# Sundaland

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{{Short description|Biogeographic region of Southeast Asia}}
{{Distinguish|Sunderland}}
{{Redirect|Sundas|the Greater Sundas|Greater Sunda Islands|the Lesser Sundas|Lesser Sunda Islands}}
{{For|the continental shelf of Southeast Asia|Sunda Shelf}}

[[File:Sundaland-at-the-Last-Glacial-Maximum-showing-the-modern-distribution-of-land-in-dark.png|thumb|400px|[Sundaland](/source/Sundaland) during the [Last Glacial Maximum](/source/Last_Glacial_Maximum)]]

'''Sundaland''' (also called '''Sundaica''' or the '''Sundaic region''') is a [biogeographical](/source/Biogeography) region of [Southeast Asia](/source/Southeast_Asia) corresponding to a larger landmass that was exposed throughout the [last 2.6 million years](/source/Pleistocene) during periods when sea levels were lower. It includes [Bali](/source/Bali), [Borneo](/source/Borneo), [Java](/source/Java), and [Sumatra](/source/Sumatra) in [Indonesia](/source/Indonesia), and their surrounding small islands, as well as the [Malay Peninsula](/source/Malay_Peninsula) on [Mainland Southeast Asia](/source/Mainland_Southeast_Asia).

==Extent==

The area of Sundaland encompasses the [Sunda Shelf](/source/Sunda_Shelf), a tectonically stable extension of Southeast Asia's continental shelf that was exposed during [glacial period](/source/glacial_period)s of the last 2 million years.<ref name=":4">{{Cite book|title=Phillipps's Field Guide to the Mammals of Borneo and Their Ecology: Sabah, Sarawak, Brunei, and Kalimantan|last1=Phillipps|first1=Quentin|last2=Phillipps|first2=Karen|publisher=Princeton University Press|year=2016|isbn=978-0-691-16941-5|location=Princeton, New Jersey, USA}}</ref><ref name=":14">{{Cite journal|last1=de Bruyn|first1=Mark|last2=Stelbrink|first2=Björn|last3=Morley|first3=Robert J.|last4=Hall|first4=Robert|last5=Carvalho|first5=Gary R.|last6=Cannon|first6=Charles H.|last7=van den Bergh|first7=Gerrit|last8=Meijaard|first8=Erik|last9=Metcalfe|first9=Ian|date=2014-11-01|title=Borneo and Indochina are Major Evolutionary Hotspots for Southeast Asian Biodiversity|journal=Systematic Biology|volume=63|issue=6|pages=879–901|doi=10.1093/sysbio/syu047|pmid=25070971|issn=1063-5157|url=http://ro.uow.edu.au/cgi/viewcontent.cgi?article=3379&context=smhpapers|doi-access=free}}</ref> It is also roughly coterminous with the [Sunda plate](/source/Sunda_plate).<ref name=Whitten>{{cite book |last=Whitten |first=T |author2=Soeriaatmadja, R. E. |author3=Suraya A. A. |title=The Ecology of Java and Bali |publisher=Periplus Editions Ltd |year=1996 |location=Hong Kong |pages=87 |isbn=978-9625938882}}</ref>

The extent of the Sunda Shelf is approximately equal to the 120-meter [isobath](/source/isobath).<ref name=":2" /> In addition to the Malay Peninsula and the islands of Borneo, Java, and Sumatra, it includes the [Java Sea](/source/Java_Sea), the [Gulf of Thailand](/source/Gulf_of_Thailand), and portions of the [South China Sea](/source/South_China_Sea).<ref name="Wang 5–39">{{Cite journal|last=Wang|first=Pinxian|date=1999-03-15|title=Response of Western Pacific marginal seas to glacial cycles: paleoceanographic and sedimentological features|journal=Marine Geology|volume=156|issue=1–4|pages=5–39|doi=10.1016/S0025-3227(98)00172-8|bibcode=1999MGeol.156....5W}}</ref> In total, the area of Sundaland is approximately 1,800,000&nbsp;km<sup>2</sup>.<ref name=":3">{{Cite journal|last1=Hanebuth|first1=Till|last2=Stattegger|first2=Karl|last3=Grootes|first3=Pieter M.|date=2000|title=Rapid Flooding of the Sunda Shelf: A Late-Glacial Sea-Level Record|jstor=3075104|journal=Science|volume=288|issue=5468|pages=1033–1035|bibcode=2000Sci...288.1033H|doi=10.1126/science.288.5468.1033|pmid=10807570}}</ref><ref name=":2" /> 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 its maximum extent.<ref name=":14"/>

