Nepenthes fusca is listed as Vulnerable on The IUCN Red List of Threatened SpeciesTM. This carnivorous pitcher plant is widespread in mountain habitats on the island of Borneo. It is not certain what prey this species catches, however, it almost certainly traps a variety of small insects, such as ants and flies, and the occasional spider or cockroach. These insects provide the plant with supplementary nutrients that are scarce in its habitat, such as nitrogen and phosphorous.
The primary threat to Nepenthes fusca appears to be habitat destruction, as large tracts of montane forest in Borneo have been cleared or disturbed over the last 20 to 30 years. Although some Nepenthes species are threatened by the illegal collection of plants from the wild, this species is of limited interest to enthusiasts of the genus. Furthermore, Nepenthes fusca generally grows as a non-parasitic epiphyte (i.e., uses another plant for support) in the canopy of montane rainforests, which means that most sub-populations are beyond the reach of plant poachers.
Nepenthes fusca is not currently the subject of any dedicated conservation measures, but several sub-populations occur in well-managed conservation areas in Borneo.