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C05_006A
NJ
PA
NY
CT
MA
ATLANTIC OCEAN
Croton
Aqueduct
New York City
Long Island
Sound
East Delaware
Aqueduct
West Delaware
Aqueduct
Catskill/Delaware
Watersheds
Catskill
Aqueduct
Croton
Watershed
Delaware
Aqueducts
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20 mi
Dennis Flaherty/Photodisc/Getty Images
It is difficult to attach an economic value to the
services that a healthy biosphere provides.
However, some scientists and economists have
attempted to do just that. In the 1990s, New
York City was faced with the decision of how to
improve the quality of its drinking water. A
large percentage of New York City’s drinking
water was supplied by watersheds, as shown in
Figure 7
. Watersheds are land areas where the
water on them or the water underneath them
drains to the same place. The Catskill and
Delaware watersheds did not meet clean water
standards and no longer could supply quality
drinking water to the city.
The city was faced with two choices: build a new
water filtration system for more than
$
6 billion
or preserve and clean up the watersheds for
approximately 1.5 billion dollars. The economic
decision was clear in this case. A healthy
ecosystem was less expensive to maintain than
using technology to perform the same services.
This example shows that nature can provide services, such as water that is safe for human con-
sumption, at less expense than using technology to provide the same service. Some scientists
think the natural way should be the first choice for providing these services. Research indicates
that when healthy ecosystems are preserved, the services the ecosystems provide will continue to
be less expensive than performing the same services with technology.
Aesthetic and scientific values
Biodiversity and healthy ecosystems have aesthetic and scientific values. Sustaining biodiversity
helps humanity by preserving landscapes of recreational or inspirational value, such as the
ecosystem shown in
Figure 8
.
Figure 7
New York City’s drinking water is supplied by the
Catskill and Delaware watersheds.
Infer
What types of human activities could affect a watershed
and decrease its water quality?
Figure 8
This photo of Lake Tahoe’s Emerald Bay shows the aesthetic value of preserving the environment.
Lesson 1 • Biodiversity
103