Предыдущая страница реферата | 8  9  10  11  12  13  14  15  16  17  18 | Следующая страница реферата

When European settlers first arrived in North America, half of the land on the continent was covered with forests. The forests of the eastern and northern portions of the country were fairly continuous. Beginning with the early colonists, the natural vegetation was altered drastically as farmers cleared land for crops and pastures, and cut trees for firewood and lumber. In the north and east, lumbermen quickly cut all of the valuable trees before moving on to other locations. Only 10 percent of the original virgin timber remains. Almost two thirds of the forests that remain have been classified as commercial resources.

Forests still cover 23 percent of the United States. The trees in the nation’s forests contain an estimated 7.1 billion cu m (249.3 billion cu ft) of wood suitable for lumber. Private individuals and businesses, including farmers, lumber companies, paper mills, and other wood-using industries, own about 73 percent of the commercial forestland. Federal, state, and local governments own the remaining 27 percent.

Softwoods (wood harvested from cone-bearing trees) make up about three- fourths of forestry production and hardwoods (wood harvested from broad- leafed trees) about one-fourth. Nearly half the timber output is used for making lumber boards, and about one-third is converted to pulpwood, which is subsequently used to manufacture paper. Most of the remaining output goes into plywood and veneer. Douglas fir and southern yellow pine are the primary softwoods used in making lumber, and oak is the most important hardwood.

About half of the nation’s lumber and all of its fir plywood come from the forests of the Pacific states, an area dominated by softwoods. In addition to the Douglas fir forests in Washington and Oregon, this area includes the famous California redwoods and the Sitka spruce along the coast of Alaska. Forests in the mountain states of the West cover a relatively small area, yet they account for more than 10 percent of the nation’s lumber production. Ponderosa pine is the most important species cut from the forests of this area.

Forests in the South supply about one-third of the lumber, nearly three- fifths of the pulpwood, and almost all the turpentine, pitch, resin, and wood tar produced in the United States. Longleaf, shortleaf, loblolly, and slash pine are the most important commercial trees of the southern coastal plain. Commercially valuable hardwood trees, such as gum, ash, pecan, and oak, grow in the lowlands along the rivers of the South.

The Appalachian Highland and parts of the Great Lakes area have excellent hardwood forests. Hickory, maple, oak, and other hardwoods removed from these forests provide fine woods for the manufacture of furniture and other products.

In the 1990s the forest products industry was undergoing a transformation. New environmental requirements, designed to protect wildlife habitat and water resources, were changing forest practices, particularly in the West. The amount of timber cut on federal land declined by 50 percent from 1989 to 1993.

A3 Fishing

The U.S. waters off the coast of North America provide a rich marine harvest, which is about evenly split in commercial value between fish and shellfish. Humans consume approximately 80 percent of the catch as food.
The remaining 20 percent goes into the manufacturing of products such as fish oil, fertilizers, and animal food.

In 1997 the United States had a commercial fish catch of 5.4 million metric tons. The value of the catch was an estimated $3.1 billion in
1998. In most years, the United States ranks fifth among the nations of the world in weight of total catch, behind China, Peru, Chile, and Japan.

Marine species dominate U.S. commercial catches, with freshwater fish representing only a small portion of the total catch. Shellfish account for only one-sixth of the weight of the total catch but nearly one-half of the value; finfish represent the remaining share of weight and value.
Alaskan pollock and menhaden, a species used in the manufacture of oil and fertilizer, are the largest catches by tonnage. The most valuable seafood harvests are crabs, salmon, and shrimp, each representing about one-sixth of the total value. Other important species include lobsters, clams, flounders, scallops, Pacific cod, and oysters.

Alaska leads all states in both volume and value of the catch; important species caught off Alaska’s coast include pollock and salmon. Other leading fishing states, ranked by value, are Louisiana, Massachusetts,
Texas, Maine, California, Florida, Washington, and Virginia. Important species caught in the New England region include lobsters, scallops, clams, oysters, and cod; in the Chesapeake Bay, crabs; and in the Gulf of
Mexico, menhaden and shrimp.

Much of the annual U.S. tonnage of commercial freshwater fish comes from aquatic farms. The most important species raised on farms are catfish, trout, salmon, oysters, and crawfish. The total annual output of private catfish and trout farms in the mid-1990s was 235,800 metric tons, valued at more than $380 million. In the 1970s catfish farming became important in states along the lower Mississippi River. Mississippi leads all states in the production of catfish on farms.

A4 Mining

As a country of continental proportions, the United States has within its borders substantial mineral deposits. America leads the world in the production of phosphate, an important ingredient in fertilizers, and ranks second in gold, silver, copper, lead, natural gas, and coal.
Petroleum production is third in the world, after Russia and Saudi
Arabia.

