The Australasian ecozone covers Australia, New Guinea and the easternmost islands of the Indonesian archipelago, including Sulawesi and the Lesser Sundas. New Zealand is also part of this ecozone.
The boundary between Australasia and Indomalaya follows the Wallace Line, named after the naturalist Alfred Russel Wallace who noted the differences in fauna between the islands either side of the line. The Islands to the west, 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.
To the East, Australia and New Guinea are distinguished by 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.
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 cliffs are the rocky land edges that face the sea. These are complex and diverse habitats that lie above the water line, where exposure to salty spray, wind, sun and rain all play their part, as does the type of rock.
Desert and dry scrubland describes 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.
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 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 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.
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 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 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 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 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.
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 an ecological perspective the Australasia ecozone is a distinct region with a common geologic and evolutionary history and a great many unique flora and fauna. In this context, Australasia is limited to Australia, New Guinea, New Zealand, New Caledonia, and neighbouring islands, including the Indonesian islands from Lombok and Sulawesi eastward. The biological dividing line from the Indomalaya ecozone of tropical Asia is the Wallace Line – Borneo and Bali lie on the western, Asian side.
Australia, New Zealand and New Caledonia are all fragments of the ancient supercontinent Gondwana, the marks of which are still visible in the Christmas Island Seamount Province and other geophysical entities. These three land masses have been separated from other continents, and from one another, for tens millions of years. All of Australasia shares the Antarctic flora, although the northern, tropical islands also share many plants with Southeast Asia.
Australia, New Guinea, and Tasmania are separated from one another by shallow continental shelves, and were linked together when the sea level was lower during the Ice Ages. They share a similar fauna which includes marsupial and monotreme mammals and ratite birds. Eucalypts are the predominant trees in much of Australia and New Guinea. New Zealand has no native land mammals, but also had ratite birds, including the kiwi and the extinct moa. The Australasia ecozone includes some nearby island groups, like Wallacea, the Bismarck Archipelago, Solomon Islands, and Vanuatu, which were not formerly part of Gondwana, but which share many characteristic plants and animals with Australasia.
Note that this zonation is based on flora; animals do not necessarily follow the same biogeographic boundaries. In the present case, many birds occur in both "Indomalayan" and "Australasian" regions, but not across the whole of either. On the other hand, there are few faunistic commonalities shared only by Australia and New Zealand, except some birds. Meanwhile, Australia, Melanesia and the Wallacea are united by a large share of similar animals, but few of these occur farther into the Pacific – but on the other hand, much of the Polynesian fauna is related to that of Melanesia.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.