Australasia

Habitats in this ecozone

• Broadleaf forest

  Broadleaf forests are the dominant habitat of the UK and most of temperate northern Europe. There's little left of Britain's ancient wildwood, but isolated pockets of oak, beech and mixed deciduous and evergreen woodlands are scattered across the continent, and dictate its biodiversity.

• Coastal

  The coastal habitat represents the strip of land above the high tide mark, but still near or influenced by the sea. It includes places such as cliffs where seabirds can nest, the splash zone where salt-tolerant lichens grow and areas of dunes and marram grass behind the beach.

• Desert

  Desert is any area that receives less than 250mm of rainfall a year. Not just the endless, baking sand dunes of popular conception, it includes arid areas in temperate regions.

• Mangroves

  Mangrove forests grow on tropical coasts with soft soils and are flooded twice daily by the tide. They are important nursery areas for many species of fish.

• Mediterranean forest

  Mediterranean forest includes the fynbos of South Africa, the matorral of Chile and forests in parts of California. Hot, dry summers, contrast with much milder, wetter winters.

• Mountain grassland

  Mountain grasslands such as those in the Ethiopian highlands, on the Tibetan Plateau and up in the Andes, include the alpine tundra above the treeline as well as grasslands below it. These high altitude grasslands often exist as isolated 'islands' in a sea of another habitat type.

• Rainforest

  Rainforests are the world's powerhouses, the most vital habitats on the planet. Characterised by high rainfall, they only cover 6% of the Earth across the tropical regions, but they contain more than half of its plant and animal species.

• Temperate grassland

  Temperate grasslands include the prairies of North America, the steppes of Russia and the pampas of Argentina. Summers here are mild to hot and the winters can sometimes be very cold – for instance, blizzards can blanket the great plains of the United States.

• Tropical dry forest

  Tropical dry forests, in contrast to rainforest, have to survive a long dry season each year, so the predominantly deciduous trees shed their leaves to cope with it. Sunlight can then reach the ground, so the season that's bad for the trees is good for the forest floor.

• Tropical grassland

  Tropical grasslands include the savanna usually associated with Africa, and savanna-type grasslands found in India, Australia, Nepal and the Americas. They are characterised by drought-resistant shrubs and grasses, dotted with trees such as acacias or baobabs.

• Tundra

  Tundra is the cold, treeless region around the poles that has permafrost as one of its defining features. Even at the height of summer, the soil a few centimetres under the surface remains frozen.

About

The Australasian zone is an ecological region that is coincident, but not synonymous (by some definitions), with the geographic region of Australasia. The ecozone includes Australia, the island of New Guinea (including Papua New Guinea and the Indonesian province of Papua), and the eastern part of the Indonesian archipelago, including the island of Sulawesi, the Moluccan islands (the Indonesian provinces of Maluku and North Maluku) and islands of Lombok, Sumbawa, Sumba, Flores, and Timor, often known as the Lesser Sundas. The Australasian ecozone also includes several Pacific island groups, including the Bismarck Archipelago, Vanuatu, the Solomon Islands, and New Caledonia. New Zealand and its surrounding islands are a distinctive sub-region of the Australasian ecozone. The rest of Indonesia is part of the Indomalayan ecozone.

From a biological point of view, Australasia is a distinct region with a common evolutionary history and a great many unique plants and animals, some of them common to the entire area, others specific to particular parts but sharing a common ancestry. The long isolation of Australasia from other continents allowed it to evolve relatively independently, and makes it home to many unique families of plants and animals.

Australia and New Guinea are distinguished by their marsupial mammals, including kangaroos, possums, and wombats. The last remaining monotreme mammals, the echidnas and the platypus, are endemic to Australasia. Prior to the arrival of humans about 50,000 years ago, only about one-third of Australasian mammal species were placental.

The boundary between Australasia and Indomalaya follows the Wallace Line, named after the naturalist Alfred Russel Wallace who noted the differences in mammal and bird fauna between the islands either side of the line. The Islands to the west of the line, including Java, Bali, Borneo, and the Philippines share a similar fauna with East Asia, including tigers, rhinoceros, and apes. During the ice ages, sea levels were lower, exposing the continental shelf that links these islands to one another and to Asia, and allowed Asian land animals to inhabit these islands. Similarly, Australia and New Guinea are linked by a shallow continental shelf, and were linked by a land bridge during the ice ages. A group of Australasian islands east of the Wallace line, including Sulawesi, Halmahera, Lombok, Flores, Sumba, Sumbawa, and Timor, is separated by deep water from both the southeast Asian continental shelf and the Australia-New Guinea continental shelf. These islands are called Wallacea, and contain relatively few Australian or Asian mammals. While most land mammals found it difficult to cross the Wallace Line, many plant, bird, and reptile species were better able to make the crossing.

Australia, New Zealand, and New Caledonia are all portions of the ancient supercontinent of Gondwana, which started to break into smaller continents in the Cretaceous era, 130-65 million years ago. New Zealand broke away first, more than 80 million years ago, and Australia finally broke free from Antarctica about 45 million years ago. All the Australasian lands are home to the Antarctic flora, descended from the flora of southern Gondwana, including the coniferous podocarps and Araucaria pines, and the broadleafed southern beech (Nothofagus), and proteas (Proteaceae).

As Australia moved north into the desert latitudes, the continent became hotter and drier, and the soils poorer and leached of nutrients, causing the old Antarctic flora to retreat to the humid corners of the continent in favor new drought- and fire-tolerant flora, dominated by the Eucalyptus, Casuarina, and Acacia trees, and by grasses and scrub where the rainfall was too scarce to support trees. Presently Australia is the smallest continent, and also the driest continent and the flattest (lowest in elevation) continent.

Read more at Wikipedia