Australian Experts Uncover Reasons Behind Indonesia's Natural Division
Indonesia is divided into two regions along an imaginary line. The Wallace Line separates approximately 25,000 regions across Southeast Asia through to Australia, a division that has persisted for the past 160 years.
This line was mapped by explorer Alfred Wallace during his travels through Indonesia, Singapore, the Philippines, and Papua New Guinea. During his journeys, Wallace observed distinct species differences across each region. His observations addressed a long-standing mystery regarding why Asian species could cross certain territories whilst Australian species could not.
Recent research from Australia has attempted to explain this phenomenon. According to the researchers, the division resulted from extreme climate changes caused by tectonic activity 35 million years ago.
This geological process caused the Australian continent to separate from Antarctica and collide with Asia, leading to the formation of the Indonesian archipelago (Nusantara).
The researchers employed computer modelling to explain these effects. They calculated the dispersal capabilities, ecological preferences, and evolutionary relationships of more than 20,000 species on both sides of the Wallace Line.
“When Australia separated from Antarctica, it opened up a deep ocean area surrounding Antarctica, which is now where the Antarctic Circumpolar Current (ACC) is located,” said Alex Skeels, lead author of the study and evolutionary biologist at the Australian National University, as cited by Live Science.
The ACC in Antarctica is the world’s largest ocean current and plays a crucial role in regulating Earth’s climate.
Through their modelling, the researchers revealed that climate change did not affect all species equally. The climate in the Southeast Asian Peninsula and Indonesia became warmer and wetter, whilst Australia experienced colder and drier seasons.
These seasonal changes impacted the adaptation capabilities of living creatures in these regions. Asian species could adapt to Indonesian conditions and cross the Wallace Line to move into Australian zones, whereas Australian species lacked the capacity to make similar transitions.