World’s newest great ape faces habitat loss, multiple threats: Will it survive?

World’s newest great ape faces habitat loss, multiple threats: Will it survive?

JAKARTA — When scientists made the bombshell announcement in 2017 that the Tapanuli orangutan (Pongo tapanuliensis) was a new species, the apes were immediately put under the global spotlight.

With fewer than 800 individuals surviving in a tiny tract of forest in the western part of Indonesia, scientists declared the Tapanuli orangutan as the rarest great ape as well as the most threatened great ape.

Within a month of its identification as a unique species, a report by the IUCN calculated the apes’ population had plummeted by 83% over the course of three generations.

The decline was attributed to killings by hunters or as a result of conflict with humans, along with habitat loss from agriculture and industrial development, including a gold mine and a planned hydroelectric plant.

So what does becoming the most endangered ape in the world overnight get you?

Apparently not much, according to Amanda Hurowitz, the senior director for Asia at U.S.-based campaign group Mighty Earth.

“Since it [the species] was described, not much has changed. You would think new species of orangutan, new species of great ape, the world would pull up its sleeves and decide to save it,” she told Mongabay. “Unfortunately, the Tapanuli orangutan face many of the same threats they did in 2017.

“So they’re really a species that we identified when they’re already on the brink, and unfortunately our actions have probably pushed them further to the brink of extinction,” Hurowitz said.

A numbers game

In its orangutan conservation action plan document published in 2019 (and later officially revoked) the government estimated that the number of Tapanuli orangutans ranges from 577 to 760 individuals.

In the same document, scientists projected 1.2% of Tapanuli orangutans would be lost in the next decade.

These apes survive in a tiny tract of forest, estimated to be 29,192 hectares (72,135 acres), about half the size of Chicago.

These forests are divided into three blocks — the west block, which the researchers calculated to house about 581 orangutans, the east block with 162 individuals and the south block with 24 individuals.


Map of the Batang Toru ecosystem, home to the Tapanuli orangutan (Pongo tapanuliensis) in Sumatra.
Map of the Batang Toru ecosystem, home to the Tapanuli orangutan (Pongo tapanuliensis) in Sumatra.

The government is currently in the process of updating the estimated Tapanuli orangutan population through a process called the orangutan population and habitat viability assessment (PHVA). The process was last conducted in 2019, but, like the action plan published that same year, the 2019 PHVA was officially revoked on orders from Indonesia’s Ministry of Environment and Forestry.

Hurowitz said numbers coming back from ongoing surveys are quite low. “It suggests that the population may unfortunately be declining further,” she said.

By contrast, Rudianto Saragih Napitu, the North Sumatra provincial wildlife conservation head, said the government had seen an increase in the number of orangutan nests in the region.

Therefore, he said the government believed the Tapanuli orangutan population is growing.

Government population estimates have recently been a subject of controversy, particularly after the government sanctioned foreign researchers who publicly questioned claims by officials that Indonesia’s orangutan populations are bouncing back.

Regardless of the survey results, Hurowitz said it’s important for the government to make the data of the Tapanuli orangutan population available to the public.

“In order to come up with a viable, comprehensive plan to protect the species, we need to understand where the populations are located and how ongoing development projects are impacting these subgroups,” she said. “Transparency is key to the scientific process.”

Hurowitz said this transparency could be achieved by putting the results of the surveys in the Ape Populations, Environments and Surveys (A.P.E.S.) database, an information service for great ape conservation and research built by the IUCN SSC Primate Specialist Group.

“I would hope the results of each of these surveys are put into the A.P.E.S. database so scientists from around the world can contribute their expertise in advising the government of Indonesia on how best to ensure the Tapanuli orangutan is not pushed further to extinction,” she said.

Land cleared as a staging area for the building of a new hydroelectric dam. New orangutan species discovered in Batang Toru, North Sumatra. They are on the brink of extinction due to a hydropower dam project. Image by Andrew Walmsley.
Land cleared as a staging area for the building of a new hydroelectric dam. New orangutan species discovered in Batang Toru, North Sumatra. They are on the brink of extinction due to a hydropower dam project. Image by Andrew Walmsley.

