User:SkyBlueWater/sandbox

Long Term Environmental Change Article: Sundaland
I will primarily be adding to the "history" section. I will focus on adding recent research on how forest extent has changed throughout time. This will likely be a separate subsection. I may also add some research about how the long-term environmental history of Sundaland has affected biodiversity in the region; it is currently only briefly touched on, and there is a lot of recent work on the topic. Another minor area of work will be adding some of the information that is currently in the Sunda Shelf article to the Sundaland article. The Sunda Shelf Talk page includes discussion of combining the two articles, but the consensus was to keep them separate.

Preliminary sources (still need to figure out how to get Wikipedia to put these as references only, not citations):

Bird, M. I., D. Taylor, and C. Hunt. 2005. Palaeoenvironments of insular Southeast Asia during the Last Glacial Period: a savanna corridor in Sundaland? Quaternary Science Reviews 24:2228–2242.

Cannon, C. H., R. J. Morley, and A. B. G. Bush. 2009. The current refugial rainforests of Sundaland are unrepresentative of their biogeographic past and highly vulnerable to disturbance. Proceedings of the National Academy of Sciences 106:11188–11193.

De Bruyn, M., B. Stelbrink, R. J. Morley, R. Hall, G. R. Carvalho, C. H. Cannon, G. Van Den Bergh, E. Meijaard, I. Metcalfe, L. Boitani, L. Maiorano, R. Shoup, and T. Von Rintelen. 2014. Borneo and Indochina are Major Evolutionary Hotspots for Southeast Asian Biodiversity. Systematic Biology 63:879–901.

Leite, Y. L. R., L. P. Costa, A. Carolina, R. G. Rocha, H. Batalha-filho, and A. C. Bastos. 2016. Neotropical forest expansion during the last glacial period challenges refuge hypothesis. Proceedings of the National Academy of Sciences 113:1008–1013.

Metcalfe, I. 2011. Tectonic Framework and Phanerozoic Evolution of Sundaland. Gondwana Research 19:3–21.

Pelejero, C., M. Kienast, L. Wang, and J. O. Grimalt. 1999. The flooding of Sundaland during the last deglaciation : imprints in hemipelagic sediments from the southern South China Sea 171:661–671.

Raes, N., C. H. Cannon, R. J. Hijmans, T. Piessens, L. G. Saw, P. C. van Welzen, and J. W. F. Slik. 2014. Historical distribution of Sundaland’s Dipterocarp rainforests at Quaternary glacial maxima. Proceedings of the National Academy of Sciences of the United States of America 111:16790–5.

Russell, J. M., H. Vogel, B. L. Konecky, S. Bijaksana, Y. Huang, M. Melles, N. Wattrus, K. Costa, and J. W. King. 2014. Glacial forcing of central Indonesian hydroclimate since 60,000 y B.P. Proceedings of the National Academy of Sciences 111:5100–5105.

Slik, J. W. F., S. Aiba, M. Bastian, F. Q. Brearley, C. H. Cannon, and K. A. O. Eichhorn. 2011. Soils on Exposed Sunda Shelf Shaped Biogeographic Patterns in the Equatorial Forests of Southeast Asia. Proceedings of the National Academy of Sciences 108:12343–12347.

Tougard, C., and S. Montuire. 2006. Pleistocene paleoenvironmental reconstructions and mammalian evolution in South-East Asia : focus on fossil faunas from Thailand. Quaternary Science Reviews 25:126–141.

Wurster, C. M., M. I. Bird, I. D. Bull, F. Creed, C. Bryant, J. a J. Dungait, and V. Paz. 2010. Forest contraction in north equatorial Southeast Asia during the Last Glacial Period. Proceedings of the National Academy of Sciences 107:15508–15511.

Wurster, C. M., H. Rifai, J. Haig, J. Titin, G. Jacobsen, and M. Bird. 2017. Stable isotope composition of cave guano from eastern Borneo reveals tropical environments over the past 15, 000 cal yr BP. Palaeogeography, Palaeoclimatology, Palaeoecology 473:73–81.

copied from Sunda Shelf
Definition

Biogeographically, Sundaland is a term for the region of Southeastern Asia which encompasses these areas of the Asian continental shelf that were exposed during the last ice age. Sundaland included the Malay Peninsula on the Asian mainland, as well as the large islands of Borneo, Java, and Sumatra and their surrounding islands. The same steep undersea gradients that mark the eastern boundary of Sundaland are identified biogeographically by the Wallace Line, identified by Alfred Russel Wallace, which marks the eastern boundary of the Asia's land mammal fauna, and is the boundary of the Indomalaya and Australasia ecozones.

