The central part of the ecoregion lies in the trade wind belt, and receives the highest rainfall, up to 3000 mm annually.

Forests nearer the shore are of short to medium stature, with the trees Heliotropium arboreum, Guettarda speciosa, Pisonia grandis, Pandanus tectorius, Allophylus timoriensis, Cordia subcordata, Hernandia nymphaeifolia, and Thespesia populnea.

The mature Ochrosia and Pisonia forests form a dense canopy, and little grows in the shady understory.

[1] On drier islands and in areas exposed to salt spray, vegetation includes low grasses and beach creepers, coastal scrub, and low-canopied mixed forests.

The Insular flying fox (Pteropus tonganus) and Pacific sheath-tailed bat (Emballonura semicaudata) are the only native non-marine mammals.