Sustaining Terrestrial Biodiversity:
The Ecosystem Approach
Chapter 10
10-1 What Are the Major Threats to
Forest Ecosystems?
 Concept 10-1A Forest ecosystems provide
ecological services far greater in value than the
value of raw materials obtained from forests.
 Concept 10-1B Unsustainable cutting and
burning of forests, along with diseases and
insects, are the chief threats to forest ecosystems.
 Concept 10-1C Tropical deforestation is a
potentially catastrophic problem because of the
vital ecological services at risk, the high rate of
tropical deforestation, and its growing contribution
to global warming.
Forests Vary in Their Make-up, Age, and Origins
 Old-growth forest:
Original forests that have
not been disturbed for
logging, road building, or
development
• Sometimes called primary,
ancient, virgin, or primeval
forests
• 36% of world’s forest
• High biodiversity because
of many specialized niches
Forests Vary in Their Make-up, Age, and Origins
Remaining Old-Growth Forests in the U.S.
Forests Vary in Their Make-up, Age, and Origins
Second-growth forest:
 Area which has re-grown after
a major disturbance such as
fire, insect, or timber harvest
 60% of world’s forest
 The area is reclaimed by the
natural process of secondary
succession
• Small shrubs and trees
followed by the larger trees
Forests Vary in Their Make-up, Age, and Origins
 Tree plantation (tree farm):
Planted stands of a particular tree species that are
maintained, harvested, and replanted
• Typically used for paper or particle board
Forests Provide Important Economic and
Ecological Services
Estimated
annual value:
Economic services
$1.8 trillion
Ecological services
$4.7 trillion
Unsustainable Logging is a Major Threat to
Forest Ecosystems
 Building roads into previously inaccessible forests
paves the way for increased erosion, habitat
fragmentation, loss of biodiversity, and invasion by
non-native species.
• For this reason, many federal wilderness areas do
not allow the construction of roads.
Unsustainable Logging is a Major Threat to
Forest Ecosystems
 Three major tree
harvesting methods:
• Selective cutting
• Clear-cutting
• Strip cutting
Unsustainable Logging is a Major Threat to
Forest Ecosystems
 Selective Cutting:
• Mature trees are
harvested individually
from diverse forests
• Younger trees left to
harvest later
• Reduces crowding
• Removes diseased trees
• Encourages growth of
younger trees
Unsustainable Logging is a Major Threat to
Forest Ecosystems
Clear-cutting:
• Removing all trees
in a single pass.
Unsustainable Logging is a Major Threat to
Forest Ecosystems
Clear-cutting
Unsustainable Logging is a Major Threat to
Forest Ecosystems
 Strip-cutting:
• A type of clear cutting that
involves clear trees along
the contours of the land.
• Less erosion
Fire, Insects, and Climate Change Can
Threaten Forest Ecosystems
 Forest fires can either benefit or harm forests
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•
•
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Burn away flammable ground material
Prevent larger, more destructive fires
Release valuable mineral nutrients
Stimulate new forest growth
Fire, Insects, and Climate Change Can
Threaten Forest Ecosystems
 Surface fires
• Usually burn leaf litter and undergrowth
• May provide food in the form of vegetation that sprouts after fire
 Crown fires
• Extremely hot, burns whole trees, jump from treetop to treetop
• Fierce and hard to control
Fire, Insects, and Climate Change Can
Threaten Forest Ecosystems
 Accidental or
deliberate
introduction of
foreign diseases
and insects are
also a major
threat to forests.
We Have Cut Down Almost Half
of the World’s Forests
 Human activities have reduced the earth’s forest cover
by as much as half.
 Deforestation – temporary or permanent removal
of large areas of forests
• Results from unsustainable cutting of trees
 Losses are concentrated in developing countries.
• Use it for fuel – heating and/or cooking
• Tropical forests
• Especially in Latin America, Indonesia, and Africa
• Boreal forests
• Especially in Alaska, Canada, Scandinavia, and Russia
We Have Cut Down Almost Half
of the World’s Forests
Tropical Forests Are Disappearing Rapidly
 Large areas of ecologically and economically
important tropical forests are being cleared and
degraded at a rapid rate.
Tropical Forests Are Disappearing Rapidly
Tropical Forests Are Disappearing Rapidly
 Large areas of tropical forest are
burned to make way for cattle
ranches and crops.
• Soil in the rainforest is very poor
• Farmers burn the trees down to
provide nutrients for the soil
• Heavy rain leaches away the
nutrients so they move to
another area and burn again
Tropical Forests Are Disappearing Rapidly
 At least half of the world’s terrestrial plants and animals live
in tropical rain forests.
 About 2,100 of the 3,000 plants identified by the National
Cancer Institute as sources of cancer-fighting chemicals
come from tropical rain forests.
Tropical Forests Are Disappearing Rapidly
10-2 How Should We Manage
and Sustain Forests?
 Concept 10-2 We can sustain forests by
emphasizing the economic value of their ecological
services, protecting old-growth forests, harvesting
trees no faster than they are replenished, and using
sustainable substitute resources.
