BharatNotes
Biogeographic Classification of India
India's extraordinary biodiversity is shaped by its location at the junction of three biogeographic realms (Palearctic, Indo-Malayan, and Afrotropical), its diverse physiography (from sea level to 8,000+ m), and its climatic range (tropical to arctic). Rodgers and Panwar (1988) of the Wildlife Institute of India (WII) classified India into 10 biogeographic zones and 27 biogeographic provinces for systematic biodiversity conservation and planning of the protected area network.
The 10 Biogeographic Zones of India
| Zone | Key Features | Representative Fauna |
|---|---|---|
| 1. Trans-Himalayan | Cold desert, high plateau (Ladakh, Spiti, Lahaul); arid with sparse vegetation; altitude 3,000-6,000+ m | Snow leopard, Tibetan wild ass (kiang), black-necked crane, Tibetan wolf |
| 2. Himalayan | Ranges from subtropical foothills to alpine meadows; altitudinal zonation of vegetation; includes Western, Central, and Eastern Himalayas | Kashmir stag (hangul), musk deer, red panda, Himalayan tahr, Western tragopan |
| 3. Desert | Thar Desert (Rajasthan, Gujarat); hot and arid; sand dunes, scrub vegetation | Great Indian bustard, Indian wild ass (khur), chinkara, desert fox |
| 4. Semi-Arid | Transition between desert and wetter zones; thorny scrub, dry deciduous forests; Punjab, Haryana, parts of Rajasthan, Gujarat | Blackbuck, Indian gazelle, wolf, lesser florican |
| 5. Western Ghats | Ancient mountain chain along western coast; tropical evergreen to montane grasslands; one of the world's richest biodiversity hotspots | Lion-tailed macaque, Nilgiri tahr, Malabar giant squirrel, purple frog |
| 6. Deccan Plateau | Peninsular India; dry and moist deciduous forests; relatively flat terrain | Tiger, Indian leopard, sloth bear, dhole, Indian giant squirrel |
| 7. Gangetic Plain | Indo-Gangetic alluvial plain; highly fertile, densely populated; remnant grasslands and wetlands | Gangetic dolphin, gharial, one-horned rhinoceros (terai), Bengal florican |
| 8. North-East | India's most biodiverse region; dense tropical and subtropical forests; high rainfall; part of Indo-Burma hotspot | Hoolock gibbon, clouded leopard, golden langur, Namdapha flying squirrel |
| 9. Coastal | West and East coasts; mangroves, lagoons, estuaries, coral reefs; Sundarbans, Gulf of Mannar, Gulf of Kutch | Olive Ridley turtle, saltwater crocodile, dugong, Irrawaddy dolphin |
| 10. Islands | Andaman & Nicobar (Bay of Bengal) and Lakshadweep (Arabian Sea); unique island ecosystems; high endemism | Narcondam hornbill, Nicobar pigeon, Andaman wild pig, dugong, leatherback turtle |
Prelims Fact: Rodgers and Panwar (1988) of WII classified India into 10 biogeographic zones and 27 provinces. This classification is widely used in UPSC questions on protected area planning and biodiversity conservation.
Biodiversity Hotspots in India
India is home to four of the world's 36 biodiversity hotspots. A region qualifies as a hotspot if it contains at least 1,500 endemic plant species and has lost 70% or more of its original habitat.
