Located in the two northern-most provinces of Sumatra (Aceh and North Sumatra), its 2.6 million hectares are exceptionally rich in biological diversity. Because of this and owing to its dramatic topography, the ecosystem functions as a life-support system for more than four million people living in the surrounding area.

The ecosystem is the largest remaining undisturbed refuge of Malesian rainforest in the world. In its realm it is the richest rainforest wilderness known to science, harbouring numerous species of mammals, birds, reptiles, fish and an unknown numbers of invertebrates, plants and other organisms.

The Leuser Ecosystem is one of the most important conservation areas on earth

Its fauna is the richest of any known Asian area. It is home to 105 recorded species of mammals, 382 species of birds, and at least 95 species of reptiles and amphibians (54% of Sumatra’s terrestrial fauna). It is considered to be the last place in SE Asia of sufficient size and quality to maintain viable populations of many rare and charismatic species including tigers, orangutans, rhinos, elephants, and clouded leopard.

With its two mountain ranges and widely varying habitats, the ecosystem provides many ecological functions or services, the most important of which is a constant supply of water to the surrounding regions and the regulation of local climate. Other services include the mitigation of erosion and flash floods, the prevention of pest outbreaks, carbon sequestration (for global climate regulation), natural beauty and spectacular biodiversity (for tourism), hydropower potential, germplasm (for horticulture), pollination of commercially important crops, airborne dust filtration (leading to soil fertility)

Despite the local and global importance of the Leuser Ecosystem there are major challenges facing its conservation and sustainable utilisation. Many groups have a consumptive interest in the area – for timber, rattan, plantations, wildlife and harvesting. While most of the ecosystem is made up of protection forests and conservation areas, there are also plantation estates, timber concessions, community forests and a few isolated villages.