Sundaland [1] (also called Sundaica or the Sundaic region) is a biogeographical region of Southeast Asia corresponding to a larger landmass that was exposed throughout the last 2.6 million years during periods when sea levels were lower. It includes Bali, Borneo, Java, and Sumatra in Indonesia, and their surrounding small islands, as well as the Malay Peninsula on the Asian mainland.
The area of Sundaland encompasses the Sunda Shelf, a tectonically stable extension of Southeast Asia's continental shelf that was exposed during glacial periods of the last 2 million years. [2] [3]
The extent of the Sunda Shelf is approximately equal to the 120-meter isobath. [4] 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. [5] In total, the area of Sundaland is approximately 1,800,000 km2. [6] [4] 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. [3]
The western and southern borders of Sundaland are clearly marked by the deeper waters of the Sunda Trench – some of the deepest in the world – and the Indian Ocean. [4] The eastern boundary of Sundaland is the Wallace Line, 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 and Australasian realms. The islands east of the Wallace line are known as Wallacea, 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. [4] The northern border of Sundaland is more difficult to define in bathymetric terms; a phytogeographic transition at approximately 9ºN is considered to be the northern boundary. [4]
Greater portions of Sundaland were most recently exposed during the last glacial period from approximately 110,000 to 12,000 years ago. [7] [6] 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. [2] 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. [8] In contrast, the sea level was higher during the late Pliocene, and the exposed area of Sundaland was smaller than what is observed at present. [4] Sundaland was partially submerged starting around 18,000 years ago and continuing until about 5000 BC. [9] [10] During the Last Glacial Maximum the sea level fell by approximately 120 meters, and the entire Sunda Shelf was exposed. [2]
All of Sundaland is within the tropics; 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; [4] rainfall exceeds evapotranspiration throughout the year and there are no predictable dry seasons like elsewhere in Southeast Asia. [11]
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 [12] and an important driver of the Hadley circulation and the El Niño-Southern Oscillation (ENSO), particularly in January when it is a major heat source to the atmosphere. [4] ENSO also has a major influence on the climate of Sundaland; strong positive ENSO events result in droughts throughout Sundaland and tropical Asia.
The high rainfall supports closed canopy evergreen forests throughout the islands of Sundaland, [11] transitioning to deciduous forest and savanna woodland with increasing latitude. [4] The remaining primary (unlogged) lowland forest is known for giant dipterocarp trees and orangutans; after logging, forest structure and community composition change to be dominated by shade intolerant trees and shrubs. [13] Dipterocarps are notable for mast fruiting events, where tree fruiting is synchronized at unpredictable intervals resulting in predator satiation. [14] Higher elevation forests are shorter and dominated by trees in the oak family. [11] Botanists often include Sundaland, the adjacent Philippines, Wallacea and New Guinea in a single floristic province of Malesia, based on similarities in their flora, which is predominantly of Asian origin. [11]
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, apes, tigers, tapirs, and rhinoceros. 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". [15] The fish is now found in the Kapuas River on the island of Borneo, and in the Musi and Batanghari rivers in Sumatra. [16] Selective pressure (in some cases resulting in 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. [17] 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. [17] Island area and number of terrestrial mammal species are related, with the largest islands of Sundaland (Borneo and Sumatra) having the highest diversity. [7]
The name "Sunda" goes back to antiquity, appearing in Ptolemy's Geography, written around 150 AD. [18] In an 1852 publication, English navigator 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. [19]
Explorers and scientists began measuring and mapping the seas of Southeast Asia in the 1870s, primarily using depth sounding. [20] In 1921 Gustaaf Molengraaff, a Dutch geologist, postulated that the nearly uniform sea depths of the shelf indicated an ancient peneplain that was the result of repeated flooding events as ice caps melted, with the peneplain becoming more perfect with each successive flooding event. [20] Molengraaff also identified ancient, now submerged, drainage systems 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 in his Geography of Indonesia in 1949, based on his research during World War II. The ancient drainage systems described by Molengraaff were verified and mapped by Tjia in 1980 [21] and described in greater detail by Emmel and Curray in 1982 complete with river deltas, floodplains and backswamps. [22] [23]
The climate and ecology of Sundaland throughout the Quaternary has been investigated by analyzing foraminifera l δ18O and pollen from cores drilled into the ocean bed, δ18O in speleothems from caves, and δ13C and δ15N in bat guano from caves, as well as species distribution models, phylogenetic analysis, and community structure and species richness analysis.