The Four Hotspots
| Hotspot | Geographic Extent in India | Key Statistics |
|---|---|---|
| Western Ghats | 1,600 km from Gujarat to Tamil Nadu (Kerala, Karnataka, Goa, Maharashtra) | UNESCO World Heritage Site; ~7,402 plant species (24 endemic genera); ~508 bird species (29 endemic); 131 amphibian species (114 endemic — 87%); 227 reptile species (107 endemic); 137 mammal species (16 endemic) |
| Eastern Himalayas | NE India (Arunachal Pradesh, Sikkim, NE states), Bhutan, southern Tibet | ~10,000 plant species (3,160 endemic); 163 globally endangered species; includes one-horned rhinoceros, wild Asian water buffalo |
| Indo-Burma | NE India (Manipur, Mizoram, Nagaland, southern Assam), Myanmar, mainland SE Asia | Exceptionally rich in freshwater species; endemic turtles, freshwater fish; Hoolock gibbon range |
| Sundaland | Andaman & Nicobar Islands (in the Indian context); extends to Malay Peninsula, Sumatra, Borneo | 25,000 vascular plants (15,000 endemic); 380 endemic bird species across the full hotspot; A&N Islands contribute unique endemic fauna |
Endemism Levels in the Western Ghats
| Taxon | Total Species | Endemic Species | Endemism % |
|---|---|---|---|
| Flowering plants | ~5,000 | ~1,700+ | ~34% |
| Trees | ~650 | ~351 | ~54% |
| Amphibians | ~131 | ~114 | ~87% |
| Reptiles | ~227 | ~107 | ~47% |
| Freshwater fish | ~290 | ~154 | ~53% |
| Mammals | ~137 | ~16 | ~12% |
For Mains: The Western Ghats have the highest amphibian endemism rate (~87%) of any region in India. The purple frog (Nasikabatrachus sahyadrensis), discovered only in 2003, is a living fossil that diverged from its closest relative over 100 million years ago. Such discoveries highlight how much remains undocumented in Indian biodiversity.
Flora Distribution — Forest Types by Region
India's forest classification follows the Champion and Seth (1968) system, which identifies 16 major forest types and over 200 sub-types based on climate, soil, and altitude.
Major Forest Types and Their Distribution
| Forest Type | Region | Key Features |
|---|---|---|
| Tropical Wet Evergreen | Western Ghats (Kerala, Karnataka), NE India (Assam, Meghalaya, Arunachal Pradesh), A&N Islands | Rainfall >250 cm; dense, multi-layered canopy; rosewood, ebony, mahogany; no distinct dry season |
| Tropical Semi-Evergreen | Western Ghats transition zone, NE India | Rainfall 200-250 cm; some deciduous species mixed; laurel, teak |
| Tropical Moist Deciduous | Along Western Ghats eastern slopes, Central India (MP, Chhattisgarh, Odisha, Jharkhand) | Rainfall 100-200 cm; teak, sal, bamboo; trees shed leaves in dry season |
| Tropical Dry Deciduous | Peninsular India, Rajasthan, UP, Bihar, MP | Rainfall 70-100 cm; teak, sal, tendu; open canopy; most widespread forest type in India |
| Tropical Thorn | Rajasthan, Gujarat, parts of Haryana, Karnataka | Rainfall <70 cm; thorny bushes, xerophytic plants; babool, khejri, date palm |
| Montane Subtropical | Outer Himalayas (1,000-2,000 m), NE hills | Wet hill forests (Shillong, Cherrapunji); chir pine forests |
| Montane Temperate | Himalayas (1,500-3,000 m) | Oak, deodar, chestnut, spruce, fir; distinct seasonal variation |
| Sub-Alpine and Alpine | Himalayas (3,000-5,000 m) | Juniper, birch, rhododendron; alpine meadows (bugyal); treeline at ~3,500-4,000 m |
| Mangrove | Sundarbans (WB), Gulf of Kutch, A&N Islands, Bhitarkanika (Odisha), Pichavaram (TN) | Saltwater-tolerant trees; Rhizophora, Avicennia, Sonneratia; critical coastal buffer |
| Littoral and Swamp | Coastal areas, deltas, backwaters | Casuarina along coasts; freshwater swamp forests in Assam |
Fauna Distribution — Major Species by Zone
Mammals — Key Species by Region
| Region | Key Species | Conservation Status (IUCN) |
|---|---|---|
| Trans-Himalaya | Snow leopard | Vulnerable |
| Western Himalaya | Kashmir stag (hangul) | Critically Endangered; ~289 individuals (2023 census); 275 in Dachigam, 14 in Tral; expected to cross 300 in 2025 census |
| Eastern Himalaya | Red panda | Endangered |
| NE India | Hoolock gibbon (India's only ape) | Endangered |
| Western Ghats | Lion-tailed macaque | Endangered; ~3,000-3,500 individuals; no subpopulation exceeds 250 |
| Western Ghats | Nilgiri tahr | Endangered; 2,668 individuals (2025 census — 1,365 in Kerala, 1,303 in Tamil Nadu); largest population at Eravikulam NP (841) |
| Gangetic Plain | One-horned rhinoceros | Vulnerable; ~4,000+ individuals, mostly in Kaziranga NP |
| Thar Desert | Great Indian bustard | Critically Endangered; ~150 individuals remaining |
| Deccan | Indian pangolin | Endangered |
| Coastal | Dugong | Vulnerable; found in Gulf of Mannar, Palk Bay, A&N |
| Islands (A&N) | Narcondam hornbill | Vulnerable; 300-650 mature individuals, found only on Narcondam Island |
Prelims Fact: The Kashmir stag (hangul) is Critically Endangered with ~289 individuals (2023 census), primarily in Dachigam NP. The Nilgiri tahr population was recorded at 2,668 in the 2025 census. The lion-tailed macaque is Endangered with 3,000-3,500 individuals.
