Sundaland, also referred to as the Sundaic area, is a bio-geographical area of south-eastern Asia. It includes part of the continental shelf of Asia which was exposed during the previous ice age. Sundaland consists of the islands of Sumatra, Java, and Borneo among the other surrounding islands and the mainland cape on the Asian mainland. The term "Sundaland" was first proposed in 1949 by Van Bemmelen, followed by Katili in 1975, Hamilton in 1979, and finally Hutchison in 1989.
How Big Is the Sundaland?
Sundaland encompasses the Sunda-shelf which is a tectonically stable extension of the continental shelf of Southeast Asia which was exposed during the last glacial era in the last 2 million years. Other than the Malay Peninsula and the islands of Sumatra, Borneo, and Java, Sundaland also includes part of the South China Sea, the Java Sea, and the Thailand Gulf. In total, Sundaland covers an area of about 694,983.88 miles squared in size. The size of the Sundaland fluctuated in the last two million years and the current land is half the maximum size of Sundaland. The Wallace line is the boundary of the Sundaland. Alfred Wallace identified the eastern border which is also the boundary of the Australasia and Indomalaya ecozones. The Wallace line matches with the deep-water channel which has never been crossed using a bridge. The orogenic belt situated at the juncture of Pacific-Philippines, Australian, Eurasian, and Indian sea plates surrounding the Sundaland stretches from the Philippines to Sumatera via East Indonesia. The Indian Ocean marks the western and southern borders.
Exposure of the Sundaland
The bigger portion of continental shelf got exposed from 110,000 to 12,000 years ago in the previous Glacial-period. When the sea-level decreased by over 98.43 feet, the land bridges which connects the islands of Java, Borneo, and Sumatra to mainland Asia and the Malay Peninsula were exposed. During the previous glacial maximum (the ice age), the sea level decreased by over 393.7 feet thus the whole Sunda shelf got exposed. The most widespread glaciations in the ice age lasted for 21,000 years, and many scientists consider it to be the newest event of the bigger ice age which dates back to over 2 million years.
The Sundaland Climate
Sundaland is in the tropics, and the equator passes through central Borneo and Sumatra. Sundaland is ever-wet with above 2,000mm of rain every year. The rain pours throughout the year and there is no predictable dry season in this landmass like it is in Southeastern Asia. The shallow and warm sea on the Sunda shelf is part of the western Pacific warm-pool a crucial drive of the El-Nino South Oscillation and the Hadley movement. The El-Nino South Oscillation can affect the climate of this landmass; strong positive El-Nino-Southern oscillation events can cause drought in the tropical Asia and Sundaland.
Biodiversity in the Sundaland
Before the emergence of this landmass during early Pleistocene and late Pliocene era about 2.4 million years ago, the island of Java was without any mammals. With the sea level dropping, numerous species like the dwarf elephantoid colonized this land. After that, other animals moved in including tigers, the Indian elephant, and the Sumatran rhinoceros, among others.
Today, the Sundaland hosts 25% of Earth’s fishes and 17% of Earth’s birds. Some of the animals found in the Sundaland include Proboscis monkeys, Komodo dragons, Asian Arowanas, Java hawk-eagles, Bali starlings, and pig-tailed langurs. Although the 17,000 islands of the Sundaland cover about 1% of the world’s land, this land mass hosts approximately 10% of the flowering species on Earth. About 60% of the 25,000 vascular plants in Sunda are endemic. These islands have over 2,000 orchid species and hosts Rafflesia and Titan Arum which buds the largest flower on Earth.
Massive deforestation and poaching have threatened the wild animals of the Sunderland, including in the extinction of the Sumatra Javan tiger and the drastic reduction of the Sumatran Rhino population. However, numerous public and private conservations programs working in Sundaland have tried to reduce deforestation while conserving various national parks including Komodo National Park in Indonesia.
An ecoregion is a geographically and ecologically defined region which is smaller than the bioregion. Ecoregions cover large portions of water or land and homes numerous distinct group of natural species and communities. Some of the ecoregions in Sundaland include:
1) Borneo LowLand Rain Forest
This ecoregion is located in the subtropical and tropical moist broadleaf forests biome of Borneo in Southeast Asia. The climate of the lowland rainforest is ideal for different types of plants, supporting over 10,000 different plant species, including 3,000 trees and 2,000 orchids. It is also home to over 380 bird species and numerous mammal species.
2) Borneo Montane Rain Forest
This rainforest is an ecoregion of the cloud-forest located in the subtropical and tropical moist broadleaf jungle biome in Borneo Island in southeastern Asia. This ecoregion is situated in the middle of Borneo with parts of it in Indonesia, Brunei-owned territories, and Malaysia. The cloud forest is home to some of the distinctive and vibrant plants from both Australian and Asian origin including orchids, nepenthes plants, and rhododendrons. Some of the distinct fauna calling the cloud forest home include the civet, tree shrew, and orangutans among others. There are fewer birds in the Borneo mountains than in the lowlands, and the rainforest hosts some of the endemic species in Borneo. The marshes have 171 different bird species.
3) Borneo Peat Swamp Forest
Located in the subtropical and tropical moist broadleaf jungle biome, the swamp-forest is divided between three countries: Malaysia, Indonesia, and Brunei. Peat swamp forest forms when the water-logged soil stops the wood and dead leaves from decomposing entirely, resulting in the creation of a thick acidic peat layer. These swamp-forests can be found in Sarawak, Malaysia, and in the Kalimantan and the Belait district of Brunei in Indonesia. The forest is home to some of the most distinct mammals including the orangutan, gibbons, Borneo round-leaf bat, and the endangered proboscis monkey. The peat swamp forest is also home to two of the common birds in Borneo which includes Javan white-eye birds and hook-billed bulbul birds. There are over 200 bird species in the jungle. The rivers in the region host some of the endangered small fishes such as the Parosphomenus.