Hydropower plant threat

The main threat to these apes comes from a Chinese-backed hydropower plant, which is currently being built in the middle of the orangutan’s habitat in the forest of Batang Toru in northern Sumatra island, Hurowitz said.

The $1.6 billion project, part of the Chinese-backed Belt and Road Initiative, was meant to go into operation in 2022, but has been pushed to 2026 because of pandemic-related delays.

A 2021 study by Riverscope, a geospatial assessment tool for hydropower, estimated the project might be further delayed to 2034 due to social and environmental challenges.

Among the environmental challenges is the concern that the hydropower dam will jeopardize the connectivity between the orangutan’s three subpopulations — the west, east and south blocks.

“This is a dam that’s being built in an area that has the most dense population of Tapanuli orangutans before the project started,” Hurowitz said. “So the population is segmented into three different blocks. It will permanently separate these blocks. So the west, the east and the south will be permanently separated. And so it’s a dam that’s being built in an exact wrong place.”

This fragmentation would dramatically cut the diversity of the ape’s gene pool, leading to inbreeding, disease and the eventual extinction of each subpopulation.

PT North Sumatera Hydro Energy (NSHE), the hydropower developer, said the project has complied with standards set by the World Bank’s International Finance Corporation, including guidelines on biodiversity conservation.

To protect the orangutans, PT NSHE has established a consortium with Swiss-based NGO PanEco Foundation, which does research on orangutans in the Batang Toru area. Ian Singleton, the director of conservation at PanEco Foundation, said in 2020 the project’s impacts would be minimum as long as PT NSHE carried out all the necessary mitigation work.

However, a 2021 study on the population of the orangutan in the hydropower project’s area found the project’s construction had already resulted in the loss of potential orangutan habitat, with 371.68 hectares (918 acres) of the potential habitat cleared by 2019.

Some 87 ha (215 acres) were cleared for permanent constructions, while the remaining 285 ha (704 acres) were for temporary construction purposes. The researchers predicted this construction and deforestation would disturb the apes and change their behavior patterns.

But the orangutans could return to their original habitat once the construction was finished as long as their habitat was restored, corridors were created to facilitate orangutan movement and other potential threats such as human access was restricted, according to the study.

“Indeed, based on our research, there are some orangutans around the hydropower dam,” Wanda Kuswanda, a senior researcher at the applied zoology department of the National Research and Innovation Agency who co-wrote the study, told Mongabay. “I know that some orangutans have started to move to higher forest [because of construction activities].”

In 2018, for instance, the forestry ministry reported that the project’s construction work had driven a group of Tapanuli orangutans out of their habitat and into nearby plantations.

In 2019, a severely injured and malnourished orangutan was rescued in a plantation just 2.5 kilometers (1.55 miles) from the hydropower project site.

A malnourished and severely injured male Tapanuli orangutan in North Sumatra, Indonesia. Image courtesy of Orangutan Information Center (OIC).
A malnourished and severely injured male Tapanuli orangutan in North Sumatra, Indonesia. Image courtesy of Orangutan Information Center (OIC).

Construction work for the project is still ongoing. Indonesian state-owned explosives company PT Dahana is currently working on blasting out a 12.5-km (7.8-mi) main tunnel and 2.7 km (1.7 mi) of secondary tunnels that will channel water from the Batang Toru River to the turbines.

Nearby villagers have complained about loud blasts from the explosives used to build the tunnels, and they have also reported a recent increase in sightings of the Tapanuli orangutans since work on the dam began. The villagers said they believed the orangutans were disturbed by the construction and thus fled to local farms and settlements.

The Martabe gold mine in Batang Toru, North Sumatra, Indonesia. Image courtesy of Mighty Earth.
The Martabe gold mine in Batang Toru, North Sumatra, Indonesia. Image courtesy of Mighty Earth.

Gold mine threat

Another major threat to the Tapanuli orangutan is a gold mine located in the west block of the orangutan habitat, according to Hurowitz.

