Transcript Concept To Learn in Sect. 9-1: Ecologically valuable forest

ENVIRONMENTAL SCIENCE
CHAPTER 9:
Sustaining Biodiversity:
The Ecosystem Approach
9-1: What Are Major Threats to
Forest Ecosystems?
• Concept To Learn in Sect. 9-1:
Ecologically valuable forest
ecosystems are being cut and burned
at unsustainable rates in many parts
of the world.
Types (categories) of Forests
• Forests cover 30% of earth’s land
surface, and are of three types:
1. Old-growth forests: uncut or
regenerated forest, which haven’t been
disturbed by humans or natural disasters
for hundreds of years.
2. Second-growth forests: a forest
which grows after deforestation by
humans or natural disaster.
Types (categories) of Forests
3. Tree plantations (commercial forest):
one to two species are grown on a tract
of land to a point where they reach
commercial value, then are clear-cut
a. Examples?
b. Downside to tree plantations?
Science Focus: Putting a Price Tag
on Nature’s Ecological Services
• Estimated value of earth’s ecological
services:
1. $33.2 trillion per year
2. $4.7 trillion per year for forests
• Need to start factoring these values into
land use. Why??
• Ecological services can be a sustainable
source of ecological income
Steps in Harvesting Forests:
• Step one: build roads to transport timber, and
will lead to:
1. Erosion of soil & run-off into waterways
2. An increase in invasive species
3. Easier access for human invasion
• Step two: logging operations; Types:
1. Selective cutting- small areas are cleared
2. Clear cutting- entire areas are cleared
3. Strip cutting- strip is cut along land contour
Types of Fires Affecting Forests
• Surface fires: natures “beneficial” fire
1. Burn undergrowth only (not tree tops)
2. Cool fire (comparatively)
3. Ecological benefits (frees seeds &
minerals, controls disease & insects)
• Crown fires: destroys almost everything!
1. Burns the entire tree
2. Much hotter fire
3. Occurs in forests with lack of surface fires
Loss of Original Forests
• Deforestation: temporary/permanent removal
of large expanses of forests
1. done for agriculture or expansion
2. 46% loss in 8,000 years (60% since 1950)
3. Most deforestation has occurred in tropical
areas & developing countries
4. If this rate continues, there will be an
estimated additional loss of 40% intact forests
within next 20 years
Good News on Forests!
• 2000–2007 has seen our “net” total
forested area as stabilized or increased
• Most of the increase due to tree
plantations
• Overall though, there is a net loss of
terrestrial biodiversity
Return of Forests in the United
States
• U.S. forests presently:
1. Cover ~30% of land
2. Contain ~80% of wildlife species
3. Supply ~67% of nation’s surface water
• Forest cover is greater now than in 1920
• Forests have grown back in areas
previously cleared by secondary
succession
Return of Forests in the United
States
• Second and third-growth forests are
becoming fairly diverse
• At present, more wood grown than is cut
• 40% of forests are now “protected” in the
National Forest System
• Some forests transformed into tree
plantations
1. but now have less biodiversity
Tropical Forests: see the most
deforestation!
• Cover 6% of earth’s land area
• Habitat for 50% of terrestrial plants and
animals
1. Houses the species most vulnerable to
extinction (contain specialized niches)
• See rapid losses of 50,000–170,000 km2
per year
• Some second-growth forests exist
Causes of Tropical Forest
Deforestation and Degradation
• Population growth and poverty
• Economic reasons
1. Logging
2. Ranching
3. Farming
• Government subsidies
• Fires lead to raised temperatures and
cause reduced rainfall.
Sect. 9-2: How Should We
Manage and Sustain Forests?
• Concept to Learn in Sect. 9-2: We
can sustain forests by emphasizing the
economic value of their ecological
services, removing government
subsidies that hasten their destruction,
protecting old-growth forests, harvesting
trees no faster than they are
replenished, and planting trees.
Management of Forest Fires
• Our current education campaign has
saved lives, trees & wildlife.
