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AP Environmental
Science
Mr. Grant
Lesson 65
Forest Ecosystems And Forest
Resources
Forest Loss
&
Forest Management
© 2011 Pearson Education, Inc.
Objectives:
• Define the term maximum sustainable yield.
• Summarize the ecological roles and economic contributions of
forests.
• Outline the history and current scale of deforestation.
• Assess aspects of forest management and describe methods of
harvesting timber.
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Define the term maximum sustainable
yield.
Maximum Sustainable Yield: The maximum
usable production of a biological resource that
can be obtained in a specific time period. The
MSY level is the population size that results at
maximum sustainable yield.
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Summarize the ecological and economic
contributions of forests.
• Many kids of forests exist.
• Forests are ecologically complex and support a wealth
of biodiversity.
• Forests contribute ecosystem services, including carbon
storage.
• Forests provide us timber and other economically
important products and resources.
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Many kinds of forests exist
• Forest = any ecosystem with a high density of trees
- Boreal forest = in Canada, Scandinavia, and Russia
- Tropical rainforest = South and Central America,
Africa, Indonesia, and southeast Asia
- Temperate deciduous forests, temperate rainforests,
and tropical dry forests also exist
- Woodlands = ecosystems with lower density of trees
• Plant communities differ due to soil and climate
- Forest types = are defined by predominant tree species
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Forests cover 31% of Earth’s surface
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Forest types
• The Eastern U.S. has 10
forest types
- Spruce-fir, oakhickory, longleaf-slash
pine
• The Western U.S. holds
13 forest types
- Douglas fir, ponderosa
pine, pinyon-juniper
woodlands
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Forests are ecologically complex
• Forests are some of the richest ecosystems for biodiversity
- They are structurally complex, with many niches
- They provide food and shelter for multitudes of species
- Fungi and microbes have parasitic and mutualistic
relationships with plants
• Plant diversity leads to greater overall organism diversity
- Succession changes species composition
• Old-growth forest diversity exceeds that of young forests
- They have higher structural diversity, habitats, and
resources
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A cross-section of a mature forest
The scarlet tanager lives in
the eastern U.S. temperate
deciduous forest
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Forests provide ecosystem services
• Forests provide cultural, aesthetic, health, and
recreation values
• Forests also provide vital ecosystem services
- Stabilize soil and prevent erosion
- Slow runoff, prevent flooding, purify water
- Store carbon, release oxygen, influence weather
patterns, and moderate climate
• Roots draw minerals to surface soil layers
- Plants return organic material to the topsoil as
litter
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Carbon storage helps limit climate change
• Carbon storage by forests is of great international interest
- Nations debate how to control climate change
• Trees absorb carbon dioxide and store carbon
- The world’s forests store 280 billion metric tons of C
• Cutting forests worsens climate change
- Dead plants decompose and release carbon dioxide
- Fewer trees soak up less carbon dioxide
• Preserving forests keeps carbon out of the atmosphere
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Forests provide us valuable resources
• Benefits: medicines, food,
fuel, shelter, ships, paper
• Help us achieve a high
standard of living
• Logging locations:
- Boreal forests: Canada,
Russia
- Rainforests: Brazil,
Indonesia
- Conifer forests/pine
plantations: U.S.
In 2010, 30% of all
forests were designated
for timber production
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Outline the history and current scale of
deforestation.
• We have loss forests to clearance for agriculture and
over-harvesting for wood.
• Developed nations deforested much of their land as
settlement, farming and industrialization proceeded.
• Today deforestation is taking place most rapidly in
developing nations.
• Carbon offsets are one new potential solution to
deforestation.
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Demand for wood leads to deforestation
• Deforestation = the clearing
and loss of forests
- Changes landscapes and
ecosystems
- Reduces biodiversity
- Worsens climate change
- Disrupts ecosystem
services
- Ruins civilizations
Although the rate of deforestation is slowing,
we still lose 12.8 million acres/year
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Deforestation fed the growth of the U.S.
