The Nusa Tenggara (lit. Southeast Islands), or Lesser Sunda Islands, are a group of islands in the middle-south part of the Malay Archipelago. Together with the Greater Sunda Islands to the west they make up the Sunda Islands. The islands are part of a volcanic arc, the Sunda Arc, formed by subduction along the Java Trench.
The geology and ecology of Nusa Tenggara shares much similar history, characteristics and processes with the neighbouring Maluku Islands region. There is a long history of geological study of these regions since Indonesian colonial times, however, the geological formation and progression is not fully understood, and theories of the island's geological evolution have changed extensively in recent decades. Nusa Tenggara comprises some of the most geologically complex and active regions in the world. Biodiversity and its distribution in Nusa Tenggara is affected by various tectonic activities; most of the islands are geologically young being from 1 million to 15 million years old, and have never been attached to the larger landmassess.
The Nusa Tenggara islands differ from other areas in Indonesia; they contain some of the country's smallest islands, coral island reefs scattered through some of the deepest seas in the world, and no large islands such as Java or Sumatra. Flora and fauna immigration between islands is thus restricted, leading to the evolution of a high rate of endemic biota. The ecology of Nusa Tenggara has fascinated collectors for centuries; Alfred Wallace's famous book, The Malay Archipelago was the first significant recording of this natural history, and remains one of the most important sources on Indonesian natural history.
While many ecological problems affect both small islands and large landmasses, small islands suffer their particular problems and are highly exposed to external forces. Development pressures on small islands are increasing, although their effects are not always anticipated. Although Indonesia is richly endowed with natural resources, the resources of the small islands of Nusa Tenggara are limited and specialised; furthermore human resources in particular are limited.
General observations about small islands that can be applied to Nusa Tenggara include: