A small brown line snakes its way through the rainforest in northern Sumatra, carving 300 metres through dense patches of meranti trees, oak and mahua. Picked up by satellites, the access road – though modest now – will soon extend 2km to connect with the Tor Ulu Ala pit, an expansion site of Indonesia’s Martabe mine. The road will help to unlock valuable deposits of gold, worth billions of dollars in today’s booming market. But such wealth could come at a steep cost to wildlife and biodiversity: the extinction of the world’s rarest ape, the Tapanuli orangutan.