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Sundaland (also called Sundaica or the Sundaic region) is a
biogeographical Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time. Organisms and biological communities often vary in a regular fashion along geographic gradients of latitude, elevation, ...
region of
South-eastern Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainland ...
corresponding to a larger landmass that was exposed throughout the last 2.6 million years during periods when sea levels were lower. It includes
Borneo Borneo (; id, Kalimantan) is the List of islands by area, third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java Isl ...
,
Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's mo ...
, and Sumatra in
Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...
, and their surrounding small islands, as well as the
Malay Peninsula The Malay Peninsula ( Malay: ''Semenanjung Tanah Melayu'') is a peninsula in Mainland Southeast Asia. The landmass runs approximately north–south, and at its terminus, it is the southernmost point of the Asian continental mainland. The are ...
on the Asian mainland.


Extent

The area of Sundaland encompasses the
Sunda Shelf Geologically, the Sunda Shelf is a south-eastern extension of the continental shelf of Mainland Southeast Asia. Major landmasses on the shelf include the Bali, Borneo, Java, Madura, and Sumatra, as well as their surrounding smaller island ...
, a tectonically stable extension of Southeast Asia's continental shelf that was exposed during
glacial period A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate bet ...
s of the last 2 million years. The extent of the Sunda Shelf is approximately equal to the 120-meter
isobath Bathymetry (; ) is the study of underwater depth of ocean floors (''seabed topography''), lake floors, or river floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography. The first recorded evidence of water de ...
. In addition to the Malay Peninsula and the islands of Borneo, Java, and Sumatra, it includes the Java Sea, the
Gulf of Thailand The Gulf of Thailand, also known as the Gulf of Siam, is a shallow inlet in the southwestern South China Sea, bounded between the southwestern shores of the Indochinese Peninsula and the northern half of the Malay Peninsula. It is around in l ...
, and portions of the
South China Sea The South China Sea is a marginal sea of the Western Pacific Ocean. It is bounded in the north by the shores of South China (hence the name), in the west by the Indochinese Peninsula, in the east by the islands of Taiwan and northwestern Phil ...
. In total, the area of Sundaland is approximately 1,800,000 km2. The area of exposed land in Sundaland has fluctuated considerably during the past recent 2 million years; the modern land area is approximately half of the maximum extent. The western and southern borders of Sundaland are clearly marked by the deeper waters of the
Sunda Trench The Sunda Trench, earlier known as and sometimes still indicated as the Java Trench, is an oceanic trench located in the Indian Ocean near Sumatra, formed where the Australian- Capricorn plates subduct under a part of the Eurasian Plate. It is ...
- some of the deepest in the world - and the
Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by ...
. The eastern boundary of Sundaland is the
Wallace Line The Wallace Line or Wallace's Line is a faunal boundary line drawn in 1859 by the British naturalist Alfred Russel Wallace and named by English biologist Thomas Henry Huxley that separates the biogeographical realms of Asia and Wallacea, a tran ...
, identified by Alfred Russel Wallace as the eastern boundary of the range of Asia's land mammal fauna, and thus the boundary of the
Indomalayan The Indomalayan realm is one of the eight biogeographic realms. It extends across most of South and Southeast Asia and into the southern parts of East Asia. Also called the Oriental realm by biogeographers, Indomalaya spreads all over the Indi ...
and
Australasian realm The Australasian realm is a biogeographic realm that is coincident with, but not (by some definitions) the same as, the geographical region of Australasia. The realm includes Australia, the island of New Guinea (comprising Papua New Guinea an ...
s. The islands east of the Wallace line are known as
Wallacea Wallacea is a biogeographical designation for a group of mainly Indonesian islands separated by deep-water straits from the Asian and Australian continental shelves. Wallacea includes Sulawesi, the largest island in the group, as well as ...
, a separate biogeographical region that is considered part of Australasia. The Wallace Line corresponds to a deep-water channel that has never been crossed by any land bridges. The northern border of Sundaland is more difficult to define in bathymetric terms; a
phytogeographic Phytogeography (from Greek φυτόν, ''phytón'' = "plant" and γεωγραφία, ''geographía'' = "geography" meaning also distribution) or botanical geography is the branch of biogeography that is concerned with the geographic distribution ...
transition at approximately 9ºN is considered to be the northern boundary. Greater portions of Sundaland were most recently exposed during the last glacial period from approximately 110,000 to 12,000 years ago. When sea level was decreased by 30–40 meters or more, land bridges connected the islands of Borneo, Java, and Sumatra to the Malay Peninsula and mainland Asia. Because sea level has been 30 meters or more lower throughout much of the last 800,000 years, the current state of Borneo, Java, and Sumatra as islands has been a relatively rare occurrence throughout the Pleistocene. In contrast, sea level was higher during the late
Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58 Sundaland was partially submerged starting around 18,000 years ago and continuing till about 5000 BC. During the
Last Glacial Maximum The Last Glacial Maximum (LGM), also referred to as the Late Glacial Maximum, was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent. Ice sheets covered much of Northern North America, Northern Eu ...
sea level fell by approximately 120 meters, and the entire Sunda Shelf was exposed.


