BORNEO BIODIVERSITY: RAINFORESTS, NEW, RARE SPECIES, THREATS

WILDLIFE AND PLANTS IN BORNEO

Wallace's flying frog

The rain forests of Borneo —the world’s third largest island after Greenland and New Guinea— are among the most ecologically diverse in the world, with about 15,000 types of plants, more than 600 species of birds and an animal population that also includes the clouded leopard and pygmy elephant.” Nick Meo wrote in The Times, Borneo “is a biological treasure that staggers scientists newly arrived from Europe. It is home to thousands of tree frogs, bats and orchids. More than 1,000 insects have been identified in a single tree... Charles Darwin, who explored the giant island before writing The Origin of Species, called it “one great untidy luxuriant hothouse made by nature for herself”. [Source: Nick Meo, The Times, February 3, 2006]

Mammals: 220 species, including: Bornean Orang-utan (Pongo pygmaeus) classified as Endangered by IUCN. An estimated 1,000 individuals are resident within the Lower Kinabatangan floodplain; 9 species of the 13 primates are found in the Kinabatangan area: Proboscis Monkey (Nasalis lavatus); Western Tarsir (Tarsius bancanus); Long-tailed Macaque (Macaca fascicularis); Pig-tailed Macaque (Macaca nemestrina); Dusky, Silver-leaf and Maroon Langurs; Bornean Gibbon (Hylobates muelleri) and Slow Loris (Nycticebus menagensis) Bornean Pygmy Elephant (Elephas maximus borneensis) classified as Endangered by IUCN, is a sub-species genetically distinct from mainland Asian Elephants with an estimated population of 200 individuals found within the Lower Kinabatangan Floodplain.

Birds: Over 434 species of breeding birds out of a total of 622 species recorded, including the Storm’s Stork (Ciconia stormi) classified as Endangered by IUCN Borneo's 8 species of Hornbills that can all be found in the Lower Kinabatangan; including the Rhinoceros (Buceros rhinoceros) and Helmeted Hornbills (Rhinoplax vigil). Reptiles and Amphibians: Over 250 species, Plants: 15,000 species. Over 60 percent of plants found in Borneo are endemic to the island, and over 360 new species to science have been discovered in recent times.

Ecosystems, Rainforest and Peat Swamps of Borneo

Land use in Sabah and Sarawak (Malaysian Borneo)

Historically, Borneo was almost entirely covered by dense rainforest. The rainforests of Borneo have been estimated to be approximately 140 million years old, making them among the oldest rainforests on Earth. The dominant group of trees in the lowland rainforests, known as dipterocarps, has prevailed for millions of years and continues to shape the structure of these forests today. Borneo is a major centre for the evolution and distribution of endemic plant and animal species, many of which are found nowhere else in the world. The rainforest also provides one of the last remaining natural habitats for the endangered Bornean orangutan, along with other rare forest species such as the Borneo elephant, the eastern Sumatran rhinoceros, the Bornean clouded leopard, the Bornean rock frog, Hose’s palm civet, and the Dayak fruit bat. [Source: Wikipedia]

The World Wide Fund for Nature (WWF) has divided Borneo into seven distinct ecological regions. Most of these are lowland environments. The Borneo lowland rainforests cover the majority of the island, extending across more than four hundred twenty seven thousand square kilometres. Montane rainforests occur in the central highlands at elevations above one thousand metres. At the highest elevations of Mount Kinabalu, montane alpine meadows form a unique subalpine and alpine shrubland environment that supports a remarkable concentration of endemic species, including many distinctive orchids.

Other major ecosystems include peat swamp forests, kerangas forests also known as Sundaland heath forests, freshwater swamp forests in the western and southern lowlands, and mangrove forests along the Sunda Shelf coastlines. Peat swamp forests line much of the coastline of Borneo. The soils in these forests are relatively infertile, yet they support a wide variety of wildlife, particularly bird species such as the hook billed bulbul, the helmeted hornbill, and the rhinoceros hornbill.

