The Wallace Line — Where Asia Meets Australia

An invisible line runs through Indonesia — between Bali and Lombok, between Borneo and Sulawesi — dividing the wildlife of the archipelago into two fundamentally different worlds. The Wallace Line, named after the British naturalist Alfred Russel Wallace, marks the boundary between the Asian and Australian fauna.

West of the line (Sumatra, Java, Borneo, Bali) live Asian animals: tigers, elephants, orangutans, rhinos. East (Sulawesi, Flores, Moluccas, Papua) are Australian relatives: tree kangaroos, birds of paradise, and the Komodo dragon — a relic from when Australia was closer to Southeast Asia.

The explanation: During the ice ages, when sea levels were 120 meters lower, Sumatra, Java, and Borneo were connected to the Asian mainland by land bridges. East of the Wallace Line, the ocean was always deep enough to act as a barrier. The animals couldn't swim across — and so completely different ecosystems developed on both sides.

For travelers, this means: When you travel from Java to Flores, you cross one of the most important biogeographical boundaries on Earth — even if you don't see it.