Modern climate

All of Sundaland is within the
tropics The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred ...
; the
equator The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can al ...
runs through central Sumatra and Borneo. Like elsewhere in the tropics, rainfall, rather than temperature, is the major determinant of regional variation. Most of Sundaland is classified as perhumid, or everwet, with over 2,000 millimeters of rain annually; rainfall exceeds
evapotranspiration Evapotranspiration (ET) is the combined processes by which water moves from the earth’s surface into the atmosphere. It covers both water evaporation (movement of water to the air directly from soil, canopies, and water bodies) and transpir ...
throughout the year and there are no predictable dry seasons like elsewhere in Southeast Asia. The warm and shallow seas of the Sunda Shelf (averaging 28 °C or more) are part of the Indo-Pacific Warm Pool/
Western Pacific Warm Pool The Tropical Warm Pool (TWP) or Indo-Pacific Warm Pool is a mass of ocean water located in the western Pacific Ocean and eastern Indian Ocean which consistently exhibits the highest water temperatures over the largest expanse of the Earth's surface. ...
and an important driver of the
Hadley circulation The Hadley cell, named after George Hadley, is a global-scale tropical atmospheric circulation that features air rising near the equator, flowing poleward at a height of 10 to 15 kilometers above the earth's surface, descending in the subtropics, ...
and the
El Niño-Southern Oscillation EL, El or el may refer to: Religion * El (deity), a Semitic word for "God" People * EL (rapper) (born 1983), stage name of Elorm Adablah, a Ghanaian rapper and sound engineer * El DeBarge, music artist * El Franco Lee (1949–2016), American ...
(ENSO), particularly in January when it is a major heat source to the atmosphere. ENSO also has a major influence on the climate of Sundaland; strong positive ENSO events result in droughts throughout Sundaland and tropical Asia.


Modern ecology

The high rainfall supports closed canopy evergreen forests throughout the islands of Sundaland, transitioning to deciduous forest and savanna woodland with increasing latitude. Remaining primary (unlogged) lowland forest is known for giant
dipterocarp Dipterocarpaceae is a family of 16 genera and about 695 known species of mainly tropical lowland rainforest trees. The family name, from the type genus ''Dipterocarpus'', is derived from Greek (''di'' = two, ''pteron'' = wing and ''karpos'' = fru ...
trees and
orangutan Orangutans are great apes native to the rainforests of Indonesia and Malaysia. They are now found only in parts of Borneo and Sumatra, but during the Pleistocene they ranged throughout Southeast Asia and South China. Classified in the gen ...
s; after logging, forest structure and community composition change to be dominated by shade intolerant trees and shrubs. Dipterocarps are notable for mast fruiting events, where tree fruiting is synchronized at unpredictable intervals resulting in predator satiation. Higher elevation forests are shorter and dominated by trees in the oak family. Botanists often include Sundaland, the adjacent
Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...
,
Wallacea Wallacea is a biogeographical designation for a group of mainly Indonesian islands separated by deep-water straits from the Asian and Australian continental shelves. Wallacea includes Sulawesi, the largest island in the group, as well as ...
and
New Guinea New Guinea (; Hiri Motu: ''Niu Gini''; id, Papua, or , historically ) is the world's second-largest island with an area of . Located in Oceania in the southwestern Pacific Ocean, the island is separated from Australia by the wide Torr ...
in a single
floristic province A phytochorion, in phytogeography, is a geographic area with a relatively uniform composition of plant species. Adjacent phytochoria do not usually have a sharp boundary, but rather a soft one, a transitional area in which many species from both r ...
of
Malesia Malesia is a biogeographical region straddling the Equator and the boundaries of the Indomalayan and Australasian realms, and also a phytogeographical floristic region in the Paleotropical Kingdom. It has been given different definitions. ...
, based on similarities in their flora, which is predominantly of Asian origin. During the last glacial period, sea levels were lower and all of Sundaland was an extension of the Asian continent. As a result, the modern islands of Sundaland are home to many Asian mammals including
elephants Elephants are the largest existing land animals. Three living species are currently recognised: the African bush elephant, the African forest elephant, and the Asian elephant. They are the only surviving members of the family Elephantidae ...
,
monkey Monkey is a common name that may refer to most mammals of the infraorder Simiiformes, also known as the simians. Traditionally, all animals in the group now known as simians are counted as monkeys except the apes, which constitutes an incom ...
s,
ape Apes (collectively Hominoidea ) are a clade of Old World simians native to sub-Saharan Africa and Southeast Asia (though they were more widespread in Africa, most of Asia, and as well as Europe in prehistory), which together with its sister ...
s,
tiger The tiger (''Panthera tigris'') is the largest living cat species and a member of the genus '' Panthera''. It is most recognisable for its dark vertical stripes on orange fur with a white underside. An apex predator, it primarily preys on ...
s,
tapir Tapirs ( ) are large, herbivorous mammals belonging to the family Tapiridae. They are similar in shape to a pig, with a short, prehensile nose trunk. Tapirs inhabit jungle and forest regions of South and Central America, with one species inh ...
s, and
rhinoceros A rhinoceros (; ; ), commonly abbreviated to rhino, is a member of any of the five extant taxon, extant species (or numerous extinct species) of odd-toed ungulates in the family (biology), family Rhinocerotidae. (It can also refer to a member ...
. The flooding of Sundaland separated species that had once shared the same environment. One example is the river threadfin ('' Polydactylus macrophthalmus'', Bleeker 1858), which once thrived in a river system now called "North Sunda River" or "Molengraaff river". The fish is now found in the Kapuas River on the island of Borneo, and in the Musi and Batanghari rivers in Sumatra.
Selective pressure Any cause that reduces or increases reproductive success in a portion of a population potentially exerts evolutionary pressure, selective pressure or selection pressure, driving natural selection. It is a quantitative description of the amount of ...
(in some cases resulting in
extinction Extinction is the termination of a kind of organism or of a group of kinds ( taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed ...
) has operated differently on each of the islands of Sundaland, and as a consequence, a different assemblage of mammals is found on each island. However, the current species assemblage on each island is not simply a subset of a universal Sundaland or Asian fauna, as the species that inhabited Sundaland before flooding did not all have ranges encompassing the entire Sunda Shelf. Island area and number of terrestrial mammal species are positively correlated, with the largest islands of Sundaland (Borneo and Sumatra) having the highest diversity.


