The Tapanuli orangutan (Pongo tapanuliensis) is the rarest great ape species on Earth. Fewer than 800 individuals remain on the Indonesian island of Sumatra, where the species is declining further from deforestation and hunting. The apes are already split into three populations, and the proposed development of a hydroelectric dam on the river that connects these groups could obliterate the species.

The dam construction will increase deforestation, inundate tracts of land and generate 20 kilometres of access roads and 14 kilometres of transmission lines. This will render two of the ape populations non-viable. Although the Indonesian government is proposing mitigation measures, the scientific consensus is that nothing can offset the negative impacts on the species (see S. A. Wich et al. Conserv. Sci. Pract. http://doi.org/c5tx; 2019).

Indonesia seems to be facing a stark choice: a dam for energy security versus the survival of an ape species.