Environmental Engineering Reference
In-Depth Information
and Greenland). Most of this damage has come from
filling in wetlands and converting grasslands and
forests to crop fields and urban areas. The 2005 UN
Millennium Report, prepared by nearly 1,400 experts,
found that human activities are causing massive dam-
age to the earth's natural capital and laid out common-
sense strategies for protecting the earth's biodiversity.
About 82% of temperate deciduous forests have
been cleared, fragmented, and dominated because
their soils and climate are very favorable for growing
food and urban development. Temperate grasslands,
temperate rain forests, and tropical dry forests have
also been greatly disturbed by human activities.
In the United States, at least 95% of the virgin
forests in the lower 48 states have been logged for lum-
ber and to make room for agriculture, housing, and in-
dustry. In addition, 98% of the tallgrass prairie in the
Midwest and Great Plains has disappeared, and 99%
of California's native grassland and 85% of its original
redwood forests are gone.
Human activities are also degrading the earth's
aquatic biodiversity.
About half of the world's wetlands
(including half of U.S. wetlands) were lost during the
last century. An estimated 27% of the world's diverse
coral reefs have been severely damaged. By 2050, an-
other 70% may be severely damaged or eliminated.
Three-fourths of the world's 200 commercially
valuable marine fish species are either overfished or
fished to their estimated sustainable yield. According
to a 2003 report by the U.S. Commission on Ocean Pol-
icy, about 40% of U.S. commercial fish stocks are de-
pleted or overfished.
Human activities also contribute to the
premature
extinction of species.
Biologists estimate that the current
global extinction rate of species is at least 100 times
and probably 1,000-10,000 times what it was before
humans existed. These threats to the world's biodiver-
sity are projected to increase sharply during the next
few decades.
Figure 8-3 outlines the goals, strategies, and tactics
for preserving and restoring the terrestrial ecosystems
and aquatic systems that provide habitats and re-
sources for the world's species (as discussed in this
chapter) and preventing the premature extinction of
species (as discussed in Chapter 9).
The Ecosystem Approach
The Species Approach
Goal
Goal
Protect species from
premature extinction
Protect populations of
species in their natural
habitats
Strategy
Strategies
Preserve sufficient areas
of habitats in different
biomes and aquatic
systems
•
Identify endangered
species
•
Protect their critical
habitats
Tactics
•
Protect habitat areas
through private purchase
or government action
•
Eliminate or reduce
populations of nonnative
species from protected
areas
•
Manage protected areas
to sustain native species
•
Restore degraded
ecosystems
Tactics
•
Legally protect
endangered species
•
Manage habitat
•
Propagate endangered
species in captivity
•
Reintroduce species into
suitable habitats
Figure 8-3
Solutions:
goals, strategies, and tactics for pro-
tecting biodiversity.
Biodiversity researchers contend that we should act to
preserve the earth's overall diversity because its genes,
species, ecosystems, and ecological processes have
two types of value.
First,
they have
intrinsic value
be-
cause these components of biodiversity exist, regard-
less of their use to us.
Second,
they have
instrumental
value
because of their usefulness to us.
Two major types of instrumental values exist. One
consists of
use values
that benefit us in the form of eco-
nomic goods and services, ecological services, recre-
ation, scientific information, and preserving options
for such uses in the future. The other type consists of
nonuse values.
For example, there is
existence value
—
knowing that a redwood forest, wilderness, or endan-
gered species (Figure 8-4) exists, even if we will never
see it or get direct use from it.
Aesthetic value
is another
nonuse value—many people appreciate a tree, a forest,
a wild species (Figure 8-5), or a vista because of its
beauty.
Bequest value,
a third type of nonuse value, is
based on the willingness of some people to pay to pro-
tect some forms of natural capital to ensure their avail-
ability for use by future generations.
Examine the details on how human activities are threatening
biodiversity around the world at Environmental ScienceNow.
Science, Economics, and Ethics: Why Should
We Care about Biodiversity?
Biodiversity should be protected from degradation by
human activities because it exists and because of its
usefulness to us and other species.
