The Himalayan Range is very rich in species diversity. Which one among the following is the most appropriate reason for this phenomenon?

Answer: (b) It is a confluence of different biogeographical zones

The Himalaya is where the Indo-Malayan, Palaearctic and Sino-Japanese realms meet, and its altitude adds tropical-to-alpine belts in a short distance.

The idea

The Himalaya stands where several great natural regions of plants and animals meet: the cold lands of Central Asia and Europe to the north and west, tropical South-East Asia to the east, and the Indian peninsula to the south. Species from all of them live here. Height then stacks many climates one above another.

Foothills: sal forest → Lower hills: chir pine and oak → Higher: deodar, fir, spruce → Near the tree line: birch and rhododendron → Above: alpine meadows (bugyals) → Top: snow

Why the others are wrong

(a) Much of the western Himalaya is dry, yet still species-rich — rain alone doesn’t explain it.

(c) Invasives like Lantana have spread widely in the Himalaya.

(d) The Himalaya has heavy human use — terraces, grazing, roads.

The trap

(d) is a common assumption about mountains. The Himalaya is not untouched.

Also know

The eastern Himalaya is wetter and richer in species than the western. India is divided into ten biogeographic zones, of which the Himalaya and the Trans-Himalaya are two.