TROPICAL RAINFORESTS: Types of Forest
Wallace LineThe Wallace Line more or less marks the edge of the Asian continental shelf: the shaded regions mark the areas that were exposed during recent ice ages resulting from the drop in global ocean levels. It is evident that two major land masses existed in the Australian-Southeast Asian zone. Each of these is now considered its own biogeographical realm. The islands in the middle, notably Sulawesi, were isolated and therefore independent of the two zones and subsequently have species characteristic of neither realm.
Continued: Structure of the tropical rainforest