I'm only asking for a quantifiable description of 'invasive' - we can't
do it based on where organisms originally evolved. Distributions of all
biota has changed dramatically in the last 18,000 years, so drawing
lines based on where species originally came from does not make a whole
lot of sense. The policy at some national parks has been to try to
preserve based on what we think the composition was like before the
arrival of Columbus to the New World. Such a view does not take into
account the fact that these communities are dynamic - distributions are
still changing in response to climate change since the last glaciation
(not counting human effects on climate). Distributions and community
composition will continue to change - these systems are naturally
dynamic. But this reality does not jive well with current views of
conservation biology whose main purpose seems to be an attempt to freeze
systems in time or to return them to some state that we think they use
to have. As conservationists we should focus on conserving natural
processes, not entities. Those processes lead to changes in
distributions, hybridization, change in community structure, and even
extinction. Fire policy is a great example - look at how are view of
the role of fire in ecosystems has changed over the last 100 years. We
need to have a similar recalculation of our policies for other aspects
of conservation biology - a focus on allowing natural processes to run
their course no matter where they might lead. South Florida is just a
great example of a dynamic system.
So perhaps a definition of 'aggressive behavior' no matter what the
origin of the aggressor would be appropriate. Even then we have to make
decisions on if and when it would be appropriate to intervene.
On 9/11/2011 10:42 AM, [email protected] wrote:
---- Mitch Cruzan<[email protected]> wrote:
(stuff cut)
What about the South Florida tropical flora/fauna? Many
species in those systems only arrived on this continent only within the
last 5000 years - are they invasive? Are entire communities in the
everglades invasive?
Hmmm. How long ago did Florida emerge?
Are you suggesting we should not be concerned about pythons in Florida, because
though they are relative newcomers by Florida standards, all of the Floridian
biota constitututes newcomers by geological standards? As another poster said,
perhaps it is invasive behavior that matters. But of course, these snakes are
not invasive -- they are tightly tied to the conditions where they evolved.
They were brought by people, then released. But they do wreak havoc on native
fauna once present. Not a problem, since Florida is recently emerged, so has
only recently arrived biota?
David McNeely
