Up to 1,500 chimpanzees could be killed by a new Chinese dam that will swamp a crucial sanctuary for the endangered primate in Guinea, experts have warned.

The 294MW Koukoutamba dam will be built by Sinohydro, the world’s biggest hydroelectric power plant construction company, in the middle of a newly declared protected area called the Moyen-Bafing National park.

The Chinese company is already facing similar criticism for building a dam in Indonesia that threatens the only known habitat of a newly discovered species of orangutan.

Its executives signed a contract this week with local representatives eager to secure a power project that will bring energy and funds to one of Africa’s poorest countries.

The flooding of swathes of the park is expected to force the displacement of 8,700 people. It will also increase the pressure on western chimpanzees, which have declined by 80% in the past 20 years, and are now considered critically endangered – the highest level of risk – by the International Union for Conservation of Nature.

The highlands of Guinea are home to Africa’s healthiest remaining population of about 16,500 western chimpanzees. In most other countries, this subspecies is either extinct or perilously threatened in populations of less than 100 individuals.

The Moyen-Bafing reserve was established in 2016 as a “chimpanzee offset” and funded by two mining companies – Compagnie des Bauxites de Guinée and Guinea Alumina Corporation – in return for permission to open mineral excavation sites inside other territories of the primate.

The Koukoutamba falls in Guinea on the Bafing river of Guinea-Conakry is home to newly discovered species of aquatic herb also endangered by the planning of a hydro-electric dam. Photograph: Kew Gardens

Rebecca Kormos, a primatologist who has been researching the animal for decades, has warned that a dam inside the park would have the biggest impact a development project has ever had on chimpanzees.

“I hope Sinohydro will reconsider engaging in a project that could drive the western chimpanzee into extinction. Once a species goes, it’s gone forever,” she said.

She estimates 800 to 1,500 chimpanzees will die as a result of the project, either by having their habitats flooded or as a result of territorial conflicts if they try to move.

The ape is not the only species at risk. Scientists have recently discovered a critically endangered aquatic herb near the Koukoutamba falls.

The plan for the dam is popular in Guinea. But conservationists say the local population is unaware that the electricity will not be generated for them. “This is not a case of the international community putting chimpanzees before people. Three-quarters of the energy will be sold to neighbouring countries and the remaining quarter is for the mining industry,” Kormos said.

Almost 150,000 people have signed petitions urging Guinea to halt the construction of the dam and adopt solar power, which the World Bank has offered to facilitate. If the dam goes ahead, conservationists say Sinohydro should engage with biologists to mitigate the impact.

Sinohydro did not respond to requests for comment.