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Wallace Line
Context
The Wallace Line is a fascinating example of how geography shapes evolution. Scientists now see it as a transition zone rather than a strict boundary. Modern studies show that some species can cross the line over time. Climate change and habitat destruction threaten these ecosystems, making it important to understand how species will adapt in the future.
What is the Wallace Line?
- The Wallace Line is an invisible boundary that separates the unique animal species of Asia from those of Australia.
- First identified by English naturalist Alfred Russel Wallace in the 19th century, this line runs through the Malay Archipelago, passing between the islands of Bali and Lombok and continuing north between Borneo and Sulawesi.
- Significance:
- It marks a dramatic shift in biodiversity over a very short distance.
- Animals on the Asian side (Borneo, Bali) resemble those from mainland Asia (e.g., tigers, monkeys).
- Animals on the Australian side (Sulawesi, Lombok) resemble those from Australia (e.g., marsupials like kangaroos and cuscuses).
Why Does This Division Exist?
The answer lies in plate tectonics and evolution.
- Millions of years ago, Australia broke away from Antarctica and started drifting north.
- Meanwhile, Asia remained connected to its mainland, allowing animals to spread across.
- Over time, as sea levels rose and fell, some islands were submerged while others remained connected to larger land masses.
- This led to species evolving separately on different islands, creating the distinct biodiversity seen today.
Why is Sulawesi Special?
- Sulawesi, located near the Wallace Line, has species from both sides—some of Asian origin (like the anoa, a type of buffalo) and others of Australian origin (like the dwarf cuscus, a marsupial).
- This puzzled Wallace because most other islands had a clear division.
- Scientists now believe Sulawesi was formed from fragments of both continental plates, allowing species from both regions to settle there.
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