1. Chapter 18 Table of Contents Section 1 Global Change
The Environment
Table of Contents
Section 1 Global Change
Section 2 Effects on Ecosystems
Section 3 Solving Environmental Problems

2. Chapter 18 Objectives Recognize the causes and effects of acid rain.
Section 1 Global Change
Objectives
Recognize the causes and effects of acid rain.
Evaluate the long-term consequences of atmospheric ozone depletion.
Explain how the burning of fossil fuels has changed the atmosphere.
Analyze the proposed relationship between the greenhouse effect and global warming.

3. The Atmosphere and Ecosystems
Chapter 18
Section 1 Global Change
The Atmosphere and Ecosystems
Acid Rain
Human-induced environmental changes are affecting ecosystems worldwide and may lead to global change.
Sulfur introduced into the atmosphere by smokestacks can combine with water vapor to produce sulfuric acid.
The sulfuric acid is carried back to Earth’s surface in acidified precipitation is called acid rain.

4. The Atmosphere and Ecosystems, continued
Chapter 18
Section 1 Global Change
The Atmosphere and Ecosystems, continued
Acid Rain
Research suggests that the acid in precipitation added by human activity is having a dramatic effect.
In the United States and Canada, thousands of lakes are “dying” as their pH levels fall below 5.0.
Forests in the eastern United States and southern Canada are also being damaged.

5. Chapter 18
Section 1 Global Change
Acid Precipitation

6. Chapter 18 The Ozone Layer The Ozone Hole
Section 1 Global Change
The Ozone Layer
The Ozone Hole
In 1985, a researcher in Antarctica noticed that ozone levels in the atmosphere seemed to be as much as 35 percent lower than the average values during the 1960s.
Alarmed, scientists examined satellite images taken in previous years. They found that the disintegration of the Earth’s ozone shield was evident as far back as 1978.
Every year since then, more ozone has disappeared, and the ozone hole has grown larger.

7. Ozone “Hole” over Antarctica
Chapter 18
Section 1 Global Change
Ozone “Hole” over Antarctica

8. The Ozone Layer, continued
Chapter 18
Section 1 Global Change
The Ozone Layer, continued
The Ozone Hole
Because the decrease in ozone allows more ultraviolet radiation to reach the Earth’s surface, scientists expect an increased incidence of diseases caused by exposure to ultraviolet radiation.
In fact, in the United States, the number of cases of malignant melanoma, a potentially lethal form of skin cancer, has almost doubled since 1980.

9. Chapter 18
Section 1 Global Change
Ozone and Ecosystems

10. The Ozone Layer, continued
Chapter 18
Section 1 Global Change
The Ozone Layer, continued
What Is Destroying Ozone?
The major cause of ozone destruction is a class of chemicals called chlorofluorocarbons (CFCs).
High in the atmosphere, ultraviolet radiation from the sun is able to break the usually stable bonds in CFCs. The resulting free chlorine atoms then enter into a series of reactions that destroys ozone.
Today many countries limit or ban the use of CFCs.

11. Chapter 18 Global Temperatures
Section 1 Global Change
Global Temperatures
The average global temperature has been steadily increasing for more than a century, particularly since the 1950s.
In Earth’s long history there have been many such periods of global warming, often followed by centuries of cold.
Many scientists suspect, however, that human activity may be significantly contributing to global warming in modern times.

12. Change in Global Temperature
Chapter 18
Section 1 Global Change
Change in Global Temperature

13. Global Temperatures, continued
Chapter 18
Section 1 Global Change
Global Temperatures, continued
The Greenhouse Effect
The chemical bonds in carbon dioxide molecules absorb solar energy as heat radiates from Earth.
This process, called the greenhouse effect, traps heat within the atmosphere in the same way glass traps heat within a greenhouse.
There has been a large increase in carbon dioxide in the Earth’s atmosphere in recent times, which seems to be related to the burning of fossil fuels that has accompanied clearing of forests.

