Photograph by Andrew Walmsley
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Sumatra's Tapanuli orangutan is a new species of great ape that was identified in 2017. Just 800 of these extremely wary tree-dwelling apes remain in the wild, and a hydroelectric power plant and dam are being built in their remaining habitat.

Photograph by Andrew Walmsley

Hydroelectric Dam Threatens to Wipe Out World's Rarest Ape

A hydroelectric plant and dam, already in the works, could drive the newly identified Tapanuli orangutan to extinction.

The world’s rarest great ape, discovered only in 2017, will not survive the building of a $1.6 billion hydroelectric power plant and dam in the middle of its remaining habitat in Sumatra, Indonesia, wildlife experts warn.

Only 800 of the newly identified Tapanuli orangutans remain in the wild, all in northern Sumatra’s Batang Toru Forest. It’s one of the most biodiverse spots in Indonesia, home to such rare species as Sumatran tigers and the critically endangered Sunda pangolin.

In this same area, forest clearing has already begun for the hydro project, which is being financed and built by state-controlled Chinese companies under China’s Belt and Road. This multi-trillion-dollar initiative involves more than 7,000 infrastructure projects around the world.

It was less than a year ago when the world learned that a new great ape species had been discovered. Although researchers have studied it since 2005, it took them that long to definitely identify the Tapanuli orangutan as genetically and physically distinct from the Bornean (Pongo pygmaeus) and Sumatran orangutans (Pongo abelii), the other two species. (See: New species of orangutan Is rarest great ape on Earth)

Pleas and Protests

There is no way this project should be built where these tree-dwelling apes live, says Bill Laurance of the Centre for Tropical Environmental and Sustainability Science at Australia’s James Cook University. The dam and power plant—and all the associated roads, electrical lines, an eight-mile-long tunnel, and other infrastructure—will permanently fragment the animal’s habitat, Laurance says.

"They’re a critically endangered species and could rapidly go extinct with any further fragmentation of the primary forest," says Laurance, a world expert on the impacts of habitat fragmentation. "The science is solid on this. It’s lunacy to go ahead with this project."

A road is the same as an impassible wall to an exclusively arboreal, or tree-dwelling, species, Laurance says. Over the course of more than 3,000 hours of observations, scientists have never observed the Tapanuli orangutan (Pongo tapanuliensis) touching a foot to ground—likely because of the presence of the endangered Sumatran tiger.

It took years to habituate a few Tapanuli orangutans to observers’ presence in the forest, says Gabriella Fredriksson, a wildlife biologist with the Sumatran Orangutan Conservation Programme. Normally this takes a few weeks, but the orangutans are extremely wary, she says, likely because local people have hunted them. It also took a long time to find a full skeleton to measure. That revealed significant differences compared to the other two species, such as a smaller skull.

New Species of Orangutan Is Rarest Great Ape on Earth A new species of orangutan has been identified living on the island of Sumatra.

Pushed To The Brink

The estimated 800 apes are already split into three populations over a 420-square-mile area. Only one of these, with 500 individuals, is considered large enough to remain viable.

One problem for maintaining a population is that orangutans are extremely slow breeders. Females have their first offspring at around 15 years of age, giving birth to one or, more rarely, two individuals every eight to nine years. That’s one reason, Fredriksson says, why researchers have been trying for years to reconnect the three populations.

And now a hydropower dam is being built in the orangutans’ most critical habitat, an area with the highest densities of individuals. The state-owned area has no conservation or other protections. The dam will bring roads and other infrastructure permanently fragmenting the habitat of the one viable population of 500, and pushing the species towards extinction, Fredriksson says.

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Forest clearing has already begun for the Chinese-financed hydroelectric power plant and dam in Sumatra’s Batang Toru Forest highlands. Experts say the project will push the world’s rarest ape, the Tapanuli orangutan, into extinction.

North Sumatera Hydro Energy, the Indonesian company behind the project, has told Indonesian media that the hydro power plant won’t be in primary forest and that much of the 650 hectares of land disrupted will be returned to a near-original state. “These claims are ridiculous, and the company should be castigated for trying to confuse the public about the rock-solid scientific conclusions,” says Laurance. Both the World Bank’s International Finance Corporation and the Asian Development Bank refused to support the same project, largely on environmental grounds, he says.

The Batang Toru dam is scheduled to be operational in 2022, generating 510 megawatts of electricity. It involves blasting a tunnel eight miles long and more than 30 feet wide through a rugged region of primary forest. The dam is also unusual in that it will store water for 18 hours and then release this deluge for six-hour spans during peak periods to generate electricity. These sudden pulses of water will have big impacts on the Batang Toru river and downstream communities, such as flooding and halting migration of the highly valued “Jurung fish,” Fredriksson says.

Experts question the need for such a project. Not only does Sumatra currently have excess electricity production, there is a geothermal electricity project nearby that could be expanded without impacting orangutans, she says. Moreover, the dam is being built in a region prone to dangerous earthquakes, such as the 2016 Aceh temblor that killed 100 people.

Last July 25, scientists appealed directly in a hand-delivered letter to Indonesian President Joko Widodo to halt the hydropower project and protect the Tapanuli orangutan habitat. Avaaz, a global activist organization, has more than 1.2 million signatures on an online petition asking President Widodo to cancel the project in order to protect the orangutans.

“The fate of this entire species rests in your hands,” the message reads in part. Avaaz plans to do more to alert the world to what is happening in Sumatra, an organizer from the group says.

I think the government is starting to wake up to the issue,” Fredriksson says.