The western and southern borders of Sundaland are clearly marked by the deeper waters of the [Sunda Trench](/source/Sunda_Trench) – some of the deepest in the world – and the [Indian Ocean](/source/Indian_Ocean).<ref name=":2" /> The eastern boundary of Sundaland is the [Wallace Line](/source/Wallace_Line), identified by [Alfred Russel Wallace](/source/Alfred_Russel_Wallace) as the eastern boundary of the range of Asia's land [mammal](/source/mammal) fauna, and thus the boundary of the [Indomalayan](/source/Indomalayan_realm) and [Australasian realm](/source/Australasian_realm)s. The islands east of the Wallace line are known as [Wallacea](/source/Wallacea), a separate biogeographical region that is considered part of [Australasia](/source/Australasia). The Wallace Line corresponds to a deep-water channel that has never been crossed by any land bridges.<ref name=":2">{{Cite journal|last1=Bird|first1=Michael I.|last2=Taylor|first2=David|last3=Hunt|first3=Chris|date=2005-11-01|title=Palaeoenvironments of insular Southeast Asia during the Last Glacial Period: a savanna corridor in Sundaland?|journal=Quaternary Science Reviews|volume=24|issue=20–21|pages=2228–2242|doi=10.1016/j.quascirev.2005.04.004|bibcode=2005QSRv...24.2228B}}</ref> The northern border of Sundaland is more difficult to define in bathymetric terms; a [phytogeographic](/source/Phytogeography) transition at approximately 9ºN is considered to be the northern boundary.<ref name=":2" />

Greater portions of Sundaland were most recently exposed during the [last glacial period](/source/last_glacial_period) from approximately 110,000 to 12,000 years ago.<ref name=":5">{{Cite journal|last=Heaney|first=Lawrence R.|date=1984|title=Mammalian Species Richness on Islands on the Sunda Shelf, Southeast Asia|jstor=4217198|journal=Oecologia|volume=61|issue=1|pages=11–17|pmid=28311380|doi=10.1007/BF00379083|bibcode=1984Oecol..61...11H|citeseerx=10.1.1.476.4669|s2cid=4810675}}</ref><ref name=":3" /> When the 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.<ref name=":4" /> Because the sea level was 30 meters or more lower throughout much of the last 800,000 years, the current status of Borneo, Java, and Sumatra as islands has been a relatively rare occurrence throughout the Pleistocene.<ref>{{Cite journal|last1=Bintanja|first1=Richard|last2=Wal|first2=Roderik S.W. van de|last3=Oerlemans|first3=Johannes|title=Modelled atmospheric temperatures and global sea levels over the past million years|journal=Nature|volume=437|issue=7055|pages=125–128|doi=10.1038/nature03975|pmid=16136140|year=2005|bibcode=2005Natur.437..125B|s2cid=4347450}}</ref> In contrast, the sea level was higher during the late [Pliocene](/source/Pliocene), and the exposed area of Sundaland was smaller than what is observed at present.<ref name=":2" /> Sundaland was partially submerged starting around 18,000 years ago and continuing until about 5000 BC.<ref name="phys">{{cite web|url=https://phys.org/news/2018-04-island-hopping-route-people-australia.html|website=phys.org|title=Island-hopping study shows the most likely route the first people took to Australia|accessdate=2018-08-09}}</ref><ref name="google">{{cite book|title=Prehistory of the Indo-Malaysian Archipelago: Revised Edition|author=Bellwood, P.|date=2007|publisher=ANU E Press|isbn=9781921313127|url=https://books.google.com/books?id=4obAfGBGKY0C&pg=PA36|page=36|accessdate=2018-08-09}}</ref> During the [Last Glacial Maximum](/source/Last_Glacial_Maximum) the sea level fell by approximately 120 meters, and the entire Sunda Shelf was exposed.<ref name=":4" />

==Modern climate==

[[File:Map of Sunda and Sahul.svg|thumb|250px|upright=1.75|The [Sahul Shelf](/source/Sahul_Shelf) and the [Sunda Shelf](/source/Sunda_Shelf) today. The area in between is called "[Wallacea](/source/Wallacea)"]]

All of Sundaland is within the [tropics](/source/tropics); the [equator](/source/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;<ref name=":2" /> rainfall exceeds [evapotranspiration](/source/evapotranspiration) throughout the year and there are no [predictable dry seasons](/source/Monsoon) like elsewhere in Southeast Asia.<ref name=":6">{{Cite book|title=On the Forests of Tropical Asia: Lest the memory fade|last=Ashton|first=Peter|publisher=Royal Botanic Gardens, Kew|year=2014|isbn=978-1-84246-475-5|location=Kew, Richmond, Surrey, UK}}</ref>

