Southeast Asia, Oceania, and Antarctica: Climate and Vegetation

A HUMAN PERSPECTIVE During the Vietnam War, American troops were sent to fight in unfamiliar Southeast Asia. Among the hardships they endured was the tropical climate. Few had ever lived in a place that had a monsoon season with constant rain. One soldier wrote to his wife, “We live in mud and rain. I'm so sick of rain that it is sometimes unbearable. At night the mosquitoes plague me. . . . The rain drips on me until I go to sleep from exhaustion.”

Another soldier wrote to a friend about the vegetation: “Try to imagine grass 8 to 15 feet high so thick as to cut visibility to one yard, possessing razor-sharp edges. Then try to imagine walking through it.” As these letters make clear, climate and vegetation can create serious obstacles to military operations—or other activities.

Widespread Tropics

Although the conditions that American soldiers encountered seemed unusual to them, they really aren't rare. Vietnam is just one of many countries in this region with a tropical climate. In fact, tropical climates cover most of Southeast Asia and Oceania. Tropical climates fall into two categories, depending on when it rains during the year.

YEAR-ROUND RAINS

A tropical wet climate is found in coastal parts of Myanmar, Thailand, Vietnam, and Oceania, and in most of Malaysia, Indonesia, and the Philippines. Temperatures are high. For example, most of Southeast Asia has an average annual temperature of 80°F. Parts of Southeast Asia receive over 100 inches of rain a year, with some places receiving more than 200 inches.

Although the climate is fairly consistent, variations do exist within the region. Elevation, ocean breezes, and other factors can create cooler temperatures. For example, Indonesia has some locations at such a high elevation that they have glaciers.

WET AND DRY SEASONS

Bordering the wet climate is the tropical wet and dry climate, in which monsoons shape the weather. As you read in Unit 8, monsoons are winds that cause wet and dry seasons. This climate is found in parts of Myanmar, Thailand, Laos, Cambodia, and Vietnam—generally to the north or inland of the wet climate. Parts of Oceania and northern Australia also have this climate.

Although temperatures are consistently hot, rainfall varies greatly within the climate zone. Local conditions and landforms can affect precipitation amounts.

For example, mountains create rain shadows.

Areas with monsoons often experience disastrous weather. During the wet season, typhoons can occur in Southeast Asia and Oceania.

TROPICAL PLANTS

Southeast Asia has one of the greatest diversities of vegetation of any region. For example, it has a remarkable number of tree species. Near the equator are tropical evergreen forests, while deciduous forests are more common in the wet and dry climate zone. Teak, a valuable tree that Asians harvest commercially, comes from these deciduous forests. Southeast Asia also has many types of plants. In general, Oceania does not have diverse vegetation. The low islands have poor soil and small amounts of rain, so plants don't grow well. Some high islands have rich, volcanic soil and plentiful rain. These islands have abundant flowers and trees, such as the coconut palm.

Bands of Moderate Climate

Australia is the only inhabited continent that lies completely in the Southern Hemisphere. New Zealand is even farther south. Australia and New Zealand have generally moderate climates.

HOT SUMMERS, MILD WINTERS

As Section 1 explained, a mountain chain runs parallel to the east coast of Australia. The strip between the mountains and ocean is divided mostly into two climate zones. The northern part of this strip has a humid subtropical climate, with hot summers, mild winters, and heavy rainfall. It is one of Australia's wettest regions, receiving an average of 126 inches of rain a year. This climate also exists in northern Vietnam, Laos, Thailand, and Myanmar.

MILD SUMMERS, COOL WINTERS

New Zealand and the southern part of Australia's east coast share a marine west coast climate. The seasons have mild temperatures because ocean breezes warm the land in the winter and cool it in the summer. New Zealand's forests consist primarily of evergreens and tree ferns, which thrive in such a climate.

New Zealand receives rainfall year-round, although the amount varies dramatically from one part of the country to another. For example, the mountains of South Island cause rain to fall on their western slopes, so the eastern part of the island is dryer. Mountains change the climate in another way. The mountainous inland areas of New Zealand are cooler than the coastal areas. Temperatures drop about three-and-ahalf degrees for every 1,000-foot rise in elevation.

Mountains influence Australia's climates, too. The Great Dividing Range forces moisture-bearing winds to rise and shed their rain before moving inland. For that reason, the marine west coast and humid subtropical climates exist only on the east coast. That coast is Australia's most heavily populated region. The moist coasts are also the only parts of Australia with enough rain for trees that grow taller than 300 feet.

Hot and Cold Deserts

As you learned earlier in this book, there are many types of desert. For example, two very different deserts exist in Australia and Antarctica.

ARID AUSTRALIA

One-third of Australia is desert, lying in an oval in the center of the continent. This region receives less than 10 inches of rain a year and is too dry for agriculture or for grazing. Encircling the desert is a band of semiarid climate that receives no more than 20 inches of rain a year. Crops can only be grown there by using irrigation.

Several factors cause Australia's dryness. Because it lies in the tropics and subtropics, Australia is very hot, so rain evaporates easily. And as you read earlier, mountains and uplands force the winds from the ocean to rise and shed their rain on the coasts instead of the interior.

Very few people live in the dry interior. Australians call the unpopulated inland region the outback. The few people who live in the outback receive medical care from the Royal Flying Doctor Service.

THE WHITE DESERT

With its lands located around the South Pole, Antarctica is earth's coldest, driest continent. It has an icecap climate. In the winter, inland temperatures can fall to 70°F below zero or colder.

Cold air doesn't hold moisture well, so Antarctica's air has only onetenth the water vapor found in the atmosphere of temperate regions. As a result, Antarctica receives little precipitation and is often called a polar desert. But it has heavy snow and ice cover because the snow that does fall rarely melts.

Antarctica's only plants are those, such as lichens and mosses, that can survive severe cold and long periods of darkness. Its animals are mostly sea life and birds, including several types of penguins. In Section 3, you will learn about examples of human-environment interaction in this region.