Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chapter 6
Lecture
Outline
Learning Outcomes
After studying this chapter, you should be able to answer the following
questions:
• What portion of the world’s original forests remain?
• What activities threaten global forests? What steps can be
taken to preserve them?
• Why is road construction a challenge to forest conservation?
• Where are the world’s most extensive grasslands?
• How are the world’s grasslands distributed, and what
activities degrade grasslands?
• What are the original purposes of parks and nature
preserves in North America?
• What is a wilderness? Why are wilderness areas both
important and controversial?
• What are some steps to help restore natural areas?
6-2
What a country chooses to save is what a
country chooses to say about itself.
–Mollie Beatty, former director, U.S. Fish
and Wildlife Service
6-3
6.1 World Forests
• Forests and grasslands together occupy almost 60 percent of global land
cover.
• These ecosystems provide many of our essential resources.
• They also provide essential ecological services.
6-4
Boreal and tropical forests are most abundant
• Old-growth forests are those that cover a large
enough area and have been undisturbed by
human activities long enough that trees can live
out a natural life cycle.
• Some of the world’s most biologically diverse
regions are undergoing rapid deforestation,
including Southeast Asia and Central America.
• Forests are a huge carbon sink, storing some 422
billion metric tons of carbon in standing biomass.
6-5
Forests provide many valuable products
• Wood plays a part in
more activities of the
modern economy than
does any other
commodity.
6-6
Tropical forests are being cleared rapidly
Causes of deforestation
6-7
Forest protection
• About 12 percent of all world forests are in
some form of protected status, but the
effectiveness of that protection varies greatly.
• Costa Rica has one of the best plans for forest
guardianship in the world.
• Attempts are being made there not only to
rehabilitate the land (make an area useful to
humans) but also to restore the ecosystems to
naturally occurring associations.
6-8
Debt-for-nature swaps
• Banks, governments, and lending institutions now hold
nearly $1 trillion in loans to developing countries.
• There is little prospect of ever collecting much of this
debt, and banks are often willing to sell bonds at a
steep discount—perhaps as little as 10 cents on the
dollar.
• Conservation organizations buy debt obligations on the
secondary market at a discount and then offer to
cancel the debt if the debtor country agrees to protect
or restore an area of biological importance.
6-9
Temperate forests also are at risk
• Many endemic species,
such as the northern
spotted, are so highly
adapted to the unique
conditions of these
ancient forests that they
live nowhere else.
• Less than 10 percent of
old-growth forest in the
United States remains
intact.
6-10
Harvest methods
• Most lumber and pulpwood in the United States and Canada
currently are harvested by clear-cutting, in which every tree
in a given area is cut, regardless of size.
6-11
Should we subsidize logging
on public lands?
• People in the U.S. are calling for an end to all logging
on federal lands because ecological services, from
maintaining river levels for fish and irrigation to
recreation, generate more revenue at lower costs.
• Many communities depend on logging jobs, but
these jobs depend on subsidies.
• The federal government builds roads, manages
forests, fights fires, and sells timber for less than the
administrative costs of the sales.
6-12
Fire management
6-13
Ecosystem management
• Ecosystem management is an U.S. Forest Service policy that
attempts to integrate sustainable ecological, economic, and
social goals in a unified, systems approach.
6-14
6.2 Grasslands
• Grasslands, chaparral, and open woodlands
are attractive for human occupation, so they
frequently are converted to cropland, urban
areas, or other human-dominated landscapes.
• Worldwide the rate of grassland disturbance
each year is three times that of tropical forest.
• Desertification is the process of conversion of
once fertile land to desert.
6-15
Overgrazing threatens many rangelands
6-16
Some biomes are relatively
unprotected.
6-17
6.3 Parks and Preserves
6-18
Marine ecosystems
need greater protection
6-19
Conservation and economic
development can work together
• Ecotourism is
tourism that is
ecologically and
socially sustainable.
6-20
Species survival can depend
on preserve size and shape
6-21
Landscape Ecology
• A science that examines
the relationship
between spatial
patterns and ecological
processes
6-22
Practice Quiz
1. What do we mean by closed-canopy forest and old-growth
forest?
2. What land use is responsible for most forest losses in Africa?
In Latin America? In Asia? (fig. 6.7).
3. What is a debt-for-nature swap?
4. Why is fire suppression a controversial strategy? Why are
forest thinning and salvage logging controversial?
5. What portion of the United States’ public rangelands are in
poor or very poor condition due to overgrazing? Why do some
groups say grazing fees amount to a “hidden subsidy”?
6-23
Practice Quiz continued…
6. What is rotational grazing, and how does it mimic natural
processes?
7. How do the size and design of nature preserves influence their
effectiveness? What do landscape ecologists mean by interior
habitat and edge effects?
8. What percentage of the earth’s land area has some sort of
protected status? How has the amount of protected areas
changed globally (fig. 6.18)?
9. What is ecotourism, and why is it important?
10. What is a biosphere reserve, and how does it differ from a
wilderness area or wildlife preserve?
6-24