• Our current education campaign has
also lead to:
1. Fire suppression in all types of
forests
2. Increased amounts of underbrush
3. Increased probability of crown fires
Management of Forest Fires
• Ecologists are now recommending:
1. Prescribed fires to get rid of
underbrush
2. Allowing some fires to burn
3. Thinning vegetation from forests
4. Thinning forests around vulnerable
homes
5. Decreasing the flammability of homes
Science Focus: Certifying
Sustainably Grown Timber
• Forest Steward Council: a certification
group, which evaluates companies for
sustainable timber practices, reviewing:
1. Environmentally sound practices
2. Sustainable yield harvest (??)
3. Minimal erosion from operations
4. Retention of dead wood for wildlife habitat
Should our government give tax breaks to
grow timber this way? Explain.
Paper production: From Trees
or From Something Else?
• Many trees are cut for paper production
• Alternatives to trees:
1. Pulp from rice straw and agricultural
residues (China)
2. Kenaf (U.S.) = non-tree fibers, from
plants like the Kudzu vine
3. Hemp = a type of non-tree fiber
Ways to Reduce Tropical
Deforestation
• Debt-for-nature swaps:
1. A country will protect its rainforests in
exchange for financial aid or debt relief from a
participating country.
• Conservation concessions: similar to above
• Gentler logging methods:
1. Strip cutting, selective cutting
• Encourage use of wood substitutes: use of
bamboo, recycled wood products, plastic, etc.
Sect. 9-3 How Should We Manage
and Sustain Grasslands?
• Concept to Learn in Sect. 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% are grazed by cattle, sheep, and goats.
Two types:
1. Rangeland: open, unfenced grasslands
a. Supply forage (vegetation) for animals
2. Pasture: managed, enclosed grasslands
a. Planted with domesticated grasses
Overgrazing of Grasslands
• Overgrazing: when grazing exceeds
the carrying capacity of the rangeland.
1. Leads to:
a. Soil erosion
b. Soil compaction
c. Enhances growth of invasive
species
Our Job: Manage Rangelands
Sustainably!
• Can be accomplished by:
1. Practice rotational grazing
2. Fence out riparian zone areas
a. Areas near bodies of water
3. Suppress invader plants by:
a. Using herbicides
b. Mechanical removal
c. Controlled burning
d. Short-term trampling
Sect. 9-4: How Should We Manage and
Sustain Parks and Nature Reserves?
• Concept to Learn in Sect. 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
• There are presently 1,100 national parks in
120 countries
• Only 1% of parks in developing countries are
protected (due to lack of funding)
– Local people invade parks to survive
– Logging
– Mining
– Poaching
Problems Protecting National
Parks
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Illegal logging
Illegal mining
Wildlife poaching (for tusks, etc)
Most of the existing parks are too small
to protect large animals
• Invasion of nonnative species cause
competition for the protected species.
Stresses on U.S. National Parks
• There are 58 major national parks in US
• Biggest problem for them is popularity
1. attract dune buggies, dirt bikes, etc.
2. causes destruction of vegetation
• Damage from nonnative species
1. Ex: intro of wild boars
• Threatened islands of biodiversity
1. surrounding human activity threaten them
• Need $6 billion for overdue repairs
Nature Reserves Occupy a
Fraction of Earth
• 12% of earth’s land protected, but not
fully
• Only 5% is fully protected – 95% reserved
for human use
• Needed for conservation:
1. Minimum 20% of land in biodiversity
reserves
2. Protection for all biomes
Reasons/Solutions for Protection of
natures reserves
• They serve as an “Ecological insurance policy”
for all species
• Use of buffer zones around protected areas
1. inner, protected core
2. just outside inner core, can extract
resources
• Locals to manage reserves and buffer zones
• United Nations: has created 531 biosphere
reserves in 105 countries
Science Focus: Reintroducing the Gray
Wolf to Yellowstone National Park
• Reduced to a few hundred (from 350,000) in
lower 48 by 1973
• Gray wolves are a keystone species, by
controlling the populations of other species
• Restoration proposal angered ranchers,
hunters & loggers
• 1995 - reintroduced in Yellowstone, growing to
124 by 2008
• Positive ripple effect after reintroduction to the
ecosystem.