Birds — Endemic and Iconic Species
| Species | Region | IUCN Status | Significance |
|---|---|---|---|
| Great Indian bustard | Thar Desert (Rajasthan, Gujarat) | Critically Endangered | India's most threatened bird; only ~150 remaining; power line collisions a major threat |
| Jerdon's courser | Andhra Pradesh (Sri Lankamalleshwara WS) | Critically Endangered | Nocturnal; rediscovered in 1986 after being thought extinct since 1900 |
| Western tragopan | Western Himalayas (HP, J&K) | Vulnerable | State bird of Himachal Pradesh; found in dense forests at 2,400-3,600 m |
| Nicobar pigeon | A&N Islands | Near Threatened | Closest living relative of the extinct dodo |
| Narcondam hornbill | Narcondam Island (A&N) | Vulnerable | Found only on a single volcanic island of 6.8 sq km |
| Malabar pied hornbill | Western Ghats | Near Threatened | Key seed disperser in evergreen forests |
Faunal Regions — Oriental Realm
India lies primarily within the Oriental (Indo-Malayan) biogeographic realm, with the Trans-Himalayan region forming a transition to the Palearctic realm.
Wallace's Line and Faunal Boundaries
| Boundary | Significance |
|---|---|
| Wallace's Line | Separates Oriental and Australasian realms (between Borneo/Bali and Sulawesi/Lombok) — not in India but defines the eastern limit of India's faunal affinities |
| Himalayan barrier | Separates Oriental fauna (south) from Palearctic fauna (north); the highest biogeographic barrier on Earth |
| Palearctic influence | Trans-Himalayan zone (Ladakh, Spiti) has Palearctic fauna — Tibetan wild ass, snow leopard, Tibetan wolf, black-necked crane |
| Indo-Malayan affinity | NE India and A&N Islands show strong Southeast Asian faunal links — Hoolock gibbon, slow loris, hornbills, flying squirrels |
| African/Ethiopian affinity | Western Ghats show ancient Gondwanan connections — purple frog, caecilians, Nilgiri tahr share evolutionary links with African species |
Altitudinal Zonation — Tropical to Alpine
The Himalayas display a remarkable altitudinal gradient of vegetation and fauna, compressing multiple biomes into a short horizontal distance.
| Zone | Altitude | Vegetation | Fauna |
|---|---|---|---|
| Tropical | Up to 1,000 m | Sal, teak forests; bamboo | Tiger, elephant, deer, monkeys |
| Subtropical | 1,000-2,000 m | Chir pine, oaks; wet hill forests | Leopard, barking deer, kalij pheasant |
| Temperate | 2,000-3,000 m | Deodar, blue pine, spruce, fir; broad-leaved oaks and rhododendrons | Musk deer, Himalayan black bear, monal pheasant |
| Sub-Alpine | 3,000-3,500 m | Birch, juniper; rhododendron scrub; transition to grasslands | Snow leopard (lower range), Himalayan tahr, blood pheasant |
| Alpine | 3,500-5,000 m | Alpine meadows (bugyals); mosses, lichens; dwarf shrubs | Snow leopard, blue sheep (bharal), pika, Himalayan marmot |
| Nival/Glacial | Above 5,000 m | Virtually no vegetation; snow, ice, bare rock | Sporadic — snow leopard (transient), some insects and microorganisms |
For Mains: The concept of altitudinal zonation is analogous to latitudinal zonation — ascending 1,000 m in the Himalayas is roughly equivalent to travelling 1,000 km northward at sea level. This makes the Himalayas a critical refuge during climate change — species can migrate upward, but only if corridors are intact. Discuss the implications for conservation.
