Dennis the knowledgable sez:

>Finally, as far as people and dog control, when the pond system becomes
>extensive enough, how about throwing in a few big alligators?

Being from Portland, I haven't found this thread all that interesting,
other than the fact that we face similar issues with areas in PDX.

Paulson's sentence above makes the entire thread more than
worthwhile!

Aren't crocs more effective at people control, though? Maybe
not our native crocs. Much like gambusia, I imagine importing
Nile crocs would have unforseen environmental effects, unfortunately.
Also, in this case the pests vote.

This thread makes me even more appreciative of our two largely undeveloped
"wet spots" - Oaks Bottom and Smith & Bybee lakes. Oaks Bottom is
heavily used by joggers, and many folks bring their dogs. The
place is so big and wet, though, that the dogs generally stay
on trails or nearby. There is good isolation for many of the
areas used by waterfowl and heron.

I was out there with the EPA wetlands ecologist who works with
the city on managine the area and he was showing me areas
which were absent of canary reedgrass. Apparently dependent
on very subtle changes in soil moisture due to very subtle
depressions in what we call the north fill. This was last
year, and there are plans to try some active management
to see if they can replicate conditions to drive some of
the canary grass stuff out (these areas also had quite
a selection of native plants normally choked out by the canary
grass). There is no illusion that more than small areas
can be cleared in this manner, but it would help maintain
a little diversity of native plants.

There's also been good success managing mosquito populations
by managing water levels in this area, and PDX management
is progressive enough to have decided to take this approach
rather than using chemicals.

The plan involved building a "water control structure" (you
and I would call it a "dam"). It got delayed for two years
for funding reasons, but I didn't realize it as the area's
water level became stabilized even without the dam.

Eventually I learned that beaver had come in and did the job
for the city, for free. They didn't quite get the water levels
exactly right, though, and the city got the money and built
the "real" dam. The beavers apparently didn't like the
new management regime, and continued for quite some time to
impose their own thinking on water management by building
a bigger dam.

- Don Baccus, Portland OR <donb at rational.com>