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      Bali's Biogeography

      Bali is a relatively 'young' island, having probably first emerged above the waves some 3 million years ago. It is one of the most volcanically active islands in the world and volcanoes have played an important role in shaping the natural history of Bali. Periodic eruptions spew forth great streams of molten balsatic lava which, when they have cooled, are broken down by natural erosion to form a fertile sediment in the valleys and plains. These rich soils supported the great swathe of forest that once covered most of the island and which can still be found in the west.

      In historical times, much of this forest cover has been lost to agriculture, the natural fertility of the island allowing the cultivation of two rice crops a year to feed an ever-growing human population, which today stands at roughly 3 million.

      Island Biogeography

      Bali is a so-called continental island, that is to say, an island which sits on the continental shelf and is typically situated close to the mainland, in this case Java. Surrounded by shallow seas, it is periodically connected to the mainland at times of lowered sea levels which occur whenever there are ice ages. The latter circumstances allow an exchange of species—both plant and animal— with the mainland, with the result that the native flora and fauna of the island generally resembles that of the mainland, though the diversity of island species is usually less.

      Bali is no exception to this rule, though the island does have at least one known endemic species, that is to say, a species which is unique to Bali and found nowhere else in the world. This is the famed Bali starling (Lucospar rothschildi) which was only discovered by Western science as recently as 1911. In the past, there was also a subspecies of tiger (Panthera tigris balica), but that has become extinct, a fate which also threatens the Bali starling.