Millions of years of isolation from the mainland has given rise to a distinct flora and fauna, including many endemic species.

The central group includes Nancowry, Katchal, Kamorta, Teressa, Chowra, Tillangchong, and several smaller islets.

Great Nicobar is the largest (921 km2 (356 sq mi)), highest (Mount Thullier, 670 m), and southernmost island.

The Ten Degree Channel separates the Car Nicobar from the southernmost of the Andaman Islands 150 km north.

Heavier rainfall coincides ith the monsoon winds, which come from the southwest from May to September, and from the northeast between October and December.

Coastal forests feature widespread Indo-Pacific seashore plants, including the trees Barringtonia sp., Pandanus sp., and Casuarina equisetifolia, with the shrubs Scaevola frutescens, Hibiscus tiliaceus, and Clerodendrum inerme.

[4] The evergreen forests on Great Nicobar, Kamorta, and Katchal are dominated by the trees Calophyllum soulattri, Sideroxylon longipetiolatum, Garcinia xanthochymus, Pisonia excelsa, and Mangifera sylvatica, with Artocarpus peduncularis, Radermachera lobbi, Symplocos leiostachya, and Bentinckia nicobarica also present on Kamorta and Katchal.

[1] Some of the northern and central islands, including Car Nicobar, Kamorta, Katchall, and Nancowry, have extensive areas of grassland in the interior.

Typical species include the grasses Imperata cylindrica, Saccharum spontaneum, Heteropogon contortus, Chloris barbata, Chrysopogon aciculatus, and Scleria cochinchinensis, together with herbs and shrubs.

Areca triandra, Calamus andamanicus, Caryota mitis, Korthalsia laciniosa, Licuala peltata, and Pinanga manii are more widespread species native to the islands.

Large mammals include the wild boar (Sus scrofa) and Nicobar macaque (Macaca fascicularis umbrosa).

Most Nicobarese live in villages, and grow a variety of tree, root, and vegetable crops for food, fiber, and building materials, including coconut, areca palm, papaya, banana, breadfruit, jackfruit, and yams.

Pigs and chickens are kept for food, and wild fruits, roots, tubers, and fibers are gathered from the forests.

[4] Larger plantations of coconut have been established near the coast, and tapioca, sweet potato, sugarcane, and cashew are grown in the interior of the more populated islands.