Of the twenty-five hotspots of biodiversity, recognized in the world, two are found in India, which extend into the neighboring countries:
(i) The Indo-Burma region covering the Eastern Himalayas and (ii) the Western Ghats – Sri Lankan region.
The hotspots are rich in floral wealth, reptiles, amphibians, mammals and also in their endemism.
The botanical hotspots of India include:
(1) Western Ghats,
(2) North-East India,
(3) Himalayas and
(4) Andaman and Nicobar Islands (Table 19.3).
As compared to the Western Himalayas that are colder and drier, the Eastern Himalayan ranges are much wetter with suitable climatic conditions. This supports endemism and biodiversity. The Eastern Himalayas comprise of .parts of Nepal, Bhutan, Sikkim, Arunanchal Pradesh and extends up to Burma. The forest vegetation ranges from tropical rain forests to temperate alpine forests. Rhododendron is the dominant tree of this region.
The topography in the Eastern Himalayan region is quite varied that helps biodiversity and endemism. The rugged mountains and valleys support the virgin forests which are rich in many endemic plant species. In the Indian part of the Eastern Himalayan hotspot, about 5800 plant species are found of which around 2000 are endemic. Sikkim is one of the most blessed Indian states so far as endemism is concede; as of the 4250 plant species found there, 60% are endemic to the region.
Palaeobotanists consider the Indo-Burma region to be one of the centres of origin for the flowering plants (angiosperms). Many primitive angiosperm families occurring there, such as Magnoliaceae, Winteraceae, etc. support this contention. The Eastern Himalayas are home to around 8000 species of angiosperms of which nearly 40% are endemic. The characteristic floras are Rhododendron, Alnus, Betula, Magnolia, etc.
The animals include members of the goat family, antelopes, musk deer, snow leopard, brown bear, black bear and the red panda. Due to continuous habitat destruction and hunting, many of these species are highly endangered. Andaman and Nicobar Islands are rich in littoral and Island type floras. About 2500 species of flowering plants have been recorded from there, of which 250 species are endemic. The important hotspots of Andaman & Nicobar Islands are North Andaman, spike Island, Table Island. South reef Island, Little and Great Nicobars.
Western Himalayas are well-known for Alpine flora which abounds in Gymnosperms. Some 5000 species of flowering plants are known to occur in this region of which 800 species are endemic. The valley of flowers, Pithoragarh, Gori Valley, Mandal Chopta Valley, Karakoram and Laddakh are some of the major hotspots of this region.
The Western Ghats run parallel to the west coast of India and constitute more than 16,000 km strip of forests in the states of Maharashtra, Goa, Karnataka, Tamil Nadu and Kerala. Locally they are also known as the Sahyadris. The Western Ghats are characterised by low hills; however, it achieves the highest elevation of 2675 m at Annamalai up to an elevation of 500 m the forests are evergreen in nature, while the forests occurring between 500-1500 m altitude are of semi-evergreen type.
The Western Ghats by virtue of having a humid tropical climate and geological stability supports one of the most biodiversity rich areas of the country. According to an estimate, of the 17,000 flowering plants species reported from India, more than 4,500 occur in the Western Ghats region. The Botanical Survey of India has listed 518 endangered species endemic to Peninsular India, the majority of which occur in the Western Ghats.
The dominating plant families are Acanthaceae, Graminae, Orchidaceae, Rubiaceae, Labiatae, Compositeae and Leguminoseae. More than 200 species of rare orchids, many of them are endemic, are found in Western Ghats. Many economically important plants such as banana, rice, black pepper, ginger, etc. have spread to other parts of the country from here.
The Western Ghats are home to a rich variety of fauna which are unique and many are endemic to this region. Nilgiri Langur, Lion-tailed Macaque, tiger, leopard, elephant, rare species of tortoise and other amphibians represent the faunal wealth. Many varieties of birds and fishes are also found here.
These real hotspots of biodiversity are protected and worshiped by tribals due to religious sanctity. These are known as Devaskadu in Karnataka Devarahati in Maharashtra and Lakyntok in Meghalaya. These forests contain many rare endangered and endemic species.
Mangroves are salt tolerant forest ecosystems found in Saline habitat, tropical and subtropical intertidal zones near estuaries. The total area under mangrove vegetation in India is estimated to be 6740 km^ and of this 4200 km2 is covered by mangrove forest of sundarban alone and the second being in the Andaman & Nicobar Islands.