The warm and shallow seas of the [Sunda Shelf](/source/Sunda_Shelf) (averaging 28&nbsp;°C or more) are part of the Indo-Pacific Warm Pool/[Western Pacific Warm Pool](/source/Western_Pacific_Warm_Pool)<ref>{{Cite journal|last1=Yan|first1=Xiao-Hai|last2=Ho|first2=Chung-Ru|last3=Zheng|first3=Quanan|last4=Klemas|first4=Vic|date=1992|title=Temperature and Size Variabilities of the Western Pacific Warm Pool|jstor=2882071|journal=Science|volume=258|issue=5088|pages=1643–1645|bibcode=1992Sci...258.1643Y|doi=10.1126/science.258.5088.1643|pmid=17742536|s2cid=35015913}}</ref> and an important driver of the [Hadley circulation](/source/Hadley_cell) and the [El Niño-Southern Oscillation](/source/El_Ni%C3%B1o%E2%80%93Southern_Oscillation) (ENSO), particularly in January when it is a major heat source to the atmosphere.<ref name=":2" /> ENSO also has a major influence on the climate of Sundaland; strong positive ENSO events result in [droughts throughout Sundaland and tropical Asia](/source/El_Ni%C3%B1o).

==Modern ecology==
The high rainfall supports closed canopy evergreen forests throughout the islands of Sundaland,<ref name=":6" /> transitioning to deciduous forest and savanna woodland with increasing latitude.<ref name=":2" /> The remaining primary (unlogged) lowland forest is known for giant [dipterocarp](/source/Dipterocarpaceae) trees and [orangutan](/source/orangutan)s; after logging, forest structure and community composition change to be dominated by shade intolerant trees and shrubs.<ref>{{Cite journal|last1=Slik|first1=J. W. Ferry|last2=Breman|first2=Floris|last3=Bernard|first3=Caroline|last4=van Beek|first4=Marloes|last5=Cannon|first5=Charles H.|last6=Eichhorn|first6=Karl A. O.|last7=Sidiyasa|first7=Kade|date=2010|title=Fire as a selective force in a Bornean tropical everwet forest|jstor=40926702|journal=Oecologia|volume=164|issue=3|pages=841–849|pmid=20811911|doi=10.1007/s00442-010-1764-4|bibcode=2010Oecol.164..841S|s2cid=9545174}}</ref> Dipterocarps are notable for [mast fruiting events](/source/Mast_(botany)), where tree fruiting is synchronized at unpredictable intervals resulting in predator satiation.<ref name=":12">{{Cite journal|last1=Wurster|first1=Christopher|last2=Bird|first2=Michael|last3=Bull|first3=Ian|date=2010|title=Forest contraction in north equatorial Southeast Asia during the Last Glacial Period|journal=Proceedings of the National Academy of Sciences|volume=107|issue=35|pages=15508–15511|doi=10.1073/pnas.1005507107|pmid=20660748|pmc=2932586|s2cid=13598147|doi-access=free}}</ref> Higher elevation forests are shorter and dominated by trees in the [oak family](/source/Fagaceae).<ref name=":6" /> Botanists often include Sundaland, the adjacent [Philippines](/source/Philippines), [Wallacea](/source/Wallacea) and [New Guinea](/source/New_Guinea) in a single [floristic province](/source/floristic_province) of [Malesia](/source/Malesia), based on similarities in their flora, which is predominantly of Asian origin.<ref name=":6" />

During the [last glacial period](/source/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](/source/elephants), [monkey](/source/monkey)s, [ape](/source/ape)s, [tiger](/source/tiger)s, [tapir](/source/tapir)s, and [rhinoceros](/source/rhinoceros). The flooding of Sundaland separated species that had once shared the same environment. One example is the river threadfin (''[Polydactylus](/source/Polydactylus) macrophthalmus'', Bleeker 1858), which once thrived in a river system now called "North Sunda River" or "Molengraaff river".<ref>[https://www.researchgate.net/publication/227696790_Maps_of_Pleistocene_sea_levels_in_Southeast_Asia_Shorelines_river_systems_and_time_durations Maps of Pleistocene sea levels in Southeast Asia: Shorelines, river systems and time durations]</ref> The fish is now found in the Kapuas River on the island of Borneo, and in the Musi and Batanghari rivers in Sumatra.<ref>{{cite web | title=Polydactylus macrophthalmus | website=fishbase.sinica.edu.tw | url=http://fishbase.sinica.edu.tw/FieldGuide/FieldGuideSummary.php?GenusName=Polydactylus&SpeciesName=macrophthalmus&pda=&sps= | ref={{sfnref | fishbase.sinica.edu.tw}} | access-date=2019-10-19 }}{{Dead link|date=September 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> [Selective pressure](/source/Evolutionary_pressure) (in some cases resulting in [extinction](/source/extinction)) has operated differently on each of the islands of Sundaland, and as a consequence, a different assemblage of mammals is found on each island.<ref name=":13">{{Cite journal|last1=Okie|first1=Jordan G.|last2=Brown|first2=James H.|date=2009-11-17|title=Niches, body sizes, and the disassembly of mammal communities on the Sunda Shelf islands|journal=Proceedings of the National Academy of Sciences|language=en|volume=106|issue=Supplement 2|pages=19679–19684|doi=10.1073/pnas.0901654106|issn=0027-8424|pmc=2780945|pmid=19805179|bibcode=2009PNAS..10619679O|doi-access=free}}</ref> 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.<ref name=":13" /> Island area and number of terrestrial mammal species are related, with the largest islands of Sundaland (Borneo and Sumatra) having the highest diversity.<ref name=":5" />