The Martabe gold mine was bought by U.K. conglomerate Jardine Matheson Holdings Ltd. (Jardines) in 2018 through its Indonesian subsidiary, Astra International, the largest conglomerate in the Southeast Asian country. The mine, in turn, is operated by an Astra International subsidiary, PT Agincourt Resources.

In recent years, Mighty Earth has detected deforestation within the mining concession, with 13 ha (32 acres) of forest loss in 2021 on top of the 100 ha (247 acres) of deforestation detected there from 2016 to 2020.

According to Mighty Earth, the vast majority of the most recent forest loss in the Martabe concession was detected within the habitat of the Tapanuli orangutans and areas mapped as high carbon stock (HCS) forest.

Mighty Earth said the detected forest loss indicates the mine operator is expanding its operations by clearing forest areas within the immediate vicinity of the Martabe processing plant.

According to Jardine’s document, the deforestation was necessary to safely develop the mine and its tailings management facility.

The mining company continued to clear 15 hectares (37 acres) of forest in 2022.

In a January 2023 statement, the company said in order to continue to operate the mine safely and responsibly, it will need to develop additional land this year. This work will include the construction of a new tailings management facility and an access road.

However, PT Agincourt Resources recently announced that it would reduce the volume of its gold production from the Martabe mine by around 10-20% in 2023 compared with 2022, which PT Agincourt Resources deputy president director Ruli Tanio told local media was necessary to allow the company to focus on long-term plans to mitigate environmental impacts and improve sustainability of the mine.

Given the fragility of the Batang Toru ecosystem and the Tapanuli orangutan habitat, Hurowitz said PT Agincourt Resources should stop expanding completely.

“We would hope that Jardines and the mine would follow international best practice like the Equator Principles and not develop or explore in any key biodiversity area,” she said.

An adult and juvenile Tapanuli orangutan, photographed in the Batang Toru ecosystem. Image by Andrew Walmsley.
An adult and juvenile Tapanuli orangutan, photographed in the Batang Toru ecosystem. Image by Andrew Walmsley.

Other threats

In addition to the hydropower dam and the gold mine, Hurowitz said there are other smaller-scale threats, including deforestation from community incursion for livelihood, such as planting food crops like palm oil and bananas in the east block.

A spatial analysis by the University of North Sumatra found that the expansion of agricultural plantations and settlements had driven much of the deforestation in the Tapanuli orangutan habitat from 2007 to 2020.

During that time, the habitat’s forest area decreased from 25,038 ha (61,870 acres) to 21,734 ha (53,705 acres).

At the same time, agricultural plantations like rubber and oil palm increased from 1,874 ha (4,631 acres) to 5,837 ha (14,423 acres) and settlements from 151 ha (373 acres) to 249 ha (615 acres).

This finding is in line with another 2021 study published in the journal PLOS ONE, which found that over the past 130 years, the Tapanuli orangutan had lost 97.5% of its original habitat. The study attributed this historical deforestation to smallholder agriculture and the expansion of industrial-scale plantations.

Another threat, Wanda said, is a new road planned by the government for east block of the orangutan habitat. “The road will separate the orangutan habitat in the east block with the remaining orangutans in the Dolok Sipirok Nature Reserve,” he said.

Julius Siregar, the head of the in situ conservation division at the Foundation for Sustainable Ecosystem (YEL), an NGO that runs an orangutan conservation program in Sumatra together with PanEco Foundation, said based on the map of the road that he had seen, the road will fragment forested ecosystems.

“If we look at the forest cover, they [the government] will actually clear forests which still have good forest cover,” he told Mongabay, adding that the forests are also home to other critically endangered species like the Sumatran tiger (Panthera tigris sumatrae).

Julius said he heard the construction of the road could start as soon as next year.

The Batang Toru River, the proposed power source for a Chinese-funded hydroelectric dam. Image by Ayat S. Karokaro/Mongabay-Indonesia.
The Batang Toru River, the proposed power source for a Chinese-funded hydroelectric dam. Image by Ayat S. Karokaro/Mongabay-Indonesia.

Conservation efforts

While the apes continue to face myriad threats, it’s not all doom and gloom with the Tapanuli orangutan, Wanda said.

