United States Geography

B14

c

Population

In 2007 Hawaii’s population was 1,283,388 and was very diverse, with no single ethnic group forming a majority. The original island inhabitants are thought to be Polynesian, or Pacific Islanders, who may have arrived as early as ad 750. Beginning in the mid-1800s, immigrants from China, Japan, the Philippines, Korea, Samoa, and other Pacific islands moved to Hawaii in response to U.S. sugar planters’ need for inexpensive labor. According to the 2000 census, people of Asian ancestry make up 41.6 percent of Hawaii’s permanent population. In recent years, a large influx of whites has added to the rich and complex “melting pot” found in the Hawaiian region. During the 1980s, Hawaii’s population grew by 23 percent, with the majority of this growth occurring in the city of Honolulu, located on the central island of Oahu.

Honolulu is the major city of the islands and the state capital. Approximately 75 percent of Hawaii’s citizens live in this metropolitan area, making it the state’s dominant economic, political, and population center. The islands’ other main urban centers, also located on Oahu, include Aiea, Kailua, Kaneohe, Pearl City, and Waipahu. All have fewer than 50,000 residents.

IV

Climates and Climatic Regions

Many people confuse weather with climate. Although the two are closely related, they have distinctly different meanings. Weather changes from day to day and sometimes from one hour to the next. It involves the temperature, precipitation, humidity, and wind factors at a particular time. Short-term decisions about matters such as whether to play baseball during the afternoon or carry an umbrella to work are based on weather.

Climate, however, represents weather conditions over extended periods of time. Repeating cycles of precipitation and temperature, along with complex interactions of wind patterns and seasonal sun, give us our climates. Long-term decisions about storing heating fuels, planning for irrigation, raising particular crops, or choosing particular features for housing designs all require a consideration of climate. The United States is a large country, and different types of climates are found in different parts of the country.

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A

Climate and Soil

Climate has a profound effect on soil composition. Soil types are composed of minerals, organic matter (decaying plant and animal material), water, and air. Soils differ depending on how much of these different ingredients they contain, and climate contributes to those differences. Climatic conditions, such as high wind and heavy rain, can accelerate the breakup of rocks into the small particles that form the basic material of soil. In addition, precipitation controls the movement of nutrients and chemicals in soils. For example, continuous heavy rains can cause leaching, a percolating process that carries away minerals that support plant life.

Climate also affects soils indirectly by acting through vegetation and animal life. A favorable climate that supports a large number of plants and animals may produce more productive soil due to the presence of humus, decaying plant and animal material that adds rich nutrients to the soil.

In the United States, soil characteristics vary considerably by climatic region. For example, soils in cooler continental climates are known as podzols, a soil type that is not very fertile. The leaching action of heavy rain and water runoff removes many of the nutrients from podzols. Lateritic soils, one of the least fertile soil types, are found in wetter and hotter climates. They are the dominant soil type in the southeast, particularly in Georgia, Alabama, and Mississippi. Rich, dark soils called chernozems are found in the Midwest and in grassland areas to the west. These are some of the richest soils in the world.

B

Climate and Ecological Systems

Climate plays a crucial role in establishing a region’s ecological system. Climate influences the processes that make soil, and it interacts with the soil to determine what plants and animals are able to live in a particular place. A dry, hot climate with poor soil will limit the variety of plants and animals to those specially adapted to survive on small amounts of water and few nutrients. On the other hand, a wet and warm climate with productive soil will promote a rich and varied range of plant and animal species.

Climate also influences the living habits of humans. Individuals in regions with severe winters wear heavy clothing to protect themselves from the cold, and they live in houses that are insulated for warmth. Those who reside in tropical regions wear lighter clothing and live in houses with maximum ventilation for relief from the heat. Economically, climate has a strong effect on agricultural activities. In climates that have long warm seasons and plentiful rain, agricultural crops thrive, but in drier regions, cattle ranching tends to be more prominent.

In order to understand all of the complexities of climates, geographers have long classified them according to temperature, moisture, and vegetation. As a result, unique plant varieties came to be associated with certain climatic regions. Also, animal groups depend on particular kinds of vegetation for food. When a natural interactive system of plants and animals develops, it is called an ecosystem. It includes the living organisms–plants, animals, bacteria, and viruses–as well as the nourishing matter they depend on. Nonliving matter includes water, soil nutrients, oxygen, and carbon dioxide from the air.

Ecosystems consist of all the plants and animals in a specific area and the ways in which they interact with nonliving elements of the environment. Ecosystems exist in water (both fresh and salt water) and on land, and they also include interactions with atmospheric influences. Examples of natural ecosystems are the equatorial and tropical zone rain forests, the monsoon forests, subtropical evergreen forests, midlatitude deciduous forests, cold needle-leaf forests, tall grass prairie, semideserts, desert, and arctic and alpine tundra.

C

Climatic Regions of the United States

Because of its midlatitude location and vast size, the United States experiences a wide variety of climates. At one extreme are the tropical islands of Hawaii; at the other, the arctic conditions of northern Alaska. The majority of Americans live between these two extremes in a group of climatic regions with unique moisture and temperature patterns.

Geographers have traditionally divided the 48 contiguous United States into two broad patterns of continental climate: the humid East and the arid West. The dividing line most often used is 100 degrees west longitude, an imaginary north-south line extending through the Great Plains from Texas to North Dakota.

The humid east receives abundant precipitation throughout the year. Winters in the northern part are very cold with much snowfall. In the southern part, rainfall is plentiful; summers are very hot but winters are mild. Because of its bountiful moisture, the humid east has also traditionally been a very important agricultural area. Once a land of vast forests, early settlers cleared the land as they moved westward. In some areas, cleared lands were cultivated, abused, exhausted, and eroded away. In other areas, vast forests have been replanted, as in the South, the Appalachians, and parts of the Midwest.

A climatic transition zone occurs on either side of the 100 degrees west longitude line. The eastern woodlands gradually give way to tall grass prairies, which in turn give way to steppes, where short grasses flourish. Few natural tall grass prairies exist today on the Plains. Over the past few centuries, farmers cultivated and planted most of the region with corn or wheat.

In the arid West, precipitation diminishes from east to west and eventually reaches the point where it becomes impossible to raise crops without irrigation. Some desert areas of Arizona, Nevada, and southern California receive less than 125 mm (5 in) of precipitation annually. The grazing of livestock is an important agricultural activity in these areas of mesquite bushes and cacti.

Not all of the West is dry. In fact, one of the wettest areas of the United States is located in the Pacific Northwest. On the west-facing slopes of the Cascades and the Coast Ranges, moisture-laden winds blow from the Pacific Ocean and drop their rain on the mountain slopes. This type of mountain-induced rainfall is known as orographic precipitation. It occurs when wet air rises along the slope of a mountain. As the air moves upward into cooler temperature zones, it expands and cools, releasing the moisture as precipitation. Because of this effect, the climate of the Northwest is cool and moist, and the land is covered with vast, coniferous forests.

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