===Ecoregions===
;[Tropical and subtropical moist broadleaf forests](/source/Tropical_and_subtropical_moist_broadleaf_forests)
{{Div col}}
* [Eastern Java–Bali rain forests](/source/Eastern_Java%E2%80%93Bali_rain_forests) ([Java](/source/Java_(island)), [Bali](/source/Bali))
* [Eastern Java–Bali montane rain forests](/source/Eastern_Java%E2%80%93Bali_montane_rain_forests) ([Java](/source/Java_(island)), [Bali](/source/Bali)). 
* [Western Java montane rain forests](/source/Western_Java_montane_rain_forests) ([Java](/source/Java_(island)))
* [Western Java rain forests](/source/Western_Java_rain_forests) ([Java](/source/Java_(island)))
* [Borneo lowland rain forests](/source/Borneo_lowland_rain_forests) ([Borneo](/source/Borneo))
* [Borneo montane rain forests](/source/Borneo_montane_rain_forests) ([Borneo](/source/Borneo))
* [Borneo peat swamp forests](/source/Borneo_peat_swamp_forests) ([Borneo](/source/Borneo))
* [Mentawai Islands rain forests](/source/Mentawai_Islands_rain_forests) ([Mentawai Islands](/source/Mentawai_Islands))
* [Peninsular Malaysian montane rain forests](/source/Peninsular_Malaysian_montane_rain_forests) ([Malay Peninsula](/source/Malay_Peninsula))
* [Peninsular Malaysian peat swamp forests](/source/Peninsular_Malaysian_peat_swamp_forests) ([Malay Peninsula](/source/Malay_Peninsula))
* [Peninsular Malaysian rain forests](/source/Peninsular_Malaysian_rain_forests) ([Anambas Islands](/source/Anambas_Islands), [Malay Peninsula](/source/Malay_Peninsula))
* [Southwest Borneo freshwater swamp forests](/source/Southwest_Borneo_freshwater_swamp_forests) ([Borneo](/source/Borneo))
* [Sumatran freshwater swamp forests](/source/Sumatran_freshwater_swamp_forests) ([Sumatra](/source/Sumatra))
* [Sumatran lowland rain forests](/source/Sumatran_lowland_rain_forests) ([Sumatra](/source/Sumatra), [Nias](/source/Nias), [Bangka Island](/source/Bangka_Island))
* [Sumatran montane rain forests](/source/Sumatran_montane_rain_forests) ([Sumatra](/source/Sumatra))
* [Sumatran peat swamp forests](/source/Sumatran_peat_swamp_forests) ([Sumatra](/source/Sumatra))
* [Sundaland heath forests](/source/Sundaland_heath_forests) ([Indonesia](/source/Indonesia))
{{Div col end}}
;[Tropical and subtropical coniferous forests](/source/Tropical_and_subtropical_coniferous_forests)
* [Sumatran tropical pine forests](/source/Sumatran_tropical_pine_forests) ([Sumatra](/source/Sumatra))
;[Montane grasslands and shrublands](/source/Montane_grasslands_and_shrublands)
* [Kinabalu montane alpine meadows](/source/Kinabalu_montane_alpine_meadows) ([Borneo](/source/Borneo))
;[Mangroves](/source/Mangroves)
* [Sunda Shelf mangroves](/source/Sunda_Shelf_mangroves) ([Borneo](/source/Borneo), [Sumatra](/source/Sumatra), [Riau Islands](/source/Riau_Islands))

==History==

===Early research===
The name "Sunda" goes back to antiquity, appearing in [Ptolemy](/source/Ptolemy)'s [''Geography''](/source/Geography_(Ptolemy)), written around 150 AD.<ref>{{cite book|last1=Heeren|first1=Arnold Herman Ludwig|title=The Historical Works of Arnold H.L. Heeren: Politics, intercourse and trade of the Asiatic nations|date=1846|publisher=H.G. Bohn|page=430|url=https://books.google.com/books?id=CisZAAAAYAAJ&q=ptolemy+sunda&pg=PA430|access-date=2 December 2017}}</ref> In an 1852 publication, English navigator [George Windsor Earl](/source/George_Windsor_Earl) advanced the idea of a "Great Asiatic Bank", based in part on common features of mammals found in Java, Borneo and Sumatra.<ref name=":15">{{cite book|last1=Earl|first1=George Windsor|title=Contributions to the Physical Geography of South-Eastern Asia and Australia ...|date=1853|publisher=H. Bailliere|page=40|url=https://books.google.com/books?id=qXJZAAAAcAAJ&pg=PA40|access-date=2 December 2017}}</ref>

