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Chapter 23: Sustaining
Terrestrial Biodiversity
How is Land Used?
No nation has set aside as much land–
about 42%--for public use, resource
extraction, enjoyment and wildlife as
the United States.
and pasture
Major types of U.S. Public Lands
Multiple Use Lands
• National Forest System—used for logging,
mining, livestock grazing, farming, oil and gas
extraction, recreation, sport hunting, fishing,
and conservation.
Moderately Restricted-Use Lands
• National Wildlife Refuges—protest habitats
and breeding areas for waterfowl and big
game, provide game for hunting. Some
activities from above permitted on a limited
Restricted-Use Lands
• National Park System—camping, hiking,
sport fishing, and boating.
How should public land be
Most conservation biologists believe
the following should be followed:
• Protect biodiversity and wildlife
• No tax breaks for extracting resources
• Public get fair compensation for use of
their property
• Users be responsible for
environmental damage.
Managing Forest
Economic Important of Forests
• Fuel wood (50% of global use)
• Industrial timber and lumber
• Pulp and paper
• Medicines
• Mineral extraction and recreation
Managing Forests
Types of Forest:
• Old-growth (virgin) forest—have not
been seriously disturbed by human
activities for a least several hundred
• Second-growth forest –stands of trees
resulting from secondary succession
• Tree plantations—tree farms:
managed tracts of uniformly aged
trees of one species.
Layers of
in a Douglas
Types of Forest Management
Even-aged Management—also called
industrial forestry and tree plantation
replaces a diverse forest with one or
two fast-growing species that can be
harvested every 6-100 years.
Uneven-aged Management—
maintaining a variety of tree species.
Harvested by selective cutting of
individual trees.
How are Trees harvested?
The first step in forest management is to build
roads for access. Even with careful design,
logging roads have a number of harmful
• Increased erosion
• Habitat fragmentation
• Pathways for exotic species
• Accessibility for humans
Selective Cutting
Intermediate-aged or mature trees are
cut singly in an uneven-aged forest.
Shelterwood Cutting
Removes all mature trees in two or
three cuttings over a period of about
10 years.
Seed-tree Cutting
Harvest nearly all trees in one cutting,
leaving a few seed-producing trees to
regenerate the stand.
Clear Cutting
Remove all trees from an area in a
single cutting.
Strip Cutting
A variation of clear cutting—cutting a
strip of trees narrow enough to allow
natural regeneration. Then cutting
other strips over several decades.
Sustainable Forestry
• Longer rotations between cuttings
• Selective or strip cutting
• Minimize fragmentation
• Improve road building techniques
• Certify trees sustainably grown
Forest Pathogens
Insect Pests
• Bark beetles—bore channels through layer
beneath the bark of conifers
• Spruce budworm and gypsy moth larvae—
introduced from Europe—kill trees by
consuming foliage needed for
• Hemlock woolly adelgid—introduced
from Asia, now controlled by a beetle
from Japan. Feeds by sucking sap from
hemlock trees.
Parasitic Fungi
• Chestnut blight—introduced from
China—killed almost all American
chestnut trees. Until the early 1950s ,
the largest most impressive tree in the
eastern United States forest was the
American chestnut.
• Dutch Elm disease—from Asia by way
of Europe.
• White pine blister rust—from Europe
Affects of Fires
Fires are important to maintain certain
• Savanna
• Temperate grasslands
• Chaparral
• Southern pine forest
• Sequoia trees
Types of Fires
Surface Fires—burn only
undergrowth, occasional surface fires
stimulate the germination of certain
tree seeds and help maintain the
Crown Fires—may start on the ground
but eventually burn whole trees.
Usually occur in area that have had no
surface fires for decades. These fires
destroy most vegetation, kill wildlife,
and increase soil erosion.
Fig. 23-17 p. 607
Forest Resources:
• Habitat for threatened and
endangered species
• Water purification
• Recreation
• Timber harvest
Tropical Deforestation
• Rapid and increasing
• Loss of biodiversity
• Cultural extinction
• Unsustainable
agriculture and ranching
• Commercial logging
• Fuel wood
Reducing Tropical Deforestation
• Identification of critical ecosystems
• Reducing poverty and population growth
• Sustainable tropical agriculture
• Protection of large tracts of land
• Less destructive timber harvesting methods
National Parks
Worldwide about 1100 national parks larger than 10
sq. km. (4 sq. miles).
The U. S. national park system, established in 1912
has 55 national parks, most of them in the west.
Problems Managing National
• Most are too small to maintain biodiversity
• Invasion by exotic species
• Too popular—too many visitors, traffic jams, noise,
and air pollution
Social principles useful in establishing, managing, and
protecting reserves:
• Include local people in the planning and design
• Create user-friendly reserves that allow local people to
use a surrounding buffer-zone for sustainable timber
cutting, livestock grazing, hunting, and fishing.
Areas of Top Priority
Prevention strategy—designed to reduce the
future loss of biodiversity. Establishing a variety of
reserves in the world’s most biodiverse countries.
Emergency action—identifies and quickly protects
biodiversity hot spots—Areas especially rich in
plant and animal species that are found nowhere
else in great danger of extinction.
Ecological Restoration
Rehabilitation—any attempt to restore at least some
of a degraded system’s natural species and ecosystem
functions. Such as removing pollutants and replanting
Replacement—replacing a degraded ecosystem with
another type of ecosystem. Such as replacing a
degraded forest with a pasture or tree plantation.
Creating artificial ecosystems