Because of this species? association with riverine and coastal habitat, the major cause for its recent decline is thought to be habitat destruction. People favour these animals? habitats for logging, cultivation, and settlement. The planned land use for Central Kalimantan cited by E. Meijaard illustrates this tendency, with much of the riverine forest being marked for conversion. Clearing riverbanks and mangroves has a significant impact. Forest fires, especially those along the rivers, have a major impact on distribution. The 1997-1998 Bornean forest fires were thought to have destroyed the greatest proportion of remaining habitat of any primate in Kalimantan.

The species is relatively lethargic and easily hunted; with little effort entire populations can be hunted to extirpation. Opportunistic hunting of Nasalis larvatus for food occurs; the species is also hunted for bezoar stones, an intestinal secretion used in traditional Chinese medicine. Hunting has been felt most significantly in the Bornean interior, but is increasing in coastal areas (Meijaard and Nijman 2000).