World Wildlife Fund

As habitat dwindles, Borneo and Sumatra's unique species hang in the balance.
© WWF-Canon/Alain Compost

The forests of Borneo and Sumatra are some of the most biologically diverse habitats on Earth, possessing staggeringly high numbers of unique plant and animal species. 

The smallest of tigers, the Sumatran tiger has heavy black stripes on an orange background.
© WWF-Canon/Frédy Mercay

Sumatran tiger
Right now, fewer than 500 Sumatran tigers live in the wild. This endangered population is found only on the island of Sumatra - the last stronghold for tigers in Indonesia. These magnificent animals were formerly widespread in the region, but are disappearing because of accelerating deforestation and rampant poaching across their range. A TRAFFIC study of illegal trade in Sumatran tigers found an active poaching network and vast markets for tiger parts.

Wild orangutans have been observed making tools.
© WWF-Canon/Alain Compost

Orangutan
Orangutans are the largest tree-living mammals and the only great ape species to live outside of Africa. They are found only on Borneo and Sumatra, with separate species on each island. The Borneo orangutan has a round face, while Sumatran orangutans have an oval face and lighter hair. They are active during daylight hours and construct large tree nests to sleep in at night. Adult orangutans measure 4 to 5 feet from head to toe, with males weighing 110 to 220 pounds. The numbers of wild orangutans have declined continuously with the accelerating loss of forest habitat, and both species of orangutan are threatened with extinction.
 

The critically endangered Sumatran rhino is the only Asian rhino with two horns.
© WWF-Canon/Alain Compost

Sumatran rhino
The Sumatran, or hairy, rhino is the smallest of the living rhinoceroses, weighing just 1,300-1,700 pounds. It has fringed ears, reddish-brown skin variably covered with long hair, and wrinkles around its eyes. Today, the world population of Sumatran rhinos may be below 300 individuals in the wild. Urgent measures are needed to save the forests where this rhino still survives. Moreover, it is imperative that trade in rhino products be halted immediately. 

According to recent DNA evidence, pygmy elephants were isolated about 300,000 years ago from their cousins on mainland Asia and Sumatra.
© WWF-Canon/A. Christy Williams

Pygmy elephant
Borneo is home to a unique population of elephants which are smaller, more rotund and less aggressive than other elephants. Their gentle nature led to the belief that they were the semi-tame remnants of a domesticated herd abandoned on the island years ago. But a WWF study proved that wrong and Borneo's pygmy elephants are likely to be officially declared a new subspecies. That makes them a high conservation priority. They remain the least-understood elephants in the world. There may be fewer than 1,000 pygmy elephants remaining on the island, making them the most endangered Asian elephant subspecies. 

WWF has tried for more than a year to capture additional photographs of the Bornean red carnivore.
© WWF Indonesia

Mystery mammal: Bornean red carnivore
In 2003 our camera traps snapped two photos of a red mammal, slightly larger than a domestic cat, in the Kayan Menatarang area of Borneo. It could be a new species of civet or marten. For now it has been dubbed the Bornean red carnivore. The photos were shown to local people and international mammal experts but no one had seen this creature before. It appears to be an unknown mammal species. 

Plant species

Borneo and Sumatra present a staggering, and largely undiscovered, wealth of diverse plant species. Borneo is conservatively estimated to contain 15,000 plant species (of which 6,000 occur only here) and may well have the highest plant diversity of any region on earth. A WWF study in Sumatra found that the Tesso Nilo forest harbors more plant species per test plot than any other forest studied: some 218 species in just 2,100 square feet. In the last 25 years, some 422 new species of plants were discovered in Borneo alone.