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The Batang Toru Ecosystem is situated south of the lake Toba in the province North Sumatra. It is the home of the last 800 Tapanuli orangutans, currently the most endangered great ape species in the world. The upland rainforest of Batang Toru is under serious pressure and with it, the habitat of the orangutan and many other critically endangered species, such as the Sumatran tiger and the pangolin. Since 2005, the Batang Toru-project has been campaigning with the Sumatran Orangutan Conservation Programme for the preservation of the ecosystem and the Tapanuli orangutan.


Studies published in early November 2017 have confirmed that the Tapanuli orangutan differs significantly genetically, morphologically and behaviourally from the Sumatran orangutan that occurs north of Lake Toba, and also differ significantly from the Bornean orangutan. With the description of this new species, the conservation of remaining Tapanuli orangutans and their habitat has become even more urgent. Merely 800 Tapanuli orangutans survive currently in the Batang Toru Ecosystem. A large array of biodiversity studies carried out over the last decade have shown that the Batang Toru Ecosystem is home to an extraordinary rich wildlife. Close to 100 mammal species have been recorded so far, among them eighteen species listed as endangered or even critically endangered on the IUCN Red List. Additionally, the Batang Toru rainforest is extremely important to the people who live in the surroundings. The forest is their main source of drinking water and a buffer against flooding and erosion. Furthermore, the forest plays a major role in carbon storage.


Hydro-electric dam

A newly planned hydro-electric dam along the Batang-Toru-river is the greatest threat to the long term future of the Tapanuli orangutan. The hydro dam is planned in an area with the highest density of orangutans and highest biodiversity values of the whole ecosystem. Some 10% of the Tapanuli orangutans reside in the area. The construction of this hydrodam and related infrastructure, powerlines and associated land speculation will cause severe fragmentation of the rainforest and isolation of sub-populations of the Tapanuli orangutan, making them prone to extinction.


The southwest of the Batang Toru Ecosystem is threatened by a goldmine. The mining’s activities have dug away a whole mountain, which until recently was prime habitat for the Tapanuli orangutan. It further endangers the water supply of the surrounding communities, as it lies near the Sumatran rift valley, and had one of the highest density of earthquakes of Sumatra.


The company PT Teluk Nauli still owns has a licence to carry out logging in the Batang Toru Ecosystem, despite the fact that the area has been allocated as «protection forest» now. The company is not active anymore, but the threat of a «valid» license still looms, and the abandoned logging road from their logging activities in the 1990s has facilitated large scale encroachment.

Encroachment and poaching

Above all the forest is endangered by encroachment and poaching. From 2001 to 2010, almost 35 square kilometres of rainforest were cut down. Most of the clearing took place in areas that had already been declared as «protection forest» alongside an abandoned logging road and close to a goldmine.


Since 2005, we have been working with our local partner YEL to protect the Batang Toru Ecosystem. The following activities entail some of our efforts to protect the Batang Toru Ecosystem, and have been much to the benefit of the local communities and the endangered species residing in the forest, especially the Tapanuli orangutan.

Advocacy and Awarness building

We have worked many years with the district government to propose a status change from «production forest» to «protection forest» covering some 85% of the Batang Toru Ecosystem. Finally in 2014 the Forestry Department agreed to the status change. About 85% of the Batang Toru forest were placed under protection.
A great success! But unfortunately, some very sensitive and important areas are still not protected, like the canyon of the Batang Toru river in South Tapanuli. The primary forest in this area has the highest biodiversity of the entire Batang Toru Ecosystem and harbours the highest density of Tapanuli orangutans.

Forest boundary socialization

In cooperation with the local government, our local teams provide ongoing information events in the villages bordering the forest. A special focus is on the western border where immigrants from the island of Nias have settled in the protection forest and are opening up new lands. Specific socialization programmes have been held to inform these communitites of the protection status of the forest, the protected species, as well as the importance of the ecosystem. More than 100 information panels were strategically installed at key locations.

Socio-economic studies

PanEco/YEL in cooperation with the local partners carried out large scale socio-economic surveys interviewing more than 2800 people in 18 sub-districts around the Batang Toru forest. The survey aimed to evaluate in what way the ecosystem affects the lives of the local communities. The survey also showed that hunting is a serious threat to wildlife: 80% confirmed to go hunting in the forest.

Monitoring station

Since 2006 a monitoring station has been established in the west of the ecosystem. Scientists from many different local universities carry out research on the behaviour of the orangutan and the biodiversity in the forest.


The emphasis in our efforts in Batang Toru is to halt any further fragmentation of the Tapanuli orangutan populations and to work towards reconnecting their populations. This is essential to the species since there are about 800 apes left. We are working on the development of wildlife corridors.
Our aim is to help develop a fully functioning local Forest Management Unit that will protect the Batang Toru Ecosystem, its environmental functions and its amazing wildlife and Tapanuli orangutans for perpetuity!