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Lecture 28
Biodiversity & Human Impact
Global Changes & Challenges
 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
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Pollution
Acid precipitation
Ozone hole
Greenhouse effect
Loss of nonreplaceable resources
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
Modern Agricultural
 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
 Becoming more concentrated as they
moved up the food chain
 Modern agriculture also requires lots
of fossil fuels:
 The green revolution increased fossil
fuel use in agriculture by 50-100%
 Today it takes 1 calorie of fossil fuels
to produce 1 calorie of food,
excluding processing, packaging, &
transportation
 It takes 29% more energy to produce
ethanol from corn than the amount of
energy produced by the ethanol
Acid Precipitation: Sulfur Pollution
 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)
 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!
 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
 Problems in implementation
 Who pays for the expense?
 Polluter and recipient are far from one another
The Ozone Hole: CFC Pollution
 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) that
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
 Every 1% drop in ozone content is estimated to lead to a 6% increase in
the incidence of skin cancers
The Greenhouse Effect: CO2 Pollution
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For over 150 years, our industrial society
has been relying on the burning of fossil
fuels
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This has greatly increased atmospheric levels of
carbon dioxide (CO2)
CO2 transmits radiant energy from the sun, but
traps infrared light, or heat and creates what is
known as the greenhouse effect
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The accumulation of CO2 and other
“greenhouse gases” (such as CFCs) have
led to global warming or climate change
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Average global temperatures could increase from 1oC to 4oC
Global warming will have serious effects on
 Rain patterns
 Areas experiencing droughts may see even less rain
 Agriculture
 The yields of some crops will increase, while the yields of other crops will
decrease
 Sea levels
 Melting of large stores of ice will cause water levels to rise increasing flooding of
low-lying lands
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!
 Economists have identified an
“optimum” amount of pollution
based on how much it costs to
reduce pollution versus the
social and environmental cost of
allowing pollution
 However, The indirect costs of
pollution often are not taken into
account!
Reducing Pollution
 In the US, three approaches have been proposed to curb
pollution
 Antipollution laws
 All cars are required to eliminate automobile smog
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Catalytic converters, more efficient gas engines, hybrids, and alternate fuel vehicles are a result
 The Clean Air Act of 1990 requires that power plants eliminate sulfur emissions
 Pollution taxes
 In effect, a government-imposed price hike that adds the “hidden” environmental
costs to the price of production.
 This can discourage consumption or encourage desired behavior
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The recycling tax on bottles and cans is an example
 Pollution trading (being tried in California)
 “Acceptable” pollution totals are set for each pollutant
 Companies own rights to pollute a given amount
 If one company wants to pollute more, or a new company wants to add
pollution, they have to buy the rights from someone who is not using theirs or
who will change behavior to produce less
 The cost of polluting then becomes subject to market values while the overall
level of pollution is kept within target levels
Preserving Nonreplaceable Resources
 The consumption or destruction of nonreplaceable resources is the
most serious problem humans face
 In addition to fossil fuels, key nonreplaceable resources are:
 Topsoil
 Groundwater
 Biodiversity
Preserving Nonreplaceable Resources
 Topsoil
 Is being lost at a rate of centimeters per decade
 The US has lost 25% of its topsoil since 1950!
 Solutions
 Terracing to recapture lost topsoil
 Alternate farming methods that do not rely on nitrogen fertilizers
 Creating ethanol from corn is trading topsoil for energy!
 Creating ethanol from cellulose biomass is potentially better for the soil
 Groundwater
 Seeped into its underground reservoir very slowly during the last ice
age over 12,000 years ago
 It is being wasted and polluted
 While we should all conserve our personal use of water
 It is also notable that if Californians quit watering all lawns (home and golf course) it would
reduce California water use by < 10%
 Agriculture consumes 85% of all freshwater resources
Preserving Nonreplaceable Resources
 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
 Species from these areas have been the basis of many of our modern wonder
drugs
 Marshes and swamps have been and continue to be drained for
economic development
 They play a major role in cleaning the water in our aquifers
 Commercial seed companies are replacing local farmers’ seeds and
reducing the genetic base of food crops
 In the early the 1970s 70% of the U.S. corn crop was lost to Southern corn
blight due to the narrow genetic base of commercial seed corn
 Marine resources are being threatened by over fishing, pollution, and
global warming.
 Loss of species entails three costs
 Direct economic value of the products
 Indirect economic value of the benefits
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For example, water purification by marshlands
 Ethical and aesthetic value
Loss of Biodiversity
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> 99% of species known to science are
now extinct
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Current rates of extinction are alarmingly high
Conservation biologists have identified
three key factors
1.
