we (or can we) control and
> eliminate the
> worst invasives? Or are we condemned to an eternal effort to just
> limit and
> contain them? Or should we, as some have suggested, just accept the
> inevitable and learn to live with them and the resultant degraded
> ecosystems?
>
> Warren W. Aney
> Senior Wildlife Ecologist
> Tigard, Oregon
>
> -----Original Message-----
> From: Ecological Society of America: grants, jobs, news
> [mailto:[EMAIL PROTECTED] Behalf Of James J. Roper
> Sent: Tuesday, November 20, 2007 4:32 AM
> To: [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
>
> 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.
>
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> de Vertebrados Terrestres
>
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>
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>
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