Explorers and scientists began measuring and mapping the seas of Southeast Asia in the 1870s, primarily using [depth sounding](/source/depth_sounding).<ref name=":9">{{Cite journal|last=Molengraaff|first=G. A. F.|date=1921|title=Modern Deep-Sea Research in the East Indian Archipelago|jstor=1781559|journal=The Geographical Journal|volume=57|issue=2|pages=95–118|doi=10.2307/1781559|bibcode=1921GeogJ..57...95M |url=https://zenodo.org/record/1449362}}</ref> In 1921 [Gustaaf Molengraaff](/source/Gustaaf_Adolf_Frederik_Molengraaff), a Dutch geologist, postulated that the nearly uniform sea depths of the shelf indicated an ancient [peneplain](/source/peneplain) that was the result of repeated flooding events as ice caps melted, with the peneplain becoming more perfect with each successive flooding event.<ref name=":9" /> Molengraaff also identified [ancient, now submerged, drainage systems](/source/Sunda_Shelf) that drained the area during periods of lower sea levels.

The name "Sundaland" for the peninsular shelf was first proposed by [Reinout Willem van Bemmelen](/source/Reinout_Willem_van_Bemmelen) in his ''Geography of Indonesia'' in 1949, based on his research during [World War II](/source/World_War_II). The ancient drainage systems described by Molengraaff were verified and mapped by Tjia in 1980<ref>{{Cite journal|last=Tija|first=H.D.|date=1980|title=The Sunda Shelf, Southeast Asia|journal=Zeitschrift für Geomorphologie|volume=24|issue=4|pages=405–427|doi=10.1127/zfg/24/1884/405|bibcode=1980ZGm....24..405T |s2cid=131985735 }}</ref> and described in greater detail by Emmel and Curray in 1982 complete with [river delta](/source/river_delta)s, [floodplain](/source/floodplain)s and backswamps.<ref>{{Cite journal|last1=Moore|first1=Gregory F.|last2=Curray|first2=Joseph R.|last3=Emmel|first3=Frans J.|title=Sedimentation in the Sunda Trench and forearc region|journal=Geological Society, London, Special Publications|volume=10|issue=1|pages=245–258|doi=10.1144/gsl.sp.1982.010.01.16|year=1982|bibcode=1982GSLSP..10..245M|s2cid=130052162}}</ref><ref name=":7">''The physical geography of Southeast Asia'' by Avijit Gupta, 2005, {{ISBN|0-19-924802-8}}, page 403</ref>

===Data types===
The climate and ecology of Sundaland throughout the Quaternary has been investigated by analyzing [foraminifera](/source/foraminifera)<nowiki/>l [''δ''<sup>18</sup>O](/source/%CE%9418O) and pollen from cores drilled into the ocean bed, [''δ''<sup>18</sup>O](/source/%CE%9418O) in [speleothem](/source/speleothem)s from caves, and [''δ''<sup>13</sup>C](/source/%CE%9413C) and [''δ''<sup>15</sup>N](/source/%CE%9415N) 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](/source/Miocene); though there is evidence for several periods of drier conditions, a perhumid core persisted in Borneo.<ref name=":6" /> The presence of fossil coral reefs dating to the late Miocene and early [Pliocene](/source/Pliocene) suggests that, as the Indian monsoon grew more intense, seasonality increased in some portions of Sundaland during these epochs.<ref name=":6" /> [Palynological](/source/Palynology) 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&nbsp;°C cooler than present.<ref name=":11">{{Cite journal|last1=Newsome|first1=J.|last2=Flenley|first2=J. R.|date=1988|title=Late Quaternary Vegetational History of the Central Highlands of Sumatra. II. Palaeopalynology and Vegetational History|jstor=2845436|journal=Journal of Biogeography|volume=15|issue=4|pages=555–578|doi=10.2307/2845436|bibcode=1988JBiog..15..555N }}</ref>

Most recent research agrees that Indo-Pacific [sea surface temperature](/source/sea_surface_temperature)s were at most 2-3&nbsp;°C lower during the [Last Glacial Maximum](/source/Last_Glacial_Maximum).<ref name=":2" /> 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.<ref>{{Cite journal|last=Heaney|first=Lawrence R.|date=1991|title=A synopsis of climatic and vegetational change in Southeast Asia|journal=Climatic Change|volume=19|issue=1–2|pages=53–61|doi=10.1007/bf00142213|bibcode=1991ClCh...19...53H|s2cid=154779535}}</ref> 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.<ref>{{Cite journal|last1=De Deckker|first1=P|last2=Tapper|first2=N. J|last3=van der Kaars|first3=S|date=2003-01-01|title=The status of the Indo-Pacific Warm Pool and adjacent land at the Last Glacial Maximum|journal=Global and Planetary Change|volume=35|issue=1–2|pages=25–35|doi=10.1016/S0921-8181(02)00089-9|bibcode=2003GPC....35...25D}}</ref><ref name="Wang 5–39" /> Others posit that changes in precipitation have been minimal<ref>{{Cite journal|last1=Wang|first1=XiaoMei|last2=Sun|first2=XiangJun|last3=Wang|first3=PinXian|last4=Stattegger|first4=Karl|date=2009-07-15|title=Vegetation on the Sunda Shelf, South China Sea, during the Last Glacial Maximum|journal=Palaeogeography, Palaeoclimatology, Palaeoecology|volume=278|issue=1–4|pages=88–97|doi=10.1016/j.palaeo.2009.04.008|bibcode=2009PPP...278...88W}}</ref> 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.<ref name=":10" />

