The Mahakam, one of Indonesia’s mightiest rivers, is home to endangered freshwater dolphins in Kalimantan. Conservation group Rare Aquatic Species of Indonesia (RASI) estimates their number at 80. Pollution from the mining industry and logging has been largely blamed for their endangerment. The Jakarta Post correspondent in Balikpapan, East Kalimantan, Nurni Sulaiman, recently joined researchers and activists on a three-week trip along the Mahakam River to monitor the animals’ degrading habitat and conservation efforts.

by Nurni Sulaiman

Sailing upstream from the provincial capital of Samarinda to Kutai Kartanegara, some 75 kilometers to the northwest, we passed countless vessels of all sorts. In Kalimantan, a vast but sparsely populated island, rivers are just like busy highways in the more developed Java. In downstream areas closer to the estuary, staggering coal-laden bulk carriers looked like clusters of floating hills from afar. Further upstream, in the area of Ulu in Kutai Kartanegara, vessels carrying mostly timber are headed for sawmills dotting the 980-km long river. Locals and researchers fondly remember sighting groups of dolphins along the Mahakam River from the upstream Kutai region down to the estuary in Samarinda. That was a few decades ago, when traffic on the river was light. Today, it is teeming with vessels of all sizes that environmentalists partly blame for the dwindling population of the treas...