These biodiversity notes for OPSC/UPSC (Part I) cover the levels and measures of biodiversity, its distribution patterns, the causes of loss, biodiversity hotspots, and India’s biodiversity regions, with the Odisha angle and mains analysis. Prelims asks mostly definitions, hotspot criteria and region matches, while mains uses the same material for conservation, climate and sustainable development answers. Conventions, IUCN lists, laws, flagship species and conservation strategies are in Part II.
Biodiversity Notes for OPSC/UPSC: Meaning, Levels and Measures
The variety of life at all levels: genes, species and ecosystems. The term was coined by Walter G. Rosen in 1985 and popularised by E. O. Wilson in 1988. UPPSC 2013
Levels of biodiversity
| Level | Meaning | Example |
|---|---|---|
| Genetic diversity | Variation within a species | The many mango varieties of India differ in flavour, colour, fibre and shelf life because of genetic diversity |
| Species diversity | Variety of species in an area | The Western Ghats hold many more species than the Thar desert |
| Ecosystem diversity | Variety of habitats and communities | Mangroves, wetlands, rainforest and desert in one country |
- The three recognised levels are genetic, species and ecosystem diversity. ‘Environmental diversity’ is not one of them.
Alpha, beta and gamma diversity
R. H. Whittaker described diversity at different spatial scales. RAS/RTS 2018
| Measure | Meaning |
|---|---|
| Alpha diversity | Species richness within one community or habitat |
| Beta diversity | Change in species composition between communities or habitats (diversity between habitats) |
| Gamma diversity | Total diversity across a landscape or region |
Mispaired-definition questions swap alpha and beta. Remember: alpha is within, beta is between and gamma is overall.
Value of biodiversity
- The most significant aspect is the maintenance of ecosystems, through services such as nutrient cycling, climate regulation and water purification. UPPSC 2010
- Biodiversity supports soil formation, prevention of soil erosion, recycling of waste and pollination of crops. UPSC 2011
- Direct uses include food, medicine, fibre and industrial raw materials. Indirect and option values include ecotourism, cultural value and future potential.
- The Economics of Ecosystems and Biodiversity (TEEB) tries to put an economic value on these services.
Patterns of Biodiversity: Latitude, Altitude and Area
- Latitudinal gradient: species diversity is highest in the tropics and falls towards the poles. UKPSC 2012 The Amazon rainforest is the richest region. Tropical evergreen forests hold the maximum plant diversity. UPPSC 2012 UPPSC 2019
- Reasons: a warm, stable climate over long periods, high productivity, and more niches in the tropics.
- Altitudinal gradient: along mountain slopes biodiversity is greater at lower altitudes than at higher altitudes. Both gradients hold. UPSC 2011
- Species-area relationship: Alexander von Humboldt noted that richness rises with the area explored. On log scales this is a straight line, and habitat fragmentation lowers richness by shrinking the area.
- Butterflies illustrate the pattern: their species are most numerous in the tropics because they cannot tolerate low temperatures. UPPSC 2019
Diversity increases towards the equator and decreases with altitude. The Himalaya is rich in species because it is a confluence of different biogeographical zones and has a very wide altitude range. UPSC 2011
Major biomes (revision)
| Biome | Local name |
|---|---|
| Temperate grasslands of Eurasia | Steppes |
| Temperate grasslands of North America | Prairies |
| Temperate grasslands of South America | Pampas |
| Temperate grasslands of South Africa | Veld |
Threats to Biodiversity: Causes of Loss
The leading causes are summarised by the ‘evil quartet’: habitat loss and fragmentation, over-exploitation, alien species invasion and co-extinctions, along with pollution and climate change.
| Threat | Explanation and example |
|---|---|
| Habitat destruction | The biggest danger to biodiversity UPPSC 2017 UPPSC 2016; deforestation, agricultural expansion and roads in Uttarakhand UKPSC 2006 |
| Fragmentation | Divides habitats into small patches that support fewer species |
| Over-exploitation | Hunting, fishing and harvesting beyond regeneration |
| Invasive alien species | Prosopis juliflora, Lantana camara, water hyacinth and the African catfish harm native species |
| Pollution | Pesticides, chemical fertilisers and mosquito repellents together with habitat loss reduce bird populations UPPSC 2001 |
| Climate change | Shifts ranges, bleaches coral and changes timing of breeding |
| Shifting cultivation | Jhum with short fallows destroys habitats JPSC 2010 |
- Sacred groves conserve biodiversity and are not a reason for its decline. NDA 2020 Afforestation on degraded land helps and is not a cause of loss. UKPSC 2006
- Promotion of vegetarianism is not recognised as a threat to biodiversity. UPSC 2012
- Bio-pesticides and organic manure benefit birds, while chemical agriculture harms them.
Biodiversity Hotspots: Criteria and Global List
A region with exceptional species richness and endemism that is under serious threat. Norman Myers introduced the idea in 1988, and Conservation International adopted and refined it.
