Lecture 28Biodiversity & 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 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

California Condor @ Pinnacles Nat. Monument

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