The most biodiversity rich area in India is

The correct answer is C) Western Ghats. The Western Ghats and Sri Lanka form one of the world's 36 biodiversity hotspots, and the Western Ghats was inscribed as a UNESCO World Heritage Site in 2012. Its combination of high species richness and high endemism, driven by the wet evergreen forests and the north-south mountain barrier, makes it the richest region in the country.

• A) Gangetic plain: Heavily cultivated and urbanised, with low natural forest cover and few endemic species. It is fertile, not biodiversity-rich.
• B) Trans Himalayas: Cold arid deserts such as Ladakh and Spiti. Species are few, though some are specially adapted, so this is a sparse rather than rich zone.
• D) Central India: Mostly dry deciduous teak forests. These are valuable but far less diverse and endemic than the Western Ghats.

Core concept: biodiversity richness is measured by species count and endemism, not by area or altitude. This links directly to GS-III on environment, conservation and protected areas, and to Western Ghats ecology in Mains answers on development versus conservation.

Trap: Aspirants often pick the Himalayas because they are the largest mountain system. Size and biodiversity are not the same thing.