• IUCN Red List of Threatened Species, also called IUCN Red List, one of the most well-known objective assessment systems for classifying the status of plants, animals, and other organisms threatened with extinction. The International Union for Conservation of Nature (IUCN) unveiled this assessment system in 1994. It contains explicit criteria and categories to classify the conservation status of individual species on the basis of their probability of extinction.The IUCN system uses a set of five quantitative criteria to assess the extinction risk of a given species. In general, these criteria consider: 
  • The rate of population decline 
  • The geographic range 
  • Whether the species already possesses a small population size
  • Whether the species is very small or lives in a restricted area
  • Whether the results of a quantitative analysis indicate a high probability of extinction in the wild

Categories of IUCN Red List 

• Extinct (EX), a designation applied to species in which the last individual has died or where systematic and timeappropriate surveys have been unable to log even a single individual
• Extinct in the Wild (EW), a category containing those species whose members survive only in captivity or as artificially supported populations far outside their historical geographic range
• Critically Endangered (CR), a category containing those species that possess an extremely high risk of extinction as a result of rapid population declines of 80 to more than 90 percent over the previous 10 years (or three generations), a current population size of fewer than 50 individuals, or other factors 
• Endangered (EN), a designation applied to species that possess a very high risk of extinction as a result of rapid population declines of 50 to more than 70 percent over the previous 10 years (or three generations), a current population size of fewer than 250 individuals, or other factors
• Vulnerable (VU), a category containing those species that possess a very high risk of extinction as a result of rapid population declines of 30 to more than 50 percent over the previous 10 years (or three generations), a current population size of fewer than 1,000 individuals, or other factors
• Near Threatened (NT), a designation applied to species that are close to becoming threatened or may meet the criteria for threatened status in the near future
• Least Concern (LC), a category containing species that are pervasive and abundant after careful assessment 
• Data Deficient (DD), a condition applied to species in which the amount of available data related to its risk of extinction is lacking in some way. Consequently, a complete assessment cannot be performed. Thus, unlike the other categories in this list, this category does not describe the conservation status of a species 
• Not Evaluated (NE), a category used to include any of the nearly 1.9 million species described by science but not assessed by the IUCN.

Biodiversity Status of India 

• India is one of the recognized mega-diverse countries of the world, harbouring nearly 7-8% of the recorded species of the world, and representing 4 of the 34 globally identified biodiversity hotspots. India is also a vast repository of traditional knowledge associated with biological resources.
• Along with species richness, India also possesses high rates of endemism. In terms of endemic vertebrate groups, India’s global ranking is tenth in birds, with 69 species; fifth in reptiles with 156 species; and seventh in amphibians with 110 species. Endemic-rich Indian fauna is manifested most prominently in Amphibia (61.2%) and Reptilia (47%).
• India is also recognized as one of the eight Vavilovian centres of origin and diversity of crop plants, having more than 300 wild ancestors and close relatives of cultivated plants, which are still evolving under natural conditions. 
• 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 and semi-arid regions cover 38.8% of India’s total geographical area.
  • The cold arid zone located in the Trans-Himalayan region covers 5.62% of the country’s area. The region is the stronghold of three cat predators – the lion, leopard and tiger. Of the 140 species of known birds, the Great Indian Bustard is a globally threatened species. 
  • The flora of the Indian desert comprise 682 species, with over 6% of the total plant species being endemic. 
  • The cold desert is the home of rare endangered fauna, such as the Asiatic Ibex, Tibetan Argali, Wild Yak, Snow Leopard, etc., and the flora is rich in endemism and economically important species. 
• India has a variety of wetland ecosystems ranging from high altitude cold desert wetlands to hot and humid wetlands in coastal zones with diverse flora and fauna. About 4,445 km2 of the country is under mangroves. India is blessed with rich fish diversity that dwells in the inland waters. The major rivers of India and their tributaries traverse through varied geoclimatic zones, displaying high diversity in their biotic and abiotic characteristics throughout their 28,000 km linear drift.
• India has a vast coastline of 7,517 km, of which 5,423 km belong to Peninsular India and 2,094 km to the Andaman, Nicobar and Lakshadweep Islands, and an EEZ of 2.02 million km2 with a very wide range of habitats (e.g. estuaries, lagoons, mangroves, backwaters, salt marshes, rocky coasts, stretches and coral reefs, all of which are characterized by rich and unique biodiversity components). 
• Another crucial ecosystem for India is its forest, covering 23.39% of the geographical area of the country (of which 75% occurs in the north-eastern states) and counting over 16 major forest types and 251 sub-types. Against the global trend of deforestation, it is worth underlining the achievement made by India in stabilizing its area under forest cover over the years.
• The mountain ecosystems of India are largely described under two global hotspots, viz., the Eastern Himalaya, and the Western Ghats and Sri Lanka. They contribute prominently in geographic extent, biophysical and socio-cultural diversity and uniqueness. 
• As per the IUCN Red List version 2010.4, 94 species of mammals, 78 species of birds, 66 species of amphibians, 30 species of reptiles, 122 species of fish, 113 species of invertebrates and 255 species of plants in India are listed as Critically Endangered, Endangered and Vulnerable. So far, 758 animal and plant species are listed as globally threatened in India by IUCN, which is about less than 1% (i.e. 0.55%) of species documented in India.