In the varied landscapes of the Leuser Ecosystem, ranging from coastal areas, through lowland and mountain rainforest into the subalpine zone, grow about 8500 species of plants and trees.

Sumatran lowland rainforest is one of the most diverse forests on Earth and also one of the most threatened. It supports 111 dipterocarp species, including 6 endemics.

Herbs, flowers and fruits

Most trees and plants depend on insects for pollination and animals for seed dispersal as there is little air movement under the dense canopy.

Rafflesia, Amorpha and Taka

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Five of the sixteen species of the parasitic Rafflesia plant are found in Sumatra and occur mainly in lowland forest. Rafflesia arnoldii produces a large orange-brown flower that at nearly 1 metre wide is the largest flower in the world.


Orchids and other epiphytes such as moss, lichen, and liverworts are common in montane forest.

Fungi are essential to the forest ecosystem, making nutrients in dead matter available to other plants and animals. Unseen for most of their lives, they appear in many beautiful forms when it is time to reproduce.

Gunung Leuser National Park is home to a number of species whose populations in the wild have dropped to a critically endangered level.

Monkeys and Apes

Feeding in different levels of the canopy, there are many monkeys and apes co-existing in the forest, including orangutans, gibbons, langurs, macaques and Thomas leaf monkeys.


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Indonesia has more species of mammal than any other nation, and nearly a third of these animals are threatened species.

There are more than 350 bird species in the National Park, including the critically endangered Rueck’s blue flycatcher, several hornbill species and the great argus pheasant, famed for its dramatic mating displays.

Among the numerous reptiles in the forest are many species of snake, lizard, iguana, turtle, and tortoise. Snakes include pythons, King Cobra, Black Cobra, Banded Krait, Sumatran Pit Viper and Mangrove snake.

Insects and Arachnids

The incredible creativity of nature shows its hand in the many varied ways that insects disguise or show themselves to deter and confuse predators.


Amphibians such as frogs, toads, salamanders, newts, and worm-like caecilians are found in virtually all rainforest habitats, ranging from the high canopy to streams and creeks.