Borneo’s complex geography has created hundreds of specialized habitats, from isolated river systems to mountain slopes, allowing species to evolve in narrow ecological niches. Many newly discovered organisms are confined to a single river or mountain range. Scientists emphasized that even large, immobile organisms such as trees continue to be found, underscoring how incomplete current knowledge remains. Much of this biological wealth is concentrated in the Heart of Borneo, a vast central rainforest increasingly threatened by human development. In response, conservation organizations are working with governments in Indonesia, Malaysia, and Brunei to expand protected areas and promote sustainable forest management in the region. [Source: John Roach, National Geographic News, December 19, 2006]

Extraordinary Biodiversity in Borneo

Borneo holds six percent of the world’s species of plants and animals. Of the 220 mammal species there are 44 only found on the island. Borneo is home to around 3,000 species of trees, of which 277 belong to the dipterocarp family. Its rivers and wetlands contain roughly 4,40 species of freshwater fish, a number comparable to the combined total of Sumatra and Java. One particularly rare species, the Borneo river shark, is known only from the Kinabatangan River in Sabah. In 2010, the World Wide Fund for Nature reported that 123 new species had been discovered in Borneo since the signing of the Heart of Borneo conservation agreement in 2007.

paradise tree snake in mid-glide

Many animals such as pygmy elephants, Sumatran rhinos, orangutans as well as the clouded leopard, the sun bear and the Bornean gibbon top the list of Borneo’s endangered species. A total of 361 new species were discovered between 1995 and 2005. Lewis Smith and Lucy Alexander wrote in The Times, “The remote and inaccessible forests in the heart of Borneo are one of the world’s final frontiers for science and many undiscovered species are still waiting to be found.” The WWF reported in April 2005 that at least 361 species had been newly identified on the island between 1994 and 2004, a rate of three animals and plants a month. Borneo’s estimated total of 15,000 plants is thought to be the highest plant diversity of any region on Earth. It has the highest documented tree diversity in the world, at 1,175 species in a 52-hectare plot. The island is one of two places where the orangutan still survives, though they are threatened with catastrophic population loss because of deforestation. [Source: Lewis Smith and Lucy Alexander, The Times, December 18, 2006 /]

Among the species discovered in 2005 and 2006 are two frogs, three tree species, 16 types of ginger, 30 fish, and a plant that produces only a single leaf. One of the most striking discoveries was a tiny fish, Paedocypris micromegethes, measuring about 8.8 millimeters in length and ranking as the world’s second smallest vertebrate. It inhabits highly acidic peat swamp waters in shaded forest areas, where it lives in pools and slow moving streams. Its close relative, Paedocypris progenetica from Sumatra, is even smaller. Conservationists warned that many peat swamp habitats surveyed during this research have already been destroyed, placing these newly identified endemic species at immediate risk of extinction. According to a report by the WWF, scientists expect that thousands more species remain undiscovered in Borneo.[Source: Lewis Smith and Lucy Alexander, The Times, December 18, 2006]

On hunting on Borneo in the 1840s, Henry Keppel wrote in “Expedition to Borneo of H.M.S. Dido for the Suppression of Piracy”: “But, while on the subject, I may mention that of pig- shooting, which I found an amusement not to be despised, especially if you approach your game before life is extinct. The jaws are long, tusks also, and sharp as a razor; and when once wounded, the animals evince a strong inclination to return the compliment: they are active, cunning, and very fast. I shot several at different times. The natives also describe a very formidable beast, the size of a large bullock, found further to the northward, which they appear to hold in great dread. This I conceive to be a sort of bison ; and if so, the sporting in Borneo altogether is not so bad.” [Source: “The Expedition to Borneo of H.M.S. Dido For the Suppression of Piracy” by Henry Keppel and James Brooke (1847)-]

In Borneo there are around 160 different species of snakes, divided into nine families. Most are harmless. Only snakes which have a venom gland, a duct to carry the fang to inject that venom, are considered as venomous. Of the 160 different species, only 24 are front-fanged and highly poisonous, of which 17 are Sea Snakes and two Coral Snakes from the Hydrophiidae family. The remainder are from the Elapidae and the Veperidae families. Among the species of venomous snakes found in Borneo are the Wagler’s pit viper and several species of krait.