Island Biogeography — Andaman & Nicobar and Lakshadweep
Andaman & Nicobar Islands
| Feature | Detail |
|---|---|
| Location | Bay of Bengal; ~572 islands (37 inhabited) |
| Biogeographic affinity | Southeast Asian (Indo-Malayan); part of Sundaland hotspot |
| Total species | ~9,130 animal species recorded |
| Endemic species | 1,032 species are endemic (11.3% of total) — including 576 endemic insect species, 88 land molluscs, 78 birds, 29 reptiles, 19 mammals, 10 arachnids |
| Endemic birds | 28 endemic bird species/subspecies — including Narcondam hornbill, Andaman woodpecker, Andaman crake, Andaman teal |
| Marine biodiversity | Coral reefs, dugong habitat, nesting beaches for leatherback, hawksbill, green, and olive Ridley turtles |
| Threats | Habitat loss from infrastructure projects (Great Nicobar mega-project), invasive species (feral elephants, spotted deer), poaching |
| Protected areas | Mahatma Gandhi Marine NP, Rani Jhansi Marine NP, Saddle Peak NP, Campbell Bay NP |
Lakshadweep Islands
| Feature | Detail |
|---|---|
| Location | Arabian Sea; 36 islands (10 inhabited); coral atolls |
| Biogeographic affinity | Limited terrestrial biodiversity due to small size; rich marine biodiversity |
| Marine life | Coral reefs (atoll ecosystem); reef fish, sea turtles, dolphins, whale sharks |
| Vegetation | Coconut palms dominant; limited native forest; some mangroves |
| Threats | Coral bleaching due to rising sea temperatures; sea-level rise; waste management challenges |
Island Biogeography Theory (MacArthur and Wilson, 1967)
| Principle | Application to Indian Islands |
|---|---|
| Species-area relationship | Larger islands (Great Nicobar, South Andaman) have more species than smaller islands |
| Distance effect | Islands closer to mainland (A&N to Southeast Asia) have more species than remote islands (Lakshadweep) |
| Equilibrium theory | Species number reflects balance between immigration and extinction rates |
| Endemism | Long isolation (A&N separated from mainland for millions of years) drives speciation — hence high endemism |
Prelims Fact: The A&N Islands harbour 1,032 endemic species (11.3% of their total fauna). The Narcondam hornbill is found only on Narcondam Island (6.8 sq km). The Nicobar pigeon is the closest living relative of the extinct dodo.