Costa Rica: A leader in
conservation
• A “superpower” of biodiversity
• Conserves 25% of its land (more than any other
country!) **We’re 42nd on the list!
• Has 8 mega-reserves (inner core, with 2 buffer
zones)
• Government eliminated deforestation subsidies
1. Instead, paid landowners to maintain and
restore tree coverage
• Boosts ecotourism ( those who come to see it!)
Protecting Wilderness Protects
Biodiversity
• Wilderness: large areas of undeveloped land
1. Preserves biodiversity
2. allows for micro-evolution in response to
unpredictable environmental changes
• Preserving wilderness has been controversial.
1. constant opposition to it.
2. only 4.6% of US is protected wilderness, &
mostly in Alaska.
3. only 2% in the continental US!
Protecting Wilderness Protects
Biodiversity
• 1964 Wilderness Act was put into use
1. prevented undeveloped public land
from being used
2. placed land into the “National
Wilderness Preservation System”
• Ten-fold increase from 1970 to 2008,
but still US ranks 42nd in the world in
preserving wilderness.
9-5 How Can We Help to
Sustain Terrestrial Biodiversity?
• Concept to Learn in Sect. 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 We Can Use to
Protect Ecosystems:
1. Map and inventory the world’s terrestrial and
aquatic ecosystems:
a. All species
b. Ecosystem services it provides
2. Locate and protect the most endangered
ecosystems, with a focus on protecting
biodiversity
3. Seek to restore as many degraded
ecosystems as possible
Protecting Global Biodiversity
Hotspots: A Priority!
• 17 mega-diversity countries, mostly in tropics
and subtropics, contain two-thirds of the
world’s biodiversity
• Developing countries are economically poor
and biodiversity rich!
• Protect biodiversity hotspots
1. areas rich in plant species that are in great
danger of extinction.
2. are vulnerable to human population growth
and the resulting pressure on natural resources
Ecological Restoration
• Ecological Restoration: the process of
repairing damage caused by humans to the
biodiversity & natural dynamics of natural
ecosystems, accomplished thru;
1. Restoration to natural state
2. Rehabilitation to functional ecosystem
3. Replacement with another ecosystem
4. 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
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: an
example of “reconciliation ecology”
1. Purposeful planning of areas for preserving
biodiversity, in places that we live
9-6 How Can We Help to
Sustain Aquatic Biodiversity?
• Concept to Learn in sect 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
• 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
• Freshwater habitat disruption
1. Dams
2. Water withdrawals from rivers
• Likely extinction
1. 34% marine fish species
2. 71% freshwater species
3. Greater than any other group of species
Overfishing
• Fishery: a concentration of an aquatic species
that is suitable for commercial harvesting
1. A competitive field.
2. At present, we consume more than is
sustainable
3. Fishprint: the area of ocean necessary to
sustain the consumption of the average person
a. Globally shows157% overfishing rate!!
• 90% of large open-ocean fishes have
disappeared since 1950
Case Study: Industrial Fish
Harvesting Methods
• Use gps & sonar to find fish
1.Trawler fishing: drags net on ocean floor,
catching shellfish (ie shrimp) & cod
2.Purse-seine fishing: like a giant, open purse
that has a drawstring closure at top.
a. Good for top-swimming fish (tuna)
3. Longlining: long lines, with 100’s of hooks
4. Drift-net fishing: long nets, which stretch deep
into water.
Why Is Protection of Marine
Biodiversity So Difficult?
• Human aquatic ecological footprint
expanding
1. difficult to monitor the impact it has
• Not visible to most people (out of sight….)
• Viewed as an inexhaustible resource
• Most ocean areas outside jurisdiction of a
country
1. makes it an open-access resource
Solutions for Marine
Ecosystems
• Protect endangered and threatened
species
• Establish protected marine sanctuaries
1. don’t prevent dredging/trawling
• Marine reserves – work well and quickly
• Integrated coastal management
• Protect existing coastal wetlands