[1][3] The islands are volcanic in origin, formed as the Pacific Plate moved west-northwest over a geologic hotspot.

Makatea was created when the islands were uplifted to expose ancient coral reefs, and often forms rough and uncultivable terrain.

Tubuai has two central peaks which rise above 400 meters, and are surrounded and separated by makatea at lower elevations.

The island was geologically uplifted, creating a continuous makatea rim along the shore that reaches 50 to 60 meters high.

Raivavae is an heavily eroded extinct volcano with a central peak (Hiro, 438 meters), with makatea outcrops along the shore, and surrounded by a lagoon and encircling barrier reef.

[1] Montane forests on Tubuai include the trees Metrosideros collina, Aleurites moluccanus, Celastrus vitiensis, Myrsine spp., Ixora spp., Psychotria spp., Cantium barbatum, and Charpentiera australis, along with the tree fern Sphaeropteris medullaris and the large fern Angiopteris.

[1] The lowland forests on the main high islands have mostly been destroyed by conversion to agriculture, anthropogenic fires, and uncontrolled grazing by introduced goats, pigs, cattle, and horses.

Outside cultivated areas, secondary vegetation includes thickets of Hibiscus tiliaceus with introduced orange trees and common guava (Psidium guajava), Dicranopteris linearis fernlands, and grasslands.

On Tubuai Falcataria falcata, Furcraea foetida, Hedychium flavescens, Lantana camara, Leucaena leucocephala, Melia azedarach, Merremia peltata, Psidium guajava, and Syzygium cumini are naturalized, and Melinis minutiflora, Paspalum conjugatum, Psidium cattleianum, Rubus rosifolius, Stachytarpheta urticifolia, Syzygium jambos, and Tecoma stans are considered invasive.

Psidium cattleianum or Chinese guava covers many mountain ridges on Tubuai, the former habitat of Charpentiera australis and other native species.

[3] Brown rats (Rattus norvegicus) were introduced to some of the islands by humans, and have decimated some of the local birds, including Kuhl's lorikeet.