Borneo Rainforests Full of Rare Species

In 2003, Reuters reported, wildlife researchers photographed a mysterious fox like mammal in the Indonesian part of the island of Borneo. Scientists believed this sighting represented the first discovery of a new carnivorous mammal species on the island in more than one hundred years. Since that time, numerous additional species of plants and animals have been identified, reinforcing the view among conservationists that Borneo, the world’s third largest island, remains a vast reservoir of biological diversity with many species still waiting to be discovered. [Source: Diyan Jari and Reuben Carder, Reuters, March 29, 2006 \~/]

These discoveries were considered especially remarkable given the extensive environmental damage Borneo has experienced over recent decades. Large areas of forest have been lost to commercial logging, slash and burn agriculture, the expansion of oil palm plantations, and widespread poaching. Despite these pressures, conservationists remain hopeful that the island will continue to yield new scientific discoveries. Gusti Sutedja, project director for the Kayan Mentarang National Park for the World Wide Fund for Nature in Indonesia, emphasized the island’s promise, describing the park as a vast protected area where the newly observed mammal, informally referred to as the Bornean Red Carnivore, was captured by a night time camera trap. The animal is considered extremely rare and has never been captured alive.

Researchers involved in joint fieldwork have reported further discoveries. In two thousand three, collaborative surveys with Malaysian scientists led to the identification of many previously unknown species of lower plants. During the same period, three newly discovered frog species were sent for further study by researchers in Germany, and five bird species not previously recorded in the area were documented during a forest survey. Some conservationists have suggested that Borneo could become the next so called “Lost World,” comparable to recent discoveries of butterflies, birds, and frogs in remote forests of New Guinea.

Borneo is also notable for having more species of tree shrew than any other place in the world. Despite their name, tree shrews are not true shrews, and most species do not live primarily in trees. They are generally active and energetic animals that belong to their own distinct biological order, known as Scandentia. In the Indonesian language, the local word for tree shrews, “tupai,” is the same term used to describe squirrels, reflecting their superficial similarity in appearance and behavior.

123 New Species Discovered in Borneo in the Late 2000s

In April 2010, CNN reported that scientists working in the dense forests of central Borneo had uncovered a remarkable collection of new life forms. Among the discoveries were color changing frogs, the world’s longest stick insect, and a slug capable of firing so called “love darts.” Since 2007, when the three governments that administer the island signed an agreement to protect its forests, researchers have identified 123 new species of animals, insects, and plants in this region of Southeast Asia. [Source: Hilary Whiteman, CNN, April 22, 2010]

These discoveries were highlighted in a report released by the World Wildlife Fund to coincide with Earth Day and to emphasize the importance of conserving areas rich in biodiversity. David Norman, the organization’s director of campaigns, noted that while many of the newly discovered small animals attract attention, plants may be even more significant because of their potential medical value. He emphasized that about half of all synthetic medicines are derived from natural sources, particularly plants and, in some cases, animals, underscoring the high cost of species loss.

Plants accounted for the largest share of the discoveries made in Borneo during the previous three years. Scientists identified 67 new plant species, exceeding the combined total of all other groups. In addition, researchers recorded 29 new invertebrates, 17 fish species, one bird, five amphibians, and five reptiles. The World Wildlife Fund described the region as a global treasure filled with unique and extraordinary forms of life.

Some of the most unusual findings involved amphibians. One newly described species, a color changing and gliding frog known as Rhacophorus penanorum, measures only about 3.5 centimeters in length. Its skin turns bright green at night and brown during the day. These frogs live in trees in the Tapin Valley of Gunung Mulu National Park in Sarawak, using their fully webbed feet to glide distances of up to 15 meters between branches.

Another striking discovery was the world’s longest stick insect, Phobaeticus chani, which can exceed half a meter in length and inhabits the upper canopy of the rainforest. Only three specimens have ever been recorded, making the species exceptionally rare. Equally unusual is the long tailed slug, Ibycus rachelae, whose tail is three times longer than its head and curls around its body when it sleeps. During mating, this slug releases a sharp structure known as a love dart, made of calcium carbonate, which injects a hormone into its partner to improve the chances of successful reproduction.

