[Taxacom] "Invasive species" reconsidered

[Stephen Thorpe]

I just had an interesting chat with someone who works for an invasive species 
database. their understanding of the term is interesting, but does not agree 
with a lot of stuff out there which talks about "invasive species". Basically, 
their suggestion is this:

a pest is a species with a quantifiable dollar impact (i.e., a cost)

an invasive species does not have quantifiable dollar impact, but instead has a 
negative effect on native ecosystems by decreasing native biodiversity therein

what this means is that my assumption that the meaning of "invasive species" is 
not idiomatic (=jargon) is incorrect

it would have been better for a new word to have been coined for it, 
for "invasive species"  unfortunately also has a literal meaning broader than 
the intended meaning in this context

i.e. an "invasive species" is an invasive species which has a negative effect on 
native ecosystems by decreasing native biodiversity therein