Sundaic

Sundaland (also called the Sundaic region) is a biogeographical region of Southeastern Asia corresponding to a larger landmass that was exposed throughout the during periods when sea levels were lower. It includes the Malay Peninsula on the Asian mainland, as well as the large islands of Borneo, Java, and Sumatra and their surrounding islands.

The area of Sundaland encompasses the Sunda Shelf, a tectonically stable extension of Southeast Asia’s continental shelf that was exposed during glacial periods of the last 2 million years.

The extent of the Sunda Shelf is approximately equal to the 120 meter isobath. In addition to the Malay Peninsula and the islands of Borneo, Java, and Sumatra, it includes the Java Sea, the Gulf of Thailand, and portions of the South China Sea. In total, the area of Sundaland is approximately 1,800,000 km², The area of exposed land in Sundaland has fluctuated considerably during the past recent 2 million years; the modern land area is approximately half of the maximum extent.

The western and southern borders of Sundaland are clearly marked by the deeper water of the Indian Ocean. The eastern boundary of Sundaland is the Wallace Line, identified by Alfred Russel Wallace as the eastern boundary of the range of 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, a separate biogeographical region that is considered part of Australasia. The Wallace Line corresponds to a deep-water channel that has never been crossed by any land bridges. The northern border of Sundaland is more difficult to define in bathymetric terms; a phytogeographic transition at approximately 9ºN is considered to be the northern boundary.

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