Hi, Melissa.

I doubt if anyone disagrees with your post on invasive species. I
hope you understand that those of us who are criticizing the
activities of some agencies at some times have quite good reasons for
doing so. I'm vehement and outspoken against introducing non-native
species, but they often provide the only habitats available in areas
that would otherwise be wastelands - fallow agricultural fields, for
example, where none of the original native vegetation is present,
often where there are no propagules to revegetate with natives.

The clearing of Casuarinas and other non-natives at the Dry Tortugas
was not followed by revegetation with native trees, although I'm sure
on Loggerhead Key native shrubs did better when the Australian pines
were gone. The fact that the NPS was considering taking out large
broadleaf ornamental trees from Garden Key, none of them invasive or
troublesome species, gave me the clue of their know-nothing adherence
to protocol, in at least that case.

The success of Russian olives in the Columbia Basin is in large part
due to their colonizing areas that were cleared of the original shrub-
steppe vegetation and where the water table has risen sufficiently
that shrub-steppe vegetation would probably not recolonize, but
instead a weedy mixture of rabbitbrush (a native "weed") and exotic
grasses and forbs would have prevailed. Russian olives are a distinct
improvement.

Many of the invasives being discussed have invaded these already
highly disturbed area; some of them are successful only in such
areas. The answer is, of course, to leave the original native
habitats undisturbed!

All I and others are calling for is some good sense, I think, which I
believe is your message also. ;-)

Dennis
-----
Dennis Paulson
1724 NE 98 St.
Seattle, WA 98115
206-528-1382
-----
Date: Tue, 4 Apr 2006 17:05:28 -0700
From: "MELISSA WILLOUGHBY" <mawilloughby1 at comcast.net>
Subject: [Tweeters] RE: range expansions - invasive species
To: <tweeters at u.washington.edu>
Message-ID:
<mailman.0.1144263602.15540.tweeters at mailman1.u.washington.edu>
Content-Type: text/plain; charset="us-ascii"

Hi Tweets-
On the issue of invasives creating habitat for certain species...

Yes, this is a very complicated issue. But please everyone keep in mind
that when non-native species invade a habitat, they eliminate the
original
diversity of plant and animal life. The new crop of invasive plants
may add
habitat for some species, but they certainly take away habitat for
others.
Original animals and birds are squeezed out. Others move in that can
adapt
to the change. Many of those are other non-native species.

This is a tough issue because it is hard to determine when human
intervention is a good thing and when we should let nature take its
course.
I don't think it is unfortunate that our land management agencies are
taking
a stand to help habitats control invasion from non-natives. This is
happening because over time we have learned that when we do nothing,
invasives can take over to a state beyond any control.

While nothing taken in extremes is a good thing - I don't think our
agencies
are saying if it isn't native take it out. Habitat restoration is
happening
is small, planned segments of targeted areas where we think we can
make a
difference. They are doing this to save habitat for native species -
which
I'm sure we all enjoy.

While I agree that judging when to intervene is complicated - I just
don't
agree that it's a good thing to let invasives (brought here mostly by
human
mistake - read "Tinkering with Eden - A Natural History of Exotic
Species in
America" by Kim Todd) run rampant.

Happy spring birding-
Melissa Willoughby
Seattle

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