• Deforestation propelled the expansion and growth of
the U.S. and Canada
• Eastern deciduous forests were the first to be logged
- Timber companies moved south to the Ozarks, west
to the Rockies
• Primary forest = natural forest uncut by people
- Little remained by the 20th century
• Second-growth trees = grown to partial maturity after
old-growth timber has been cut
• Secondary forest = contains second-growth trees
- Smaller trees, very different species and structure
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Most primary forest is gone
The entire eastern half of the
continent used to be covered
in primary forest
Most primary forest was cut
for agriculture and timber
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Loggers lose their jobs with deforestation
• As each region is deforested, the timber industry declines
and timber companies move on
- Local loggers lose their jobs
• Once the remaining ancient trees of North America are
gone, loggers will once again lose jobs
- Companies will simply move to another area
- Most move to developing countries
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Rapid deforestation in developing nations
• Uncut tropical forests still remain in many developing
countries (Brazil, Indonesia, and West Africa)
- Technology allows for even faster exploitation
• Developing countries are so desperate for economic
development, they have few logging restrictions
• Concession = corporations pay the government for the
right to extract resources
- Temporary jobs are soon lost, along with the resources
- Wood is exported to North America and Europe
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Deforestation affects people
• In Malaysia, foreign corporations have deforested
millions of acres of tropical rainforest
- Affecting 22 tribes of hunter-gatherers
- The government did not consult the tribes
• Deforestation decreased game
- Oil palm agriculture’s pesticides and fertilizers killed
fish
• The people peacefully protested
- The government wants to convert tribes to farmers
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Palm oil plantations
• Palm oil is used in snack
foods, soaps, cosmetics,
biofuel
• Borneo has lost most of its
forest cover
• Clearing encourages further
development and illegal
logging
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Solutions to deforestation are emerging
• Conservation concessions = organizations team up to
reduce deforestation and illegal logging
• Carbon offsets = curb deforestation and climate change
- Forest loss causes 12–25% greenhouse gas emissions
- The Kyoto Protocol does not address this
• REDD = Reducing Emissions from Deforestation and
Forest Degradation
- From the 2009 Copenhagen climate conference
- Wealthy nations would pay poor nations to conserve
forests
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REDD
• The Copenhagen conference ended without a binding
agreement
- The REDD plan fell through
- But some of the $100 billion/year going to poor
nations may go to REDD
• Guyana is taking a leading role in REDD
- It is poor financially but rich in forests
- Cutting forests would provide $580 million/year
- Norway will pay $20 million in 2010 for conservation
and up to $250 million in 2015
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Assess aspects of forest management and
describe methods of harvesting timber.
• Forestry is one type of resource management.
• Resource managers have long managed for maximum
sustainable yield and are beginning to implement
ecosystem-based management and adaptive
management.
• The U.S. National forests were established to conserve
timber and allow its sustainable extraction.
• Most U.S. timber today comes from private lands.
• Plantation forestry, featuring single species, even-aged
stands, is widespread and growing.
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Assess aspects of forest management and
describe methods of harvesting timber.
• Harvesting methods include clear-cutting and other even-aged
techniques, as well as selection strategies that maintain
uneven-aged stands that more closely resemble natural forest.
• Foresters are beginning to manage for recreation, wildlife
habitat, and ecosystem integrity.
• Fire policy has been politically controversial, but scientists
agree that we need to address the impacts of a century of fire
suppression.
• Climate change is affecting forests.
• Certification of sustainable forest products allows consumer
choice in the marketplace to influence forestry practices.
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Forest management
• Forestry (silviculture) = forest management
- Sustainable forest management is spreading
• Foresters = professional managers who must balance
demand for forest products (short-term benefits) vs. the
importance of forests as ecosystems (long term)
• Resource management = strategies to manage and
regulate potentially renewable resources
- Sustainable management does not deplete resources
- Managers are influenced by social, political, and
economic factors
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Maximum sustainable yield
• Maximum sustainable yield = aims to achieve the
maximum amount of resource extraction without
depleting the resource from one harvest to the next
• Populations grow fastest at an intermediate size
- Population size is at half its carrying capacity
• Harvesting to keep the population at this size results
in maximum harvest
- While sustaining the population
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Maximum sustainable yield has problems
• Managed populations are much smaller than they would
naturally be
• Reducing populations so drastically affects other species
- Changing the entire ecosystem
• Trees are cut long before they grow to maximum size
- Changing forest ecology
- Eliminating habitats
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Ecosystem-based management
• Ecosystem-based management = managing resource
harvesting to minimize impacts on ecosystems and
ecological processes
• Sustainably certified forestry plans protect areas
- Restore ecologically important habitats
- Consider patterns at the landscape level
- Preserve the forest’s functional integrity
• It is challenging to implement this type of management
- Ecosystems are complex
- Our understanding of how they operate is limited
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Adaptive management
• Adaptive management = testing different approaches
and aiming to improve methods through time
- Monitoring results and adjusting methods as needed
- Time-consuming and complicated, but effective
• The 1994 Northwest Forest Plan resolved disputes
between loggers and preservationists over the last U.S.
old-growth temperate rainforests
- The plan let science guide management
- It allowed limited logging while protecting species
and ecosystems
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Fear of a “timber famine” spurred forest
protection
• Depletion of eastern U.S. forests caused alarm
• National forest system = public lands set aside to grow
trees, produce timber, protect watersheds, and ensure
future timber supplies
- 77 million ha (191 million acres)—8% of U.S. land
area
• The U.S. Forest Service was established in 1905
- Manages forests for the greatest good of the greatest
number in the long run
- Management includes logging and replanting trees
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Federal agencies own land in the U.S.