Ecoregions

;
Tropical and subtropical moist broadleaf forests Tropical and subtropical moist broadleaf forests (TSMF), also known as tropical moist forest, is a subtropical and tropical forest habitat type defined by the World Wide Fund for Nature. Description TSMF is generally found in large, disco ...
*
Eastern Java–Bali rain forests The Eastern Java-Bali rain forests ecoregion (WWF ID: IM0113) covers the lowland areas of the eastern half of the island of Java, and the island of Bali, in Indonesia. This ecoregion is distinct from the Eastern Java-Bali montane rain forests, w ...
(
Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's mo ...
,
Bali Bali () is a province of Indonesia and the westernmost of the Lesser Sunda Islands. East of Java and west of Lombok, the province includes the island of Bali and a few smaller neighbouring islands, notably Nusa Penida, Nusa Lembongan, and Nu ...
) *
Eastern Java–Bali montane rain forests The Eastern Java–Bali montane rain forests ecoregion (WWF ID: IM0112) covers the higher altitude mountain rainforests on the eastern side of the island of Java, and most of the center of the island of Bali in Indonesia. The region has a number ...
(
Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's mo ...
,
Bali Bali () is a province of Indonesia and the westernmost of the Lesser Sunda Islands. East of Java and west of Lombok, the province includes the island of Bali and a few smaller neighbouring islands, notably Nusa Penida, Nusa Lembongan, and Nu ...
). * Western Java montane rain forests (
Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's mo ...
) * Western Java rain forests (
Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's mo ...
) *
Borneo lowland rain forests The Borneo lowland rain forests is an ecoregion, within the tropical and subtropical moist broadleaf forests biome, of the large island of Borneo in Southeast Asia. It supports approximately 15,000 plant species, 380 bird species and several m ...
(
Borneo Borneo (; id, Kalimantan) is the List of islands by area, third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java Isl ...
) *
Borneo montane rain forests The Borneo montane rain forests are an ecoregion, of cloud forest, within the tropical and subtropical moist broadleaf forests biome, of the island of Borneo in Southeast Asia. Location and description This ecoregion consists of tropical mount ...
(
Borneo Borneo (; id, Kalimantan) is the List of islands by area, third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java Isl ...
) *
Borneo peat swamp forests The Borneo peat swamp forests ecoregion, within the tropical and subtropical moist broadleaf forests biome, are on the island of Borneo, which is divided between Brunei, Indonesia and Malaysia. Location and description Peat swamp forests occur ...
(
Borneo Borneo (; id, Kalimantan) is the List of islands by area, third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java Isl ...
) *
Mentawai Islands rain forests The Mentawai Islands rain forests is a tropical moist broadleaf forest ecoregion in Indonesia. It covers the Mentawai Islands, an archipelago in the Indian Ocean off the west coast of Sumatra. The islands have been separated from Sumatra since th ...
(
Mentawai Islands Mentawai may refer to: * Mentawai Islands * Mentawai Strait * Mentawai people * Mentawai language {{dab Language and nationality disambiguation pages ...
) *
Peninsular Malaysian montane rain forests The Peninsular Malaysian montane rain forests is an ecoregion on Malay Peninsula. It occupies the mountainous spine of the peninsula in Malaysia and southernmost Thailand. It is in the tropical and subtropical moist broadleaf forests biome. G ...
(
Malay peninsula The Malay Peninsula ( Malay: ''Semenanjung Tanah Melayu'') is a peninsula in Mainland Southeast Asia. The landmass runs approximately north–south, and at its terminus, it is the southernmost point of the Asian continental mainland. The are ...
) * Peninsular Malaysian peat swamp forests (
Malay peninsula The Malay Peninsula ( Malay: ''Semenanjung Tanah Melayu'') is a peninsula in Mainland Southeast Asia. The landmass runs approximately north–south, and at its terminus, it is the southernmost point of the Asian continental mainland. The are ...
) *
Peninsular Malaysian rain forests The Peninsular Malaysian rain forests is an ecoregion on Malay Peninsula and adjacent islands. It is in the tropical and subtropical moist broadleaf forests biome. Geography The ecoregion covers most of the southern Malay Peninsula in Malaysia a ...
(
Anambas Islands Anambas Islands Regency ( id, Kabupaten Kepulauan Anambas) is a small archipelago of Indonesia, located northeast of Batam Island in the North Natuna Sea between the Malaysian mainland to the west and the island of Borneo to the east. Geograph ...
,