10-2 How Should We Manage
and Sustain Forests?
 We can use forests
more sustainably by
emphasizing:
• Economic value of
ecological services
• Harvesting trees no
faster than they are
replenished
• Protecting old-growth
and vulnerable areas
We Can Improve the Management of Forest Fires
 Fire prevention programs have been
very effective…too effective.
• Large amounts of highly flammable
underbrush have accumulated
• Leads to larger, more destructive
crown fires
 To reduce fire damage:
• Set controlled surface fires (Prescribed Fires).
• Allow fires to burn on public lands if they don’t
threaten life and property.
• Clear small areas around property subject to fire.
10-3 How Should We Manage and
Sustain Grasslands?
 Concept 10-3 We can sustain the productivity
of grasslands by controlling the number and
distribution of grazing livestock and restoring
degraded grasslands.
10-3 How Should We Manage and
Sustain Grasslands?
 Important ecological services of grasslands:
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•
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Soil formation
Erosion control
Nutrient cycling
Storage of atmospheric carbon dioxide in biomass
Maintenance of diversity
10-3 How Should We Manage and
Sustain Grasslands?
 Almost half of the world’s livestock graze on natural grasslands
(Rangelands) and managed grasslands (Pastures).
 We can sustain rangeland productivity by controlling the
number and distribution of livestock and by restoring
degraded rangeland.
Some Rangelands Are Overgrazed
 Overgrazing occurs when too
many animals graze for too
long and exceed carrying
capacity of a grassland area.
• Grass/shrubs are damaged
beyond repair
• Reduces grass cover
• Leads to erosion of soil by
water and wind
Some Rangelands Are Overgrazed
 Desertification - The degradation
of land that results in a desert
• Caused by overgrazing,
deforestation, or overuse
• The worlds deserts are getting bigger
 Prevention of overgrazing:
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•
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Rotational grazing
Replant barren areas
Apply fertilizer
Reduce soil erosion
10-4 How Should We Manage and Sustain
Parks and Natural Reserves?
 Concept 10-4 Sustaining biodiversity will
require protecting much more of the earth’s
remaining undisturbed land area as parks and
nature reserves.
10-4 How Should We Manage and Sustain
Parks and Natural Reserves?
Important Definitions:
 Conservation
Focuses on the proper use of nature
• Seeks to regulate the human use of wilderness
and its resources
 Preservation
Focuses on the protection of nature from use
• Seeks to eliminate the human use of wilderness
and its resources
10-4 How Should We Manage and Sustain
Parks and Natural Reserves?
 National park – a reserve of land, usually, but not always
declared and owned by a national government, protected from
most human development and pollution.
 Countries have established more than 1,100 national parks,
but most are threatened by human activities.
• Local people invade park for wood, cropland, and other
natural resources.
• Loggers, miners, and wildlife poachers also deplete
natural resources.
• Many are too small to sustain large-animal species.
• Many suffer from invasive species.
10-4 How Should We Manage and Sustain
Parks and Natural Reserves?
 58 Major national parks in the U.S.
 Overused due to popularity – litter,
trampling, off road vehicles, etc.
 Many species are isolated and
fragmented from the ecosystems
around them
 Air pollution from areas outside of park
10-4 How Should We Manage and Sustain
Parks and Natural Reserves?
 Nature Reserves (Nature Preserves)
Protected areas of importance for wildlife, geological features,
or other special interests, which are reserved and managed
for conservation.
 Nature reserves may be designated by government
institutions, by private landowners, or by charities and
research institutions.
• Currently 12% of earth’s land area is protected.
• Only 5% is strictly protected from harmful human activities
• Conservation biologists call for full protection of at least 20% of
earth’s land area
10-4 How Should We Manage and Sustain
Parks and Natural Reserves?
 Wilderness is land legally set aside in a large enough
area to prevent or minimize harm from human activities.
 Only a small percentage of the land area of the United
States has been protected as wilderness.
 Wilderness Act of 1964
• Established 9.1 million
acres of federally
protected wilderness in
national forests
Federally protected Wilderness
10-5 What is the Ecosystem Approach
to Sustaining Biodiversity?
 Concept 10-5A We can help sustain biodiversity
by identifying severely threatened areas and
protecting those with high plant diversity and those
where ecosystem services are being impaired.
 Concept 10-5B Sustaining biodiversity will require
a global effort to rehabilitate and restore damaged
ecosystems.
 Concept 10-5C Humans dominate most of the
earth’s land, and preserving biodiversity will require
sharing as much of it as possible with other species.
10-5 What is the Ecosystem Approach
to Sustaining Biodiversity?
 We can prevent or slow down losses of biodiversity by
concentrating efforts on protecting global “biodiversity hot
spots” where significant biodiversity is under immediate threat.
10-5 What is the Ecosystem Approach
to Sustaining Biodiversity?
10-5 What is the Ecosystem Approach
to Sustaining Biodiversity?