Lecture 28 Biodiversity & Human Impact. Global Changes & Challenges Damage done to one of the...
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Transcript of Lecture 28 Biodiversity & Human Impact. Global Changes & Challenges Damage done to one of the...
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 Pollution Acid precipitation Ozone hole Greenhouse effect Loss of nonreplaceable resources
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
Chemical Pollution
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
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
Starting in 1975, the earth’s ozone shield began to disintegrate creating an ozone hole
The Greenhouse Effect: CO2 Pollution
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 and creates what is known as the greenhouse effect
The accumulation of CO2 and other “greenhouse gases” (such as CFCs) have led to global warming or climate change
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
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
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
For example, water purification by marshlands Ethical and aesthetic value
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 factors1. Habitat loss
Destruction Pollution Human disruption Habitat fragmentation
2. Species overexploitation Species that are hunted or harvested by humans
are at great risk of extinction
3. Introduced species 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! Habitat restoration Captive propagation Sustaining genetic diversity Preserving keystone species Conserving ecosystems
In many situations, habitat conservation is no longer an option
Three programs for restoration, depending on the cause of the habitat loss
1. Pristine restoration2. Removing introduced species3. Cleanup and rehabilitation
Habitat Restoration
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
Captive Propagation
Smaller populations have little genetic diversity
Sustaining 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
Removal of keystone species can have disastrous consequences on ecosystems
Preserving Keystone Species
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
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
Conserving Ecosystems
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 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
Nuclear power may provide plentiful cheap energy; however, several problems must be overcome:1. Safe operation
Fears of vast radioactive contamination
2. Waste disposal Spent nuclear fuel remains radioactive for thousands of years
3. Security Fears of terrorists getting their hands on plutonium
4. Insuring energy payback Is nuclear really an alternative energy?
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: 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 Note that his calculations did not include storing and monitoring the radioactive
waste for hundreds or thousands of years
The Costs of Nuclear Energy
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
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
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
The Nashua River
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
Lake Washington
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
Coming to grips with a widely ignored ethical issue in our society: Is generating profits (or comfort) for ourselves by forcibly shifting the costs (or
discomfort) to someone else (present or future) ever ethical?
Recognizing that our own lifestyles (belief systems & behaviors) are contributing to or causing many of these problems Technology may help us solve some problems and still maintain our lifestyle
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 problem1. Assessment
2. Risk analysis
3. Public education
4. Political education
5. Follow-through
Doing nothing has the potential of destroying our planet as we know it Life will likely go on regardless of what we do
Just not human life!
Solving Environmental Problems