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.<ref name=":10">{{Cite journal|last1=Russell|first1=James M.|last2=Vogel|first2=Hendrik|last3=Konecky|first3=Bronwen L.|last4=Bijaksana|first4=Satria|last5=Huang|first5=Yongsong|last6=Melles|first6=Martin|last7=Wattrus|first7=Nigel|last8=Costa|first8=Kassandra|last9=King|first9=John W.|date=2014-04-08|title=Glacial forcing of central Indonesian hydroclimate since 60,000 y B.P|journal=Proceedings of the National Academy of Sciences|language=en|volume=111|issue=14|pages=5100–5105|doi=10.1073/pnas.1402373111|issn=0027-8424|pmc=3986195|pmid=24706841|bibcode=2014PNAS..111.5100R|doi-access=free}}</ref> Alternatively, the physical and chemical processes that underlie the method of inferring precipitation from [''δ''<sup>18</sup>O](/source/%CE%9418O) records may have operated differently in the past.<ref name=":10" /> 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.<ref name=":11" />

===Ecology===
Sundaland, and in particular Borneo, has been an evolutionary hotspot for [biodiversity](/source/biodiversity) since the early [Miocene](/source/Miocene) due to repeated immigration and [vicariance](/source/vicariance) events.<ref name=":14"/> 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.<ref name=":14"/>
<ref>{{Cite journal|last1=Cannon|first1=Charles H.|last2=Morley|first2=Robert J.|last3=Bush|first3=Andrew B. G.|date=2009-07-07|title=The current refugial rainforests of Sundaland are unrepresentative of their biogeographic past and highly vulnerable to disturbance|journal=Proceedings of the National Academy of Sciences|language=en|volume=106|issue=27|pages=11188–11193|doi=10.1073/pnas.0809865106|issn=0027-8424|pmc=2708749|pmid=19549829|bibcode=2009PNAS..10611188C|doi-access=free}}</ref>

==== Savanna corridor theory ====
[Dipterocarp](/source/Dipterocarpaceae) trees characteristic of modern Southeast Asian tropical rainforest have been present in Sundaland since before the [Last Glacial Maximum](/source/Last_Glacial_Maximum).<ref name=":1">{{Cite journal|last1=Raes|first1=Niels|last2=Cannon|first2=Charles H.|last3=Hijmans|first3=Robert J.|last4=Piessens|first4=Thomas|last5=Saw|first5=Leng Guan|last6=Welzen|first6=Peter C. van|last7=Slik|first7=J. W. Ferry|date=2014-11-25|title=Historical distribution of Sundaland's Dipterocarp rainforests at Quaternary glacial maxima|journal=Proceedings of the National Academy of Sciences|language=en|volume=111|issue=47|pages=16790–16795|doi=10.1073/pnas.1403053111|issn=0027-8424|pmc=4250149|pmid=25385612|bibcode=2014PNAS..11116790R|doi-access=free}}</ref> There is also evidence for [savanna](/source/savanna) vegetation, particularly in now submerged areas of Sundaland, throughout the [last glacial period](/source/last_glacial_period).<ref>{{Cite journal|last1=Earl of Cranbrook|last2=Cranbrook|first2=Earl of|title=Late quaternary turnover of mammals in Borneo: the zooarchaeological record|journal=Biodiversity and Conservation| language=en|volume=19|issue=2|pages=373–391|doi=10.1007/s10531-009-9686-3|year=2009|s2cid=25993622}}</ref> 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.<ref name=":2" />