The shelf has resulted from millennia of volcanic activity and erosion of the Asian continental mass, and the build up and consolidation of debris along the margins as sea levels rose and fell.

The seas between the islands cover relatively stable ancient pene-plains that are characterised by low seismicity, low isostatic gravity anomalies and no active volcanoes with the exception of Sumatra, Java, and Bali, which while connected to the Sunda Shelf, belong geologically to the young Sunda Arc orogenic system (i.e., the Sunda Mountain System). During glacial periods, the sea level falls, and great expanses of the Sunda Shelf are exposed as a marshy plain. The rise of sea level during a meltwater pulse 14,600 to 14,300 years Before Present was as much as 16 meters within 300 years.

Present sea levels submerge a number of Pleistocene Paleo River Systems that drained much of Sundaland during the last glacial maximum 18,000 to 20,000 years ago.

To the east of the Sunda Shelf is the Sahul Shelf. Separating these two regions of shallow seas is Wallacea, which encompasses Sulawesi and the thousands of smaller islands making up Nusa Tenggara and Maluku. Within Wallacea lie some of the deepest seas in the world with depths of up to 7,000 metres. Passing between Bali and Lombok, and Borneo and Sulawesi, the Wallacea is marked by a transition zone of flora and fauna first described by Alfred Russel Wallace. The complicated history of island formation on the Sunda Shelf and changing landbridge connections with mainland Southeast Asia have resulted in a high degree of endemism and local distribution discontinuities, discussed at Sundaland, the biogeographical province that has resulted from these changes.

The exposure of the Sunda Shelf during eustatic sea level changes has effects on the El Niño oscillation.

W. Earle in 1845 was the first to describe the general features of the Sunda and Sahul Shelves, which he termed the "Great Asiatic Bank" and the "Great Australian Bank" respectively.

copied from Sundaland
History

The South China Sea and adjoining landmasses had been investigated by scientists such as Molengraaff and Umbgrove, who had postulated ancient, now submerged, drainage systems. These were mapped by Tjia in 1980 and described in greater detail by Emmel and Curray in 1982 complete with river deltas, floodplains and backswamps. The ecology of the exposed Sunda shelf has been investigated by analyzing cores drilled into the ocean bed. The pollens found in the cores have revealed a complex ecosystem that changed over time.

The flooding of Sundaland separated species that had once shared the same environment such as the river threadfin (Polydactylus macrophthalmus, Bleeker 1858), that had 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.

The islands of Sundaland rest on an extension of Asia's shallow continental shelf, called the Sunda shelf. During the ice ages, sea levels were lower and all of Sundaland was an extension of the Asian continent.

As a result, the islands of Sundaland are home to many Asian mammals including elephants, monkeys, apes, tigers, tapirs, and rhinoceros. The Wallace Line, which includes the Lombok Strait between Bali and Lombok, and the Makassar Strait between Borneo and Sulawesi, marks the end of the Asian continental shelf. The islands of Wallacea are separated from Asia and from Australia and New Guinea by deep ocean.

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.

Ecology

The islands of Sundaland rest on an extension of Asia's shallow continental shelf, called the Sunda shelf. During the ice ages, sea levels were lower and all of Sundaland was an extension of the Asian continent.

As a result, the islands of Sundaland are home to many Asian mammals including elephants, monkeys, apes, tigers, tapirs, and rhinoceros. The Wallace Line, which includes the Lombok Strait between Bali and Lombok, and the Makassar Strait between Borneo and Sulawesi, marks the end of the Asian continental shelf. The islands of Wallacea are separated from Asia and from Australia and New Guinea by deep ocean.

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.

Missing Things/Planned Additions for Sundaland

 * Descriptionf shallowneness of the oceans in (around?) Sundaland; possible map of bathymetry?
 * Description of unusually warm temperatures and low salinity of oceans in Sundaland(Indo-Pacific Warm Pool)
 * General MODERN climate information; expand modern vegetation (in ecology section)
 * Paleoclimate/paleogeography information (tentative section heading of paleogeography?) --> overall organization scheme will be chronological
 * Climate and vegeation in the past (look at table in Bird et al. 2005 for more sources!)
 * "Rainforest refugia" hypotheses
 * Expand on these sentences in current article : "The ecology of the exposed Sunda shelf has been investigated by analyzing cores drilled into the ocean bed. The pollens found in the cores have revealed a complex ecosystem that changed over time. "
 * During Pliocene, probably was more flooded
 * During Pleistocene, more was exposed
 * Bat guano evidence for period with reduced monsoonal precipitation
 * Fire regimes?
 * Savanna theory
 * Links to pages on the different paleomethods!
 * Add link to section Submerged River Systems (in Sunda Shelf page)
 * Track down/expand on/add to this information from Sunda Shelf: "The shelf has resulted from millennia of volcanic activity and erosion of the Asian continental mass, and the build up and consolidation of debris along the margins as sea levels rose and fell. The seas between the islands cover relatively stable ancient pene-plains that are characterised by low seismicity, low isostatic gravity anomalies and no active volcanoes with the exception of Sumatra, Java, and Bali, which while connected to the Sunda Shelf, belong geologically to the young Sunda Arc orogenic system (i.e., the Sunda Mountain System). During glacial periods, the sea level falls, and great expanses of the Sunda Shelf are exposed as a marshy plain. The rise of sea level during a meltwater pulse 14,600 to 14,300 years Before Present was as much as 16 meters within 300 years."

