Borneo is surrounded by the South China Sea to the north and northwest, the Sulu Sea to the northeast, the Celebes Sea and the Makassar Strait to the east, and the Java Sea and Karimata Strait to the south. To the west of Borneo are the Malay Peninsula and Sumatra. To the south and east are islands of Indonesia: Java and Sulawesi, respectively. To the northeast are the Philippine Islands. With an area of 743,330 square kilometres (287,000 sq mi), it is the third-largest island in the world, and is the largest island of Asia (the largest continent). Its highest point is Mount Kinabalu in Sabah, Malaysia, with an elevation of 4,095 m (13,435 ft). Before sea levels rose at the end of the last Ice Age, Borneo was part of the mainland of Asia, forming, with Java and Sumatra, the upland regions of a peninsula that extended east from present day Indochina. The South China Sea and Gulf of Thailand now submerge the former low-lying areas of the peninsula. Deeper waters separating Borneo from neighbouring Sulawesi prevented a land connection to that island, creating the divide known as Wallace’s Line between Asian and Australia-New Guinea biological regions.
The largest river system is the Kapuas in West Kalimantan, with a length of 1,000 km (620 mi). Other major rivers include the Mahakam in East Kalimantan (920 km long (570 mi)), the Barito in South Kalimantan (900 km long (560 mi)), Rajang in Sarawak (565 km long (351 mi)) and Kinabatangan in Sabah (560 km long (350 mi)). Borneo has significant cave systems. In Sarawak, the Clearwater Cave has one of the world’s longest underground rivers while Deer Cave is home to over three million bats, with guano accumulated to over 100 metres (330 ft) deep. The Gomantong Caves in Sabah has been dubbed as the “Cockroach Cave” due to the presence of millions of cockroaches inside the cave. The Gunung Mulu National Park in Sarawak and Sangkulirang-Mangkalihat Karst in East Kalimantan which particularly a karst areas contains thousands of smaller caves.
The Borneo rainforest is estimated to be around 140 million years old, making it one of the oldest rainforests in the world. It is the centre of the evolution and distribution of many endemic species of plants and animals, and the rainforest is one of the few remaining natural habitats for the endangered Bornean orangutan. It is an important refuge for many endemic forest species, including the Borneo elephant, the eastern Sumatran rhinoceros, the Bornean clouded leopard, the hose’s palm civet and the dayak fruit bat. Peat swamp forests occupy the entire coastline of Borneo. The soil of the peat swamp are comparatively infertile, while it is known to be the home of various bird species such as the hook-billed bulbul, helmeted hornbill and rhinoceros hornbill. There are about 15,000 species of flowering plants with 3,000 species of trees (267 species are dipterocarps), 221 species of terrestrial mammals and 420 species of resident birds in Borneo. There are about 440 freshwater fish species in Borneo (about the same as Sumatra and Java combined). The Borneo river shark is known only from the Kinabatangan River. In 2010, the World Wide Fund for Nature (WWF) stated that 123 species have been discovered in Borneo since the “Heart of Borneo” agreement was signed in 2007. The WWF has classified the island into seven distinct ecoregions. Most are lowland regions:
Borneo lowland rain forests cover most of the island, with an area of 427,500 square kilometres (165,100 sq mi);
Borneo’s economy depends mainly on agriculture, logging and mining, oil and gas, and ecotourism. Brunei’s economy is highly dependent on the oil and gas production sector, and the country has become one of the largest oil producers in Southeast Asia. The Malaysian states of Sabah and Sarawak are both top exporters of timber. Sabah is also known as the agricultural producer of rubber, cacao, and vegetables, and for its fisheries, while both Sabah and Sarawak export liquefied natural gas (LNG) and petroleum. The Indonesian provinces of Kalimantan are mostly dependent on mining sectors despite also being involved in logging and oil and gas explorations.
