Download File

1
Chapter 5-The United States
LESSON 1
Physical Geography of the United States
ESSENTIAL QUESTION • How do physical systems and human systems shape a place?
With over 3.5 million square miles (9 million sq. km) of land, the United States is the thirdlargest country in the world. Its natural environment is diverse and makes the country one of the
world’s most productive regions.
Landforms
How has tectonic activity helped create so many of the landforms in the
United States?
Many of the landforms of the United States can be traced back to glacial activity and the tectonic
plate movement of the Earth’s crust. The Pacific and Rocky Mountain ranges in the west and the
Appalachian Mountains in the east are the result of powerful tectonic plate activity. The tectonic
forcesshifted giant rock slabs upward.
Considered young in geologic terms, the Pacific Ranges of the United States consist of the Sierra
Nevada, the Cascade Range, the Coast Range, and the Alaska Range. Mount McKinley in the
Alaska Range, at 20,320 feet (6,194 m), is the highest point in the United States. The Rocky
Mountains begin in New Mexico and stretch northward over 3,000 miles (4,828 km). Between
the Pacific Ranges and the Rocky Mountains is an area of plateaus and dry basins that was
formed by volcanic lava seeping upward through cracks in the Earth’s crust. These lava
flows altered, or changed, the land forming the Columbia Plateau. Farther south are the flattopped mesas of the Colorado Plateau and the spectacular gorge of the Grand Canyon, which
plunges more than a mile into the Earth at its deepest points.
Extending eastward from the Rockies, the landscape flattens considerably to form the Great
Plains, which stretch from 300 miles (483 km) to over 700 miles (1,126 km) wide. The land of
the plains is higher in the west and slopes downward until it reaches the Central Lowlands. The
plains continue eastward to the base of the Appalachian Mountains, the oldest mountain range on
the North American continent. This range extends 1,500 miles (2,414 km), from Canada into the
state of Alabama. As tectonic plates within the Earth’s crust collided and pushed upward, they
formed the Appalachians. The resulting peaks were shaped further by ice and water. Between the
Appalachian Mountains and the Atlantic Coastal Plain lies the Piedmont, a low-rolling, fertile
plateau cut by many rivers.
The Hawaiian Islands, located about 2,400 miles (3,862 km) off the western coast of the
mainland United States, were formed when magma erupted from a spot on the seafloor, called a
hot spot. This hot spot created a string of 8 major and 124 smaller islands that make up the
Hawaiian Island chain.
Explaining How were the Pacific Ranges formed?
Water Systems
2
How have rivers and lakes been important to the economic development of
the United States?
Many lakes, rivers, and tributaries play a crucial role in many aspects of life. The Mississippi
River is one of the longest rivers in North America. It flows 2,350 miles (3,782 km) from
its headwaters, or source, in Minnesota and reaches a width of 1.5 miles (2.4 km) at its mouth,
where it empties into the Gulf of Mexico. The Colorado River and the Rio Grande both have
their headwaters in the Rocky Mountains where many tributaries merge to form these two major
waterways.
A physical feature called a divide determines the direction of river flow. The Continental Divide
is a high ridge in the Rocky Mountains. Waterways to the west of the divide flow into the Pacific
Ocean. Waterways to the east of the divide flow toward the Arctic Ocean, Hudson Bay, Atlantic
Ocean, and Mississippi River system.
In the eastern United States, the fall line marks the place where the higher land of the Piedmont
drops to the lower Atlantic Coastal Plain. Along the fall line, eastern rivers break into rapids and
waterfalls, preventing ships from the Atlantic Ocean from traveling farther inland. Many cities,
such as Philadelphia, Baltimore, and Washington, D.C., were established along the fall line.
Formed when glacier basins filled with water, Lake Superior, Lake Huron, Lake Erie, Lake
Ontario, and Lake Michigan make up the Great Lakes. The glaciers uncovered major deposits of
natural resources, including iron ore and coal, that later spurred explosive economic growth. The
Great Lakes serve many economic and recreational purposes, but none more valuable than the
Great Lakes–St. Lawrence Seaway System, a series of canals, rivers, and waterways linking the
Great Lakes with the Atlantic Ocean. The seaway helped make cities along the Great Lakes, such
as Chicago, powerful trade and industrial centers.
