Peering into the past: The Wallace Line's ancient secrets

image credit : https://medium.com/the-geopolitical-economist

British biologist and naturalist Alfred Russel Wallace gives his name to the Wallace Line, an invisible division that separates two worlds in Southeast Asia, in Indonesia. It is not on any map but marks a zoogeographical border between two ecosystems.

Understanding how different species function in their environments is crucial for protecting biodiversity. This is especially important in Southeast Asia and Australasia, where climate change poses a serious threat to many species. By knowing how these species interact with each other and their surroundings, we can better understand how to conserve them and help them adapt to changing conditions.

The Arafura Sea is a big body of water that lies between Asia and Australia. It's like a deep, clear path that divides two underwater areas called the Sunda platform and the Sahul platform. This path separates islands like Borneo, Bali, Sumatra, and Java from Australia, New Guinea, and the smaller islands around them.

The Wallace Trench is a deep underwater valley or chasm where the Sunda tectonic plate meets the Banda and Timor plates. Although you can’t see it from the surface of the ocean, it’s a very important place. It’s where these massive plates of Earth’s crust are pushing against each other, causing earthquakes and volcanic activity.

For a very long time (over 50 million years), the deep water between two big land areas (continental shelves) acted like a wall, stopping plants and animals from moving between Australia and Asia. This wall was probably an ocean, because the islands on both sides are very similar. So, the Wallacea region has islands that stayed separate from each other, and only the plants and animals that could swim or fly between the islands ended up living there.

The "line" barrier is a deep underwater wall that formed a very long time ago, during the Pleistocene Era (which was about 50 million years ago). It's like a giant underwater mountain range that has been there for a long time but never uniting Asia with Australia

Imagine a line drawn across a land. North of this line, you’ll find animals like elephants, tigers, and rhinoceroses. South of it, you’ll see kangaroos, marsupials, and rodents. These animals don't live together. This strange separation led scientists to think that natural things, like mountains or rivers, might keep different animals from mixing.

Birds often stay on land and many birds do not cross even the shortest stretches of open ocean water even for short trips. Bats are different – they fly over the ocean. Big land animals usually stay on one side of the ocean or the other. In Australia, you'll find many marsupials (like kangaroos) and monotremes (like platypuses), as well as some native rodents. 

The reason animals like tigers and elephants can be found in Asia but not in Australia is because they couldn't swim across the ocean. During cold times, the sea level was lower, and there were land bridges between places like Asia and Europe. Animals could walk across these bridges to new homes. But where the Wallace Line is, the ocean is very deep, and there was never a land bridge. So, animals couldn't cross and live in both places.

Plants can be found on both sides of the line, because plants can spread across water more easily than animals, so they don’t always follow the same rules. One kind of plant, the eucalyptus, is usually only found in Australia and New Zealand. But there’s one kind of eucalyptus, called E. deglupta, that grows on an island called Mindanao in the Philippines. This is the only eucalyptus that grows outside of Australia and New Zealand.

ref : https://www.msn.com/en-US/news/scienceandtechnology/what-is-the-wallace-line-the-invisible-barrier-that-fish-cannot-cross/ar-AA1pB6zJ

In conclusion, this vast and diverse landmasses between Australia and Asia has a fascinating history. Over millions of years, the Earth's tectonic plates moved and shifted, forming mountains, islands, and deep oceans. This geological activity, combined with changes in climate and sea levels, created a complex patchwork of habitats. As a result, different species evolved in isolation, leading to the unique biodiversity we see today. 

Wallace's line, a hypothetical boundary proposed by Alfred Russel Wallace, helps explain this pattern by separating Australian and Asian species. By understanding the geological history of this region, scientists can better understand how plants and animals have evolved and spread across the continents.

Thank you for reading.