Rainforest Biodiversity

Image of a female orangutan in a tree. The orangutan is holding a leaf and putting it up to her lips. A small, young orangutan is holding onto her side. Both orangutans are a deep red-orange color.
Image Courtesy of Orangutan Kutai Project

Each of these organisms is dependent on the whole ecosystem functioning – like a house of cards is dependent on all of its cards. If whole areas of forest are clear-cut, the whole system fails; habitats for thousands of species disappear, and are lost forever. Once the forest is gone, the tropical, acidic, and nutrient poor soils make it difficult for crops to prosper for more than a few years, eventually being replaced by weeds or coarse grasses such as alang-alang in Indonesia. Such plants as alang-alang have no economic uses, are very hardy, are not edible and may be alleliotrophic, meaning that other plants are repelled from growing nearby. These areas become much like a desert.

Plant Life

Of the approximately 250,000 known flowering plants, 170,000 can be found within Earth’s tropics and subtropic regions. This makes the tropical rainforests amongst the most diverse and complex living environments on the planet.

Islands within Indonesia, such as Borneo and Sumatra are known to have some of the richest and most complex of any biological community on the planet. Borneo alone has approximately 10,000 to 15,000 species of flowering plants. 6,000 of these plants are endemic, meaning they cannot be found anywhere else in the world. A small 1.12 hectare of Bornean rainforest has found to include at least 264 species of tree, not including palms, lianas, orchids, ferns, and other vegetation.

The flora that can be found on the island of Borneo includes:
species of trees
species of orchids
species of ferns

Of the many various plants that reside on Borneo, one of the most interesting would be Rafflesia arnoldii in the parasitic genus Rafflesia. The Rafflesia arnoldii flower is one of three national flowers in Indonesia, with the others being white jasmine and the moon orchid. This plant is also referred to as the “corpse plant” due to its emission of an unpleasant scent like that of rotting flesh. It is also the world’s largest flower and is found on Borneo growing to be up to 100 cm. in diameter and weigh up to 10 kilogram.


Sumatra and Bornean rainforests are also known to house the greatest diversity of Nepenthes, also known as carnivorous tropical pitcher plants. Pitcher plants have cupped, pitcher-shaped leaves that form a deep cavity that is often referred to as “pitfall traps” that are used to lure and trap insects in their digestive liquids. The pitcher contains a liquid, or nectar, which drowns the insect and causes it to dissolve and be digested by the plant. While pitcher plants primarily consume insects, there have also been reports of a Nepenthes rajah “eating” a rodent. The photo to the left is of Nepenthes rafflesiana, which is endemic to South East Asia. You can read more about Nepenthes here.


As previously noted, Borneo is home to approximately 2,000 to 3,000 species of colorful and fragrant orchids and is noted to have the greatest number of varieties of orchids of anywhere else on the planet. The orchid pictured to the left is of Paphiopedilum lowii, which is found throughout the islands of South East Asia. Many of these orchid species are highly endangered and have even faced extinction due to habitat loss from fires, forest damage, and logging.

Animal Life

Borneo’s animal life is no less diverse. It supports on the order of 222 mammals, 420 birds, 166 serpents, 100 amphibians, and 394 fresh-water fish, not to mention the invertebrates, by far the most numerous animal species in tropical rainforests. Many of these life forms are endemic, or unique to the island — proboscis monkeys, hornbills, gibbons, clouded leopards, and orangutans.

Some of the many species that are found in Borneo and Sumatra:​
Sumatran Rhino (Dicerorhinus sumatrensis) – Critically Endangered
darren-welsh-bKmy6LM3yKA-unsplash-2-1024x683 (1)
Sun Bear (Helarctos malayanus) – Vulnerable
Proboscis-Monkey-Adult8-1 (1)
Proboscis Monkey – Endangered
Bornean Gibbon (Hylobates muelleri) – Endangered
Sumatran Tiger (Panthera tigris sondaica) – Critically Endangered
Long-Tailed Macaques (Macaca fascicularis) – Least Concern

Threats to Biological Diversity

Today roads cross much of Borneo’s remote interior. Commercial logging concessions cover more than 30 percent of Indonesia’s landmass. Poor concession management, slash and burn agriculture, illegal logging and the massive expansion of palm oil plantations have all contributed to a decreasing rainforest habitat.

The fires of 1997 and 1998 eliminated thousands of acres of forest and were termed by the UN as one of the worst ecological disasters of the century.

It is estimated that 1/3 of the wild orangutan population was lost during this time, and Indonesian people suffered widespread respiratory and other health problems due to smoke inhalation. Massive floods and contaminated drinking water are just two of the consequences of illegal logging to the people living in Indonesia and Malaysia.


The value of biological diversity and the rainforest can only be estimated. Every time an acre of rainforest is burned or chopped down, we might lose a cure for cancer or AIDS. Scientists have already seen it happen. A chemical that was a potential cure for AIDS was found in the bark of a gum tree in Malaysia (Sarawak). Scientists took a sample of the bark and studied it to see if it killed the AIDS virus. The results looked good, so the scientists returned to Malaysia to get more samples for further study. When they got there, the tree was gone. The scientists looked for another tree like it, but none was found. It was believed that what could have been a cure for AIDS was gone forever. After several years of continued searching another tree was found in Sarawak on the island of Borneo, and the National Cancer Institute (NCI) could continue the testing on the chemical compounds of this tree. Today clinical testing on humans has begun using the medicine developed from this tree. The government of Sarawak has declared this species to be protected and formed a Biodiversity Center which will continue the search for other life-saving medical miracles.

Save the species, take action now.