Environmental Engineering Reference
In-Depth Information
Biodiversity researchers and a growing number of
foresters have called for more sustainable forest man-
agement. Figure 8-15 lists ways to achieve this goal.
Currently, forests are valued mostly for their eco-
nomic services (Figure 8-7, right). But suppose we took
into account the estimated monetary value of the eco-
logical services provided by forests (Figure 8-7, left).
According to a 1997 appraisal by a team of ecologists,
economists, and geographers—led by ecological econ-
omist Robert Costanza of the University of Vermont—
the world's forests provide us with ecological services
worth about $4.7 trillion per year—hundreds of times
more than the economic value of forests. The re-
searchers noted that their estimates could easily be too
low by a factor of 10 to 1 million or more because their
calculations included only estimates of the ecosystem
services provided by forests themselves, not the nat-
ural capital that generates them.
Based on this accounting system, most of the
world's old-growth and second-growth forests should
not be clear-cut. Instead, their ecological services
could be sustained indefinitely by selectively harvest-
ing trees no faster than they are replenished and by
using them primarily for recreation and as centers of
biodiversity.
According to ecological economist Robert Cost-
anza, “We have been cooking the topics for a long time
by leaving out the worth of nature.” Biologist David
Suzuki warns, “Our economic system has been con-
Natural Capital Degradation
Deforestation
• Decreased soil fertility from erosion
• Runoff of eroded soil into aquatic systems
•P emature extinction of species with
specialized niches
• Loss of habitat for migratory species such as
birds and butterflies
• Regional climate change from extensive clearing
• Releases CO
2
into atmosphere from burning
and tree decay
• Accelerates flooding
Figure 8-14
Natural capital degradation:
harmful environ-
mental effects of deforestation that can reduce the ecological
services provided by forests.
Critical thinking: what are the di-
rect and indirect effects of your lifestyle on deforestation?
rate of 0.3-0.8% per year, with much higher rates in
some areas. More than four-fifths of these losses took
place in the tropics. According to the WRI, if current
deforestation rates continue, about 40% of the world's
remaining intact forests will have been logged or con-
verted to other uses within 10-20 years, if not sooner.
There are also two encouraging trends.
First,
the
total area occupied by many temperate forests in North
America and Europe has increased slightly because of
reforestation from secondary ecological succession on
cleared forest areas and abandoned croplands.
Second,
some of the cut areas of tropical forest dis-
play increased tree cover from regrowth and planting
of tree plantations. But ecologists do not believe that
tree plantations, which have much lower biodiversity,
should be counted as forest any more than croplands
should be counted as grassland. According to ecologist
Michael L. Rosenzweig, “Forest plantations are just
cornfields whose stalks have gotten very tall and
turned to wood. They display nothing of the majesty
of natural forests.”
Solutions
Sustainable Forestry
• Conserve biodiversity along with water and soil
resources
• Grow more timber on long rotations
• Rely more on selective cutting and strip cutting
• No clear-cutting, seed-tree, or shelterwood cutting on
steeply sloped land
• No fragmentation of remaining large blocks of forest
• Sharply reduce road building into uncut forest areas
• Leave most standing dead trees and fallen timber for
wildlife habitat and nutrient recycling
Solutions: Managing Forests
More Sustainably
We can use forests more sustainably by
emphasizing the economic value of their
ecological services, harvesting trees no faster than
they are replenished, and protecting old-growth and
vulnerable areas.
• Certify timber grown by sustainable methods
• Include ecological services of trees and forests in
estimating economic value
Figure 8-15
Solutions:
ways to manage forests more
sustainably.
Critical thinking: which two of these solutions do
you believe are the most important?