Malay peninsula The Malay Peninsula ( Malay: ''Semenanjung Tanah Melayu'') is a peninsula in Mainland Southeast Asia. The landmass runs approximately north–south, and at its terminus, it is the southernmost point of the Asian continental mainland. The are ...
) *
Southwest Borneo freshwater swamp forests The Southwest Borneo freshwater swamp forests ecoregion (WWF ID: IM0153) covers a number disconnected patches of freshwater swamp forest along the southwestern coasts of Borneo. The swamps are generally set back a few kilometers or two from the s ...
(
Borneo Borneo (; id, Kalimantan) is the List of islands by area, third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java Isl ...
) *
Sumatran freshwater swamp forests The Sumatran freshwater swamp forests ecoregion (WWF ID: IM0157) covers disconnected patches of freshwater swamp forest on the alluvial plains of the island of Sumatra in Indonesia. The different locations vary greatly in their vegetation and wi ...
( Sumatra) *
Sumatran lowland rain forests The Sumatran lowland rain forests ecoregion (WWF ID: IM0158) covers the lowland forests running the length of the island of Sumatra in Indonesia. The region is one of exceptionally high biodiversity, similar to Borneo and New Guinea islands. Ma ...
( Sumatra,
Nias Nias ( id, Pulau Nias, Nias language: ''Tanö Niha'') (sometimes called Little Sumatra in English) is an island located off the western coast of Sumatra, Indonesia. Nias is also the name of the archipelago () of which the island is the centre ...
,
Bangka Island Bangka is an island lying east of Sumatra, Indonesia. It is administered under the province of the Bangka Belitung Islands, being one of its namesakes alongside the smaller island of Belitung across the Gaspar Strait. The 9th largest island in I ...
) *
Sumatran montane rain forests The Sumatran montane rain forests ecoregion (WWF ID: IM0159) covers the mountainous elevations (greater than 1,000 meters) of the Barisan Mountains Range that runs the length of the southwestern side of the island of Sumatra in Indonesia. The ecor ...
( Sumatra) *
Sumatran peat swamp forests The Sumatran peat swamp forests ecoregion (WWF ID: IM0160) covers the low-lying peat swamp forests along the northeast coast of the island of Sumatra in Indonesia. As is typical for peat swamp forests, this ecoregion lies between a thin strip of ...
( Sumatra) *
Sundaland heath forests The Sundaland heath forest, also known as ''Kerangas'' forest, is a type of tropical moist forest found on the island of Borneo, which is divided between Brunei, Indonesia, and Malaysia, as well as on the Indonesian islands of Belitung and Bangk ...
(
Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...
) ;
Tropical and subtropical coniferous forests Tropical and subtropical coniferous forests are a tropical forest habitat type defined by the World Wide Fund for Nature. These forests are found predominantly in North and Central America and experience low levels of precipitation and moderate v ...
*
Sumatran tropical pine forests The Sumatran tropical pine forests is a tropical coniferous forest ecoregion on the island of Sumatra in Indonesia. Location and description These pine forests are found on the higher slopes of Sumatra, especially in the north of the island n ...
( Sumatra) ;
Montane grasslands and shrublands Montane grasslands and shrublands is a biome defined by the World Wildlife Fund. The biome includes high elevation grasslands and shrublands around the world. The term "montane" in the name of the biome refers to "high elevation", rather than t ...
*
Kinabalu montane alpine meadows Mount Kinabalu ( ms, Gunung Kinabalu, Dusun: ''Gayo Ngaran or Nulu Nabalu'') is the highest mountain in Borneo and Malaysia. With an elevation of , it is third-highest peak of an island on Earth, and 20th most prominent mountain in the worl ...
(
Borneo Borneo (; id, Kalimantan) is the List of islands by area, third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java Isl ...
) ;
Mangroves A mangrove is a shrub or tree that grows in coastal saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evolution in several ...
*
Sunda Shelf mangroves The Sunda Shelf mangroves ecoregion, in the mangrove biome, are on the coasts of the islands of Borneo and eastern Sumatra in Malaysia and Indonesia. They are home to the proboscis monkey. As well as being an important habitat for terrestrial ...
(
Borneo Borneo (; id, Kalimantan) is the List of islands by area, third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java Isl ...
, Sumatra,
Riau Islands The Riau Islands ( id, Kepulauan Riau) is a province of Indonesia. It comprises a total of 1,796 islands scattered between Sumatra, Malay Peninsula, and Borneo including the Riau Archipelago. Situated on one of the world's busiest shipping l ...
)


