thanks for an informative post. Let me clarify one of my previous points,
>For a hypothetical example, suppose that a certain species of fish >existed
>only in the Los Angeles River and in order to restore it you >would have to
>move 10 million plus people out of the basin.
It's not such a hypothetical example. There's plenty of taxa found in close
proximity to urban areas. There's also no reason why we can't (and
shouldn't) maintain functioning hydrological systems even in said "urban
environments." The biggest problem facing the Los Angeles River is the
almost total revetment of the channel- it's nearly totally covered under
concrete or has a concrete channel. Depending on what the species in
question might be, it might be possible to do the following:
- reduce the area of "impermeable surfaces" in the basin. Concrete doesn't
store water, plus it gets really hot. When they DO get rain events, the
water is heated and enters channels very rapidly. It's possible to ameliate
these effects by replacing concrete parking lots with gravel or earth, by
designing shaded catchments into storm drain areas, by buffering rooftops
and parking lots with planted areas, etc.
Of course this requires public awareness- in the Chesapeake Bay system,
they've accomplished this by painting "Chesapeake Bay Drainage" on all of
the storm drains (so people aren't as likely to dump chemicals down them),
and by a huge education program, includiong signs at the watershed divides
urging folks to maintain a clean environment.
-restore natural substrates in the channel- which of course won't do a lot
of good unless you can reduce storm flows in the basin.
-keep headwaters as "watershed preservation areas," which will both increase
the amount of water available for LA to use for public consumption, as well
as leaving some for wildlife.
Of course there will be problems, and naysayers complaining about how "the
Govt is just keeping me down, telling me I can't use MY water the way I want
to..." That's to be expected. Maintaing and restoring hydrological systems
to as natural a state as possible doesn't just preserve habitat for rare
fish, it also raises awareness in keeping ECOSYSTEMS intact. This is the
key- for every native fish that goes extinct, there's probably 50 native
stream invertebrates that get wiped out, that DONT get the publicity, and
people generally don't want to try and keep THEM in tanks (well, except Moon
Biodiversity isn't just about birds, or mammals, or fish.
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