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 third-largest 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 forces shifted 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 (Denali) 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 flat-topped 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.

Water Systems

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.

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.

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 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. 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.

Lesson 2Human 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 GovernmentHow 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.

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 a constitutional 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 the Underground 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.

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 Islamist 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.

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.

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 megalopolis that 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.

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 jazz developed in African American communities throughout the United States. Jazz blended African rhythms with European harmonies.

Between 1910 and 1970, approximately 6 million African Americans migrated from the rural South to urban areas in the Northeast, West, and Midwest. Along with the movement of people, this migration spread African American music styles, including jazz and blues, around the country. As the music spread its popularity grew, and by the 1950s teenagers all over the country began buying blues albums from artists they heard on the radio. Popular blues artists at the time included Chuck Berry and Fats Domino.

Soon, artists began making music influenced by blues and jazz rhythms, combining them with other styles such as gospel and country. The result was a new and immensely popular style of music: rock-and-roll. These musicians, including Elvis Presley and Buddy Holly, gained a large following among the affluent youth of the 1950s. With the help of the boom in radio programming, rock-and-roll quickly gained popularity around the country. The blended origins and wide appeal of rock-and-roll music was an early step toward breaking down racial and social barriers that were prevalent in the nation at the time. By the 1960s, rock-and-roll had become a powerful method of protest for the country’s youth. Other popular music styles, including punk rock, country, rap, 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, gained popularity and legitimacy as it spread throughout the country and around the world.

The Global Reach of American Culture

American culture has had far-reaching influence. From movies and music to art and fashion, elements of American culture have been adopted into and adapted by other cultures around the globe. Both human migration and technology have contributed to this spread. In Australia, for example, local folk music mixed with American country and bluegrass styles in the early twentieth century. What emerged was a new type of music that combines American country sounds with themes of Australian folklore and outback life.

The enormous popularity of rock-and-roll in the 1950s likewise was not limited to the United States. The genre quickly found fans among teenagers around the world. Other musicians began to mimic the style, and soon artists like the Beatles and the Rolling Stones from Britain became international rock-and-roll sensations.

The graffiti art movement has also grown into a worldwide phenomenon. Graffiti is now immensely popular in places like São Paulo, Brazil, where tourists can take graffiti tours to view the wide range of colorful street art. In many places, including Australia, Iran, Greece, and Mexico, graffiti is used to make political or social statements. Though graffiti began as an illegal art form, today some graffiti art is commissioned by governments and private citizens for display.

Technology—including radio in the 1950s and the Internet today—has played a huge role in the diffusion of American culture, allowing people around the world to experience other cultures without leaving home. Movies and television have also played a role. Though local filmmaking continues to grow throughout the world, the United States still dominates global cinema. Through this popular media, American fashion, customs, art, and music are made available to the rest of the world. In some places, however, the growing influence of American culture has led to a backlash against “Americanization,” which is seen as a threat to local customs and ways of life.

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 postindustrial economy 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 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 long-distance 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.

Lesson 3People 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 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.

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 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 two-thirds of the continental United States had been caught in the worst drought the country had experienced in more than half a century

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 solar-powered 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 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.