He said efforts to protect the remaining apes had ramped up as attention toward the survival of the apes increased following its designation as a new species.

“I think the development in conservation has been very rapid in the last five years, with more organizations involved in conservation efforts,” Wanda said.

YEL, for instance, has been working to increase the awareness of local people on the importance of protecting the apes. Julius said the organization built learning centers at two villages in Batang Toru in 2021 and is working to develop alternative livelihood programs to discourage deforestation of orangutan habitat.

There are also efforts by various stakeholders to build corridors to connect the fragmented habitat of the orangutan, Julius said, with YEL and other NGOs conducting a study to determine where and how corridors could be created.

The private sector, including the gold mine and the hydropower dam, has also started to contribute to conservation efforts, he said.

PT Agincourt Resources, for instance, has rehabilitated 15.56 hectares (38.4 acres) of land as of 2021, and this year it plans to rehabilitate another 4.7 hectares (12 acres) of mining sites.

In the case of the hydropower dam, last year, the project’s developer planted 10,000 trees that could provide food and nesting places for the orangutans as a part of the company’s effort to rehabilitate lands that it no longer used.

The dam’s developer has also built arboreal wildlife bridges to allow the orangutan to travel between the fragmented populations.

Wanda said the effectiveness of all these conservation efforts still has to be measured.

“We don’t know if it’s effective or not, whether it can give a positive impact to the Tapanuli orangutan or not,” he said.

Hurowitz of Mighty Earth said while conservation efforts have already been put in place to protect the remaining apes, they are bogged down by lack of coordination and a comprehensive plan to tie all these efforts together.

“Really part of the issue is there really isn’t a plan,” she said. “So there are good things happening. There are some groups working on trying to change land designation and landscape-level planning. There are some groups working with communities. But unfortunately, there hasn’t really been a real coordinated effort between these multilayers of stakeholders, and the Tapanuli orangutans are the ones who lose out.”

So what does the future hold for Tapanuli orangutans?

Things could improve if a coordinated conservation approach is implemented successfully, Julius said.

“If we look at the current efforts by multiple parties, and if these efforts are in sync with each other with the same goal, then there should be improvement for the Tapanuli orangutan,” he said. “But if they still do their work separately, then things won’t change much. If we have the same goal, the local government supports and the locals agreed to give little space [for the orangutan], then I’m sure things will get better.”

But with how things are at the moment, Hurowitz said she’s not so sure the decline of the orangutan’s population and habitat will be reversed.

“It [the future] is not good. It’s possible that they will survive in the highlands where they’ve been. They prefer the lowlands, but they’ve managed to make a niche out of this area, so the west block is the most viable, and it’s possible that that population will survive,” she said. “But at the current rate, what scientists say is if more than eight adults are killed a year, the species will be on a path to extinction.”


Ekologi Orangutan (Pongo tapanuliensis). (2019). Retrieved from Kelompok Kerja Pengelolaan Lansekap Batang Toru website:

Prasetyo, D., Hadiprakarsa, Y., Kuswanda, W., & Sugardjito, J. (2021). Population status of Tapanuli orangutan (Pongo tapanuliensis) within the renewable energy development and its management implications. Forest and Society, 478-493. doi:10.24259/fs.v5i2.13529

Riverscope assessment: Batang Toru, Indonesia. (2021). Retrieved from TMP Systems website:

M. Asfa, I. A. (2022). Analisis Spasial Deforestasi pada Habitat Orangutan Tapanuli (Pongo tapanuliensis) di Kecamatan Batangtoru Menggunakan Citra Landsat. Retrieved from University of North Sumatra website:

Meijaard, E., Ni’matullah, S., Dennis, R., Sherman, J., Onrizal, & Wich, S. A. (2021). The historical range and drivers of decline of the Tapanuli orangutan. PLOS ONE, 16(1), e0238087. doi:10.1371/journal.pone.0238087

This article by Hans Nicholas Jong was first published by on 14 April 2023. Lead Image: Tapanuli Orangutans found near YEL’s orangutan study camp in the Batang Toru forest. Image by Aditya Sumitra/Mighty Earth.

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