The Lesser Sunda Islands consist of two geologically distinct archipelagos. The northern archipelago, which includes Bali, Lombok, Sumbawa, Flores and Wetar, is volcanic in origin. The islands of the southern archipelago, including Sumba, Timor and Babar, are non-volcanic
More than half of the original vegetation of the islands has been cleared for planting of rice and other crops, for settlement and by consequent forest fires. Only Sumbawa now contains a large area of intact natural forest, while Komodo, Rincah and Padar are now protected as Komodo National Park.
A number of the islands having original vegetation of dry forest rather than the rain forest that covers much of the Indonesian region, have been designated by the WWF as the Lesser Sundas deciduous forests ecoregion.