INDIA AS A MEGA DIVERSITY NATION

The term megadiverse country refers to any nation that harbours the majority of Earth's species and high numbers of endemic species.The UNEP (United Nations Environment Programme) has recognised 17 Megadiversity Nations across the world. India is one among them due to its commendable diversity of organisms. 

India has 4 out of 34 globally identified  Biodiversity Hotspots (Himalaya, Western Ghats, Indo-Burma, and Srinlanka- Sundaland). India has wide range of habitats- The varied edaphic, climatic and topographic conditions and years of geological stability have resulted in a wide range of ecosystems and habitats such as forests, grasslands, wetlands, deserts, and coastal and marine ecosystems. Arid, semi- arid and desert regions occupy 38.8% of India's land mass with 682 species of which 6% is endemic. This area is also rich with cat type predators- Lion, Leopard and Tiger. The Great Indian Bustard is a threatened bird living in this habitat. 

The cold Himalayan region covers 5.8% of the geographical area. The cold desert also harbors endangered species such as snow leopard, yak and Asiatic ibex.  

India has a good collection of wetland habitats as well with about 4500 square kilometers of Mangrove ecosystem. The fish and bird diversity is high in such regions.  We have 783 fresh water fishes, of which 223 are endemic. India has good fish diversity and the country is one of the largest fish producers of the world. 

India has a lengthy coastal habitat of 7500 kilometers, with diverse habitats like estuaries, lagoons, backwaters, salt marshes and coral reefs. These habitats are also rich in species diversity.

India has diverse forest habitats, consisting of 23.5% of total land mass of which 75% are located in North East states India. India has 16 major forest types. The mountain ecosystem of India consists of forest ecosystems. Western Ghats and Eastern Himalayas are rich in diversity of species with 40% of endemism. 

Considering the major categories of life forms, India has the following diversity:

Animals

1. Protists- 2577 (out of 31,200 in the world)
2. Mollusca- 5070 (out of 81,000)
3. Arthropoda - 68300 ( out of 9,90,000)
4. Fishes- 2546 (out of 30,000)
5. Amphibia- 209 (out of 6200)
6. Reptiles- 456 (out of 8200)
7. Birds- 1232 (out of 9900)
8. Mammals- 390 (out of 5490)

Plants (As per 2007 data)

1. Algae- 6500 (out of 40,000)
2. Bryophytes - 2825 (out of 17000)
3. Pteridophytes- 1200 (out of 13000)
4. Gymnosperms- 48 (out of 980)
5. Angiosperms- 18000 (out of 2,50,000)

Microbes

1. Bacteria- 850 (out of 8500)
2. Fungi- 14500 (out of 72000)
3. Virus- 1200 (out of ????? not estimated) as per 2019 data
4. Lichens - 2000 (out of 35000)