Explaining How were the Great Lakes formed?
Climate, Biomes, and Resources
What factors cause variations in climate and vegetation in the United
States?
The United States has a variety of climates. The climates differ for a number of reasons. The
high latitudes of Alaska have long, cold winters and brief, mild summers while the midlatitude
areas have temperate climates. Places with high elevation have cooler climates than do those
with low elevation. The United States even has tropical climates in the states of Hawaii and
Florida.
Climate Regions and Biomes
The Southeast has a humid subtropical climate that is rainy with long, muggy summers and mild
winters. Since it borders large bodies of water—the Atlantic Ocean and Gulf of Mexico—there is
3
no dry season. Maple, oak, and pine trees are plentiful, and many types of mammals, reptiles,
and amphibians are common.
Wetlands and swamps such as Florida’s Everglades shelter a great variety of vegetation and
wildlife. In late summer and early autumn, hurricanes—ocean storms hundreds of miles wide
with sustained winds of about 74 miles per hour (119 km per hour) or more—can pound the
region’s coastlines.
The climate of the Great Plains reflects its location in the center of the continent. Because this
area is far from the moderating influences of the ocean waters, it experiences very cold winters
and hot summers. This is known as a continental climate. Moreover, parts of this area have a
humid continental climate because they receive significant precipitation. This interior climate
also extends into the hills and plateaus between the Mississippi River and the Appalachian
Mountains. In the Great Plains and the eastern United States, violent spring and summer
thunderstorms called supercells often spawn tornadoes with winds that can reach 200 miles (339
km) per hour.
Some areas west of the Great Plains have a semiarid climate with a mixture of vegetation,
depending on latitude and elevation. These are transitional climates that occur between the
humid continental climates and the arid climates of the Colorado Plateau. Animals in semiarid
regions include deer, bison, coyotes, and wolves.
To the west of the semiarid regions, dry air moves down the leeward side of the mountains,
creating an arid climate. This is called the rain shadow effect. Plants in arid climates, such as
scrub bushes and cacti, have developed long root systems and other adaptations that allow them
to survive with little water.
A Mediterranean climate is found in central and southern California. Such a climate is confined
to coastal areas and is characterized by mild, wet winters and summers that are warm to hot and
dry. The vegetation consists of twisted, drought-resistant broad-leafed trees, known as chaparral
(sha•puh•RAL).
The Rockies and the Pacific Ranges have a high altitude climate characterized by cold, snowy
winters and warm, dry summers. Coniferous forests cover the middle elevations, and lichens and
mosses grow in higher elevations. In early spring, a warm, dry wind called the chinook
(shuh•NUK) blows down the eastern slopes of the Rockies. Mountain goats and mountain lions
are common. The interplay of ocean currents and westerly winds with the Pacific Ranges gives
the Pacific coast from northern California to southern Alaska a marine west coast climate. Parts
of this region receive more than 100 inches (254 cm) of rain each year. Ferns, mosses, grasses,
and coniferous forests grow here.
Large parts of Alaska have a subarctic climate with frigid winter temperatures of –70°F (–57°C)
in some places. Conifers such as pine and spruce are able to survive the cold. Many animals
thrive in the harsh climate of the subarctic, including grizzly bears, bald eagles, wolves, and
bobcats.
Natural Resources
The United States is rich with natural resources including water, fossil fuels, timber, fish, and
more. Fossil fuels were formed over hundreds of millions of years from the fossilized remains of
plants and animals. This makes them nonrenewable. Also, because they must be retrieved from
the ground, there can be damage to the environment when they are extracted from the Earth.
4
Fossil fuels include coal, petroleum, and natural gas. They can be found in great supply in Texas
and Alaska, which rank first and second respectively in U.S. petroleum reserves. The United
States has the largest known coal reserves in the world and soon may be the largest producer of
oil.