52 New Species Discovered in Borneo in the Mid 2000s

In December 2006, Associated Press reported, scientists announced that they had discovered at least 52 previously unknown species of animals and plants on Borneo since 2005, according to the WWF. Among these discoveries is a distinctive species of catfish with protruding teeth and suction cup like structures on its belly that allow it to cling to rocks. Stuart Chapman, the WWF international coordinator for research in the Heart of Borneo, a rainforest region covering about 85,000 square miles in the center of the island, stated that continued exploration consistently reveals new forms of life. He noted that these findings reinforce Borneo’s status as one of the most important centers of biodiversity in the world. [Source: Eliane Engeler, The Associated Press, December 19, 2006]

These discoveries increased the total number of new species identified as of 2006 on the island to more than 400 since 1996. Species found between July 2005 and September 2006 included six types of Siamese fighting fish, distinguished from related species by their unique colors and patterns, as well as a tree frog with bright green eyes. The newly described catfish, notable for its attractive coloration, was named Glyptothorax exodon, referring to the visible teeth that can be seen even when its mouth is closed. The suction cups on its underside allow it to remain attached to smooth stones while resisting the strong currents of the Kapuas River system in Indonesia.

In the Malaysian portion of Borneo, slow moving blackwater streams and peat swamp habitats support Paedocypris micromegethes, an extremely small fish measuring about 0.35 inches in length. Its name is derived from Greek words meaning child and small. This species is smaller than any other known vertebrate, with the exception of a slightly smaller relative measuring about 0.31 inches that was discovered on the Indonesian island of Sumatra.

Jane Smart, head of the species program at the World Conservation Union, described the discovery of 52 new species within a single year in Borneo as a realistic figure, given scientific estimates that there may be around 15 million species on Earth. She emphasized that many more species in Borneo remain undiscovered. Borneo is especially important for global biodiversity because it supports a high number of endemic species that exist nowhere else. As a result, the destruction of even small areas of forest can lead to the loss of significant portions of these species’ habitats. She warned that when forests are cleared for rubber or oil palm plantations, the species dependent on those environments may be permanently lost, raising serious conservation concerns.

Pea-Sized Frog, Chameleon Snake Found in Borneo

In April 2010, the Associated Press reported the discovery of one of the world’s tiniest frogs in Borneo, barely larger than a pea. The species was found accidentally by Indraneil Das of Universiti Malaysia Sarawak and a German colleague while they were surveying frogs in Sarawak. They encountered the frog along a mountain road in Kubah National Park in 2006. Adult males measure between 10.6 and 12.8 millimeters in length. [Source: Associated Press, August 26, 2010]

The frog was named Microhyla nepenthicola after the carnivorous pitcher plants in which it lives. Although these plants trap and digest insects, they do not harm the frogs, and the tadpoles develop in the liquid inside the pitchers. The species had previously been misidentified in a Malaysian museum as a juvenile of another frog. Because of their minute size, the frogs were located by tracking their rasping calls at dusk. The findings were published in the journal Zootaxa and were seen as further evidence of the need to protect Borneo’s rainforest biodiversity.

In June 2006, the BBC reported the discovery of a color changing water snake in the forested interior of Borneo. The snake was found in the Kapuas River within Betung Kerihun National Park in Kalimantan and belongs to the genus Enhydris. Named Enhydris gyii, it grows to about 50 centimeters in length and is venomous. Its unusual ability to change color was discovered by chance when a researcher placed the reddish brown snake in a dark container and later found it had turned almost entirely white. Scientists believe the species may be confined to a single river basin, making it especially vulnerable. Conservation groups noted that such discoveries highlight Borneo’s biological richness, even as deforestation has reduced the island’s forest cover from about 75 percent in the mid 1980s to roughly 50 percent today. [Source: BBC, June 25, 2006]