Mining contributes 1.5 percent of annual GDP and employs 0.5 percent of all U.S. workers. Although mining accounts for only a small share of the nation’s economic output, it was historically essential to U.S. industrial development and remains important today. Coal and iron ore are the basis for the steel industry, which fabricates components for manufactured items such as automobiles, appliances, machinery, and other basic products. Petroleum is refined into gasoline, heating oil, and the petrochemicals used to make plastics, paint, pharmaceuticals, and synthetic fibers.

The nation’s three chief mineral products are fuels. In order of value, they are natural gas, petroleum, and coal. In 1996 the United States produced 23 percent of the world’s natural gas, 21 percent of its coal, and 13 percent of its crude oil. From 1990 to 1995, as the inflation- adjusted prices for these products declined, the extraction of these fossil fuels declined, increasing U.S. dependence on foreign sources of oil and natural gas.

The United States contains huge fields of natural gas and oil. These fields are scattered across the country, with concentrations in the midcontinent fields of Texas and Oklahoma, the Gulf Coast region of Texas and Louisiana, and the North Slope of Alaska. Texas and Louisiana account for almost 60 percent of the country’s natural gas production. Today, oil and natural gas are pumped to the surface, then sent by pipeline to refineries located in all parts of the nation. Offshore deposits account for 13 percent of total production. Coal production, important for industry and for the generation of electric power, comes primarily from
Wyoming (29 percent of U.S. production in 1997), West Virginia (18 percent), and Kentucky (16 percent).

Important metals mined in the United States include gold, copper, iron ore, zinc, magnesium, lead, and silver. Iron ore is found mainly in
Minnesota, and to a lesser degree in northern Michigan. The ore consists of low-grade taconite; U.S. deposits of high-grade ores, such as hematite, magnetite, and limonite, have been consumed. Leading industrial minerals include materials used in construction—mainly clays, lime, salt, phosphate rock, boron, and potassium salts. The United States also produces large percentages of the world’s output for a number of important minerals. In 1997 the United States produced 42 percent of the world’s molybdenum, 34 percent of its phosphate rock, 22 percent of its elemental sulfur, 17 percent of its copper, and 16 percent of its lead.
Major deposits of many of these minerals are found in the western states.

B Manufacturing and Energy Sector B1 Manufacturing

The United States leads all nations in the value of its yearly manufacturing output. Manufacturing employs about one-sixth of the nation’s workers and accounts for 17 percent of annual GDP. In 1996 the total value added by manufacturing was $1.8 trillion. Value added is the price of finished goods minus the cost of the materials used to make them. Although manufacturing remains a key component of the U.S. economy, it has declined in relative importance since the late 1960s. From 1970 to
1995 the number of employees in manufacturing declined slightly from 20.7 million to 20.5 million, while the total U.S. labor force grew by more than 46.2 million people.

One of the most important changes in the pattern of U.S. industry in recent decades has been the growth of manufacturing in regions outside the Northeast and North Central regions. The nation’s industrial core first developed in the Northeast. This area still has the greatest number of industrial firms, but its share of these firms is smaller than in the past. In 1947 about 75 percent of the nation’s manufacturing employees lived in the 21 Northeast and Midwest states that extend from New England to Kansas. By the early 1990s, however, only about one-half of manufacturing employees resided in the same region. Since 1947, the
South’s share of the nation’s manufacturing workers increased from 19 to
32 percent, and the West’s share grew from 7 to 18 percent.

In the North, manufacturing is centered in the Middle Atlantic and East
North Central states, which accounted for 38 percent of the value added by all manufacturing in the United States in 1996. Located in this area are five of the top seven manufacturing statesa—New York, Ohio, Illinois,
Pennsylvania, and Michigan—which together were responsible for approximately 27 percent of the value added by manufacturing in all states. Important products in this region include motor vehicles, fabricated metal products, and industrial equipment. New York, New
Jersey, and Pennsylvania specialize in the production of machinery and chemicals. This area bore the brunt of the decline in manufacturing’s value of national output, losing a total of 800,000 jobs from the early
1980s to the early 1990s.

In the South the greatest gains in manufacturing have been in Texas. The most phenomenal growth in the West has been in California, which in the late 1990s was the leading manufacturing state, accounting for more than one-tenth of the annual value added by U.S. manufacturing. California dominates the Pacific region, which specializes in the production of transportation equipment, food products, and electrical and electronic equipment.

B1a International Manufacturing

Рекомендуем скачать другие рефераты по теме: доклад, сочинение на тему.



Предыдущая страница реферата | 8  9  10  11  12  13  14  15  16  17  18 | Следующая страница реферата

Поделитесь этой записью или добавьте в закладки