The United States has plentiful mineral resources as well. The Rocky Mountains yield gold and
silver. Other minerals include copper, lead, phosphates, uranium, bauxite, iron, mercury, nickel,
silver, tungsten, and zinc. Free and abundant access to this natural wealth helped to speed the
industrialization of the United States and has helped to create one of the most prosperous
countries in the world.
Fish are also an important natural resource. Commercial fishing in the Atlantic and Pacific
Oceans and the Gulf of Mexico is important to the U.S. economy. The large commercial fishing
companies and small family businesses provide employment for many people, as well as food for
domestic consumption and for export.
Identifying What factors contribute to the marine west coast climate?
LESSON 2
Human Geography of the United States
ESSENTIAL QUESTION • How do physical systems and human systems shape a place?
Urban lifestyles predominate in the United States, but traditional and rural values are still
respected. The country has also been enriched by the tens of millions of immigrants who have
come to America hoping to improve their lives.
History and Geography
How did physical geography and a spirit of independence influence the
development of the United States?
The physical environment has played a significant role in the patterns of settlement in the United
States. The largest city, New York City, is located on one of the world’s finest harbors as a result
of physical geography. Similarly, many people today choose to live in California for its
favorable climate and beautiful landscapes.
Growth, Division, and Unity
Scientific studies suggest that there were at least three migrations of people from Asia to Alaska.
They began about 15,000 years ago and occurred by land and by boat. The lives of Native
Americans, the descendants of these early peoples, were shaped by location and climate.
Native Americans occupied North America undisturbed until the mid-1500s when European
immigration began. The Spanish explored the southern region, setting up farms, ranches, military
posts, and missions. The French settled in the northeast and were involved in the fur trade.
5
After 1670, Britain controlled much of the land along the Atlantic coast, divided into three
colonial regions. The New England Colonies had rocky soil and a short growing season, but the
area’s harbors and an abundant supply of timber and fish made shipbuilding and fishing
important industries. The Middle Colonies had the fertile soil, mild winters, and warm summers
needed for growing cash crops for export. The mild climate, rich soils, and open land of the
coastal plain of the Southern Colonies were a favorable environment for plantation agriculture.
In 1763 France was forced to give up much of its North American empire to Great
Britain. Conflicts soon arose between Native Americans and colonial settlers. Settlers arriving in
the British colonies took the land of Native Americans. Loss of hunting and farming lands,
combined with European diseases, reduced Native American populations and severely disrupted
their cultures.
In the 1760s, the British government angered the colonists by imposing new taxes and limiting
their freedoms. The thirteen colonies eventually fought for independence from Britain in the
American Revolution (1775–1783). The outcome was an independent federal republic called the
United States of America.
During the 1800s, the United States more than doubled its territory. The country gained valuable
land and natural resources. For Native Americans, however, expansion led to the steady loss of
lands and restrictions on traditional ways of life.
Industrialization transformed the United States during this time. The first factories harnessed the
power of waterfalls along the fall line in the Northeast. Later, large supplies of coal in the
Midwest were used to fuel cheap steam power, thus making manufacturing profitable. As a
result, the Midwest became a leading center of industry, using the Great Lakes and rivers for
transportation.
In the South, cotton became a major cash crop as the textile industry grew in the Northeast. Land
was cleared for more plantations, and the labor of enslaved African Americans became critical to
the Southern economy. By the 1800s, however, some people were working to end slavery, and
many African Americans made their way north to freedom along theUnderground Railroad—a
network of safe houses.
Tensions between the industrialized North and the agricultural South mounted steadily until they
erupted in the American Civil War in 1861. After four bloody years, the North triumphed.
Slavery was abolished after the war and the country began rebuilding.
Changes and Challenges
In the late 1800s, the government encouraged the movement of people to the Great Plains to
speed up the settlement of the United States. New immigrants wanted land, and there was an
increasing need for food in the growing cities. Due to the dry conditions on the Great Plains,
settlers developed dry farming. Steel plows and steam tractors made farming easier, and fewer
people were needed for farm work. At the same time, the Industrial Revolution brought people to
cities in the Northeast and Great Lakes regions, or the Manufacturing Belt.