Threats to India's Biogeography
| Threat | Impact | Examples |
|---|---|---|
| Habitat loss | Deforestation, urbanisation, infrastructure — primary driver of biodiversity loss | Western Ghats: 60%+ of original habitat lost; NE India: shifting cultivation + plantations |
| Invasive species | Outcompete native species, alter ecosystems | Lantana camara (nationwide); water hyacinth (wetlands); spotted deer and elephants (A&N Islands) |
| Climate change | Species range shifts, phenological mismatches, coral bleaching | Treeline shifting upward in Himalayas; coral bleaching in Gulf of Mannar and Lakshadweep |
| Overexploitation | Poaching, overfishing, unsustainable harvesting | Tiger poaching; shark finning; overharvest of medicinal plants in Himalayas |
| Pollution | Pesticides, industrial effluents, plastic | Vulture decline from diclofenac; Ganga and Yamuna pollution affecting aquatic species |
| Linear infrastructure | Roads, railways, power lines fragment habitats | NH-44 through tiger corridors; power lines killing Great Indian bustards |
| Human-wildlife conflict | Elephant-human conflict (Kerala, Assam), leopard-human (Maharashtra), tiger-human (Sundarbans) | ~500 humans and ~100 elephants killed annually in conflict situations |
Conservation Framework — Protected Areas by Biogeographic Zone
| Zone | Notable Protected Areas |
|---|---|
| Trans-Himalayan | Hemis NP (Ladakh — largest NP in India), Changthang Wildlife Sanctuary |
| Himalayan | Great Himalayan NP (HP — UNESCO), Dachigam NP (J&K — hangul), Nanda Devi BR |
| Desert | Desert NP (Rajasthan — GIB habitat), Wild Ass Sanctuary (Little Rann of Kutch) |
| Semi-Arid | Ranthambore NP, Sariska TR, Tal Chhapar (blackbuck) |
| Western Ghats | Silent Valley NP (Kerala), Periyar TR, Bandipur NP, Kudremukh NP |
| Deccan Plateau | Panna NP (diamond mine conflict), Satpura NP, Nagarjunasagar-Srisailam TR |
| Gangetic Plain | Kaziranga NP, Manas NP, Dudhwa NP, Corbett NP |
| North-East | Namdapha NP (Arunachal — highest diversity), Keibul Lamjao NP (Manipur — only floating NP) |
| Coastal | Gulf of Mannar Marine NP, Sundarbans NP, Bhitarkanika WS, Chilika (Ramsar) |
| Islands | Campbell Bay NP, Saddle Peak NP, Mahatma Gandhi Marine NP |
Tiger Reserves by Region
| Region | Tiger Reserves (Selected) | Tiger Population (2022 Census) |
|---|---|---|
| Central India | Kanha, Pench, Bandhavgarh, Satpura, Panna | ~1,050+ |
| Western Ghats | Periyar, Bandipur, Nagarahole, Bhadra, Wayanad | ~800+ |
| NE India | Kaziranga, Manas, Nameri, Orang | ~200+ |
| Shivalik-Terai | Corbett, Rajaji, Dudhwa, Valmiki | ~600+ |
| Sundarbans | Sundarbans TR | ~100 |
| All India Total | 56 Tiger Reserves | 3,682 (2022 census — 6.7% increase from 2018) |
Biosphere Reserves of India
India has 18 Biosphere Reserves, of which 12 are part of the UNESCO World Network of Biosphere Reserves. Biosphere reserves integrate conservation with sustainable development through a three-zone structure.
Three-Zone Structure
| Zone | Purpose |
|---|---|
| Core zone | Strictly protected; no human activity; equivalent to a national park or wildlife sanctuary |
| Buffer zone | Surrounds the core; limited human activity — research, education, eco-tourism |
| Transition zone | Outermost ring; sustainable resource use by local communities; agriculture, settlements |
UNESCO-Recognised Biosphere Reserves in India
| Biosphere Reserve | State(s) | Year (UNESCO) | Key Feature |
|---|---|---|---|
| Nilgiri | TN, Kerala, Karnataka | 2000 | First Indian BR in UNESCO network; Western Ghats hotspot; Mudumalai, Bandipur, Nagarahole, Wayanad, Silent Valley |
| Gulf of Mannar | Tamil Nadu | 2001 | Marine BR; coral reefs, seagrass, dugong habitat; 21 islands |
| Sundarbans | West Bengal | 2001 | World's largest mangrove forest; Royal Bengal tiger; UNESCO World Heritage |
| Nanda Devi | Uttarakhand | 2004 | Valley of Flowers; alpine meadows; snow leopard |
| Nokrek | Meghalaya | 2009 | Red panda; citrus gene pool — wild ancestor of citrus fruits (Citrus indica) |
| Pachmarhi | Madhya Pradesh | 2009 | Satpura Range; leopard, giant squirrel; sal and teak forests |
| Simlipal | Odisha | 2009 | Melanistic tigers (black tigers); sal forests; waterfalls |
| Achanakmar-Amarkantak | MP, Chhattisgarh | 2012 | Origin of Narmada and Son rivers; tropical moist deciduous forests |
| Great Nicobar | A&N Islands | 2013 | Leatherback turtle nesting; saltwater crocodile; Galathea NP |
| Agasthyamalai | Kerala, Tamil Nadu | 2016 | Southernmost Western Ghats; lion-tailed macaque; Kalakad-Mundanthurai TR |
| Khangchendzonga | Sikkim | 2018 | Also UNESCO World Heritage; snow leopard; red panda; sacred Khangchendzonga peak |
| Panna | Madhya Pradesh | 2020 | Successful tiger reintroduction; Ken river; diamond-bearing region |
Prelims Fact: India has 18 Biosphere Reserves, of which 12 are in the UNESCO World Network. Nilgiri BR (2000) was the first Indian BR to receive UNESCO recognition. Panna BR (2020) is the most recent addition to the UNESCO list.
