Sundaland is a biogeographical region of Southeastern Asia which encompasses the Sunda shelf, the part of the Asian continental shelf that was exposed during the last ice age. It included the Malay Peninsula on the Asian mainland, as well as the large islands of Borneo, Java, and Sumatra and their surrounding islands. The eastern boundary of Sundaland is the Wallace Line, identified by Alfred Russel Wallace as the eastern boundary of the Asia's land mammal fauna, and thus the boundary of the Indomalaya and Australasia ecozones. The islands east of the Wallace line are known as Wallacea, and are considered part of Australasia. New findings from the Human Genome Project show that the maritime southeast Asian region was populated primarily through a single migration event from the south, pointing to the submerged Sundaland as a probable origin of these peoples.
The Sahul Shelf and the Sunda Shelf today. The area in between is called "Wallacea".
History
The South China Sea and adjoining landmasses had been investigated by scientists such as Molengraaff and Umbgrove, who had postulated ancient, now submerged, drainage systems. These were mapped by Tjia in 1980 and described in greater detail by Emmel and Curray in 1982 complete with river deltas, floodplains and backswamps. The ecology of the exposed Sunda shelf has been investigated by analyzing cores drilled into the ocean bed. The pollens found in the cores have revealed a complex ecosystem that changed over time. The flooding of Sundaland separated species that had once shared the same environment such as the river threadfin (Polydactylus macrophthalmus, Bleeker 1858), that had once thrived in a river system now called "North Sunda River" or "Molengraaff river". The fish is now found in the Kapuas River on the island of Borneo, and in the Musi and Batanghari rivers in Sumatra.
Human Migrations
Previously, humans were believed to have migrated southward, from the East Asia mainland to Taiwan and then to the rest of Maritime Southeast Asia. However, recent findings point to the submerged Sundaland as the probable cradle of Asian population: thus the "Out of Sundaland" theory. A study from Leeds University and published in Molecular Biology and Evolution, examining mitochondrial DNA lineages, suggested that humans had been occupying the islands of Southeast Asia for a longer period than previously believed. Population dispersals seem to have occurred at the same time as sea levels rose, which may have resulted in migrations from the Philippine Islands to as far north as Taiwan within the last 10,000 years.The population migrations were most likely to have been driven by climate change — the effects of the drowning of an ancient continent. Rising sea levels in three massive pulses may have caused flooding and the submerging of the Sunda continent, creating the Java and South China Seas and the thousands of islands that make up Indonesia and the Philippines today.
New findings from the Human Genome Project also suggest that Asia was populated primarily through a single migration event from the south.Genetic similarities were found between populations throughout Asia and an increase in genetic diversity from northern to southern latitudes. Although the Chinese population is very large, it has less variation than the smaller number of individuals living in Southeast Asia, because the Chinese expansion occurred very recently, following the development of rice agriculture — within only the last 10,000 years.
Oppenheimer locates the origin of the Austronesians in Sundaland and its upper regions. Genetic research reported in 2008 indicates that the islands which are the remnants of Sundaland were likely populated as early as 50,000 years ago, contrary to a previous hypothesis[by whom?] that they were populated as late as 10,000 years ago from Taiwan.
Ecology
The islands of Sundaland rest on an extension of Asia's shallow continental shelf, called the Sunda shelf. During the ice ages, sea levels were lower and all of Sundaland was an extension of the Asian continent.
As a result, the islands of Sundaland are home to many Asian mammals including elephants, monkeys, apes, tigers, tapirs, and rhinoceros. The Wallace Line, which includes the Lombok Strait between Bali and Lombok, and the Makassar Strait between Borneo and Sulawesi, together mark the end of the Asian continental shelf, and the islands of Wallacea are separated from Asia and from Australia and New Guinea by deep ocean. Botanists often include Sundaland, the adjacent Philippines, Wallacea and New Guinea in a single Floristic province of Malesia, based on similarities in their flora, which is predominantly of Asian origin.
Ecoregions of Sundaland
Tropical and subtropical moist broadleaf forests
Borneo lowland rain forests (Borneo)
Borneo montane rain forests (Borneo)
Borneo peat swamp forests (Borneo)
Eastern Java–Bali montane rain forests (Bali, Java)
Eastern Java–Bali rain forests (Bali, Java)
Mentawai Islands rain forests (Mentawai Islands)
Peninsular Malaysian montane rain forests (Malay peninsula)
Peninsular Malaysian peat swamp forests (Malay peninsula)
Peninsular Malaysian rain forests (Anambas Islands, Malay peninsula)
Southwest Borneo freshwater swamp forests (Borneo)
Sumatran freshwater swamp forests (Sumatra)
Sumatran lowland rain forests (Sumatra, Nias, Bangka Island)
Sumatran montane rain forests (Sumatra)
Sumatran peat swamp forests (Sumatra)
Sundaland heath forests (Indonesia)
Western Java montane rain forests (Java)
Western Java rain forests (Java)
Tropical and subtropical coniferous forests
Sumatran tropical pine forests (Sumatra)
Montane grasslands and shrublands
Kinabalu montane alpine meadows (Borneo)
Mangroves
Sunda Shelf mangroves (Borneo, Sumatra, Riau Islands)
No comments:
Post a Comment