History


Early research

The name "Sunda" goes back to antiquity, appearing in
Ptolemy Claudius Ptolemy (; grc-gre, Πτολεμαῖος, ; la, Claudius Ptolemaeus; AD) was a mathematician, astronomer, astrologer, geographer, and music theorist, who wrote about a dozen scientific treatises, three of which were of import ...
's ''Geography'', written around 150 AD. In an 1852 publication, English navigator
George Windsor Earl George Windsor Earl (1813–1865), was an English navigator and author of works on the Indian Archipelago. He coined the term 'Indu-nesian', later adopted as the name for Indonesia. Biography Earl was born in London around 1813. He travelled to ...
advanced the idea of a "Great Asiatic Bank", based in part on common features of mammals found in Java, Borneo and Sumatra. Explorers and scientists began measuring and mapping the seas of Southeast Asia in the 1870s, primarily using
depth sounding Depth sounding, often simply called sounding, is measuring the depth of a body of water. Data taken from soundings are used in bathymetry to make maps of the floor of a body of water, such as the seabed topography. Soundings were traditionall ...
. In 1921
Gustaaf Molengraaff Gustaaf Adolf Frederik Molengraaff (27 February 1860 – 26 March 1942) was a Dutch geologist, biologist and explorer. He became an authority on the geology of South Africa and the Dutch East Indies. Gustaaf Molengraaff studied mathematics ...
, a Dutch geologist, postulated that the nearly uniform sea depths of the shelf indicated an ancient
peneplain 390px, Sketch of a hypothetical peneplain formation after an orogeny. In geomorphology and geology, a peneplain is a low-relief plain formed by protracted erosion. This is the definition in the broadest of terms, albeit with frequency the usage ...
that was the result of repeated flooding events as ice caps melted, with the peneplain becoming more perfect with each successive flooding event. Molengraaff also identified ancient, now submerged, drainage systems that drained the area during periods of lower sea level. The name "Sundaland" for the peninsular shelf was first proposed by
Reinout Willem van Bemmelen Reinout Willem van Bemmelen, also known as Rein van Bemmelen, (14 April 1904 Batavia, Dutch East Indies – 19 November 1983 Unterpirkach, Austria) was a Dutch geologist whose interests were structural geology, economic geology and volcanology. ...
in his ''Geography of Indonesia'' in 1949, based on his research during the war. The ancient drainage systems described by Molengraaff were verified and mapped by Tjia in 1980 and described in greater detail by Emmel and Curray in 1982 complete with
river delta A river delta is a landform shaped like a triangle, created by deposition of sediment that is carried by a river and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or (more ra ...
s,
floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...
s and backswamps.''The physical geography of Southeast Asia'' by Avijit Gupta, 2005, , page 403


Data types

The climate and ecology of Sundaland throughout the Quaternary has been investigated by analyzing
foraminifera Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly ...
l ''δ''18O and pollen from cores drilled into the ocean bed, ''δ''18O in
speleothem A speleothem (; ) is a geological formation by mineral deposits that accumulate over time in natural caves. Speleothems most commonly form in calcareous caves due to carbonate dissolution reactions. They can take a variety of forms, depending o ...
s from caves, and ''δ''13C and ''δ''15N in bat guano from caves, as well as species distribution models, phylogenetic analysis, and community structure and species richness analysis.


