Hi y'all!
Houlahan has touched (as have others) upon perhaps the most gigantonormous
of all the elephants in the "invasive alien" room--money and power. A lot of
people (not to mention corporations) make a lot of money getting a lot of
people to stay poor out of concern for "the" environment; the financially
attached "love" and support (mainly "moral" support) the emotionally
attached. The former operate, Cheshire-cat style, in the background, while
the "environmentalists" volunteer their hearts out and march against the
evil infidels who would dare to suggest that proof should be derived from
scientific analysis and real data.
If you will permit a small anecdote: About ten years ago I was vigorously
verbally attacked ("Just kill them ALL, kill them all--that's all you need
to know!") at a seminar sponsored by Cal-IPCC and was shunned for the rest
of the meeting by the weed-whackers. Posting on this subject on listservs
like the one operated on behalf of CNPS, Cal-IPCC, and APWG, for example
will be met with cries of outrage or stony silence. A CNPS group has, at
great expense and labor, greatly reduced biodiversity on one site near my
house, planting common native shrubs that will suppress or kill uncommon
indigenous grasses, which they have whacked along with a few weeds, the
latter of which were in the process of being suppressed by an increasingly
healthy and diverse indigenous plant community. Hell hath no fury like the
self-righteous. I have become the veritable skunk at a garden party, if not
branded as an outcast by various organizations, including those I once
thought were "on the right hand of God."
The Davis et al paper could not tell all, but it did put some respectability
on this volatile issue. I may not fully agree with every detail, and perhaps
even less with some of its generalities, but I welcome it as what it is
apparently intended to be, a catalyst for reasoned examination of
questionable conclusions. Over the last several decades I have vacillated a
bit on this issue, but tend to hover around the middle somewhere. In
particular, I have found that healthy ecosystem need far less intrusion by
us than we think; they may take their time about it, but once we have
stopped whacking, grazing, grading, and otherwise messing them up, they do
tend to self-repair--maybe not to the extent that we prefer, but most often
better than we can by demanding that they live up to our expectations.
This is not to say that all whacking is always bad (maybe a little highly
selective poisoning can be, on occasion, useful), nor is all restoration
ill-advised. But it is to say that more restraint in both areas is needed,
and our track-record is spotty. We should start by paying attention to what
the feedback loops are trying to tell us about consequences and the
righteousness of our goals going without honest examination.
WT
----- Original Message -----
From: "Jeff Houlahan" <[email protected]>
To: <[email protected]>
Sent: Saturday, June 11, 2011 4:18 PM
Subject: Re: [ECOLOG-L] EcoTone: Speaking of species and their origins
Hi all, not that Esat needs me to defend him but the list of species that
can be 'googled' and identified as invasive scourges is, I suspect,
longer than the list that actually are scourges. One of the species that
was identified in Amyarta's list, purple loosestrife, is a classic
example. You can go to hundreds of websites that will identify it as a
species that competitively excludes native plant species and causes local
extirpations. The empirical evidence to support this claim is almost
non-existent (or was a couple of years ago when I checked last). There
have been several reviews done on the topic and most conclude that there
is little evidence that loosestrife causes extinctions at almost any
scale. This isn't to suggest that invasives are never a problem but my
understanding of the literature is that there is lots of evidence of
extinctions caused by invasive predators and relatively little evidence
of extinctions caused by competitive exclusion (zebra mussels are
probably an exception to that general statement). I don't think it's a
bad idea to actually step back and see if the investment in controlling
invasive species is warranted.
Jeff Houlahan
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