Biodiversity of Borneo

The previous climatic oscillation and sea level changes leading to contraction and expansion of the tropical rain contributed to the extinction and genetic divergence of species in the region. Harrison (1958) was the first to discover intermittent human habitation about 49,000 years ago in the Niah Cave National Park. Baker et al.(2007) unravelled the complexities of the late Pleistocene to Holocene habitation of the Niah Cave.

Flenley (1998) and Bird et al. (2005) suggested of a continuous savanna habitat with from the Asian mainland into Borneo and interrupted by a network of ancient Sunda River system. Dodson et al. (1995) postulated that the biogeographical history of Southeast Asia contributed to extensive admixture during Pleistocene low sea levels of genetic groups of an obligate freshwater fish (the river catfish, Hemibagrus nemurus) isolated during periods of high sea levels. During Pleistocene glacial maxima, the sea level was lower than at present and the islands of the Sunda shelf (Sumatra, Borneo and Java) and the Asian mainland were connected by lowlands traversed by rivers. Thus, the fish from Baram, Endau and Mekong rivers were genetically related.

Piper et al. (2008) identified 27 mammal, 11 bird and eight reptile taxa recovered from the Terminal Pleistocene deposits at Niah Cave. Some of these animals are extinct and extent in distribution in Borneo. Other biologists suggested Pleistocene refugia found in Borneo to explain for the gene flow and genetic divergent of certain species.

Biodiversity factors in Borneo and extinction

Borneo, made up of three countries - Malaysia (Sabah and Sarawak), Brunei (Sultanate) and Indonesia (Kalimantan), is the third largest island in the world. Borneo is a region that is rich in biodiversity. It is home to approximately 15,000 plant species, and more than 1,400 amphibians, birds, fish, mammals, reptiles and insects. The largest flower in the world, the Rafflesia, can be found in Borneo. The island covers an area of 743,330 square kilometres (287,000 sq mi) and has a wide range of biomes. A biome refers to a major ecological community characterized by dominant vegetation and organisms adapted to a particular environment. Borneo forests are some of the most biodiverse ecosystems on the planet due to their ideal tropical climate. Some of the forests in Borneo are tropical rainforests, mangroves swamp forests, peat swamp forests, montane forests, heath forests and dipterocarp forests. These physically diverse habitats provide different conditions for different organisms to live. Therefore, the biodiversity is increasing as the organisms have found their own favorite habitat to live. For example, the Orangutan exists naturally only on the islands of Borneo and Sumatra because it depends heavily on forest ecosystems for food and shelter.

High biodiversity is more likely to develop under relatively stable environmental conditions with moderate levels of disturbance. Stable conditions allow species to reproduce and adapt successfully. Although major natural disasters can cause widespread extinction, small or moderate disturbances may sometimes increase biodiversity by creating new ecological niches. For instance, small-scale forest clearing by farmers for plantations can alter habitats and encourage the growth of different plant and animal communities.

Evidence of past glacial activity has also been found on Mount Kinabalu, suggesting that snow and ice once existed even in this equatorial region during the Last Glacial Maximum (LGM). During this period, global temperatures were estimated to be 4–7°C lower than they are today. The cooler climate caused ice and snow to accumulate on mountains, disrupting the hydrological cycle and lowering sea levels by approximately 120 metres. As sea levels dropped, shallow seabeds became exposed, forming land bridges that connected Peninsular Malaysia, Borneo, Sumatra, Java, and Bali into a single large landmass. These geological changes altered wind patterns, sea currents, and the distribution of species, isolating populations in forest refuges and contributing further to the evolution and diversification of species in the region.

It is unknown if the Bornean tiger became extinct in recent times or prehistoric times.