Europeans, Chinese, Mexicans, and others immigrated to the United States. Many helped build
the railroads. Joining the Central Pacific and Union Pacific railroads created a transcontinental
railroad. A network of railways moved manufactured goods from east to west and food products
from west to east.
6
Two world wars spurred economic growth. Assembly lines increased efficiency and improved
the standard of living. The population became more mobile and urbanized. By the 1990s, many
manufacturing activities were less important than the rising high-tech industries.
Social changes also took place. Immigration from Latin America and Asia increased. Minority
groups began to participate in business and politics. Native Americans negotiated with the
government over land claims.
Terrorism became a major concern of many Americans after September 11, 2001, when terrorists
hijacked four passenger planes, crashing them into the World Trade Center, the Pentagon, and a
Pennsylvania field. After such devastation, the United States launched a war on terrorism
focused on Afghanistan and Iraq.
Explaining Why did the Midwest become a center of industry?
Population Patterns
What factors influence population patterns in the United States?
More than 315 million people live in the United States today. While about 2.5 million are Native
Americans, a majority are immigrants or the descendants of immigrants from Europe, Asia,
Africa, and Latin America. Some arrived only recently, while others belong to families whose
ancestors came to the region centuries ago.
The average population density of the United States is about 87 people per square mile (33
people per sq. km). Outside of large urban areas, however, the population is widely distributed.
The Northeast and Great Lakes regions are densely populated because they are the historic
centers of industry and commerce. The Pacific coast attracts people looking for a mild climate
and economic opportunities, resulting in a population cluster there. The least densely populated
areas of the country include the subarctic region of Alaska, the dry Great Basin, and parts of the
arid and semiarid Great Plains.
The population structure of the United States is changing. The U.S. Census Bureau projects that
the population aged 65 and older will likely grow from some 40.2 million in 2010 to about 88.5
million by the year 2050. This increase presents challenges to the federal government as costs for
Social Security and Medicare rise. The health care sector, the business sector, and families will
also be affected.
Since the 1960s, the Manufacturing Belt has suffered a decline in population and economic
strength as manufacturers relocated. Many businesses moved to Sunbelt states in the South and
Southwest. Over the years, as mechanized agriculture has required fewer workers, the United
States also has experienced urbanization, the movement of people from rural areas to cities.
Today, most people in the United States live in the country’s 366 metropolitan areas. A
metropolitan area is a city with a population of at least 50,000 people including outlying
communities, called suburbs.
7
Many U.S. population clusters lie in coastal areas with strong economies linked to world trade.
Pacific coast cities provide important links to the rest of the world, especially to the growing
Asian economies. The megalopolisthat stretches from Santa Barbara, California, to Mexico is
also an important corridor for world trade. Along the Atlantic coast, a chain of closely linked
metropolitan areas from Boston, Massachusetts, to Washington, D.C., form the Boswash
megalopolis. The Great Lakes region has three megalopolises: one centered in Chicago, Illinois,
another in Buffalo, New York, and a third in Detroit, Michigan.
Speculating Provide a specific example of how the aging of the population might affect
Americans.
Society and Culture Today
How has immigration influenced the culture of the United States?
Today, the United States has one of the most diverse populations in the world. Some immigrants
have come to the United States to seek political and religious freedom or to find economic
opportunities. Others are fleeing wars or natural disasters. Rich natural resources, industry, and
economic wealth make the United States an attractive destination.
Throughout history, immigrants have often faced discrimination, but they have invariably
enriched their new country through their hard work and talents and by bringing greater cultural
diversity to the country. In 2012 the Census Bureau reported that 13 percent of the total U.S.
population was foreign born and that more than half of the foreign-born population came from
Latin America.
Immigrants have contributed to the country’s diverse religious beliefs. Since the country’s
founding, religious freedom has been a core value in the United States. Today, most Americans
who are members of an organized religion are Christian, with the majority being Protestant.
Judaism, Islam, and Buddhism are among the other religions practiced in the United States.
About 16 percent of the U.S. population today is not affiliated with any organized religion.
