World's rarest ape threatened with extinction by hydroelectric dam

Creative Commons: Tim Laman

In 2017, scientists discovered a new species of orangutan living in the Batang Toru Forest of northern Sumatra. The exciting announcement of the new great ape was accompanied by fears of its survival. Only 800 Tapanuli orangutans remain in the wild, making it the smallest surviving great ape species population, with threats including illegal trade, hunting and habitat loss. But that hasn’t stopped the Indonesian government from approving a $1.6 billion hydroelectric power plant and dam right in the middle of the ape’s remaining habitat.

Researchers say the 510 megawatt dam will directly impact about 10-20% of the population, as its habitat is decimated to make way for the roads, electrical lines, an eight-mile-long tunnel, and other infrastructure that accompany the hydro project. Even more devastating than the immediate population loss is the fact that the power plant will form an impassible barrier through the orangutan’s home - permanently severing its eastern and western populations. Yet Sinohydro, the Chinese state-run company behind the dam is moving forward with forest clearing in the region, which is one of the most biodiverse spots in Indonesia, and home to such rare species as Sumatran tigers and the critically endangered Sunda pangolin.

Observers of the Tapanuli orangutan spent years trying to habituate a few of the species to their presence in the forest, a process that usually takes only a few weeks. Gabriella Fredriksson, a wildlife biologist with the Sumatran Orangutan Conversation Programme, says that orangutans are very wary due to their having been hunted by local people. In more than 3,000 hours of observations, scientists have never observed the Tapanuli orangutan stepping on ground - likely to avoid the endangered Sumatran tiger. Therefore, it took a long time to find a full skeleton to measure. That skeleton revealed significant differences from the other two species of orangutan living in area — such as a smaller skull — and is how researchers knew they’d found a new species. 

The estimated 800 remaining Pongo tapanuliensis are already split into three populations over a 420-square-mile area. Only one of these is considered large enough to remain viable, with just 500 individuals left. Further fracturing the population will seal their fate for extinction. In November, when the announcement of the new species was made, the Indonesian government signaled the protection of the great ape would be a priority. Yet, forest clearing continued. 

In July, scientists hand-delivered a letter to Indonesian President Joko Widodo, urging him to halt the hydropower project. Avaaz, a global activist organization, has over 1.2 million signatures on an online petition to cancel the project and protect the Tapanuli orangutan habitat. The disappearance of the Tapanuli orangutan would be the first extinction of a great ape – our closest relatives – since the Ice Age.

Last updated September 19, 2018

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