Climate

Perhumid climate has existed in Sundaland since the early
Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recent" ...
; though there is evidence for several periods of drier conditions, a perhumid core persisted in Borneo. The presence of fossil coral reefs dating to the late Miocene and early
Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58
Palynological Palynology is the "study of dust" (from grc-gre, παλύνω, palynō, "strew, sprinkle" and ''-logy'') or of "particles that are strewn". A classic palynologist analyses particulate samples collected from the air, from water, or from deposits ...
evidence from Sumatra suggests that temperatures were cooler during the late Pleistocene; mean annual temperatures at high elevation sites may have been as much as 5 °C cooler than present. Most recent research agrees that Indo-Pacific sea surface temperatures were at most 2-3 °C lower during the
Last Glacial Maximum The Last Glacial Maximum (LGM), also referred to as the Late Glacial Maximum, was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent. Ice sheets covered much of Northern North America, Northern Eu ...
. Snow was found much lower than at present (approximately 1,000 meters lower) and there is evidence that glaciers existed on Borneo and Sumatra around 10,000 years before present. However, debate continues on how precipitation regimes changed throughout the Quaternary. Some authors argue that rainfall decreased with the area of ocean available for evaporation as sea levels fell with ice sheet expansion. Others posit that changes in precipitation have been minimal and an increase in land area in the Sunda Shelf alone (due to lowered sea level) is not enough to decrease precipitation in the region. One possible explanation for the lack of agreement on hydrologic change throughout the Quaternary is that there was significant heterogeneity in climate during the Last Glacial Maximum throughout Indonesia. Alternatively, the physical and chemical processes that underlie the method of inferring precipitation from ''δ''18O records may have operated differently in the past. Some authors working primarily with pollen records have also noted the difficulties of using vegetation records to detect changes in precipitation regimes in such a humid environment, as water is not a limiting factor in community assemblage.


Ecology

Sundaland, and in particular Borneo, has been an evolutionary hotspot for
biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic ('' genetic variability''), species ('' species diversity''), and ecosystem ('' ecosystem diversity' ...
since the early
Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recent" ...
due to repeated immigration and
vicariance Allopatric speciation () – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from ...
events. The modern islands of Borneo, Java, and Sumatra have served as refugia for the flora and fauna of Sundaland during multiple glacial periods in the last million years, and are serving the same role at present.


Savanna corridor theory

Dipterocarp Dipterocarpaceae is a family of 16 genera and about 695 known species of mainly tropical lowland rainforest trees. The family name, from the type genus ''Dipterocarpus'', is derived from Greek (''di'' = two, ''pteron'' = wing and ''karpos'' = fru ...
trees characteristic of modern Southeast Asian tropical rainforest have been present in Sundaland since before the
Last Glacial Maximum The Last Glacial Maximum (LGM), also referred to as the Late Glacial Maximum, was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent. Ice sheets covered much of Northern North America, Northern Eu ...
. There is also evidence for savanna vegetation, particularly in now submerged areas of Sundaland, throughout the last glacial period. However, researchers disagree on the spatial extent of savanna that was present in Sundaland. There are two opposing theories about the vegetation of Sundaland, particularly during the last glacial period: (1) that there was a continuous savanna corridor connecting modern mainland Asia to the islands of Java and Borneo, and (2) that the vegetation of Sundaland was instead dominated by tropical rainforest, with only small, discontinuous patches of savanna vegetation. The presence of a savanna corridor—even if fragmented—would have allowed for savanna-dwelling fauna (as well as early humans) to disperse between Sundaland and the
Indochinese Mainland Southeast Asia, also known as the Indochinese Peninsula or Indochina, is the continental portion of Southeast Asia. It lies east of the Indian subcontinent and south of Mainland China and is bordered by the Indian Ocean to the west an ...
biogeographic region; emergence of a savanna corridor during glacial periods and subsequent disappearance during interglacial periods would have facilitated speciation through both
vicariance Allopatric speciation () – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from ...
(
allopatric speciation Allopatric speciation () – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from ...
) and
geodispersal In biogeography, geodispersal is the erosion of barriers to gene flow and biological dispersal (Lieberman, 2005.; Albert and Crampton, 2010.). Geodispersal differs from vicariance, which reduces gene flow through the creation of geographic barrier ...
. Morley and Flenley (1987) and Heaney (1991) were the first to postulate the existence of a continuous corridor of
savanna A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to ...
vegetation through the center of Sundaland (from the modern Malaysian Peninsula to Borneo) during the last glacial period, based on palynological evidence. Using the modern distribution of primates, termites, rodents, and other species, other researchers infer that the extent of tropical forest contracted—replaced by savanna and open forest —during the last glacial period. Vegetation models using data from climate simulations show varying degrees of forest contraction; Bird et al. (2005) noted that although no single model predicts a continuous savanna corridor through Sundaland, many do predict open vegetation between modern Java and southern Borneo. Combined with other evidence, they suggest that a 50–150 kilometer wide savanna corridor ran down the Malaysian Peninsula, through Sumatra and Java, and across to Borneo. Additionally, Wurster et al. (2010) analyzed stable carbon isotope composition in bat guano deposits in Sundaland and found strong evidence for the expansion of savanna in Sundaland. Similarly, stable isotope composition of fossil mammal teeth supports the existence of the savanna corridor. In contrast, other authors argue that Sundaland was primarily covered by tropical rainforest. Using species distribution models, Raes et al. (2014) suggest that Dipterocarp rainforest persisted throughout the last glacial period. Others have observed that the submerged rivers of the Sunda Shelf have obvious, incised meanders, which would have been maintained by trees on river banks. Pollen records from sediment cores around Sundaland are contradictory; for example, cores from highland sites suggest that forest cover persisted throughout the last glacial period, but other cores from the region show pollen from savanna-woodland species increasing through glacial periods. And in contrast to previous findings, Wurster et al. (2017) again used stable carbon isotope analysis of bat guano, but found that at some sites rainforest cover was maintained through much of the last glacial period. Soil type, rather than long-term existence of a savanna corridor, has also been posited as an explanation for species distribution differences within Sundaland; Slik et al. (2011) suggest that the sandy soils of the now submerged seabed are a more likely dispersal barrier.


