[Taxacom] Propagation of invasive species definitions

Stephen Thorpe stephen_thorpe at yahoo.co.nz
Fri Sep 10 22:16:34 CDT 2010


Fred, Fred, Fred ...

OK, start again:

let us assume (for the sake of sanity!) that the meaning of the term "invasive 
species" is not idiomatic, i.e., assume that its meaning is the conjunction of 
the meanings of its constituent terms, "invasive" and "species". Lets also 
assume that we kind of know what "species" means. So, the question now becomes: 
what does "invasive" mean? Well, it means having a tendency to invade. What does 
"invade" mean? Well, it is a bit vague, but it would seem to involve a group of 
agents entering a new area in considerable numbers, and having some sort of 
significant unwanted effect...

a Google search for "invasive species" reveals all sorts of stuff: 
http://www.google.co.nz/search?rlz=1T4SKPB_enNZ320NZ320&hl=en&source=hp&q=%22invasive+species%22&aq=f&aqi=g10&aql=&oq=&gs_rfai


this one is interesting: http://www.isinz.com/

'Invasive species are a major factor in the decline of indigenous biodiversity 
around the world'

this can be true without it being true BY DEFINITION, and I think so. I think 
that "invasive species" are just species with a tendency to invade new areas. 
This is the definition. It so happens, in fact, that many such species have 
negative impacts on biodiversity. This is true, but NOT part of the definition.

Stephen




________________________________
From: Frederick W. Schueler <bckcdb at istar.ca>
Cc: taxacom at mailman.nhm.ku.edu
Sent: Sat, 11 September, 2010 2:09:49 PM
Subject: Re: [Taxacom] Propagation of invasive species definitions

On 9/10/2010 8:47 PM, Stephen Thorpe wrote:
> on second thoughts Fred, perhaps your proposed definition:
> "a colonizing species which, in a particular area, causes a quantitative
> decline in biological diversity in habitats it colonizes."
> does capture something that mine doesn't which people tend to mean when
> they talk about "invasive species", namely that the negative effects
> must have something to do with a decrease in biodiversity, HOWEVER, two
> points:

> (1) looks like species released for biological control might count as
> "invasive species" by your definition, since they do cause a
> 'quantitative decline in biological diversity in habitats they
> colonize'. But such species are not unwanted, so don't count as
> invasives by my definition.

* but if they succeed, and make invasive species or a weed/pest species 
less dominant in a habitat, they'll increase biodiverisity, since 
conventional biological control never results in the extinction of the 
target species.

> (2) that aside, what factors make my definition "better" than yours, or
> vice versa?? If your definition is accepted, then we don't have a term
> for what I am calling "invasive species", i.e. basically pest species
> that are moving around as opposed to staying put, but this is arguably
> an important concept to have a term for.

* one could call it a weed or pest that's expanding its range, or 
becoming more common. "Pest" or "weed" is the noun, "increasing in 
abundance" is just a modifier.

> On the other hand, if my
> definition is accepted, then we don't have a term for pest species which
> tend to decrease (native, wanted) biodiversity in areas that they
> colonize, as opposed to those which might have other negative effects
> like causing itchy bites or undermining building foundations. The
> question is: do we need a special term for "invasive species" in your
> more restricted sense, or can we just deal with them in the same way as
> for species with other negative effects?

* the idea of my definition is to preserve, and quantify, the original 
idea of invasive species when I heard the term first used: at least in 
Canada it was used for alien species that colonized otherwise 
undisturbed habitats and made native species less common than they had 
previously been. This (again in North America) was a striking overthrow 
of the then-conventional idea that all that was needed for conservation 
was the protection of habitat from direct human disturbance, and it was 
a new concept that these exotic species could "force their way into" 
nature preserves or other protected habitat.

The term was so catchy that before it was adequately defined it was 
broadened to include alien forestry pests, agricultural weeds, and 
exotic species in other already-disturbed habitats. The situation is 
much different in New Zealand and other island biotas where alien 
species have long been known to crowd out otherwise undisturbed 
indigenous species - but when did these begin to be called "invasive?"

> I guess it comes down to
> whether we have dedicated teams of people who focus just on
> control/study of pest species which reduce biodiversity ... they might
> like a special term to express what they do ...

* and that term, in Canada, was "invasive species," though since 
invasive species, in my sense, don't necessarily directly degrade human 
interests, I'd question whether most of them should be called "pests."

fred.
---------------------------------------------------


>
> ------------------------------------------------------------------------
> *From:* Frederick W. Schueler <bckcdb at istar.ca>
> *To:* taxacom at mailman.nhm.ku.edu
> *Sent:* Sat, 11 September, 2010 2:07:40 AM
> *Subject:* Re: [Taxacom] Propagation of bad sameAs statements or definitions
>
> On 9/10/2010 2:28 AM, Stephen Thorpe wrote:
>  > well, I did seriously offer a definition of "invasive species", viz.
>  >
>  > an invasive species is one which has a definite tendency to expand
> its range
>  > into areas where it is unwanted
>  >
>  > Definitions which define them in terms of particular or general "negative
>  > effects" of the species are not good, because there are a great many
>  > possible particular effects and the general concept is not
> well-defined, unless
>  > you define it as an "unwanted effect", and then with a bit of
> simplification you
>  > get my definition. Basically, it is invasive if border control wants
> to keep it
>  > out ...
>
> * I've poked my oar into this one on the aliens list without converting
> anybody, but the anthropocentrism of all the widely used definitions of
> "invasive [alien] species" really annoys me, since many of them are
> effectively the same as the definition of "pest," or no different from
> "naturalised alien species."
>
> I've tried for a biocentric definition of invasive as: "a colonizing
> species which, in a particular area, causes a quantitative decline in
> biological diversity in habitats it colonizes."
>
> fred schueler
> ------------------------------------------------------------
> Frederick W. Schueler & Aleta Karstad
> Bishops Mills Natural History Centre - http://pinicola.ca/bmnhc.htm
> now in the field on the Thirty Years Later Expedition -
> http://fragileinheritance.org/projects/thirty/thirtyintro.htm
> Daily Paintings - http://karstaddailypaintings.blogspot.com/
> RR#2 Bishops Mills, Ontario, Canada K0G 1T0
> on the Smiths Falls Limestone Plain 44* 52'N 75* 42'W
> (613)258-3107 <bckcdb at istar.ca> http://pinicola.ca/
> ------------------------------------------------------------
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-- 

fred schueler
------------------------------------------------------------
          Frederick W. Schueler & Aleta Karstad
Bishops Mills Natural History Centre - http://pinicola.ca/bmnhc.htm
now in the field on the Thirty Years Later Expedition -
http://fragileinheritance.org/projects/thirty/thirtyintro.htm
Daily Paintings - http://karstaddailypaintings.blogspot.com/
    RR#2 Bishops Mills, Ontario, Canada K0G 1T0
  on the Smiths Falls Limestone Plain 44* 52'N 75* 42'W
    (613)258-3107 <bckcdb at istar.ca> http://pinicola.ca/
------------------------------------------------------------
------------------------------------------------------------


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