Sundaland (also called Sundaica or the Sundaic region) is a biogeographical 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 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, west of Sulawesi, and ea ...

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 mos ...

, 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 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 islands. I ...

, 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 betwe ...

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, 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 Phi ...

. 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 t ...

. 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 trans ...

, 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 and th ...

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 o ...

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 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 referr ...

; the equator 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 transpi ...

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 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 p ...

(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'' = f ...

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 genu ...

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 ...

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 ...

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. Th ...

, 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, monkeys,

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 g ...

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 ...

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 species (or numerous extinct species) of odd-toed ungulates in the family Rhinocerotidae. (It can also refer to a member of any of the extinct species ...

. The flooding of Sundaland separated species that had once shared the same environment. One example is the river threadfin (''

Polydactylus ''Polydactylus'' is a genus of threadfin that mainly are native to the Indian, Atlantic and Pacific Oceans, especially in coastal or brackish waters (such as mangrove or estuaries). Some may even enter rivers and a single, ''P. macrophthalmus'', ...

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 and ...

) 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, discon ...

* Eastern Java–Bali rain forests (

, Bali) * Eastern Java–Bali montane rain forests (

, Bali). *

Western Java montane rain forests The Western Java montane rain forests ecoregion (WWF ID: IM0167) covers the montane rain forest above 1,000 meters in the volcanic mountain ridges in the west of the island of Java in Indonesia. Several mammals and bird species are found only in ...

(

) *

Western Java rain forests The Western Java rain forests ecoregion (World Wildlife Fund ID: IM0168) covers the lowland rain forests below 1,000 meters in elevation in the western half of the island of Java in Indonesia. There are a variety of forest types - evergreen, semi-e ...

(

) *

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 montane rain forests (

) *

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 ...

(

) * Mentawai Islands rain forests (

Mentawai Islands Mentawai may refer to: * Mentawai Islands * Mentawai Strait * Mentawai people * Mentawai language The Mentawai language is an Austronesian language, spoken by the Mentawai people of the Mentawai Islands, West Sumatra, Indonesia. Dialects Ac ...

) *

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. Geog ...

( Malay peninsula) *

Peninsular Malaysian peat swamp forests The Peninsular Malaysian peat swamp forests is an ecoregion on Malay Peninsula, which includes portions of Malaysia. It is in the tropical and subtropical moist broadleaf forests biome. Setting The ecoregion covers an area of on both the eastern ...

( Malay peninsula) *

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 ...

(

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. Geograp ...

, Malay peninsula) * Southwest Borneo freshwater swamp forests (

) * Sumatran freshwater swamp forests ( 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 ...

) * Sumatran montane rain forests ( Sumatra) * Sumatran peat swamp forests ( 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 ...

(

) ;

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 va ...

* Sumatran tropical pine forests ( 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 th ...

* Kinabalu montane alpine meadows (

) ;

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 severa ...

* Sunda Shelf mangroves (

, 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 lan ...

)

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 importance ...

'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. In 1921 Gustaaf Molengraaff, 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 ...

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 ...

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 epoch (geology), 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 mea ...

; 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 deposit ...

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. 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'') l ...

since the early

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'' = f ...

trees characteristic of modern Southeast Asian tropical rainforest have been present in Sundaland since before the Last Glacial Maximum. 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

(

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. 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 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 nort ...

, 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

and South China Seas and the thousands of islands that make up

and the

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 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 Taiwa ...

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