Bird Species Discovered and Rediscovered in Borneo

In the summer of 2009, a new bird species known as the spectacled flowerpecker was observed feeding on mistletoe in the rainforests of the Danum Valley Conservation Area in Sabah, Malaysian Borneo. According to the BBC, the bird was first seen by University of Leeds biologist Richard Webster from a canopy walkway about 35 meters above the forest floor. The small, gray bird, roughly the size of a wren, was noted for its white markings around the eyes, belly, and breast, and was also heard singing on at least one occasion. [Source: Doreen Walton, BBC News, January 14, 2010]

The discovery was published in the Oriental Bird Club journal BirdingASIA. Using photographs, tropical ecologist David Edwards of the University of Leeds confirmed that the bird represented a previously unknown species, describing the find as the fulfillment of a lifelong goal after years of demanding fieldwork in tropical conditions.

In 2020, ornithologists rediscovered the black browed babbler, a bird that had not been documented for 170 years. The only previous specimen had been collected in the 1850s but was mistakenly labeled as originating from Java rather than Borneo, leading to decades of unsuccessful searches. Although the labeling error was eventually corrected, the species remained unseen until members of the local bird watching group BW Galeatus encountered a similar bird in South Kalimantan. In October 2020, Muhammad Suranto and Muhammad Rizky Fauzan captured one individual, photographed it, and shared the images with experts, who confirmed its identity. The rediscovery prompted strong emotional reactions among ornithologists and conservationists, who described feelings of disbelief and joy. After documentation, the bird was released back into the wild. [Source: Catherine Garcia, The Week, March 8, 2021]

Deforestation of Borneo

Borneo is rapidly losing vast areas of forest to commercial logging, timber extraction, plantation agriculture and mining activities, with weak law enforcement, and corruption hastening the pace. Analysis of satellite and forest monitoring data shows extensive forest loss over recent decades. Indonesian forestry consultant Dwi R. Muhtaman told Reuters that Indonesia’s forests are being destroyed at a rate of around 2 million hectares per year. He warned that, if current patterns continue, the forests of Borneo’s low lying areas could disappear within a relatively short period of time. Diyan Jari and Reuben Carde of Reuters wrote: [Source: Diyan Jari and Reuben Carder, Reuters, March 29, 2006]

WWF’s Sutedja estimated the rate of deforestation in Borneo was the “the equivalent of one football field per day.” Indonesia’s development of major palm oil plantations in the heart of Borneo near the border with Malaysia are particularly devastating. The area is remote highland forest from which many of the island’s largest rivers originate and has so far managed to remain intact because of its rugged terrain and distance from the coast. “There is opposition from most environmental NGOs. Their research says that areas of natural forest could be converted, and the project could affect rivers,” Sutedja said. “Flooding could occur, which would affect the indigenous Dayak people who live downstream,” he said, adding that WWF did not oppose the plan, but was concerned it be carried out in accordance with environmental principles.\~/

Between 2002 and 2019, the Indonesian portion of Borneo lost approximately 10.7 million hectares of tree cover, including about 4 million hectares of primary forest. During the same period, Malaysian Borneo lost around 4.4 million hectares of tree cover, including nearly 1.9 9 million hectares of primary forest. By 2020, Indonesian Borneo accounted for about 72 percent of the island’s remaining tree cover, Malaysian Borneo about 27 percent, and Brunei roughly one percent. Primary forest in Indonesia alone made up approximately forty four percent of Borneo’s total remaining tree cover. [Source: Wikipedia]

Causes of Deforestation in Borneo

Land use in Kalimantan (Indonesian Borneo

Between 1996 and 2006, Indonesia lost an average of nine million acres (two million hectares) of forest a year. Today only half of Borneo's original forest cover remains, according to WWF. Large swaths of forest have been cleared for timber, rubber, oil palm and pulp production. Borneo's lowland forests are primarily cleared for oil palm plantations. The rainforest-covered mountains are rich in coal and several mining companies already hold access rights. Gold mining is conducted throughout Kalimantan, Indonesia’s portion’s Borneo.

