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ENVIRONMENTAL SCIENCE 13e
CHAPTER 9:
Sustaining Biodiversity:
The Ecosystem Approach
Wangari Maathai and the Green
Belt Movement
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Began in Kenya in 1977
Organizes poor women in rural Kenya
50,000 members protect forests
Planted 20 million trees
– Fruits
– Building materials
– Firewood
• Similar programs in 30 African countries
• 2004: Nobel Peace Prize
9-1 What Are Major Threats to
Forest Ecosystems?
• Concept 9-1 Ecologically valuable
forest ecosystems are being cut and
burned at unsustainable rates in
many parts of the world.
Types of Forests
• Forests cover 30% of earth’s land
surface
• Old-growth forests
• Second-growth forests
• Tree plantation
Science Focus: Putting a Price Tag
on Nature’s Ecological Services
• Estimated value of earth’s ecological
services
– $33.2 trillion per year
– $4.7 trillion per year for forests
• Need to start factoring values into land
use
• Ecological services can be a
sustainable source of ecological income
Harvest Methods
• Step one: build roads
– Erosion
– Invasive species
– Open up for human invasion
• Step two: logging operations
– Selective cutting
– Clear cutting
– Strip cutting
Forests and Fires
• Surface fires
– Burn undergrowth only
– Cool fire
– Ecological benefits
• Crown fires
– Burn the entire tree
– Hot fire
– Occur in forests with lack of surface fires
Loss of Original Forests
• Deforestation
• 46% in 8,000 years, most since 1950
• Most in tropical areas, developing
countries
• Estimated loss of 40% intact forests
within next 20 years
Good News on Forests
• 2000–2007 net total forested area
stabilized or increased
• Most of the increase due to tree
plantations
• Net loss of terrestrial biodiversity
Return of Forests in the United
States (1)
• U.S. forests
– Cover ~30% of land
– Contain ~80% of wildlife species
– Supply ~67% of nation’s surface water
• Forest cover greater now than in
1920
• Secondary succession
Return of Forests in the United
States (2)
• Second- and third-growth forests
fairly diverse
• More wood grown than cut
• 40% of forests in National Forest
System
• Some forests transformed into tree
plantations
Tropical Forests
• Cover 6% of earth’s land area
• Habitat for 50% of terrestrial plants
and animals
– Vulnerable to extinction – specialized
niches
• Rapid loss of 50,000–170,000 km2
per year
• Some second-growth forests
Causes of Tropical Forest
Deforestation and Degradation
• Population growth and poverty
• Economic reasons
– Logging
– Ranching
– Farming
• Government subsidies
• Fires raise temperatures and reduce
rainfall
9-2 How Should We Manage
and Sustain Forests?
• Concept 9-2 We can sustain forests
by emphasizing the economic value
of their ecological services, removing
government subsidies that hasten
their destruction, protecting oldgrowth forests, harvesting trees no
faster than they are replenished, and
planting trees.
Management of Forest Fires (1)
• Fire suppression in all types of forests
• Increased amounts of underbrush
• Increased probability of crown fires
Management of Forest Fires (2)
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Prescribed fires
Allow some fires to burn
Thin vegetation from forests
Thin around vulnerable homes
Decrease flammability of homes
Science Focus: Certifying
Sustainably Grown Timber
• Forest Steward Council certification of
forest operations
– Environmentally sound practices
– Sustainable yield harvest
– Minimal erosion from operations
– Retention of dead wood for wildlife
habitat
Trees and Paper
• Many trees are cut for paper
production
• Alternatives
– Pulp from rice straw and agricultural
residues (China)
– Kenaf (U.S.)
– Hemp
9-3 How Should We Manage
and Sustain Grasslands?
• Concept 9-3 We can sustain the
productivity of rangeland by
controlling the number and
distribution of grazing livestock and
by restoring degraded grasslands.
Grasslands
• Provide important ecological services
• Second most used and altered
ecosystem by humans
• 42% grazed by cattle, sheep, and
goats – rangeland (open) and
pasture (fenced)
• Overgrazing
9-4 How Should We Manage and
Sustain Parks and Nature Reserves?
• Concept 9-4 We need to put more
resources into sustaining existing
parks and nature reserves and into
protecting much more of the earth’s
remaining undisturbed land area.