Paleofauna

Before Sundaland emerged during the late Pliocene and early Pleistocene (~2.4 million years ago), there were no mammals on Java. As sea level lowered, species such as the dwarf elephantoid ''Sinomastodon bumiajuensis'' colonized Sundaland from mainland Asia. Later fauna included tigers, Sumatran rhinoceros, and Indian elephant, which were found throughout Sundaland; smaller animals were also able to disperse across the region.


Human migrations

According to the most widely accepted theory, the ancestors of the modern-day
Austronesian Austronesian may refer to: *The Austronesian languages *The historical Austronesian peoples The Austronesian peoples, sometimes referred to as Austronesian-speaking peoples, are a large group of peoples in Taiwan, Maritime Southeast Asia, M ...
populations of the Maritime Southeast Asia and adjacent regions are believed to have migrated southward, from the East Asia mainland to
Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the northe ...
, and then to the rest of
Maritime Southeast Asia Maritime Southeast Asia comprises the countries of Brunei, Indonesia, Malaysia, the Philippines, Singapore, and East Timor. Maritime Southeast Asia is sometimes also referred to as Island Southeast Asia, Insular Southeast Asia or Oceanic Sout ...
. An alternative theory points to the now-submerged Sundaland as the possible cradle of Austronesian languages: thus the "Out of Sundaland" theory. However, this view is an extreme minority view among professional archaeologists, linguists, and geneticists. The Out of Taiwan model (though not necessarily the Express Train Out of Taiwan model) is accepted by the vast majority of professional researchers. A study from
Leeds University , mottoeng = And knowledge will be increased , established = 1831 – Leeds School of Medicine1874 – Yorkshire College of Science1884 - Yorkshire College1887 – affiliated to the federal Victoria University1904 – University of Leeds , ...
and published in ''
Molecular Biology and Evolution ''Molecular Biology and Evolution'' is a monthly peer-reviewed scientific journal published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. It publishes work in the intersection of molecular biology and evo ...
'', examining mitochondrial DNA lineages, suggested that shared ancestry between Taiwan and Southeast Asian resulted from earlier migrations. Population dispersals seem to have occurred at the same time as sea levels rose, which may have resulted in migrations from the
Philippine The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...
Islands to as far north as Taiwan within the last 10,000 years. The population migrations were most likely to have been driven by climate change — the effects of the drowning of an ancient continent. Rising sea levels in three massive pulses may have caused flooding and the submerging of the Sunda continent, creating the
Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's mo ...
and South China Seas and the thousands of islands that make up
Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...
and the
Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...
today. The changing sea levels would have caused these humans to move away from their coastal homes and culture, and farther inland throughout southeast Asia. This forced migration would have caused these humans to adapt to the new forest and mountainous environments, developing farms and domestication, and becoming the predecessors to future human populations in these regions. Genetic similarities were found between populations throughout Asia and an increase in genetic diversity from northern to southern latitudes. Although the Chinese population is very large, it has less variation than the smaller number of individuals living in Southeast Asia, because the Chinese expansion occurred very recently, within only the last 2,000 to 3,000 years.
Oppenheimer Oppenheimer is a surname. Notable people with the surname include: In arts and media * Alan Oppenheimer (born 1930), American film actor * Andrés Oppenheimer (born 1951), Argentine author and journalist known for his analysis of Latin American p ...
locates the origin of the
Austronesians The Austronesian peoples, sometimes referred to as Austronesian-speaking peoples, are a large group of peoples in Taiwan, Maritime Southeast Asia, Micronesia, coastal New Guinea, Island Melanesia, Polynesia, and Madagascar that speak Austrone ...
in Sundaland and its upper regions. From the standpoint of
historical linguistics Historical linguistics, also termed diachronic linguistics, is the scientific study of language change over time. Principal concerns of historical linguistics include: # to describe and account for observed changes in particular languages # ...
, the home of the Austronesian languages is the main island of Taiwan, also known by its unofficial Portuguese name of Formosa; on this island the deepest divisions in Austronesian are found, among the families of the native
Formosan languages The Formosan languages are a geographic grouping comprising the languages of the indigenous peoples of Taiwan, all of which are Austronesian. They do not form a single subfamily of Austronesian but rather nine separate subfamilies. The Taiwan ...
.


