Southeast Asia s politico-geographical traditions involve frequent balkanization, instability and conflict. Population tends to be strongly clustered, even in rural areas. Compared to neighboring regions, mainland Southeast Asia s physiologic population densities remain relatively low. Rapid population growth has prevailed in the island regions of Southeast Asia notably in the Philippines, during much of the 20th century. Interregional communications in Southeast Asia remain inferior.
External connection are often more effective than internal linkages.
The boundaries of the Southeast Asian realm are problematic. Transitions occur into the adjoining South Asian, Chinese and Pacific realms. The entire realm has approximately 469 million people. Southeast Asia s few dense population clusters are relatively small and lie separated from one another by areas of much sparser human settlement. Reasons for population clusters are three favorable natural environments.