The islands of Wallacea are home to a mix of plants and animals from both terrestrial realms, and have many unique species that evolved in isolation.

[citation needed] The islands are mostly mountainous, and Tatamailau on Timor is the highest point at 2986 meters elevation.

Evergreen and semi-evergreen rain forests occur in high-rainfall areas on the south side of the island.

Extensive burning for shifting cultivation, grazing by goats and other livestock, and tree harvesting has reduced much of the island to anthropogenic grassland and scrub, including many invasive exotic shrubs.

[10] Sandalwood (Santalum album) and candle nut (Aleurites moluccanus) are important tree crops harvested from the wild.

Two species were believed to have been brought to the islands long ago by humans – the Northern common cuscus (Phalanger orientalis), a marsupial originating in New Guinea, and the Javan rusa (Rusa timorensis), a deer originating in Java and Bali.

Fossils of two species of Stegodon, an elephant relative, have been found on Timor, the most recent approximately 130,000 years old.