Perhumid climate has existed in Sundaland since the early Miocene; though there is evidence for several periods of drier conditions, a perhumid core persisted in Borneo. [11] The presence of fossil coral reefs dating to the late Miocene and early Pliocene suggests that, as the Indian monsoon grew more intense, seasonality increased in some portions of Sundaland during these epochs. [11] Palynological 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. [24]
Most recent research agrees that Indo-Pacific sea surface temperatures were at most 2-3 °C lower during the Last Glacial Maximum. [4] 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. [25] 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. [26] [5] Others posit that changes in precipitation have been minimal [27] 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. [28]
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. [28] Alternatively, the physical and chemical processes that underlie the method of inferring precipitation from δ18O records may have operated differently in the past. [28] 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. [24]
Sundaland, and in particular Borneo, has been an evolutionary hotspot for biodiversity since the early Miocene due to repeated immigration and vicariance events. [3] 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. [3] [29]
Dipterocarp trees characteristic of modern Southeast Asian tropical rainforest have been present in Sundaland since before the Last Glacial Maximum. [30] There is also evidence for savanna vegetation, particularly in now submerged areas of Sundaland, throughout the last glacial period. [31] 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. [4]
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 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) and geodispersal. [32] 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, based on palynological evidence. [33] [14] [3] [34] [19] 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. [4] 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. [3] 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. [14] Similarly, stable isotope composition of fossil mammal teeth supports the existence of the savanna corridor. [35]
In contrast, other authors argue that Sundaland was primarily covered by tropical rainforest. [4] Using species distribution models, Raes et al. (2014) suggest that Dipterocarp rainforest persisted throughout the last glacial period. [30] 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. [11] 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. [4] 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. [36] 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. [37]
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. [38] Later fauna included tigers, Sumatran rhinoceros, and Indian elephant, which were found throughout Sundaland; smaller animals were also able to disperse across the region. [7]
According to the most widely accepted theory,[ citation needed ] 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, and then to the rest of 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. 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.[ citation needed ]
A study from Leeds University and published in Molecular Biology and Evolution , 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 Islands to as far north as Taiwan within the last 10,000 years. [39]
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 and South China Seas and the thousands of islands that make up Indonesia and the 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. [40]
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 fairly recently, from the mid to late-Holocene.
Oppenheimer locates the origin of the Austronesians in Sundaland and its upper regions. [41] From the standpoint of historical linguistics, 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.[ citation needed ]
Indonesia is an archipelagic country located in Southeast Asia and Oceania, lying between the Indian Ocean and the Pacific Ocean. It is located in a strategic location astride or along major sea lanes connecting East Asia, South Asia and Oceania. Indonesia is the largest archipelago in the world. Indonesia's various regional cultures have been shaped—although not specifically determined—by centuries of complex interactions with its physical environment.
Sumatra is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the sixth-largest island in the world at 482,286.55 km2 (182,812 mi.2), including adjacent islands such as the Simeulue, Nias, Mentawai, Enggano, Riau Islands, Bangka Belitung and Krakatoa archipelago.
The Sunda Islands are a group of islands in the Malay Archipelago. They consist of the Greater Sunda Islands and the Lesser Sunda Islands.
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. The original definition by the World Geographical Scheme for Recording Plant Distributions included Papuasia, but this was split off in its 2001 version.
The Malay Archipelago is the archipelago between Mainland Southeast Asia and Australia, and is also called Insulindia or the Indo-Australian Archipelago. The name was taken from the 19th-century European concept of a Malay race, later based on the distribution of Austronesian languages. It has also been called the "Malay world," "Nusantara", "East Indies" over time. The name is controversial in Indonesia due to its ethnic connotations and colonial undertones, which can overshadow the country's diverse cultures.
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 Lombok, Sumbawa, Flores, Sumba, Timor, Halmahera, Buru, Seram, and many smaller islands. The islands of Wallacea lie between the Sunda Shelf to the west, and the Sahul Shelf including Australia and New Guinea to the south and east. The total land area of Wallacea is 347,000 km2 (134,000 sq mi).
Sunda may refer to:
Geologically, the Sunda Shelf is a south-eastern extension of the continental shelf of Mainland Southeast Asia. Major landmasses on the shelf include Bali, Borneo, Java, Madura, and Sumatra, as well as their surrounding smaller islands. It covers an area of approximately 1.85 million km2. Sea depths over the shelf rarely exceed 50 metres and extensive areas are less than 20 metres resulting in strong bottom friction and strong tidal friction. Steep undersea gradients separate the Sunda Shelf from the Philippines, Sulawesi, and the Lesser Sunda Islands.
Peat swamp forests are tropical moist forests where waterlogged soil prevents dead leaves and wood from fully decomposing. Over time, this creates a thick layer of acidic peat. Large areas of these forests are being logged at high rates.
Geologically, the Sahul Shelf is a part of the continental shelf of the Australian continent, lying off the northwest coast of mainland Australia.
