Geography Reference
In-Depth Information
and sanitize our cities. For ei ciency and safety, they have been straight-
ened, armored, levied, buried, rerouted, and dammed. Out of laziness or
carelessness, they have been overharvested and polluted. Lakes and ponds
may be drained in the name of disease management or valued as urban ameni-
ties to be treated, tamed, and manicured into submission. Fish and inverte-
brate diversity typically declines.
The city of Sydney, Australia, is well known for its beautiful harbor. The
iconic opera house, with its roof sails mirroring the sails of yachts, seems to
symbolize the connection of city and water. But beneath the surface of that
water, one can see how the city's development has compromised the harbor's
life. The diversity of i shes and invertebrates is stunning but reduced by
some 16 percent relative to undeveloped harbors. Seawalls have replaced a
more gradual and sandy shore once rimmed with seagrass l ats. As a result,
seahorse populations have plummeted, many now garnering endangered spe-
cies protection. The seawall itself supports a rich variety of marine invertebrates
that i lter microscopic life from the water, graze on algae, or prey on larger fare.
Barnacles, tubeworms, oysters, and mussels are here, but the gastropod,
whelk, stari sh, and crab communities have been simplii ed. Sea urchins and
octopuses have been excluded because the cracks and crevices they require
do not exist in the smooth wall. A variety of natural and manufactured reefs
provide necessary cover, and where encrusted with mussels and algae, food
for i sh. Small i sh, such as damseli shes and wrasses, abound near pilings
and pontoons. Wrecks foster a diversity of larger i sh as well. Though af ected
by the city, the Sydney harbor's marine web of life is embracing its new urban
structures.
The i sh in North American lakes are less impressed with city life than the
mollusks of Sydney. The growth rates on developed lakes of some favorite game
i sh—bluegill, largemouth bass, and trout—are about one-third of those on un-
developed lakes. The reasons for the growth slowdown are pretty obvious, and
