Biology Reference
In-Depth Information
ers, flame retardants, and other chemicals off the landscape and into wa-
terways and estuaries.
“What people forget is that the bay is at the bottom of all of it; it's the
terminus of all the activity going on in the Sacramento-San Joaquin wa-
tershed,” says Hoenicke. “All these interconnected waterways and land-
scapes drain into the bay.”
Most of the runoff management momentum came from cities. In the
latter half of the twentieth century, the volume of runoff pollutants had
risen at an alarming rate due to new home construction, urban expansion,
and the paving of more roads and driveways. Curbing these inputs is a
matter of public education more than anything else. Most Bay Area resi-
dents have since seen or heard a message via billboard or radio urging
them to use biodegradable products to wash cars or spray weeds, or to
take old paints and motor oil to collection sites rather than pouring them
down a nearby storm drain.
Getting farmers to keep fertilizers and pesticides out of irrigation
drainage proved more difficult. Agricultural runoff not only conveys
chemicals sprayed and sprinkled on the farm into the estuary but can also
have unexpected impacts on soils and surrounding ecosystems. In the San
Joaquin Valley, where the soils are naturally laden with salts and selenium,
the long-standing practice of sending runoff through evaporation ponds
concentrated the salts and poisoned the food chain. This practice contrib-
Selenium occurs naturally in Cali-
fornia soils but is toxic at high
concentrations. Selenium from
farm drains accumulated in Kes-
terson Reservoir in the 1980s,
poisoning fish, waterfowl, and
other wildlife. A normal Black-
necked Stilt embryo is shown
above; the one below, hatched at
Kesterson Reservoir, has serious
deformities. Because the invasive
Overbite Clam (
Corbula amurensis
)
also accumulates selenium, it
causes similar problems among
North Bay Diving Ducks and White
Sturgeon, posing a health risk to
human duck and fish eaters.
(Courtesy of the U.S. Fish and
Wildlife Service)
