Australasian realm

Australasian realm
carol · CC BY-SA 3.0 · source
Name	Australasian realm
Countries	Australia; Papua New Guinea; Solomon Islands; New Guinea; New Zealand; Indonesia (eastern provinces); Timor-Leste; Vanuatu; New Caledonia; Fiji; Micronesia (some islands)

Contents

Australasian realm The Australasian realm covers parts of Australia, New Guinea, New Zealand, and neighboring islands, forming a major biogeographic division recognized alongside the Palearctic realm, Nearctic realm, Neotropical realm, Afrotropical realm, Indomalayan realm, Oceanian realm, and Antarctic realm. The realm is distinguished by long-term isolation following the breakup of Gondwana, with links to paleogeographic events such as the Cretaceous–Paleogene extinction event and plate interactions involving the Australian Plate, Pacific Plate, and Indian Plate. Conservation frameworks like the World Wildlife Fund ecoregion schemes and institutions such as the Australian Museum, Museum of New Zealand Te Papa Tongarewa, and Papua New Guinea National Museum and Art Gallery work within its boundaries.

Definition and geographic boundaries

The realm is delineated to include mainland Australia, the island of New Guinea (comprising parts of Papua New Guinea and Indonesian provinces like Papua and West Papua), the island groups of New Zealand, the Solomon Islands, Vanuatu, New Caledonia, Fiji, parts of eastern Indonesia such as the Moluccas, the Bismarck Archipelago, and nearby oceanic islands recognized by biogeographers including Alfred Russel Wallace and modern scholars at institutions like the Smithsonian Institution and the Biodiversity Heritage Library. Boundaries with the Indomalayan realm are commonly drawn near the Wallace Line and the Lombok Strait, with intermediate transition zones like Wallacea and the Weber Line marking faunal turnover recognized in studies by Thomas Huxley and Ludwig Lorenz von Liburnau.

The realm’s geology reflects the fragmentation of Gondwana during the Mesozoic era and subsequent isolation by seafloor spreading linked to the Tethys Sea closure and collision events involving the Sunda Shelf and the Banda Arc. Tectonic uplift and subsidence in areas such as the Great Dividing Range and the Papuan Highlands produced montane habitats studied by geologists at the Geological Society of Australia and the New Zealand Geological Survey. Climatic shifts driven by Pleistocene glaciations, the El Niño–Southern Oscillation, and Holocene sea-level change shaped refugia and island biotas, themes explored in research published by the Australian Academy of Science, CSIRO, and the Royal Society of New Zealand.

Floristic composition shows deep Gondwanan affinities with relict lineages such as Nothofagus (southern beeches), Proteaceae (banksias, waratahs), Myrtaceae (eucalypts, melaleucas), and ancient gymnosperms like Agathis (kauri). Island endemics include the Amborella relative in New Caledonia, and unique radiations such as Eucalyptus on Tasmania and Macropod-associated woodlands. Floristic provinces recognized by botanists at Kew Gardens, Royal Botanic Gardens, Melbourne, Royal Botanic Garden Edinburgh, and the National Herbarium of New South Wales show high levels of endemism in regions like Southwest Australia, Cape York Peninsula, the Cape York Peninsula savannas, and the Daintree Rainforest, areas compared in studies by Joseph Dalton Hooker and Ferdinand von Mueller.

Faunal assemblages are notable for marsupials (e.g., Macropodidae kangaroos, wallabies), monotremes like the Platypus and Echidna, and diverse avifauna such as kiwi in New Zealand and cassowary species in New Guinea and northern Australia. Endemic insect radiations include diverse Lepidoptera and Coleoptera in the Papuan region; freshwater fishes show endemism in basins like the Murray–Darling basin. Notable vertebrate groups studied at institutions including the Australian National University and Museum Victoria include the Dromaiidae (emus), Phascolarctidae (koalas), and unique island endemics like the Kakapo and flightless takahē in New Zealand.

The realm comprises ecoregions ranging from tropical rainforests—such as the Daintree Rainforest and New Guinea lowland rainforests—to temperate sclerophyll woodlands, mallee shrublands, Mediterranean-climate shrublands of Southwest Australia, alpine zones in the Snowy Mountains and Southern Alps (New Zealand), mangrove systems along the Arafura Sea and Gulf of Carpentaria, and coral reef provinces including the Great Barrier Reef and Coral Sea. Ecoregion classifications used by the International Union for Conservation of Nature and the Conservation International include names such as New Guinea moist forests, Australian temperate forests, New Caledonia dry forests, and Fiji tropical moist forests.

Conservation assessments by the IUCN Red List, BirdLife International, and regional agencies like the Australian Department of Agriculture, Water and the Environment and Department of Conservation (New Zealand) identify threats including habitat loss from agriculture in places like the Brigalow Belt, invasive species such as Rabbits in Australia, Cane toads, rats in the Pacific, overfishing on reefs like the Great Barrier Reef, coral bleaching linked to climate change, and mining impacts in areas like Pilbara and Mt Isa. Protected-area networks include Kakadu National Park, Uluru-Kata Tjuta National Park, Fiordland National Park, and Eketahuna Reserve initiatives, while international agreements like the Convention on Biological Diversity and the Ramsar Convention guide wetland and biodiversity targets.

Human history involves indigenous societies such as the Aboriginal Australians, Torres Strait Islanders, Papuan peoples, and the Māori who shaped landscapes through practices like fire-stick farming and agroforestry documented in ethnographic work at the Australian Institute of Aboriginal and Torres Strait Islander Studies and the Museum of New Zealand Te Papa Tongarewa. Post-contact land use includes pastoralism, mining booms in regions like Kalgoorlie and Broken Hill, urbanization in cities such as Sydney, Melbourne, Auckland, and Brisbane, and development pressures on island economies in places like Vanuatu and Fiji. Regional planning bodies and research centers including the Australian Bureau of Agricultural and Resource Economics and the New Zealand Ministry for the Environment work on sustainable land management, while transboundary collaboration occurs via forums like the Pacific Islands Forum and scientific partnerships with the University of Queensland and University of Otago.

Category:Biogeographic realms