Environmental Engineering Reference
In-Depth Information
decrease in the earth's biodiversity as a result of our
activities.
To these biologists, we are not heeding Aldo
Leopold's warning about preserving biodiversity as
we tinker with the earth: “To keep every cog and wheel
is the first precaution of intelligent tinkering.”
Characteristic
Examples
Low reproductive rate
(K-strategist)
Blue whale, giant panda,
rhinoceros
Specialized niche
Blue whale, giant panda,
Everglades kite
Narrow distribution
Many island species,
elephant seal, desert pupfish
Learn more about how growing food, cutting trees, and
other human activities affect biodiversity at Environmental
ScienceNow.
Feeds at high trophic
level
Bengal tiger, bald eagle,
grizzly bear
Fixed migratory patterns
Blue whale, whooping crane,
sea turtles
9-2
IMPORTANCE OF WILD SPECIES
Rare
Many island species,
African violet, some orchids
Science and Economics: Why Should We
Preserve Wild Species?
We should not cause the premature extinction of
species because of the economic and ecological
services they provide.
So what is all the fuss about? If all species eventually
become extinct, why should we worry about losing a
few more because of our activities? Does it matter that
the passenger pigeon, the remaining organutans (Fig-
ure 8-4, p. 157), or some unknown plant or insect in a
tropical forest becomes prematurely extinct because of
human activities?
New species eventually evolve to take the place of
ones lost through extinction spasms, mass depletions,
or mass extinctions (Figure 4-10, p. 74). So why should
we care if we speed up the extinction rate over the next
50-100 years? Because it will take at least 5 million years
for natural speciation to rebuild the biodiversity we are
likely to destroy during this century!
Conservation biologists and ecologists say we
should act now to prevent premature extinction of
species because of their instrumental value based on
their usefulness to us in the form of economic and eco-
logical services (see top half of back cover). For exam-
ple, some species provide economic value in the form
of food crops, fuelwood and lumber, paper, and medi-
cine (Figure 9-6).
Another instrumental value is the genetic informa-
tion in species that allows them to adapt to changing
environmental conditions and to form new species.
Genetic engineers use this information to produce
new types of crops (Figure 4-11, p. 75) and foods as
well as edible vaccines for viral diseases such as he-
patitis B. Carelessly eliminating many of the species
making up the world's vast genetic library is like
burning topics before we read them. Wild species also
provide a way for us to learn how nature works and
sustains itself.
The earth's wild plants and animals also provide
us with recreational pleasure.
Commercially valuable
Snow leopard, tiger,
elephant, rhinoceros,
rare plants and birds
Large territories
California condor, grizzly
bear, Florida panther
Figure 9-4 Characteristics of species that are prone to ecologi-
cal and biological extinction.
34% (51% of freshwater species)
Fish
24%
Mammals
20%
Reptiles
14%
Plants
12%
Birds
Figure 9-5 Endangered natural capital: percentage of
various types of species threatened with premature extinction
because of human activities. (Data from World Conservation
Union, Conservation International, and World Wildlife Fund)
At the same time, they point to clear evidence that
human activities have increased the rate of species ex-
tinction and that this rate is likely to rise. According to
these biologists, arguing over the numbers and wait-
ing to get better data and models should not be used as
excuses for inaction. They call for us to implement a
precautionary strategy now to help prevent a significant
Each year, Americans
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