This forest cover has been drastically reduced due to intensive logging by the Indonesian and Malaysian timber industries. Large areas of forest have also been cleared and converted into industrial scale agricultural land, often for palm oil. Approximately half of the world’s annual tropical timber production has come from Borneo. Palm oil plantations have expanded rapidly, encroaching on some of the last remaining areas of primary rainforest.

Alex Shoumatoff wrote in Smithsonian magazine: At the top of a knife-edged ridge, we look out on a 50-mile vista of nothing but rainforest and mist-filled valleys, with the 7,795-foot Mount Mulu rising in the distance. We can even see the curvature of the earth. On closer inspection, we see that all the ridges in the foreground have logging roads on them, like the one we are on. There are eroded gashes on the hillsides where big trees, cut into 30- to 40-foot lengths, were slid down to the valley floors. We hear the rumble of logging trucks down below. [Source: Alex Shoumatoff, Smithsonian magazine, March 2016]

Borneo’s rainforests are being cleared at a faster rate per acre than the Amazon’s — all because of consumer demands around the world. Timber companies fell the ancient trees and export their wood, mostly to other Asian nations. The palm oil industry follows closely, clearing the land for enormous plantations. Ninety percent of Borneo’s primary forest cover is now gone, along with some of the tallest tropical trees in the world. In their place, much of the island is now covered with a tossing ocean of oil palm trees. The oil they produce goes out to markets in the United States, Europe and just about everywhere else: It’s an essential ingredient in processed foods, baked goods, ice cream, cosmetics, cleaning agents, biodiesel, toothpaste, shampoo and countless other products.

Forest fires have further accelerated forest loss since 1997. Many of these fires were deliberately started to clear land for plantations, but their impact was intensified by unusually dry conditions associated with the El Niño climate phenomenon. The resulting fires produced thick haze that was visible in satellite imagery and regularly affected Brunei, Indonesia, and Malaysia. In severe years, the haze spread across much of Southeast Asia, reaching southern Thailand, Cambodia, Vietnam, and the Philippines, as notably occurred during the widespread haze event of two thousand fifteen.

Borneo’s Wildlife Threatened by Deforestation and the Wildlife Trade

Map of forest lost in Kalimantan (Indonesian part of island Borneo) from 1985 to 1997 according to the WRI (Global Forest Watch & Forest Watch Indonesia; 2002); East Kalimantan is the largest province in Indonesia still covered by natural forest, 32% of the total forest in Indonesia in early 1990s

The ecological consequences of deforestation in Borneo have been severe.According to the World Wildlife Fund, Borneo’s forests hold 6 percent of the planet’s plant and animal species but many are now being driven toward extinction, or wiped out even before they can even be identified. A study published in 2018 estimated that the population of Bornean orangutans declined by approximately 148,500 hundred individuals between 1999 and 2015, largely as a result of habitat loss, forest degradation, and human activity.

Diyan Jari and Reuben Carde of Reuters wrote: “Environmentalists say they are particularly worried as island ecosystems are known as much for their fragility as their ability to harbor rare animals and plants.Of approximately 800 species extinctions worldwide since accurate scientific recording began in 1500, the vast majority have been from island ecosystems, the World Conservation Union says. Green groups say hundreds of orangutans are killed or captured every year on the Indonesian part of Borneo as part of an illegal trade that is driving the primates toward extinction. \~/

“According to a study by WWF International and wildlife trade monitor TRAFFIC, between 200 and 500 Borneo orangutans are traded in various parts of Indonesia each year. The vast majority are infants sold as pets. WWF International estimates poachers have also killed most endangered rhinos in Borneo and only about 13 might have survived. “The current situation will continue until the forest is gone,” Muhtaman said.” \~/ Image Sources: Wikimedia Commons

Text Sources: New York Times, Washington Post, Los Angeles Times, Times of London, Lonely Planet Guides, Library of Congress, Compton’s Encyclopedia, The Guardian, National Geographic, Smithsonian magazine, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Wall Street Journal, The Atlantic Monthly, The Economist, Global Viewpoint (Christian Science Monitor), Foreign Policy, Wikipedia, BBC, CNN, and various books, websites and other publications.

Last updated January 2026