Transcript The Living World - Chapter 34 - McGraw Hill Higher Education

The Living World
Fourth Edition
GEORGE B. JOHNSON
34
Planet Under Stress
PowerPoint® Lectures prepared by Johnny El-Rady
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34.1 Pollution
Damage done to one of the world’s ecosystems can
have ill effects on many others
Widespread effects on the worldwide ecosystem
are termed global change
Patterns of global change include
Pollution
Acid precipitation
Ozone hole
Greenhouse effect
Loss of biodiversity
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Chemical Pollution
Major problem because of growth of heavy industry
and overly casual attitude in industrialized countries
Air pollution
Gray-air cities (include New York)
Pollutants are usually sulfur oxides emitted by industry
Brown-air cities (include Los Angeles)
Pollutants undergo chemical reactions in the sunlight
Water pollution
A serious consequence of our “Flushing it down the sink”
attitude
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Agricultural Chemicals
The spread of “modern” agriculture introduced large
amounts of chemicals into the global ecosystem
Pesticides, herbicides and fertilizers
Chlorinated hydrocarbons
(such as DDT) caused
severe environmental
problems through
biological magnification
Become more
concentrated as they
move up the food
chain
Fig. 34.1
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34.2 Acid Precipitation
In the 1950s, tall stacks were introduced to disperse
sulfur-rich smoke into winds to disperse and dilute it
The problem was exported, not solved!
Sulfur combines with water vapor to produce
sulfuric acid
Natural rain water has a pH of ~ 5.6
In the northeastern US, the pH is ~ 4.3
This pollution-acidified precipitation
is called acid rain (acid precipitation)
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34.2 Acid Precipitation
Acid precipitation destroys life
Forests and lake ecosystems in Europe and
North America have been seriously damaged
The solution is to capture and remove emissions
before their release
Serious problems in implementation
1. Expensive
2. Polluter and recipient are far from one
another
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34.3 The Ozone Hole
Starting in 1975, the earth’s ozone shield began to
disintegrate creating an ozone hole
The culprit is a class of chemicals called
chlorofluorocarbons (CFCs)
They have been used since the 1920s as
coolants and aerosol dispensers
Are very stable and thus have accumulated
in the atmosphere over time
Catalyze the conversion of ozone (O3)
into oxygen (O2) without being used up
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34.3 The Ozone Hole
Every 1% drop in ozone content is estimated to lead
to a 6% increase in the incidence of skin cancers
11.4-millionsquare-mile hole
Hole is largest during
Antarctic winter
Hole tails off as
temperature rises
Fig. 34.4 The ozone hole over Antarctica is still growing
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34.4 The Greenhouse Effect
For over 150 years, our industrial society has been
relying on the burning of fossil fuels
This has greatly increased atmospheric levels of
carbon dioxide (CO2)
CO2 transmits radiant energy from the sun, but
traps infrared light, or heat
This creates what is known as the
greenhouse effect
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34.4 The Greenhouse Effect
The accumulation
of CO2 and other
“greenhouse gases”
(such as CFCs)
have led to global
warming
Fig. 34.5
Average global temperatures could increase
from 1oC to 4oC
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34.4 The Greenhouse Effect
Global warming could have serious effects on
1. Rain patterns
Areas experiencing droughts may see even
less rain
2. Agriculture
The yields of some crops will increase, while
the yields of other crops will decrease
3. Sea levels
Melting of large stores of ice will cause water
levels to rise
Increased flooding of low-lying lands
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34.5 Loss of Biodiversity
> 99% of species known to science are now extinct
Current rates of extinction are alarmingly high
Conservation biologists
have identified three
key factors
Habitat loss
Species
overexploitation
Introduced species
Single most
important cause
Fig. 34.6
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Habitat loss
1.
2.
3.
4.
Destruction
Pollution
Human disruption
Habitat fragmentation
Rain forest of
Madagascar
Species overexploitation
Species that are hunted or
harvested by humans are
at great risk of extinction
Fig. 34.7
Introduced species
The introduction of exotic species by humans has wiped
out or threatened many native populations
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34.6 Reducing Pollution
Human activities are placing a severe stress on the
biosphere
Industrial pollution is one of the key problems
It results from a failure of our economy to set a
proper price on environmental health
The reason is money!
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Economists have identified an “optimum” amount of
pollution based on the following
How much it costs to reduce pollution versus the
social and environmental cost of allowing pollution
The indirect costs
of pollution are
usually not taken
into account
Fig. 34.8
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In the US, two effective approaches have been
devised to curb pollution
1. Antipollution laws
All cars are required to have catalytic
converters to eliminate automobile smog
The Clean Air Act of 1990 requires that power
plants eliminate sulfur emissions
2. Pollution taxes
In effect, a government-imposed artificial price
hike added to the price of production
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34.7 Finding Other Sources of Energy
Many countries are turning to nuclear power for
their growing energy needs
In 1995, > 500 nuclear reactors were producing
power worldwide
In the US, nuclear power plants have not been
popular because of
1. Ample access to cheap coal
2. Public fears of the consequences of an
accident
Three Mile Island nuclear plant in 1979
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Nuclear power can provide plentiful cheap energy
However, several problems must be overcome
1. Safe operation
Chernobyl accident in 1986
Fears of vast
radioactive
contamination
2. Waste disposal
Spent nuclear fuel
remains radioactive for
thousands of years
3. Security
Fig. 34.10
Fears of terrorists getting their hands on plutonium
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34.8 Preserving Nonreplaceable
Resources
The consumption or destruction of nonreplaceable
resources is the most serious problem humans face
The key nonreplaceable resources are
Topsoil
Groundwater
Biodiversity
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Topsoil
Is being lost at a rate of centimeters per decade
The US has lost 1/4th of its topsoil since 1950!