Family and Status of Women
Although population patterns in the United States continue to change, the family remains a vital
institution. About half of adults are married, but some are single people living alone, or single
mothers or fathers living with their children. More and more women work outside the home.
Women have also continued to make gains in college completion rates, exceeding the graduation
rate of men for the people between the ages of 25 and 34.
The Arts
The history of music in the United States can be traced back to Native American traditions.
Europeans later brought their own folk and religious music. At the start of the 1900s, a distinct
form of music known as jazzdeveloped in African American communities throughout the United
States. Jazz blended African rhythms with European harmonies. By the second half of the
century, country music and rock-and-roll had become popular, not only in North America but
8
around the world. Blues, punk rock, and hip-hop all have their origins in the United States,
though hip-hop also traces its roots to the dance hall musicians of Jamaica.
Many styles of art can also be found in the United States. In the early 1900s, a group of
American artists known as the Ashcan School painted the grim realities of urban America. In the
mid-1900s, many artists adopted European abstract styles, which express artists’ emotions and
attitudes without depicting recognizable images.
The American-born graffiti art movement, begun by disenfranchised urban youth, has grown into
a worldwide phenomenon. Graffiti is now created by artists who are commissioned by
governments and private citizens to create enormous and intricate works of art.
Identifying What is the most common religion practiced in America today?
Economic Activities
How is the U.S. economy an important part of the global economy?
The United States has always been based on a free market economy and experiences ups and
downs. Between the two world wars in the twentieth century, a long and devastating depression
affected tens of millions of Americans. As the 1950s began, the manufacturing sector became a
driving force of the economy. Manufacturers helped the economy by turning from wartime
production to the manufacturing of cars, televisions, and appliances.
Today, the U.S. economy is a free market economy that allows people to profit from owning
their own businesses. This freedom—coupled with laws that protect private property rights,
employment opportunities, and the health and safety of workers—has created a great economic
power. The country’s wealth, measured in terms of gross national product (GNP), is due to
universal education, technology and innovation, abundant natural resources, high agricultural
output, and highly developed industries. The country has important reserves of natural gas and
petroleum and is also a world leader in coal exports.
Resources, Power, and Industry
Agriculture in the United States has undergone many changes since the 1950s. The average size
of farms has grown and continues to grow. Manufacturing has also evolved. The number of
manufacturing jobs has declined while time efficiency and productivity have increased for most
U.S. factories.
While agriculture and manufacturing are still important, the postindustrialeconomy is
dominated by high-tech, biotechnology, and service industries. The service sector has grown
more than any other part of the economy in recent decades. In the high-tech industry,
California’s Silicon Valley and cities such as Seattle, Washington, and Austin and Dallas, both in
Texas, are leaders in software development. The North Carolina cities of Raleigh, Durham, and
Chapel Hill form the Research Triangle region, known for attracting biotechnology companies.
In recent years, businesses in the United States have turned to offshoring, the practice of setting
up plants abroad to produce parts or products for domestic use and international sale. While
9
offshoring decreases the costs of goods, some people argue that it takes jobs away from
American workers.
Good transportation and reliable communications are crucial to the economy of the United
States. The automobile is still the most commonly used personal transportation method in the
country. Its use has resulted in large investments in the building and maintenance of highways,
roads, and bridges. The country also relies on air travel as a major method of transportation. A
large percentage of the freight in the United States is transported by truck. The country’s longdistance communications are carried via wireless, microwave, and satellite relays. Cellular and
digital services have made mobile communication the norm, with fewer and fewer households
using traditional landline telephones.
The Economic Downturn
In 2008 the United States entered a serious economic downturn caused by an excessive number
of ill-advised home mortgage loans. This resulted in a record number of homes going
into foreclosure. The downturn was called the subprime mortgage crisis. At the same time, the
stock market became unstable and unemployment rose. The bad loans led to the failure of some
large banks and required large government investments to save many other banks. Because the
U.S. economy and financial system are so important to the global economy, many other
countries also spiraled into an economic downturn. The U.S. and global economies are
improving but still growing less than is needed for robust health.
Describing What are the characteristics of the U.S. free market economy?
