The Leuser Ecosystem

Sumatra’s giant green lungs – a life support system like no other

Named for one of the soaring mountains that runs along its spine, the Leuser Ecosystem stretches from the Indian Ocean to the Malacca Straits. It covers 2.6 million hectares, encompassing nine major river systems, two volcanoes and a mosaic of habitats that support an abundance of flora and fauna. Over 130 mammal species dwell in the forests, along with hundreds of birds and thousands of plants – many of them found nowhere else in the world.

Giant parasitic flowers, king cobras, sun bears and clouded leopards live here, along with breeding populations of Sumatran orangutans, rhino, tiger and elephant – species that no longer live side-by-side anywhere else on earth. These critically endangered animals face different threats according to their habitat and lifestyle; orangutans and elephants living in lowland forests are often displaced by plantations, while up in the mountains the secretive rhino needs time and space to meet a mate. In all cases, the fate of wildlife and forests is intertwined. LEAF’s grant partners have already delivered a range of incredible conservation successes.

Orangutan - Leuser Ecosystem – photo copyright Paul Hilton for Earth Tree

For humans too, the forests are a vital resource. On the map, the Leuser Ecosystem resembles a giant pair of green lungs – a fitting image since they clean the air and regulate water supplies to millions of people living downstream. The forests are part of Aceh’s rich cultural heritage. Today, over one thousand communities live within the ecosystem boundaries, many of them smallholders and subsistence farmers. LEAF’s partners are working hard to mitigate human-wildlife conflict, at the same time as creating practical and sustainable livelihood options.

In total, the Leuser provides ecosystem services worth at least $350 million per year, including carbon storage, the prevention of soil erosion and floods. In the long run, this exceeds the profit generated by continued forest destruction, but conventional economic markets do a poor job of ‘seeing’ ecosystem assets, which are undervalued because they are unpriced. 

International trade and finance needs to work better for forests, as does policy and law within Indonesia. Because many of the forces affecting Sumatran forests are systemic in nature, the Leuser is a very good place to do things differently. The wisdom and entrepreneurial flair of our grant partners are among the reasons LEAF’s founders were drawn to this region in the first place.