Western Tropical Pacific
The main climate regime in the tropical western pacific is the tropical wet climate. This climate produces warm termperatures and abundant rainfall year-round. Tropical winds and warm ocean waters lead to the formation of immense rain producing clouds called cumulonimbus clouds. These clouds produce heavy rainfall almost daily. The combination of warm termperatures and abundant rainfall produce tropical rain forests.
The tropical wet-and-dry climates receive abundant rainfall during the warm, rainy summer season and experience a cool and dry winter. Vegetation in wet-and-dry climates is mainly savanna, and wooded savanna.
South of the Tropic of Capricorn, in the temperate forests and woodlands of eastern Australia, rain falls year-round; summers are warm or hot and winters are mild to cool.
The western tropical Pacific features many volcanic islands covered by jungles. (Image courtesy NOAA)
Coral Reefs
The western tropical Pacific ocean is home to many of the world’s coral reefs. reefs are often called “rain forests of the ocean” because they are home to an astonishing variety of plants and sea organisms. Coral reefs are an important asset to local communities. They provide an excellent source of sea food, provide resources for the development of new medicines, help protect coastal cities from storm damage and generate income from tourism.
Coral reefs support abundant undersea life. (Photograph courtesy NOAA)
Coral reefs grow only in shallow, tropical waters. (Map courtesy Reefbase)
Rain Forest
Palm trees are common in tropical rain forest habitats. (Photograph courtesy NOAA)
Rain forest covers New Guinea and narrow strips of coastal Australia. These regions are hot year-round and have very high rainfall. Usually, every month is very rainy, but in northern Australia, some rain forests experience two to three drier months, causing some of the trees to drop their leaves for several weeks. These forests are called semi-deciduous rain forests.
Rain forests are complex, with as many as five distinct vegetation layers from top to bottom. The tallest trees may be over 60 m tall, with tops as wide as a football field. Large woody vines, called lianas, are common in may rain forests. Although tropical rain forests receive 12 hours of sunlight daily, less than 2% of that sunlight ever reaches the ground. Epiphytes (plants that grow on the branches or trunks of other plants) and epiphylls (plants growing on the leaves of other plants) are smaller plants that use the tall trees as a way to reach the light near the top of the forest.
Rain forests have higher diversity than any other habitat on earth. There can be hundreds of species of trees even in a small area. Animal diversity is also highest in this habitat, especially among insects, birds, reptiles, and amphibians. Adaptations for living in trees are common, and include the abilities to climb, jump, swing, glide, and hang from branches.
The animal life in these rain forests is very different than in African rain forest. Among the unique mammals of New Guinea are the tarsier (the world’s smaller primate), apes called orangutans, gibbons, and huge bats called flying foxes. Australian rain forests are home to fruit bats, platypuses, echidnas, squirrel gliders, pythons, and giant land birds called cassowaries that pick over the forest floor for fruits and nuts. These forests are also home to many marsupials, including types of small kangaroos that climb in trees! Insectivorous marsupials, like the bandicoot, root around on the rain forest floor for insects.
Tropical Woodlands
These habitats occur in Australia where temperatures are high all year, but there is a better-defined dry season than in the tropical rain forest. The dominant trees of most Australian open forests and woodlands are species of Eucalyptus. Tropical woodlands are shorter than rain forest; trees may reach only 10-30 m and they are more widely spaced (open canopy). Trees have thicker bark (to combat fire), small leathery leaves and dry fruits (to combat desiccation), thorns (to combat grazing), and longer roots (to reach deeper ground water).
Leaf eating herbivores include arboreal animals such as possums, and ground dwelling marsupials such as wallabies and kangaroos. Flowers and nectar are important food sources for many birds, marsupials and insects.
Savanna
Savannas occur in Australia where there is a 6 to 8 month wet summer season and a dry winter season. The dry season is marked by months of drought and fire is frequent. Without the yearly drought and widespread fire, some scientists believe that tropical savannas would eventually change into tropical forests.
The tropical savanna contains tall grasses and occasional trees. Where trees are more common, savanna may be referred to as a wooded savanna. In savannas, trees have long tap roots to reach the deep water table, and thick bark for resistance to annual fires (thus palms are prominent in many areas). They shed their leaves during the dry season, and may use their trunks for water storage.
Australian savannas lack the large, diverse herds of grazing mammals that occur in African savannas. Australian savannas are grazed by kangaroos, wombats, and the ostrich-like emu. Dingos are important predators.
In the temperate zone to the south, savannas give way to short grass prairies. They are cooler, and contain different species of grass than savannas.
Arid Interior
The arid interior of Australia is covered by shrublands and two kinds of arid grasslands, called hummock grasslands and tussock grasslands. Rainfall is sparse and sporadic, falling mainly in winter in the south and in summer in the north.
Shrublands consist of multi-stemmed plants less than 5-8 m high. The canopy may be closed or open, and several layers may be present. Shrubland dominated by Acacia species is called “mulga”. In dense mulga there may be only one species (Acacia aneura). Where soils are salty or limy, special shrubs called “chenopods” grow, and the vegetation is referred to as “saltbush”.
Temperate Eucalypt Forest
Temperate eucalypt forest occur along the southern east coast where there is a warm summer and cool winter. Very cold temperatures are only experienced at high elevations. “Tall” eucalypt forests are “gum trees”) dominate these forests; they are evergreen trees with tough, leathery, aromatic leaves. Light penetrates to the ground in these forests, thus there is a moist, lush layer of vegetation on the ground, which often contains tree ferns.
Widespread inhabitants of tall eucalypt forest are marsupials such as koalas, wombats and ringtail possums. Parrots, cockatoos, and lorakeets occur in colorful flocks in eucalypt forests. Much of the forest in this part of Australia has been cleared for agriculture, and many native species of birds, plants and marsupials are threatened with extinction.