Peer Review
Very thorough outline. I wish I had more suggestions but this is very well-developed. I suggest thinking about adding a graphic or two, pending data availability/existing graphics, that illustrate something like sea-level change over time or sea surface temperatures. Additionally, I believe this area is significant in the ENSO cycle today. Addressing the history of ENSO development is probably beyond the scope of this article, but the region's historical and modern influence in its development may be relevant to this article. The 'History' section of the article mentions a vicariance event in which fauna was separated by sea level rise. Elaborating on the effects of this event in the context of the vicariance-biodiversity cycle may be useful. Finally, the existing 'Ecology' and 'History' sections contain some redundancies that could be removed. I would even consider changing the majority of the ecology section or combining it with another section, as it isn't thematically coherent in its current form. Great outline!

Sundaland Update
Sundaland (also called the Sundaic region) is a biogeographical region of Southeastern Asia correpsonding to a larger landmass that was exposed throughout the last 2.6 million years during periods when sea levels were lower. It includes the Malay Peninsula on the Asian mainland, as well as the large islands of Borneo, Java, and Sumatra and their surrounding islands.

Extent
The area of Sundaland encompasses the Sunda Shelf, a tectonically stable extension of Southeast Asia’s continental shelf that was exposed during the glacial period s of the Pleistocene.

The extent of the Sunda Shelf is approximately equal to the 120 m isobath. 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. In total, the area of Sundaland is approximately 1,800,000 km2, roughly equivalent to the size of Europe.

The western and southern borders of Sundaland are clearly marked by the deeper water of the Indian Ocean. 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 Indomalaya and Australasia ecozones. 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. 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.

Sundaland was most recently exposed during the last glacial period from approximately 110,000 to 12,000 years ago. When sea level was decreased by 30 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. 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 located 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 ; rainfall exceeds evapotranspiration 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 28ºC or more) are part of the Indo-Pacific Warm Pool/Western Pacific Warm Pool 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. 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 trees and orangutans; 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, Wallacea and New Guinea in a single Floristic province of Malesia, 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, 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". 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 (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. 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 prior to 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.

{LINKS to ecoregions}

Quaternary History
Explorers and scientists began measuring and mapping the seas of Southeast Asia in the 1870s, primarily using depth sounding. Gustaaf Molengraff, a Dutch geologist, postulated that the nearly uniform depths of Sundaland represented 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. Molengraaf also identified ancient, now submerged, drainage systems that drained Sundaland during periods of lower sea level. These were mapped by Tjia (1980) and described in greater detail by Emmel and Curray (1982) complete with river deltas, floodplains and backswamps.

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 and lakes, 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.

Climate
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 5ºC cooler than present.

Most records agree that Indo-Pacific sea surface temperatures were at most 2-3ºC lower during the Last Glacial Maximum. 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 heterogenity in climate during the Last Glacial Maximum throughout Indonesia. Alternativley, the physical and chemical processes that underly the method of inferring precipitation from δ18O records may have 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 since the early Miocene due to repeated immigration and vicariance events. The modern islands of Borneo, Java, and Sumatra have served as refugia for the flora and fauna of Sundaland during multiple glacial periods, and are serving the same role at present. Dipterocarp 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 relative amounts of tropical rainforest and savanna that were 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 patches of savanna vegetation.

Morley and Flenley (1987) and Heaney (1991) were the first to postulate the presence of a continuous corridor of savanna vegetation through the center of Sundaland (from the modern Malaysian Peninsula to Borneo) during the last glacial period based on palynological evidence. 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. Using the modern distribution of primates, termites, rodents, and other species, some researchers infer that the extent of tropical forest contracted—replaced by savanna and open forest —during the last glacial period. Similarly, vegetation models using data from climate simulations show varying degrees of forest contraction. Bird, Taylor and Hunt (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. 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. 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. Additionally, some 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.

Wang 2009 - humid, moist vegetation. Esp pg 8

Prior to the emergence of Sundaland 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.