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Wallacea is a biogeographical designation for a group of Indonesian islands separated by deep water from the Asian and Australian continental shelves. The islands of Wallacea lie between Sundaland (the Malay Peninsula, Sumatra, Borneo, Java, and Bali) to the west, and Near Oceania including Australia and New Guinea to the south and east.
Wallacea includes the islands of Nusa Tenggara, which include Lombok, Komodo, Flores, and Sumba; Timor; Sulawesi; the islands of North Maluku, including Halmahera; and most of the province of Maluku, excluding the Aru Islands, which lie on the Australian continental shelf. The total land area of Wallacea is 347,000 km².
The boundary between Sundaland and Wallacea 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 of Sundaland to the west of the line, including Java, Bali, Borneo, share a similar mammal 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, and Australia and New Guinea share many marsupial mammals and land birds. Wallacea contains few land mammals, who find it difficult to cross open ocean. Many bird, reptile, and insect species were better able to make the crossing, and many species of Australian and Asian origin are found there. Wallacea's plants are predominantly of Asian origin, and botanists include Sundaland, Wallacea, and New Guinea as the Floristic province of Malesia.
Although the distant ancestors of Wallacea's plants and animals may have been from Asia or Australia-New Guinea, Wallacea is presently home to many endemic species. Because many of the islands are separated from one another by deep water, there is tremendous species diversity between islands as well. Conservation International has designated Wallacea as a biodiversity hotspot.
Wallacea was originally almost completely forested, mostly tropical moist broadleaf forests, with some areas of tropical dry broadleaf forest . The higher mountains are home to montane and subalpine forests, and Mangroves are common in coastal areas.
According to Conservation International, Wallacea is home to over 10,000 plant species, of which approximately 1500 (15%) are endemic. Endemism is higher among terrestrial vertebrate species; of 1142 species found there, almost half (529) are endemic. Most of Wallacea was originally forested; 45% retains some sort of forest cover, and only 52,017 km², or 15 percent, is in a more or less pristine state. Of Wallacea's total area of 147,000 km², only 20,415 km² are protected. Wallacea is home to 82 threatened and six critically endangered species of terrestrial vertebrates.
Ecoregions of Wallacea
- Banda Sea Islands moist broadleaf forests (Kai Islands, Tanimbar Islands)
- Buru rain forests (Buru)
- Halmahera rain forests (Halmahera, Morotai, Obi Islands , Bacan Island )
- Seram rain forests (Seram, Ambon Island, Saparua)
- Sulawesi lowland rain forests (Sulawesi, Banggai Islands , Sula Islands , Sangihe Islands , Talaud Islands)
- Sulawesi montane rain forests (Sulawesi)
- Lesser Sundas deciduous forests (Lombok, Sumbawa, Komodo, Flores, Alor)
- Sumba deciduous forests (Sumba)
- Timor and Wetar deciduous forests (Timor, Barat Daya Islands, Banda Islands, Babar Island, Leti Islands )
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