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Timber is extracted from public and private
land
• Private companies extract timber
from public land
- The Forest Service plans
and manages timber sales
and builds roads
- Companies log and sell
the timber for profit
Taxpayers subsidize
private timber
harvesting on public
land
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Logging on private vs. public land
• Most U.S. logging occurs on private land owned by
timber companies or small landowners
- Companies use the maximum sustained yield approach
• Management on public lands reflects social and political
factors that change over time
- Public concern, changing management philosophies,
and economics have caused harvests to decrease
- But the secondary forests that replace primary forests
are less ecologically valuable
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Plantation forestry
• The timber industry focuses on timber plantations
- Fast-growing, single-species monocultures
• Even-aged stands= all trees are the same age
• Rotation time = trees are cut after a certain time
- The land is replanted
• Uneven-aged stands = mixed ages of trees and species
Tree plantations are
crops, not ecologically
functional forests
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Harvesting timber: clear-cutting
• All trees in the area are cut
- Most cost-efficient
- Greatest ecological
impact
- May mimic some natural
disturbance (e.g., storms)
- Leads to soil erosion
• Public outrage caused
companies to use other
harvesting methods
Clear-cutting destroys
entire communities
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Harvesting: other methods
• Seed-tree approach = a few seed-producing trees are left
standing to reseed the logged area
• Shelterwood approach = some trees are left to provide
shelter for the seedlings as they grow
• Selection systems = only select trees are cut
- Single tree selection = widely spaced trees are cut
- Group tree selection = small patches of trees are cut
• All methods disturb habitat and affect species
- Change forest structure and composition
- Increased runoff, flooding, erosion, siltation, landslides
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Harvesting forests
Clear-cut logging
Selection logging
Seed-tree and shelterwood logging
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Managing public forests
• Increased public awareness caused people to urge that
forests be managed for recreation, wildlife, and
ecosystem integrity, instead of only for logging
- Critics protest federal subsidies of logging companies
• Multiple use policy = national forests are to be managed
for recreation, habitat, minerals, and other uses
- In reality, timber production is the primary use
The Forest Service loses $100 million/year of taxpayer
money and increased harvest by selling timber below cost
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The National Forest Management Act (1976)
• Every national forest must formulate plans for renewable
resource management that:
- Consider both economic and environmental factors
- Provide for and protect regional diversity
- Ensure research and monitoring of management
- Permit only sustainable harvest levels
- Ensure that profit alone does not guide harvest
method
- Protect soils and wetlands
- Assess all impacts before logging to protect resources
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New forestry
• U.S. Forest Service programs:
- Manage wildlife, non-game animals, endangered
species
- Push for ecosystem-based management
- Run programs for
ecological restoration
• New forestry = timber cuts
that mimic natural events
- Sloppy clear-cuts mimic
windstorms
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Politics influences forestry management
• The Bush administration rolled back regulations in 2004
- Freed managers from requirements of the National
Forest Management Act
- Loosened environmental protections
- Restricted public oversight
- Repealed President Clinton’s roadless rule, which
protected 31% of national forests from logging
- State governors had to petition the federal government
to protect areas
- Court rulings reinstated the roadless rule in 2009
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Fire policy also stirs controversy
• For over 100 years, the Forest Service suppressed all fires
- But many ecosystems depend on fires
- Excess vegetation produces kindling for future fires
• In the wildland-urban interface, housing developments
that are near forests are vulnerable to forest fires
Catastrophic fires have become more numerous recently
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Prescribed fires are misunderstood
• Prescribed (controlled) burns = burning areas of forests
under carefully controlled conditions
- Clear away fuel loads, nourish soil, encourage growth
of new vegetation
- Are time-intensive
- Are impeded by public misunderstanding and political
interference
• Healthy Forests Restoration Act (2003) = promotes
removal of small trees, underbrush, and dead trees
- Passed in response to forest fires
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Salvage logging
• Removal of dead trees following a natural disturbance
• It seems logical, but is really destructive
- Snags (standing dead trees) provide nesting and
roosting cavities for countless animals
- Removing timber from recently burned areas increases
erosion and soil damage
- Impedes forest regeneration and promotes future fires
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Climate change is altering forests
• The U.S. is warming and getting drier and will get worse
• Pests kill huge areas of trees, particularly plantations
• Dead trees do not remove carbon dioxide
- Intensifying climate change
• Woodlands, shrublands. or grasslands may replace forests
Increased fires and pests destroy large areas of the U.S.
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Progress toward sustainable forestry is
mixed
• The world is still losing forested land
- But advances are being made toward sustainable
forestry
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Sustainable forestry is gaining ground
• Sustainable forest certification = products produced
sustainably can be certified by organizations
- The Forest Stewardship Council (FSC) has the
strictest standards
- Companies such as Home Depot sell sustainable
wood, encouraging better logging practices
- Consumers look for logos to buy sustainably
produced timber
Strong certification standards
drive sustainability
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