Solutions
Genetic-engineering to make crops resistant to
weed-killing herbicides
Terracing to recapture lost topsoil
Groundwater
Seeped into its underground reservoir very slowly
during the last ice age over 12,000 years ago
It is being wasted (watering lawns) or polluted
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Biodiversity
In the last 20 years, ~ 1/2 of the world’s tropical
rain forests have been either burned or cut
Animal and plant species are becoming extinct
The ancient forests of the Pacific Northwest are
being cut at a ferocious rate
Loss of species entails three costs
1. Direct economic value of the products
2. Indirect economic value of the benefits
3. Ethical and aesthetic value
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34.9 Curbing Population Growth
The human population has grown explosively over
the last 300 years
6.3 billion
in 2003
Fig. 34.13
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Worldwide
Birth rate has stabilized to ~ 21 per year per 1,000 people
Death rate has fallen to ~ 9 per year per 1,000 people
This amounts to a population growth rate of 1.3% per year
The world population will double in 54 years!
Mexico City
One of the most
alarming trends is
massive movement
of people towards
urban centers
~ 26 million
inhabitants
Fig. 34.14
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The world’s population growth is unevenly
distributed among countries
Fertility rates will
determine world
population
Fig. 34.15
Growth rate in developed countries is 0.1% per year
Growth rate in developing countries is 1.9% per year
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The world population growth rate has been declining
The United Nations attributes the decline to
1. Increased family planning efforts
2. Increased economic power and social status
of women
Slowing population growth helps sustain resources,
but per capita consumption is also important
Wealthiest 20% of the world’s population accounts
for 80% of world’s resource consumption
Poorest 20% is responsible for only 1.3% of
consumption
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34.10 Preserving Endangered Species
Q: What is the most effective way to protect the
environment and prevent extinctions of species?
A: Preservation of ecosystems and monitoring
species before they are threatened
Habitat restoration
Captive propagation
Sustaining genetic diversity
Preserving keystone species
Conserving ecosystems
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Habitat Restoration
In many situations, habitat conservation is no longer
an option
Three programs for restoration, depending on the
cause of the habitat loss
1. Pristine restoration
2. Removing introduced species
3. Cleanup and rehabilitation
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Captive Propagation
Recovery programs often involve direct intervention
in natural populations to avoid extinctions
Case History: The Peregrine Falcon
Population disappeared east of the Mississippi by 1960
The culprit was DDT
Causes eggs to break before they hatch
DDT was banned by federal law in 1970
Captive breeding program started using falcons from other
parts of the country
Very good results
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Sustaining Genetic Diversity
Smaller populations have little genetic diversity
Case History: The
Black Rhino
All five species of
rhinoceros are
critically endangered
Black rhinos live in 75
small, widely
separated populations
Diceros bicornis
Fig. 34.17
To increase genetic diversity, individuals must be moved
between populations
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Preserving Keystone Species
Removal of keystone species can have disastrous
consequences on ecosystems
Pteropodid bat
Case History:
Flying Foxes
Fig. 34.18
Widespread on the South
Pacific Islands
Often the only pollinator
and seed disperser
Were being driven to extinction by human hunting
Legal protection, habitat restoration, and captive breeding
have produced a very effective preservation program
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Conserving Ecosystems
Isolated patches of habitat lose species far more
rapidly than large areas do
Conservation biologists have therefore promoted
the following
1. The creation of megareserves
Large areas of land that contain a core of one or
more undisturbed habitats
2. The preservation of intact ecosystems
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34.11 Individuals
Can Make the Difference
Two examples serve to illustrate this point
The Nashua River in New England
Lake Washington in Seattle
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The Nashua River
By the 1960s, was severely
polluted by wastes from
mills set up along its banks
Marion Stoddart organized
the Nashua River Cleanup
Committee in 1962
Greatly aided passage
of the Massachusetts
Clean Water Act of 1966
Industrial dumping is
now banned and the
river has largely
recovered
Fig. 34.19
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Lake Washington
By the 1950s, sewage dumping and fertilizer runoffs had
caused a bloom of blue-green algae
Bacteria decomposing dead algae would eventually
deplete the lake’s oxygen
In 1956, W.T. Edmondson of
the University of Washington
began a campaign to alert
public officials of the danger
A sewer was built to carry
sewage effluent to the sea
The lake is now clean
Fig. 34.20
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Solving Environmental Problems
Five components are involved in successfully
solving an environmental problem
1. Assessment
2. Risk analysis
3. Public education
4. Political education
5. Follow-through
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