Sundaland

Sundaland refers broadly to the continental shelf and associated lands of western maritime Southeast Asia, including the Malay Peninsula, Sumatra, Java and Borneo. The shelf is a southward extension of mainland Southeast Asia, now mostly covered by shallow seas such as the southern South China Sea, Gulf of Thailand and Java Sea. Its topography includes submerged lowlands and palaeoriver channels; above water, parts of the shelf remain as islands and peninsulas.

During glacial intervals, global sea level fell as water was stored in continental ice sheets, exposing large areas of the shallow Sunda Shelf. Geological reconstructions show that river networks once crossed areas that are now seabed. As ice melted after the Last Glacial Maximum, rising seas flooded these low-lying connections and divided land habitats into islands. The details and timing of flooding varied across the shelf and depend on local bathymetry and sea-level history.

Repeated exposure and inundation altered the geography of habitats and routes for dispersal. Sundaland is an important biogeographic region with many species restricted to parts of the Indo-Malayan archipelago. Researchers use reconstructed palaeolandscapes and ancient drainage maps to investigate how past connections may have affected the distribution of organisms. A population-genomic study has also proposed links between deglacial sea-level rise and prehistoric human population separation and migration; such interpretations are research findings rather than a complete account of all human movements in the region.

Scientists infer past landscapes from bathymetric data, sediment records, fossil and archaeological evidence, and models of sea-level change. Modern high-resolution maps reconstruct former drainage systems at selected depths below present sea level, allowing comparisons between palaeorivers and rivers on today's islands. These reconstructions are useful, but their resolution and conclusions depend on the data and assumptions used; they do not represent a single, unchanging landmass throughout prehistory.