Ramsar Wetlands and Biogeographic Significance
India has 85 Ramsar sites (as of 2025), covering a diverse range of wetland types across biogeographic zones. Wetlands are critical for biodiversity as they support migratory birds, freshwater fish, amphibians, and serve as breeding grounds.
Major Ramsar Sites by Biogeographic Zone
| Zone | Ramsar Sites (Selected) | Significance |
|---|---|---|
| Trans-Himalayan | Tso Kar, Tsomoriri (Ladakh) | High-altitude wetlands; breeding ground for black-necked crane and bar-headed goose |
| Himalayan | Wular Lake (J&K), Hokera (J&K) | Wular is the largest freshwater lake in India; critical for migratory waterfowl |
| Gangetic Plain | Keoladeo (Rajasthan), Haiderpur (UP) | Keoladeo — UNESCO World Heritage; major wintering ground for Siberian crane (now functionally extinct in India) |
| Coastal | Chilika (Odisha), Vembanad-Kol (Kerala) | Chilika — largest brackish water lagoon in Asia; Irrawaddy dolphin; flamingos |
| Deccan | Lonar Lake (Maharashtra) | World's only saltwater lake in basaltic rock (meteorite impact crater) |
| Western Ghats | Vembanad-Kol, Ashtamudi (Kerala) | Backwater ecosystems; rich fisheries; mangroves |
| North-East | Deepor Beel (Assam), Loktak Lake (Manipur) | Loktak — largest freshwater lake in NE India; phumdis (floating biomass); Keibul Lamjao NP (sangai deer) |
Exam Strategy
Prelims Focus Areas
- 10 biogeographic zones (Rodgers and Panwar, 1988) — names, features, representative species
- 4 biodiversity hotspots in India — Western Ghats, Eastern Himalayas, Indo-Burma, Sundaland
- Endemic species and IUCN status: hangul (CR), Nilgiri tahr (EN), lion-tailed macaque (EN), GIB (CR), snow leopard (VU)
- Nilgiri tahr count: 2,668 (2025); hangul count: 289 (2023); tiger count: 3,682 (2022)
- Champion and Seth classification: 16 major forest types
- A&N Islands: 1,032 endemic species; Narcondam hornbill — single island endemic
- Island biogeography: MacArthur-Wilson theory, species-area relationship
Mains Answer Frameworks
Q: "Discuss the biogeographic zones of India and their significance for biodiversity conservation."
Structure:
- Rodgers and Panwar classification — 10 zones, 27 provinces
- Key features of each zone (brief)
- Biodiversity hotspots overlap — Western Ghats, Eastern Himalayas, Indo-Burma, Sundaland
- Protected area network aligned with biogeographic zones
- Gaps — under-represented zones (Semi-Arid, Gangetic Plain) in protected area coverage
- Way forward — landscape-level conservation, corridors, community reserves
Q: "Examine the threats to island ecosystems in India and suggest measures for their conservation."
Structure:
- A&N Islands — endemic richness (1,032 endemics), Sundaland hotspot
- Threats — infrastructure (Great Nicobar project), invasive species, sea-level rise
- Lakshadweep — coral bleaching, rising sea temperatures
- Island biogeography theory — vulnerability of small, isolated populations
- Conservation measures — strict protection, invasive species removal, climate adaptation
- Balancing development with conservation — tribal rights (Sentinelese, Jarawa)
