Environmental Engineering Reference
In-Depth Information
acinth macaw smuggled out of Brazil. During its life-
time, a single macaw left in the wild might yield as
much as $165,000 in tourist income. A 1992 study sug-
gested that keeping a pet bird indoors for more than
10 years doubles a person's chances of getting lung
cancer from inhaling tiny particles of bird dander.
Other wild species whose populations are de-
pleted because of the pet trade include amphibians,
reptiles, mammals, and tropical fish (taken mostly
from the coral reefs of Indonesia and the Philippines).
Divers catch tropical fish by using plastic squeeze bot-
tles of cyanide to stun them. For each fish caught alive,
many more die. In addition, the cyanide solution kills
the coral animals that create the reef, which is a center
for marine biodiversity.
Things do not have to be this way. Pilai Poonswad
decided to do something about poachers taking horn-
bills—large, beautiful, and rare birds—from a rain for-
est in Thailand. She visited the poachers in their vil-
lages and showed them why the birds are worth more
alive than dead. Today, some ex-poachers are earning
much more money by taking eco-tourists into the forest
to see these magnificent birds. Because of
their vested financial interest in preserv-
ing the hornbills, they help protect them
from poachers.
Some exotic plants, especially or-
chids and cacti, are endangered because
they are gathered (often illegally) and
sold to collectors to decorate houses, of-
fices, and landscapes. A collector may
pay $5,000 for a single rare orchid. A ma-
ture crested saguaro cactus can earn cac-
tus rustlers as much as $15,000.
Clearly, collecting exotic pets and
plants kills large numbers of them and
endangers many of these species and oth-
ers that depend on them. Are such collec-
tors lovers or haters of the species they
collect? Should we leave most exotic
species in the wild?
may bring about rapid climate change during this cen-
tury. This could change the habitats of many species
and accelerate the extinction of some species.
Pollution threatens populations and species in a
number of ways. Unintended effects of pesticides
threatens some species with extinction. According to
the U.S. Fish and Wildlife Service, each year pesticides
kill about one-fifth of the United States' beneficial hon-
eybee colonies, more than 67 million birds, and 6-14
million fish. They also threaten one-fifth of the coun-
try's endangered and threatened species.
During the 1950s and 1960s, populations of fish-
eating birds such as the osprey, cormorant, brown peli-
can, and bald eagle plummeted. A chemical derived
from the pesticide DDT, when biologically magnified
in food webs (Figure 9-16), made the birds' eggshells
so fragile they could not reproduce successfully. Also
hard hit were such predatory birds as the prairie fal-
con, sparrow hawk, and peregrine falcon, which help
control rabbits, ground squirrels, and other crop
eaters.
Good news:
Since the U.S. ban on DDT in 1972,
most of these species have made a comeback.
DDT in fish-eating
birds (ospreys)
25 ppm
DDT in large
fish (needle fish)
2 ppm
DDT in small
fish (minnows)
0.5 ppm
DDT in
zooplankton
0.04 ppm
DDT in water
0.000003 ppm,
or 3 ppt
Science: Climate Change
and Pollution
Projected climate change and exposure
to pollutants such as pesticides can
threaten some species with premature
extinction.
In the past, most natural climate changes
have taken place over long periods of
time—giving species more time to adapt
or evolve into new species to cope with
the change. Considerable evidence indi-
cates that human activities such as green-
house gas emissions and deforestation
Figure 9-16
Natural capital degradation:
bioaccumulation
and
biomagnification.
DDT is a fat-soluble chemical that can accumulate in the fatty tissues of animals. In a
food chain or web, the accumulated DDT can be biologically magnified in the bodies
of animals at each higher trophic level. The concentration of DDT in the fatty tissues of
organisms was biomagnified about 10 million times in this food chain in an estuary near
Long Island Sound in New York. If each phytoplankton organism takes up from the water
and retains one unit of DDT, a small fish eating thousands of zooplankton (which feed
on the phytoplankton) will store thousands of units of DDT in its fatty tissue. Each large
fish that eats 10 of the smaller fish will ingest and store tens of thousands of units, and
each bird (or human) that eats several large fish will ingest hundreds of thousands of
units. Dots represent DDT, and arrows show small losses of DDT through respiration
and excretion.