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](/source/Indochina) biogeographic region; emergence of a savanna corridor during glacial periods and subsequent disappearance during interglacial periods would have facilitated speciation through both [vicariance](/source/vicariance) ([allopatric speciation](/source/allopatric_speciation)) and [geodispersal](/source/geodispersal).<ref>{{Cite journal|last1=van den Bergh|first1=Gert D.|last2=de Vos|first2=John|last3=Sondaar|first3=Paul Y.|date=2001-07-15|title=The Late Quaternary palaeogeography of mammal evolution in the Indonesian Archipelago|journal=Palaeogeography, Palaeoclimatology, Palaeoecology|series=Quaternary Environmental Change in the Indonesian Region|volume=171|issue=3–4|pages=385–408|doi=10.1016/S0031-0182(01)00255-3|bibcode=2001PPP...171..385V}}</ref> Morley and Flenley (1987) and Heaney (1991) were the first to postulate the existence of a continuous corridor of savanna vegetation through the center of Sundaland (from the modern Malay Peninsula to Borneo) during the [last glacial period](/source/last_glacial_period), based on palynological evidence.<ref>{{Cite journal|last=Heaney|first=Lawrence R.|date=1991|title=A synopsis of climatic and vegetational change in southeast Asia|journal=Climatic Change|volume=19|issue=1–2|pages=53–51|doi=10.1007/bf00142213|bibcode=1991ClCh...19...53H|s2cid=154779535}}</ref><ref name=":12" /><ref name=":14"/><ref>{{Cite book|title=Biogeographical evolution of the Malay archipelago|last1=Morley|first1=RJ|last2=Flenley|first2=JR|publisher=Clarendon Press|year=1987|editor-last=Whitmore|editor-first=TC|location=Oxford|pages=50–59|chapter=Late Cainozoic vegetational and environmental changes in the Malay archipelago}}</ref><ref name=":15" /> 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.<ref name=":2" /> 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 Malay Peninsula, through Sumatra and Java, and across to Borneo.<ref name=":14"/> 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.<ref name=":12" /> Similarly, stable isotope composition of fossil mammal teeth supports the existence of the savanna corridor.<ref>{{Cite journal|last1=Louys|first1=Julien|last2=Roberts|first2=Patrick|date=2020-10-15|title=Environmental drivers of megafauna and hominin extinction in Southeast Asia|url=https://www.nature.com/articles/s41586-020-2810-y|journal=Nature|language=en|volume=586|issue=7829|pages=402–406|doi=10.1038/s41586-020-2810-y|pmid=33029012|bibcode=2020Natur.586..402L |s2cid=222217295|issn=1476-4687|hdl=10072/402368|hdl-access=free|url-access=subscription}}</ref>

In contrast, other authors argue that Sundaland was primarily covered by tropical rainforest.<ref name=":2" /> Using species distribution models, Raes et al. (2014) suggest that Dipterocarp rainforest persisted throughout the last glacial period.<ref name=":1" /> 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.<ref name=":6" /> 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.<ref name=":2" /> 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.<ref>{{Cite journal|last1=Wurster|first1=Christopher M.|last2=Rifai|first2=Hamdi|last3=Haig|first3=Jordahna|last4=Titin|first4=Jupiri|last5=Jacobsen|first5=Geraldine|last6=Bird|first6=Michael|date=2017-05-01|title=Stable isotope composition of cave guano from eastern Borneo reveals tropical environments over the past 15,000 cal yr BP|journal=Palaeogeography, Palaeoclimatology, Palaeoecology|volume=473|pages=73–81|doi=10.1016/j.palaeo.2017.02.029|bibcode=2017PPP...473...73W}}</ref> 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.<ref>{{Cite journal|last1=Slik|first1=J. W. Ferry|last2=Aiba|first2=Shin-Ichiro|last3=Bastian|first3=Meredith|last4=Brearley|first4=Francis Q.|last5=Cannon|first5=Charles H.|last6=Eichhorn|first6=Karl A. O.|last7=Fredriksson|first7=Gabriella|last8=Kartawinata|first8=Kuswata|last9=Laumonier|first9=Yves|date=2011-07-26|title=Soils on exposed Sunda Shelf shaped biogeographic patterns in the equatorial forests of Southeast Asia|journal=Proceedings of the National Academy of Sciences|language=en|volume=108|issue=30|pages=12343–12347|doi=10.1073/pnas.1103353108|issn=0027-8424|pmc=3145692|pmid=21746913|bibcode=2011PNAS..10812343F|doi-access=free}}</ref>

====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''](/source/Sinomastodon) colonized Sundaland from mainland Asia.<ref>{{Cite journal|last1=van den Bergh|first1=Gert D.|last2=de Vos|first2=John|last3=Sondaar|first3=Paul Y.|date=2001-07-15|title=The Late Quaternary palaeogeography of mammal evolution in the Indonesian Archipelago|journal=Palaeogeography, Palaeoclimatology, Palaeoecology|series=Quaternary Environmental Change in the Indonesian Region|volume=171|issue=3–4|pages=385–408|doi=10.1016/s0031-0182(01)00255-3|bibcode=2001PPP...171..385V}}</ref> Later fauna included tigers, Sumatran rhinoceros, and Indian elephant, which were found throughout Sundaland; smaller animals were also able to disperse across the region.<ref name=":5" />