The Sunda flying lemur, also called Malayan flying lemur and Malayan colugo is the sole colugo species of the genus Galeopterus. It is native to Southeast Asia from southern Myanmar, Thailand, southern Vietnam, Malaysia to Singapore and Indonesia and listed as Least Concern on the IUCN Red List. Although it is called "flying lemur", it cannot fly but glides among trees and is strictly arboreal. It is active at night, and feeds on soft plant parts such as young leaves, shoots, flowers, and fruits. It is a forest-dependent species.
The flora consists of many unique varieties of tropical plants. Blessed with a tropical climate and roughly 17,000 islands, Indonesia is the nation with the second highest biodiversity in the world. The flora of Indonesia reflects an intermingling of Asian, Australian and unique, Indonesian lineages. This is due to the geography of Indonesia, located between the aforementioned continents. The archipelago consists of a variety of regions, from the tropical rain forests of the northern lowlands and the seasonal forests of the southern lowlands through the hill and mountain vegetation, to subalpine shrub vegetation. With the second longest coastline in the world, Indonesia also has many swamps and other varieties of coastal vegetation. Combined, these all give rise to a huge floral biodiversity. There are about 28,000 species of flowering plants documented in Indonesia, including 2500 orchids, 122 species of bamboo, over 350 species of rattan and 400 species of Dipterocarpus, including ebony, sandalwood and teakwood. Indonesia is also home to some unusual species of carnivorous plants. One exceptional species is known as Rafflesia arnoldi, named after Sir Thomas Stamford Raffles and Dr. Thomas Arnold, who discovered the flower in the depths of Bengkulu, southwest Sumatra. This parasitic plant has the largest flower of any plant, does not produce leaves and grows only on one species of liana on the rainforest floor. Another unusual plant is Amorphophallus titanum from Sumatra. Numerous species of insect trapping pitcher plants can also be found in Borneo, Sumatra, and other islands of the Indonesian archipelago. There are a staggering 6000 traditional medicinal plants used as Jamu.,
The Sunda crow, formerly known as the slender-billed crow, is a passerine bird of the family Corvidae, in the genus Corvus. It is found from Malaysia to Borneo. The violet crow has been shown to be distinct genetically and separated as Corvus violaceus. The small crow has been split as Corvus samarensis and the Palawan crow has also been split as Corvus pusillus.
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 mammal species. The Borneo lowland rain forests is diminishing due to logging, hunting and conversion to commercial land use.
Prehistoric Indonesia is a prehistoric period in the Indonesian archipelago that spanned from the Pleistocene period to about the 4th century CE when the Kutai people produced the earliest known stone inscriptions in Indonesia. Unlike the clear distinction between prehistoric and historical periods in Europe and the Middle East, the division is muddled in Indonesia. This is mostly because Indonesia's geographical conditions as a vast archipelago caused some parts — especially the interiors of distant islands — to be virtually isolated from the rest of the world. West Java and coastal Eastern Borneo, for example, began their historical periods in the early 4th century, but megalithic culture still flourished and script was unknown in the rest of Indonesia, including in Nias and Toraja. The Papuans on the Indonesian part of New Guinea island lived virtually in the Stone Age until their first contacts with modern world in the early 20th century. Even today living megalithic traditions still can be found on the island of Sumba and Nias.
The island of Borneo is located on the Sunda Shelf, which is an extensive region in Southeast Asia of immense importance in terms of biodiversity, biogeography and phylogeography of fauna and flora that had attracted Alfred Russel Wallace and other biologists from all over the world.
The Lesser Sunda Islands, now known as Nusa Tenggara Islands, are an archipelago in Indonesian archipelago. Most of the Lesser Sunda Islands are located within the Wallacea region, except for the Bali province which is west of the Wallace Line and is within the Sunda Shelf. Together with the Greater Sunda Islands to the west, they make up the Sunda Islands. The islands are part of a volcanic arc, the Sunda Arc, formed by subduction along the Sunda Trench in the Java Sea. In 1930 the population was 3,460,059; today slightly over 15.5 million people live on the islands. Etymologically, Nusa Tenggara means "Southeast Islands" from the words of nusa which means 'island' from Old Javanese language and tenggara means 'southeast'.
The Greater Sunda Islands are four tropical islands situated within the Indonesian Archipelago, in the Pacific Ocean. The islands, Borneo, Java, Sulawesi and Sumatra, are internationally recognised for their ecological diversity and rich culture. Together with the Lesser Sunda Islands to their southeast, they comprise the archipelago known as the Sunda Islands.
The Sunda leopard cat is a small wild cat species native to the Sundaland islands of Java, Bali, Borneo, Sumatra and the Philippines that is considered distinct from the leopard cat occurring in mainland South and Southeast Asia.
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