Bali is a relatively `young’ island, having probably first emerged above the waves some 3 million years ago. lt 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 coveted most of the island and which can still be found in the west. ln 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.