==Human migrations==
According to the most widely accepted theory,{{citation needed|date = June 2021}} the ancestors of the modern-day [Austronesian](/source/Austronesian_peoples) populations of the Maritime Southeast Asia and adjacent regions are believed to have migrated southward, from the East Asia mainland to [Taiwan](/source/Taiwan), and then to the rest of [Maritime Southeast Asia](/source/Maritime_Southeast_Asia). An alternative theory points to the now-submerged Sundaland as the possible cradle of Austronesian languages: thus [the "Out of Sundaland" theory](/source/Austronesian_peoples). However, this view is an extreme minority view among professional archaeologists, linguists, and geneticists. The [Out of Taiwan model](/source/Austronesian_peoples) (though not necessarily the Express Train Out of Taiwan model) is accepted by the vast majority of professional researchers.{{citation needed|date = June 2021}}

A study from [Leeds University](/source/Leeds_University) and published in ''[Molecular Biology and Evolution](/source/Molecular_Biology_and_Evolution)'', examining [mitochondrial DNA](/source/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](/source/Philippine) Islands to as far north as Taiwan within the last 10,000 years.<ref>{{cite web |url=http://www.physorg.com/news130761648.html |title=Climate Change and Postglacial Human Dispersals in Southeast Asia | author=Dr. Martin Richards |publisher=Oxford Journals | access-date=1 January 2011|date=2008}}</ref>

The population migrations were most likely to have been driven by [climate change](/source/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](/source/Java) and South China Seas and the [thousands of islands](/source/List_of_islands_of_Indonesia) that make up [Indonesia](/source/Indonesia) and the [Philippines](/source/Philippines) 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.<ref>{{Cite journal|doi=10.1017/S0003598X00067922|title=The prehistory of a Friction Zone: First farmers and hunters-gatherers in Southeast Asia|journal=Antiquity|volume=85|issue=328|pages=529–543|year=2015|last1=Higham|first1=C.F.W.|last2=Guangmao|first2=Xie|last3=Qiang|first3=Lin|s2cid=162768159}}</ref>

[Stephen Oppenheimer](/source/Stephen_Oppenheimer) locates the origin of the [Austronesians](/source/Austronesian_languages) in Sundaland and its upper regions.<ref>{{Cite book|title=Eden in the East : the drowned continent of Southeast Asia|last=Stephen|first=Oppenheimer|date=1999|publisher=Phoenix|isbn=978-0-7538-0679-1|oclc=45755929|url-access=registration|url=https://archive.org/details/edenineastdrowne00oppe}}</ref> From the standpoint of [historical linguistics](/source/historical_linguistics), the home of the [Austronesian languages](/source/Austronesian_languages) is the [main island of Taiwan](/source/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](/source/Formosan_languages).{{citation needed|date = June 2021}}

{{land_bridge_world_map.svg|right}}
==See also==
{{Div col}}
* [Banda Arc](/source/Banda_Arc)
* [Father Tongue hypothesis](/source/Father_Tongue_hypothesis)
* [Oceania](/source/Oceania)
** [Australasia](/source/Australasia)
*** [Australia (continent)](/source/Australia_(continent))
* [Oceanic trench](/source/Oceanic_trench)
* [Plate tectonics](/source/Plate_tectonics)
* [Sahul](/source/Sahul)
* [Sunda Arc](/source/Sunda_Arc)
* [Sundadonty](/source/Sundadonty), named after Sunda
* [Sunda Islands](/source/Sunda_Islands)
* [Wallacea](/source/Wallacea)
{{Div col end}}

==References==
{{Reflist}}

===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.
* {{cite journal | last1 = Mohd | first1 = Azlan J. | last2 = Maryanto | first2 = Ibnu | last3 = Kartono | first3 = Agus P. | last4 = Abdullah | first4 = MT. | year = 2003 | title = Diversity, Relative Abundance and Conservation of Chiropterans in Kayan Mentarang National Park, East Kalimantan, Indonesia | journal = Sarawak Museum Journal | volume = 79 | pages = 251–265 }}
* {{cite journal | last1 = Hall | first1 = LS | last2 = Richards | first2 = GC | last3 = Abdullah | first3 = MT | year = 2002 | title = The bats of Niah National Park, Sarawak | journal = Sarawak Museum Journal | volume = 78 | pages = 255–282 }}
* Wilson DE, Reeder DM. 2005. Mammal species of the world. Smithsonian Institution Press, Washington DC.

==External links==
* [https://web.archive.org/web/20060816081952/http://koenraadelst.bharatvani.org/reviews/atlantis.html Review of Oppenheimer's Eden in the East, about Sundaland]

{{Use dmy dates|date=June 2019}}
{{Submerged landmasses}}
{{Continents of the world}}
{{Borneo}}
Category:Historical continents
Category:Biogeography
Category:Continental shelves
Category:Historical geology
Category:Indomalayan realm
Category:Malesia
Category:Prehistoric Indonesia
Category:Mainland Southeast Asia

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Adapted from the Wikipedia article [Sundaland](https://en.wikipedia.org/wiki/Sundaland) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Sundaland?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.