Australasia ecozone 201212 200218472 2008-03-23T02:55:20Z CarolSpears 5000247 /* External links */ [[Image:Ecozone Australasia.svg|thumb|The Australasia Ecozone]] The '''Australasian ecozone''' is an [[ecozone|ecological region]] that is coincident, but not synonymous (by some definitions), with the [[geography|geographic]] [[region]] of [[Australasia]]. The ecozone includes [[Australia]], the island of [[New Guinea]] (including [[Papua New Guinea]] and the [[Indonesia]]n province of [[Papua (Indonesia)|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 [[Indomalaya]]n 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]] [[mammal]]s, including [[kangaroo]]s, [[possum]]s, and [[wombat]]s. The last remaining [[monotreme]] mammals, the [[echidna]]s and the [[platypus]], are [[endemic (ecology)|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 (island)|Java]], [[Bali]], [[Borneo]], and the [[Philippines]] share a similar fauna with East Asia, including [[tiger]]s, [[rhinoceros]], and [[ape]]s. During the [[ice age]]s, 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 [[conifer]]ous [[podocarpaceae|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]],[[casuarinaceae|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. ==Geology== The present distribution of Australasian plants and animals is partially a result of the geologic history of its land masses. Several of the land masses in the ecoregion are fragments of the ancient continent of [[Gondwana]], while a number of smaller islands are of more recent volcanic or tectonic origin, and were never part of Gondwana. New Guinea, Australia, and Tasmania, collectively known as [[Australia-New Guinea]], '''Sahul''', or '''Meganesia''', are connected by a shallow continental shelf, and together form the largest fragment of [[Gondwana]]. The shallow continental shelf that presently separates the islands has served as a land bridge when sea levels were lower, most recently during the last [[ice age]]. New Guinea shares many families of birds and marsupial mammals with Australia. As the [[Indo-Australian Plate]], which contains India, Australia, and the [[Indian Ocean]] floor in between, moved north, it collided with the [[Eurasian Plate]], and the collision of the two plates pushed up the [[Himalayas]], the Indonesian islands, and New Guinea's Central Range. The Central Range is much younger and higher than the mountains of Australia, so high that it is home to rare equatorial [[glacier]]s. New Guinea and Wallacea are part of the humid tropics, and many Indomalayan rainforest plants spread across the narrow straits from Asia, mixing together with the old Australian and Antarctic floras. Some botanists consider New Guinea and Wallacea to be part of the [[floristic province]] of '''[[Malesia]]''', together with the other Indonesian islands and the [[Malay Peninsula]], although Malesia is now mostly used to refer to only the Indomalayan side of the Wallace Line. New Zealand and New Caledonia are the other former fragments of Gondwana in the region. The island groups north and east of New Guinea and New Caledonia, including [[Bismarck Archipelago]], [[Admiralty Islands]], [[Solomon Islands]] and [[Vanuatu]], were pushed up by the collision of the Australian plate with other oceanic plates. These islands, collectively known as the [[East Melanesian Islands]], were colonized by plants and some animals from New Guinea and New Caledonia, and are considered part of the Australasian ecozone based on those affinities. Further north and east are the Pacific island groups of [[Micronesia]], [[Fiji]], and [[Polynesia]], which are also of relatively recent volcanic origin, and constitute the separate [[Oceania ecozone]], although they share many ecological affinities with Australasia. ==Fauna== Bats were the only mammals of New Zealand until the arrival of humans. Birds adapted to ecological niches, such as grazers, insectivores, and large predators that have elsewhere been taken by mammals. New Zealand remained in the cool and humid latitudes, and lost many plant and animal families that were intolerant of its cool climate, including the araucarias and most proteas, as well as [[crocodile]]s and [[turtle]]s. Large [[reptiles]], including crocodiles and huge [[monitor lizard]]s (family Varanidae), like the [[Komodo Dragon]] (''Varanus komodoensis''), are ecologically important predators in Australia, New Guinea, and Wallacea. There are 13 endemic [[bird]] families, including [[emu]]s, [[cassowary|cassowaries]], [[kiwi]], [[kagu]], [[cockatoo]]s, [[birds of paradise]], and [[honeyeater]]s ==Human impact== The arrival of humans to Australia and New Guinea 50-60,000 years ago brought [[dog]]s ([[dingo]]s) to Australia, and dogs and [[pig]]s to New Guinea. Pigs and [[rat]]s arrived on New Zealand with the first [[Polynesia]]n settlers 800 years ago. The arrival of the first humans coincided with the extinction of much of the native [[megafauna]] (see [[Holocene extinction event]]). The arrival of Europeans brought a whole host of new animals and plants, including [[sheep]], [[goat]]s, [[rabbit]]s and [[fox]]es, to Australasia, which have further disrupted the native ecologies; a great many Australasian plants and animals are presently endangered. ==Australasia terrestrial ecoregions== {{Australasia tropical and subtropical moist broadleaf forests}} {{Australasia tropical and subtropical dry broadleaf forests}} {{Australasia temperate broadleaf and mixed forests}} {{Australasia temperate coniferous forest}} {{Australasia tropical and subtropical grasslands, savannas, and shrublands}} {{Australasia temperate grasslands, savannas, and shrublands}} {{Australasia montane grasslands and shrublands}} {{Australasia tundra}} {{Australasia mediterranean forests, woodlands, and shrub}} {{Australasia deserts and xeric shrublands}} {{Australasia mangrove}} ==See also== * [[Australasia]] ==External links== *{{commons-inline|Australasia}} * [http://www.panda.org/about_wwf/where_we_work/ecoregions/maps/index.cfm Map of the ecozones] {{refimprove|date=June 2006}} {{Terrestrial_biomes}} {{Ecozones}} [[Category:Ecozones]] [[Category:Biogeography]] [[Category:Biogeography of Australia]] [[fr:Australasien]] [[ja:オーストラリア区]] [[ka:ავსტრალაზიის ოლქი]] [[nl:Australaziatisch gebied]] [[pl:Kraina australijska]] [[zh:澳新界]]