See also

* Austronesian languages *
Banda Arc The Banda Arc (main arc, Inner, and Outer) is a set of island arcs in eastern Indonesia. It is the result of the collision of a continent and an intra-oceanic island arc. The presently active arc is located on what appears to be oceanic crust wh ...
* Biogeography *
Father Tongue hypothesis The Father Tongue hypothesis proposes that humans tend to speak their father's language. It is based on the discovery, in 1997, of a closer correlation between language and Y-chromosomal variation than between language and mitochondrial DNA varia ...
*
List of islands of Indonesia * See also: Names of Indonesia , location = Southeast Asia and Oceania , waterbody = * Indian Ocean * Pacific Ocean , total_islands = ± 17,000–18,000 islands , major_islands = , area_km2 = 8,300,000 , area_footnotes = , rank = , length ...
*
Oceania Oceania (, , ) is a region, geographical region that includes Australasia, Melanesia, Micronesia, and Polynesia. Spanning the Eastern Hemisphere, Eastern and Western Hemisphere, Western hemispheres, Oceania is estimated to have a land area of ...
**
Australasia Australasia is a region that comprises Australia, New Zealand and some neighbouring islands in the Pacific Ocean. The term is used in a number of different contexts, including geopolitically, physiogeographically, philologically, and ecolo ...
***
Australia (continent) The continent of Australia, sometimes known in technical contexts by the names Sahul (), Australia-New Guinea, Australinea, Meganesia, or Papualand to distinguish it from the country of Australia, is located within the Southern and Eas ...
*
Oceanic trench Oceanic trenches are prominent long, narrow topographic depressions of the ocean floor. They are typically wide and below the level of the surrounding oceanic floor, but can be thousands of kilometers in length. There are about of oceanic tren ...
*
Plate tectonics Plate tectonics (from the la, label= Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large t ...
*
Sunda Arc The Sunda Arc is a volcanic arc that produced the volcanoes that form the topographic spine of the islands of Sumatra, Nusa Tenggara, and Java, the Sunda Strait and the Lesser Sunda Islands. The Sunda Arc begins at Sumatra and ends at Flores, ...
*
Sunda Islands The Sunda Islands ( id, Kepulauan Sunda) are a group of islands in the Malay Archipelago.Chisholm, Hugh, ed. (1911). "Sunda Islands" . ''Encyclopædia Britannica''. 26 (11th ed.). Cambridge University Press. They consist of the Greater Sun ...
**
Greater Sunda Islands The Greater Sunda Islands (Indonesian and Malay: ''Kepulauan Sunda Besar'') are four tropical islands situated within Indonesian Archipelago, in the Pacific Ocean. The islands, Borneo, Java, Sulawesi and Sumatra, are internationally recognise ...
**
Lesser Sunda Islands The Lesser Sunda Islands or nowadays known as Nusa Tenggara Islands ( id, Kepulauan Nusa Tenggara, formerly ) are an archipelago in Maritime Southeast Asia, north of Australia. Together with the Greater Sunda Islands to the west they make u ...
*
Sunda Shelf Geologically, the Sunda Shelf is a south-eastern extension of the continental shelf of Mainland Southeast Asia. Major landmasses on the shelf include the Bali, Borneo, Java, Madura, and Sumatra, as well as their surrounding smaller island ...
*
Sunda Trench The Sunda Trench, earlier known as and sometimes still indicated as the Java Trench, is an oceanic trench located in the Indian Ocean near Sumatra, formed where the Australian- Capricorn plates subduct under a part of the Eurasian Plate. It is ...


References


Selected faunal references in Borneo

* Abdullah MT. 2003. Biogeography and variation of ''Cynopterus brachyotis'' in Southeast Asia. PhD thesis. The University of Queensland, St Lucia, Australia. * Corbet, GB, Hill JE. 1992. The mammals of the Indomalayan region: a systematic review. Oxford University Press, Oxford. * Hall LS, Gordon G. Grigg, Craig Moritz, Besar Ketol, Isa Sait, Wahab Marni, Abdullah MT. 2004. Biogeography of fruit bats in Southeast Asia. Sarawak Museum Journal LX(81):191–284. * Karim, C., A.A. Tuen, Abdullah MT. 2004. Mammals. Sarawak Museum Journal Special Issue No. 6. 80: 221–234. * * * Wilson DE, Reeder DM. 2005. Mammal species of the world. Smithsonian Institution Press, Washington DC.


External links


Review of Oppenheimer's Eden in the East, about Sundaland
{{Borneo Biogeography Continental shelves Historical geology Indomalayan realm Malesia Prehistoric Indonesia