14. Chapter 18
Section 1 Global Change
The Greenhouse Effect

15. Chapter 18
Section 1 Global Change
The Greenhouse Effect

16. Global Temperatures, continued
Chapter 18
Section 1 Global Change
Global Temperatures, continued
Is Global Warming Occurring?
The correlation of increasing global temperatures with increasing carbon dioxide levels is very close.
In science, however, correlation does not prove cause and effect. Both global temperature and levels of greenhouse gases may be changing because of other variables that have not been recognized yet.
However, many scientists are convinced temperature and carbon dioxide levels are related.

17. Atmospheric Temperature and CO2 Levels
Chapter 18
Section 1 Global Change
Atmospheric Temperature and CO2 Levels

18. Chapter 18
Section 1 Global Change
Global Warming

19. Chapter 18
Section 2 Effects on Ecosystems
Objectives
Describe the effects of chemical pollutants on the environment.
Identify three nonrenewable resources.
Predict the potential consequences of uncontrolled population growth.
Contrast population growth in developing countries with that in industrialized countries.

20. Effects of Chemical Pollution
Chapter 18
Section 2 Effects on Ecosystems
Effects of Chemical Pollution
One important urban environmental problem is chemical pollution.
In a highly publicized example of pollution, a very large oil tanker ran aground off the coast of Alaska in Oil from the tanker heavily polluted 1,600 km (1,000 mi) of coastline and injured or killed thousands of marine animals.
Many of the most disastrous incidents of pollution involve industrial chemicals that are toxic or carcinogenic (cancer-causing).

21. Effects of Chemical Pollution, continued
Chapter 18
Section 2 Effects on Ecosystems
Effects of Chemical Pollution, continued
Agricultural Chemicals
In many countries, modern agriculture introduces large amounts of chemicals into the global ecosystem.
These chemicals include pesticides, herbicides, and fertilizers.
Industrialized countries, like the United States, now attempt to carefully monitor side effects of these chemicals.

22. Effects of Chemical Pollution, continued
Chapter 18
Section 2 Effects on Ecosystems
Effects of Chemical Pollution, continued
Agricultural Chemicals: Pesticides
Molecules of chlorinated hydrocarbons—a class of compounds that includes the pesticides DDT, chlordane, lindane, and dieldrin—break down slowly in the environment.
As these molecules pass up through the trophic levels of the food chain, they become increasingly concentrated. This process is called biological magnification.

23. Biological Magnification of DDT
Chapter 18
Section 2 Effects on Ecosystems
Biological Magnification of DDT

24. Biological Magnification of Toxins
Chapter 18
Section 2 Effects on Ecosystems
Biological Magnification of Toxins

25. Chapter 18 Loss of Resources Extinction of Species
Section 2 Effects on Ecosystems
Loss of Resources
Extinction of Species
Earth is losing many species. Some 10 percent of well-known species teeter on the brink of extinction.
Worst-case estimates are that we will lose up to one-fifth of the world’s species of plants and animals—about 1 million species—during the next 50 years.
An extinction of this size has not occurred in at least 65 million years, since the end of the age of dinosaurs.

26. Loss of Resources, continued
Chapter 18
Section 2 Effects on Ecosystems
Loss of Resources, continued
Loss of Topsoil
The United States is one of the most productive agricultural countries on Earth, largely because of its fertile soils.
This rich topsoil cannot be replaced, and it is being lost at a rate of several centimeters each decade.
Turning over the soil to eliminate weeds, allowing animals to overgraze ranges and pastures, and practicing poor land management all permit wind and rain to remove more and more of the topsoil.

27. Loss of Resources, continued
Chapter 18
Section 2 Effects on Ecosystems
Loss of Resources, continued
Ground-Water Pollution and Depletion
A third resource that we cannot replace is ground water.
Much ground water is stored within porous rock reservoirs called aquifers.
A great deal of ground water is being polluted by irresponsible disposal of chemical wastes. Once pollution enters the ground water, there is no effective way to remove it.

28. Loss of Resources, continued
Chapter 18
Section 2 Effects on Ecosystems
Loss of Resources, continued
Ground-Water Pollution and Depletion
Large amounts of ground water are being removed from many aquifers far faster than natural processes can replenish it.

29. Chapter 18
Section 2 Effects on Ecosystems
Aquifer Recharge Zone

30. Growth of the Human Population
Chapter 18
Section 2 Effects on Ecosystems
Growth of the Human Population
The human population is rapidly growing.