LESSON 3
People and Their Environment: The United States
ESSENTIAL QUESTION • How do physical systems and human systems shape a place?
Although the United States is a land of unparalleled opportunity, its natural resources are not
limitless, and its environment is not immune to potential harm. In many ways, modern life—with
its ravenous use of natural resources, destruction of habitats, and contamination of the
environment—poses a threat to American society. Efforts have occurred among concerned
citizens and their federal, state, and local governments to ensure that U.S. resources will
continue to exist in the future.
Managing Resources
Why are water and timber resources in the United States in need of
responsible management?
Forests are one of the United States’s major natural resources. However,clear-cutting, or the
removal of whole forests when harvesting timber, occurs in many areas today. Clear-cutting has
destroyed much of the country’s old-growth forests. As a result, forest ecosystems are less
diverse. In addition, wildlife is endangered and the land is subject to erosion and flooding.
In addition to threats posed by the destruction of the forests, people in some areas of the country
also face water shortages and groundwater depletion. This is due partly to the fact that people in
the United States consume much more freshwater than people in any other country. People use
water in all aspects of daily life—at home and in manufacturing, energy production, and
10
agriculture. The Environmental Protection Agency (EPA) calculates that each U.S. home uses an
average of 400 gallons (1515 l) of water daily. The EPA also estimates that industry accounts for
46 percent of water usage overall.
Pollution threatens many wetland areas, which include marshes, ponds, and swamps. Wetlands
also disappear when they are converted to agricultural or urban land uses. Wetlands are
important because they hold valuable water supplies and fisheries and in many cases buffer
coastal areas from storms and floods. In New Orleans, Louisiana, for example, the building of
levees, or raised embankments, around the city has destroyed wetlands that once protected the
area from flooding.
Successful resource management must include understanding and respecting the balances that
exist in natural ecosystems. Overfishing, which occurs when the number of fish that are caught
exceeds the number that can be resupplied by natural reproduction, has depleted many of the
region’s fisheries. The accidental or deliberate introduction of non-native plant and animal
species, on the rise because of increased global travel and trade, also causes environmental
problems. These include blocked waterways, crop destruction, and displacement of crucial native
species. Efforts to reverse the damage to the environment have begun, but the country has a long
way to go toward achieving the sustainable use of its natural resources.
Explaining What are two causes of wetland habitat destruction in the United States?
Human Impact
How can human activity lead to air and water pollution?
While economic growth and industrial development have dramatically improved the standard of
living in the United States, an unfortunate consequence has been the polluting of the air and
water. Acid rain, precipitation carrying high amounts of acidic material, affects a large area of
the eastern United States. Acid rain corrodes stone and metal buildings, damages crops, and
pollutes the soil. It is especially damaging to the region’s waters, as plant life and fish cannot
survive in highly acidic waters. Over time, lakes can become biologically dead, or unable to
support most organisms.
Smog is a second type of human-made pollution that has had long-term negative environmental
impacts in the United States. Various chemicals, largely from automobile exhaust and industrial
emissions, contribute to the production of smog. Smog is a mixture of atmospheric pollutants,
including carbon monoxide, sulfur, nitrogen oxide, hydrocarbons, and particulates. As the sun’s
rays interact with these chemicals, a visible haze forms. This haze can damage or kill plants and
harm people’s eyes, throats, and lungs. Officials in many of the metropolitan areas in the United
States measure air quality on a daily basis. When dangerous levels of smog are detected, officials
issue air quality alerts urging children, the elderly, and people with respiratory problems to limit
their physical activity and to stay indoors. Authorities may prohibit nonessential driving and the
use of other gasoline-powered engines to reduce smog.
Massive amounts of waste and pollutants are produced in the United States. Although the United
States has extensive facilities to control and treat sewage and industrial wastes, problems still
arise. As a result, water systems have become tainted. Industrial wastes may be illegally dumped
into rivers and streams or may find their way through small, unnoticed leaks into the
groundwater. Industries also cause thermal pollution by releasing heated industrial wastewater
11
into cooler lakes and rivers. Runoff from agricultural chemicals, such as fertilizers and
pesticides, can also pollute the water. One area with serious water pollution issues is the Great
Lakes region.
