Partula gibba is a tree snail species endemic to the Marianna Islands. This species has suffered major population and range declines in recent decades. Currently, it is threatened by invasive species and habitat loss. It was widespread and abundant in the early 20th century, but had declined by 1989. On Guam only one population survives, as is the case on Saipan. It is already extinct on Aguiguan, but its range has expanded on Sarigan due to habitat recovery following ungulate removal in 2000. On Pagan island a substantial population exists on the south of the island but is now potentially threatened by designation of the island as a live-fire site for military exercises. The species is assessed as Endangered based on its small area of occupancy (AOO = 16 km²), occurrence in four locations, and continuing decline in habitat quality.

The species is endemic to the Marianas islands, where it has been recorded from Guam to Pagan. Like many Partulids, it is vulnerable to threats from invasive species. It is now extinct on Aguiguan but populations survive on Guam, Saipan, Sarigan and Pagan (Gerlach 2016).

Historically, this species was highly abundant but now it is restricted to very small, isolated colonies of a few individuals on four separate islands.

This tree snail is found in wooded habitats where it occurs on trees and shrubs.

The main population crash is thought to have been caused by predation by the predatory Rosy Wolfsnail (Euglandina rosea). This predator has now been eliminated by the predatory New Guinea Flatworm (Platydemus manokwari), which also preys on Partula species. Invasive ants may also have some impacts. Habitat loss has contributed to declines on several islands. This has been due to development in some areas, but particularly to browsing by introduced goats and cattle. The best remaining populations are threatened by the designation of Pagan island as a military live-fire training ground.

Historically this species was exploited in enormous numbers for decoration (especially necklaces). Since the populations crashed in the 1970s there has been no record of exploitation.

This species has been bred in captivity but is currently not represented in conservation breeding programmes.