31. Chapter 18
Section 2 Effects on Ecosystems
Human Population

32. Growth of the Human Population, continued
Chapter 18
Section 2 Effects on Ecosystems
Growth of the Human Population, continued
Worldwide Rates of Growth
The world’s population exceeded 6 billion in October 1999, and the annual increase is now about 94 million people.
Population growth is fastest in the developing countries. It is slowest in the industrialized countries.
The United Nations projects that the world’s population will stabilize at 9.7 billion by the year 2050.

33. World Population Growth Patterns
Chapter 18
Section 2 Effects on Ecosystems
World Population Growth Patterns

34. Section 3 Solving Environmental Problems
Chapter 18
Objectives
Describe two effective approaches that have been taken to reduce pollution in the United States and abroad.
Evaluate the five major steps necessary to solve environmental problems.
Determine how individuals can take personal action to help solve environmental problems.

35. Chapter 18 A Worldwide Effort
Section 3 Solving Environmental Problems
Chapter 18
A Worldwide Effort
As human activities continue to place severe stresses on ecosystems, worldwide attention must be focused on solving these problems.
One of the most encouraging developments of the early 1990s was the global increase in efforts to reduce pollution.
International agreements to stop CFC production are one example. A great deal of progress has also been made in reducing air and water pollution.

36. A Worldwide Effort, continued
Section 3 Solving Environmental Problems
Chapter 18
A Worldwide Effort, continued
In the United States
Two effective approaches have been taken to reduce pollution in the United States.
The first approach has been to pass laws forbidding it.
A second effective approach to reducing pollution has been to make it more expensive by placing a tax on it.

37. Solving Environmental Problems
Section 3 Solving Environmental Problems
Chapter 18
Solving Environmental Problems
Five Steps to Success
There are five components to successfully solving any environmental problem:
1. Assessment: The first stage is scientific analysis of the problem, the gathering of information about what is happening.
2. Risk analysis: Using the information obtained by scientific analysis, scientists predict the consequences of different types of environmental intervention.

38. Solving Environmental Problems, continued
Section 3 Solving Environmental Problems
Chapter 18
Solving Environmental Problems, continued
Five Steps to Success
3. Public education: When it is possible to describe alternative courses of action, the public must be informed.
4. Political action: The public, through its elected officials, selects and implements a course of action.
5. Follow-through: The results of any action should be carefully monitored to see if the environmental problem is being solved.

39. Solving Environmental Problems, continued
Section 3 Solving Environmental Problems
Chapter 18
Solving Environmental Problems, continued
Two Success Stories: The Nashua River
Running through the heart of New England, the Nashua River was severely polluted by mills established in Massachusetts in the early 1900s.
The Nashua River Cleanup Committee presented bottles of dirty river water to politicians, spoke at town meetings, recruited business people to help finance a waste treatment plant, and began to clean garbage from the Nashua River’s banks.
Industrial dumping into the river is now banned, and the river has largely recovered.

40. Solving Environmental Problems, continued
Section 3 Solving Environmental Problems
Chapter 18
Solving Environmental Problems, continued
Two Success Stories: Lake Washington
Lake Washington was being polluted with nitrogen and phosphorous from 10 municipal sewage plants.
An ecology professor at the University of Washington in Seattle, W. T. Edmondson, became alarmed and began a campaign in 1956 to educate public officials about the danger.
After five years, as a direct result of his efforts, joint municipal taxes financed the cleanup of Lake Washington with a massive trunk sewer that rings the lake and carries treated discharge far out into Puget Sound.

41. Solving Environmental Problems, continued
Section 3 Solving Environmental Problems
Chapter 18
Solving Environmental Problems, continued
Your Contribution
You can save energy by walking, riding a bicycle, or taking public transportation to work or school.
Newspapers, aluminum products, glass containers, and many plastic containers can be recycled.
A resource- and energy-use inventory of your home can identify additional ways to help the environment.

42. Section 3 Solving Environmental Problems
Chapter 18
Recycling

43. Section 3 Solving Environmental Problems
Chapter 18
Conservation