Biology Reference
In-Depth Information
ers grew so concerned about the rock-bottom populations of all four of
these species between 2002 and 2005 that they gave the phenomenon a
name—Pelagic Organism Decline (POD)—and assigned a bevy of scien-
tists to pinpoint the causes and a bevy of engineers to suggest some fixes.
For Delta Smelt, however, it may be too late. The POD involves multi-
ple species in a highly variable and heavily modified environment with
multiple and often interacting stressors. As scientist Andrew Cohen put it:
“It's the idea of the perfect storm, a number of things come together and
give you something that's beyond all imagining in terms of impact from
individual causes. It tells us something about the difficulty of trying to
manage these systems. With so much uncertainty, we need to really com-
mit to adaptive management, and continually reassess and rethink
whether and how we should proceed.”
At the end of the twentieth century, many of the military bases lining the
bay closed and returned their shorelines to the people. Large, formerly
walled-off parts of the shoreline were opened up to the public. People
began visiting the bay not just to shoot ducks or dry shrimp, but to walk
dogs, fish off a pier, paddle a kayak, or watch birds.
From these new access points to the bay, anyone who has seen the re-
gion change over the past 20 years knows the water is getting cleaner and
clearer, and the shorelines prettier. Many more people take to the water to
swim, surf, sail, or board, and parents take their children to splash in the
knee-high waves without a second thought. Few get sick from sewage con-
tamination in the bay, and if a spill or a storm compromises water quality,
state and local authorities now post helpful warnings. Between 2005 and
2009, the average number of Bay Area beach closures for Alameda, San
Francisco, and San Mateo counties combined was about 30 per year, and
the number of postings 200, according to the state authorities.
Every few years, The Bay Institute issues an ecological scorecard called
the San Francisco Index. The index uses more than 36 science-based indi-
cators to grade the condition of San Francisco Bay and the effects of
human uses on its health. Among other things, the scorecard recently gave
the bay a grade of B- for water quality, an F for food web health, and a C-
for stewardship due to little perceived progress in conserving water, reduc-
ing pesticide use, and restoring freshwater flows.
The bay also earned a C- for a special index called “fishable-swim-
mable-drinkable.” The index combines measurements of the fishing suc-
cess of recreational anglers, the edibility of the fish caught (essentially a