National Parks
• >1,100 national parks in 120
countries
• Only 1% of parks in developing
countries are protected
– Local people invade parks to survive
– Logging
– Mining
– Poaching
Problems Protecting National
Parks
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Illegal logging
Illegal mining
Wildlife poaching
Most parks too small to protect large
animals
• Invasion of nonnative species
Stresses on U.S. National Parks
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58 major national parks
Biggest problem is popularity
Damage from nonnative species
Threatened islands of biodiversity
Need $6 billion for overdue repairs
Nature Reserves Occupy a
Fraction of Earth
• 12% of earth’s land protected
• Only 5% fully protected – 95%
reserved for human use
• Need for conservation
– Minimum 20% of land in biodiversity
reserves
– Protection for all biomes
Solutions for Protection
• “Ecological insurance policy”
• Buffer zones around protected areas
• Locals to manage reserves and buffer
zones
• United Nations: 531 biosphere
reserves in 105 countries
Science Focus: Reintroducing the Gray
Wolf to Yellowstone National Park
• Reduced to a few hundred in lower 48 by
1973
• Keystone species
• Restoration proposal angered ranchers,
hunters, loggers
• 1995 - reintroduced in Yellowstone, 124 by
2008
• Positive ripple effect after reintroduction
Case Study: Costa Rica
• Superpower of biodiversity
• Conserved 25% of its land, 8
megareserves
• Government eliminated deforestation
subsidies
• Paid landowners to maintain and
restore tree coverage
• Boosts ecotourism
Protecting Wilderness Protects
Biodiversity
• Wilderness
• Preserves biodiversity
• Centers for evolution
Case Study: Controversy over
Wilderness Protection in the U.S.
• 1964 Wilderness Act
• Ten-fold increase from 1970 to 2008
• 4.6% of U.S. land protected, 75% of
that in Alaska
9-5 How Can We Help to
Sustain Terrestrial Biodiversity?
• Concept 9-5 We can help to sustain
terrestrial biodiversity by identifying
and protecting severely threatened
areas (biodiversity hotspots),
rehabilitating damaged ecosystems
(using restoration ecology), and
sharing with other species much of
the land we dominate (using
reconciliation ecology).
Three Principles to Protect
Ecosystems
1. Map and inventory the world’s
terrestrial and aquatic ecosystems
2. Locate and protect the most
endangered ecosystems, with a
focus on biodiversity
3. Seek to restore as many degraded
ecosystems as possible
Protecting Global Biodiversity
Hotspots
• 17 megadiversity countries, mostly in
tropics and subtropics
– Two-thirds of biodiversity
• Developing countries economically
poor and biodiversity rich
• Protect biodiversity hotspots
Ecological Restoration
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Restoration
Rehabilitation
Replacement
Creating artificial ecosystems
Science-based Principles for
Restoration
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Identify cause of degradation
Stop abuse by reducing factors
Reintroduce species if necessary
Protect area from further degradation
Case Study: Ecological Restoration
of Tropical Dry Forest in Costa Rica
• One of world’s largest ecological
restoration projects
• Restore a degraded tropical dry forest
and reconnect it to adjacent forests
• Involve 40,000 people in the
surrounding area – biocultural
restoration
• Ecotourism
Restoration Ecology
• Creating new habitats to conserve
species diversity in areas where
people live, work, play
• People learn to protect local species
and ecosystems
• Sustainable ecotourism
• Golden Gate Park in San Francisco
9-6 How Can We Help to
Sustain Aquatic Biodiversity?
• Concept 9-6 We can help to sustain
aquatic biodiversity by establishing
protected sanctuaries, managing
coastal development, reducing water
pollution, and preventing overfishing.
Impacts on Aquatic Ecosystems
(1)
• Destroyed or degraded by human
activities
• Coastal habitats disappearing 2-10
times faster than tropical forest
• Rising sea levels will destroy coral
reefs and some low islands
• Ocean floor degradation 150 times
larger than area clear-cut annually
Impacts on Aquatic Ecosystems
(2)
• Freshwater habitat disruption
– Dams
– Water withdrawals from rivers
• Likely extinction
– 34% marine fish species
– 71% freshwater species
– Greater than any other group of species
Overfishing
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Fishery
Fishprint
157% overfishing
90% of large open-ocean fishes have
disappeared since 1950
Case Study: Industrial Fish
Harvesting Methods
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Trawler fishing
Purse-seine fishing
Longlining
Drift-net fishing
Why Is Protection of Marine
Biodiversity So Difficult?
• Human aquatic ecological footprint
expanding
• Not visible to most people
• Viewed as an inexhaustible resource
• Most ocean areas outside jurisdiction
of a country
Solutions for Marine
Ecosystems
• Protect endangered and threatened
species
• Establish protected marine
sanctuaries
• Marine reserves – work well and
quickly
• Integrated coastal management
• Protect existing coastal wetlands
Three Big Ideas from This
Chapter - #1
The economic values of the important
ecological services provided by the
world’s ecosystems need to be
included in the prices of goods and
services.
Three Big Ideas from This
Chapter - #2
We can sustain terrestrial biodiversity
by protecting severely threatened
areas, restoring damaged
ecosystems, and sharing with other
species much of the land we
dominate.