Geography Reference
In-Depth Information
Chapter 18
Impacts on the
Environment
In This Chapter
Linking the parts of ecology
Messing up a planet in so many ways
Turning small problems into big ones
Making decisions that matter
T he Chesapeake Bay is the largest estuary (an inlet where the salty tide meets freshwater current) in
the United States and perhaps the most economically important one, too. The greatest source of oysters
in the U.S., Chesapeake Bay is also the world leader in blue crab production. Striped bass, perch, shad,
flounder, and a host of other species help comprise this historically rich and robust fishery. So, natur-
ally, it's rather disturbing when fish by the thousands suddenly turn up dead.
The immediate culprits are algae, tiny aquatic plants that takes in oxygen from the water. Occasionally,
algae reproduces by the gazillions, creating algal “blooms” that deplete oxygen over large portions of
the Bay and suffocate large numbers of fish. These blooms are caused by periodic build-up of phos-
phate and nitrate in the water. Algae, it seems, just love these substances, and reproduce like crazy in
their presence.
That, of course, leads one to inquire into the origins of the bloom-producing chemicals. The Bay is not
an isolated body of water. Instead, rain and runoff connect it with a broad land expanse (see Figure
18-1). The phosphates originate mainly in sewage treatment plants that empty into rivers and streams
that empty in turn into the Bay. Nitrates originate mainly in agricultural fertilizers that run off from
farms into the same Chesapeake tributaries. Indeed, virtually hundreds of watercourses from six states
drain into the Chesapeake, collecting phosphates and nitrates from many, many sources along the way.
Maybeyou'resaying,“OK,butwhatdoesthishavetodowithgeography?Thissoundstomemorelike
chemistry or biology.” Geography is concerned with human and natural phenomena that give charac-
ter to different parts of Earth's surface. Often, of course, important characteristics that we observe in a
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