Question

Why have the Western Ghats in India been considered as a biological hot spot?

Answer 1

Firstly, we need to know about the Biological Hotspot of Biodiversity Hotspot.
A biodiversity hotspot is a biogeographical region with important levels of biodiversity that's threatened by human habitation. The hill ranges of the Western Ghats is a global biodiversity hotspot or Biological Hotspot. It extends parallel the west coast of India, starting from the river Tapti in the north to the southern tip of India. Their location ensures that the Western Ghats are biologically rich and bio geographically unique.

Complete answer:
The Western Ghats is a hotspot of Biodiversity in India. It is a $1600$ km extended mountain range that runs parallel to the western coast of India. It is one of the eight “hottest” biological hotspots in the world in terms of their significance for biodiversity conservation efforts.
As one of the world’s “hottest biological hotspots” and a UNESCO World Heritage Site. It is on the conservation watch-list for being a rich but highly susceptible region in crucial need of biodiversity conservation efforts. In spite of the bad effects of human activity and climate change new species continue to be added to the widespread list of species that are recorded here including $36$ butterflies, $124$ reptiles, $189$ fishes, $69$odonates, $16$ birds, $16$ mammals, $159$ amphibians and $1,600$ flowering plants.

Additional Information:
Norman Myers wrote about the concept of Biodiversity Hotspot in two articles in “The Environmentalist” (in $1988$) and in $1990$ he revised after thorough analysis and others “Hotspots: Earth’s Biologically Richest and Most Endangered Terrestrial Ecoregions” and a research paper published in the journal called Nature.
To meet the criteria as a biological hotspot on Myers $2000$ edition of the hotspot-map a region surely meet two strict criteria: it must hold at least $0.5\%$ or $1,500$ species of vascular plants as endemics and it has to have lost at least $75\%$ of its preliminary vegetation. In the whole world there are $36$ areas that qualify under this definition. These sites sustain nearly $60\%$ of the world's bird, mammal, plant, reptile and amphibian species with a great share of those species as endemic. Some of these hotspots sustain up to $15,000$ endemic plants and some have lost up to $95\%$ of their natural habitat.

Note:
Biodiversity hotspots or Biological Hotspots host their diverse ecosystems on just $2.4\%$ of the planet's surface. Though the area that is declared as hotspots covers a much larger proportion of the land. The original $25$ hotspots covered $11.8\%$ of the surface area of land of the Earth. Overall the present hotspots cover more than $15.7\%$ of the surface area of the land. But they have lost around $85\%$ of their habitat. This loss of habitat clarifies why approximately $60\%$ of the world's terrestrial life lives on only $2.4\%$ of the land surface area.