Water pollution has harmful effects on marine life and the birds and other animals that feed on
fish or breed in the wetlands. The toxic chemicals and wastes that pollute the water supply also
pose a danger to humans. Water pollution speeds eutrophication (yu•troh•fuh•KAY•shuhn), the
process by which a body of water becomes rich in dissolved nutrients, encouraging the
overgrowth of small plants, especially algae. The algae growth can deplete the water’s oxygen,
suffocating fish. Algae overgrowth can also turn a lake into a marsh and then, over many years,
into dry land. One wetland area that has been severely damaged in this way is the Florida
Everglades.
Another problem is the growing water shortage crisis across the country. Of major concern is the
projection that 36 states will face water shortages in the next several years. In 2012 alone, water
shortages turned into full-on droughts across much of the United States, causing billions of
dollars in crop and livestock losses. By September 2012, it was estimated that more than twothirds of the continental United States had been caught in the worst drought the country had
experienced in more than half a century.
Describing Describe how industries contribute to water pollution in the United States.
Addressing the Issues
How are environmental issues in the United States being addressed?
The United States has made major strides toward protecting the environment. Clean-air practices
have substantially reduced air pollution in some major cities. Renewable sources of energy for
power—including hydroelectric, solar, and wind—are growing in popularity. Automobile
manufacturers are producing more fuel-efficient vehicles, including hybrid vehicles that have
both an electric motor and a gasoline engine. Engineers are working to develop other
alternatives, including fuel cell vehicles, which produce electricity using hydrogen fuel and
oxygen; biofuel vehicles, which use fuel from organic sources such as plant oils; and solarpowered cars. Legislation sets limits on the amount of sulfur and other pollutants that can be
present in fuels. In addition, many individuals try to do their part to reduce smog
by abandoning automobiles in favor of other modes of transportation, such as walking,
bicycling, subways, and buses.
Reducing waste and recycling help limit pollution. Many cities and towns practice recycling to
help reduce the amount of garbage in the country’s landfills. Scientists in the United States are
also working to further this goal by developing plastics that will degrade naturally.
Since about the 1970s, many private and governmental organizations have championed the cause
of environmental conservation. For example, numerous federal agencies have stepped up their
efforts not only to conserve and protect the forests, but also to promote passage of legislation that
ensures the timber industry will behave responsibly in their use of this resource. Replanting and
conservation have also had a favorable impact on the country’s forests.
Another form of federal legislation is the Clean Water Act, passed by the federal government in
1972. It has done much to restore the quality of water throughout the United States. The Great
12
Lakes Water Quality Agreement, signed by the United States and Canada in 1972, led to the end
of asbestos dumping in the Nashua River and spurred the construction of wastewater treatment
plants. These facilities protected the river from paper pulp, chemical dyes, and other industrial
wastes. Like many of the country’s waterways, the Nashua River slowly regained its health.
Today it is once again safe for wildlife and people.
The passage of the North American Free Trade Agreement (NAFTA), however, has shifted some
environmental concerns south to the U.S.-Mexico border. Along the Rio Grande, rapid industrial
growth threatens the environment. Various agencies are monitoring the environmental effects of
NAFTA and suggesting ways to reduce pollution.
An example of human-environment interaction is the California State Water Project, the
country’s largest state-built water and power development project. It was designed to meet the
needs of California’s ever-growing population. Aqueducts, or systems of channels and pipelines,
are used to carry water for hundreds of miles to more than 25 million Californians and to
750,000 acres (303,515 ha) of irrigated farmland. County and state water commissions have
implemented plans to manage demand during times of limited supply. Similar policies have been
put into action in counties and states across the country.
In response to global warming and greenhouse gases, the United States is working to diversify
energy sources to lessen its dependence on fossil fuels. Governments offer subsidies to utility
companies to limit emissions and to include renewable energy sources in their future plans. Solar
panels and biofuels made from corn and other organic sources are among the potential renewable
energy sources.
Identifying What are three types of renewable energy sources?