Habitat loss
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2.
Species overexploitation
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3.
Destruction
Pollution
Human disruption
Habitat fragmentation
Species that are hunted or harvested by humans
are at great risk of extinction
Introduced species
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The introduction of exotic species by humans has
wiped out or threatened many native populations
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!
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Habitat restoration
Captive propagation
Sustaining genetic diversity
Preserving keystone species
Conserving ecosystems
Habitat Restoration
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In many situations, habitat conservation is no longer an option
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Three programs for restoration, depending on the cause of the habitat
loss
1. Pristine restoration
2. Removing introduced species
3. Cleanup and rehabilitation
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
 California Condor: Another captive breeding program showing success
California Condor @ Pinnacles Nat. Monument
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
 To increase genetic diversity, individuals must be moved between
populations
Preserving Keystone Species
 Removal of keystone species can have disastrous consequences on
ecosystems
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Case History: Flying Foxes
 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
Conserving Ecosystems
 Isolated patches of habitat lose species far more rapidly than large
areas do
 Conservation biologists have therefore promoted the following
 The creation of mega reserves, Large areas of land that contain a core of one or
more undisturbed habitats
 The preservation of intact ecosystems
 This has been a primary issue of contention with the Alaskan oil
pipelines
 In addition to the potential for accidental pollution
 They create barriers across the habitat and migratory routes of many large arctic
animals
Finding Other Sources of Energy
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Many countries are turning to nuclear power for
their growing energy needs
 In 1995, > 500 nuclear reactors were producing
power worldwide
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In the US, nuclear power plants have not been
popular because of
 Ample access to cheap coal
 Public fears of the consequences of an accident
 Three Mile Island nuclear plant in 1979
 Chernobyl nuclear plant in 1986
The Costs of Nuclear Energy
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Nuclear power may provide plentiful cheap energy;
however, several problems must be overcome:
1.
Safe operation
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2.
Waste disposal
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3.
Spent nuclear fuel remains radioactive for thousands of years
Security
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4.
Fears of vast radioactive contamination
Fears of terrorists getting their hands on plutonium
Insuring energy payback
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Is nuclear really an alternative energy?
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In a study for the U.S. Department of Energy in the 1960s, Howard Odum
showed that the amount of fossil fuel energy required to:
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Mine and refine the uranium
Build & maintain the nuclear power plant
Deactivate the plant at the end of its life
Was equal to the amount of nuclear generated electricity the plant produced
during its life
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Note that his calculations did not include storing and monitoring the radioactive
waste for hundreds or thousands of years
Human Population Growth
 The human population has grown
explosively over the last 300 years
 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!
 One of the most alarming trends is
massive movement of people
towards urban centers
Trends in Human Population Growth
 The world’s population growth is
unevenly distributed among
countries
 Growth rate in developed countries
is 0.1% per year
 Growth rate in developing countries
is 1.9% per year
 The world population growth rate has been declining
 The United Nations attributes the decline to
 Increased family planning efforts
 Increased economic power and social status of women
 Slowing population growth helps sustain resources, but per capita
consumption is also important
Consumption in the Developed World
 The vast majority of the world’s
population is in developing
countries
 However, the vast majority of
resource consumption is in the
developed world
 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
 This disparity can be quantified
by calculating the ecological
footprint
 The amount of productive land
required to support a person
throughout his or her life
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As countries like China & India strive to
attain our lifestyle, their ecological
footprint expands
 The world’s natural resources are
already overtaxed
Individuals Can Make the Difference
 And ecosystems can recover
 Two examples serve to illustrate this point
 The Nashua River in New England
 Lake Washington in Seattle
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
 Industrial dumping is now banned
and the river has largely recovered
 Greatly aided passage of the
Massachusetts Clean Water Act of
1966
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
Solving Environmental Problems
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Coming to grips with a widely ignored ethical issue in our society:
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Recognizing that our own lifestyles (belief systems & behaviors) are
contributing to or causing many of these problems
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Technology may help us solve some problems and still maintain our lifestyle
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Ultimately we all need to ask ourselves how we are willing to change – and
what are we willing to give up (sacrifice) – to keep our planet habitable
by humans?
If you are ready to get involved in community issues, here are five
components for successfully solving an environmental problem
1.
2.
3.
4.
5.
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Is generating profits (or comfort) for ourselves by forcibly shifting the costs (or
discomfort) to someone else (present or future) ever ethical?
Assessment
Risk analysis
Public education
Political education
Follow-through
Doing nothing has the potential of destroying our planet as we know it
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Life will likely go on regardless of what we do
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Just not human life!