- Criteria: at least 1,500 species of endemic vascular plants, and 30% or less of the original natural vegetation remaining (that is, at least 70% lost). Standard MCQ
- There are 36 hotspots in the world. They cover about 2.5% of the Earth’s land but hold more than half of the world’s endemic plant species.
- Hotspots are not only tropical; examples include the Mediterranean Basin and the California Floristic Province. UPSC 2010
- The criteria for the Western Ghats and Sri Lanka and Indo-Burma are species richness, endemism and threat perception, and not vegetation density or ethno-botanical value. UPSC 2010
| Continent | Hotspot examples |
|---|---|
| South America | Cerrado, Tropical Andes, Atlantic Forest |
| North and Central America | California Floristic Province, Madrean Pine-Oak Woodlands |
| Africa | Guinean Forests of West Africa, Succulent Karoo, Cape Floristic Region |
| Asia-Pacific | Sundaland, Indo-Burma, Himalaya, Western Ghats and Sri Lanka, Philippines |
| Europe and West Asia | Mediterranean Basin |
IMAGE (Map): World map of the 36 biodiversity hotspots
Labels: Himalaya, Indo-Burma, Western Ghats and Sri Lanka, Sundaland, Cerrado, California Floristic Province, Guinean Forests, Succulent Karoo, Mediterranean Basin
Caption: Hotspots cover a small land area but hold much of the world’s endemic plants.
Find it: Conservation International hotspots map; search biodiversity hotspots world map 36
Biodiversity of India: Hotspots and Biogeographic Zones
India as a megadiverse country
India is one of the 17 megadiverse countries and holds about 8% of the world’s recorded species on about 2.4% of its land area. It lies in the confluence of three realms: Indo-Malayan, Palaearctic and Afrotropical.
Hotspots in India
| Hotspot | Indian area |
|---|---|
| Himalaya | Himalayan arc including the Eastern Himalaya |
| Indo-Burma | North-East India (except the Brahmaputra floodplain), Andaman Islands |
| Western Ghats and Sri Lanka | Western Ghats of Maharashtra, Karnataka, Kerala and Tamil Nadu |
| Sundaland | Nicobar Islands |
- The Western Ghats are the most biodiversity-rich area of India. UPPSC 2015 UPPSC 2019 They became a UNESCO World Heritage Site in 2012.
- The Eastern Himalayas and the Western Ghats were the two original hotspots recognised in India. RAS/RTS 2008 The Vindhyas are not a hotspot. UPPSC Mains 2016 The Ganga plains and central India are not hotspots either. UPPSC 2009
- Silent Valley in Kerala is a rich tropical evergreen area where a hydro project was dropped after public protests, and it became a national park in 1984. UPPSC 2016
- Valley of Flowers is in Uttarakhand. UP Lower 2002 Namdapha in Arunachal Pradesh has a climate from tropical to arctic. UPSC 2015 The Andaman and Nicobar Islands hold mangrove, evergreen and deciduous forest together. UPSC 2015
Biogeographic zones of India
Rodgers and Panwar of the Wildlife Institute of India divided India into ten biogeographic zones: Trans-Himalaya, Himalaya, Desert, Semi-Arid, Western Ghats, Deccan Peninsula, Gangetic Plain, North-East, Coasts and Islands. The Deccan Peninsula is the largest zone.
- India’s hotspots are the Himalaya, Indo-Burma, the Western Ghats and Sri Lanka, and Sundaland. The Western Himalayas, Eastern Ghats and the Sundarbans are not separately listed. UPSC 2010
- Coral reefs occur in the Andamans, Gulf of Kachchh, Gulf of Mannar and Lakshadweep, but not in the Sundarbans. UPSC 2014
- Oak and rhododendron are Himalayan trees, while sandalwood is a peninsular tree. UPSC 2014
IMAGE (Map): Biogeographic zones and hotspots of India
Labels: Trans-Himalaya, Himalaya, Desert, Semi-Arid, Western Ghats, Deccan Peninsula, Gangetic Plain, North-East, Coasts, Islands, hotspot boundaries
Caption: India has ten biogeographic zones and four biodiversity hotspots.
Find it: Wildlife Institute of India biogeographic zones map; search Rodgers and Panwar biogeographic classification India map
Mains Analysis: Biodiversity, Climate and Livelihoods
- Why biodiversity matters: food security (crop wild relatives), medicine, ecosystem services, climate regulation and cultural value. The 2020 pandemic renewed focus on zoonotic risk from habitat loss.
- Causes of loss in India: infrastructure and mining in forests, agricultural expansion, invasive species such as Prosopis juliflora and Lantana, human-wildlife conflict, pollution and climate change.
- Hotspot management: the Western Ghats debate, with the Gadgil (2011) and Kasturirangan (2013) reports, shows the tension between conservation and development in an ecologically sensitive region.
- Livelihoods: the Forest Rights Act, 2006, community conserved areas and sacred groves link conservation with local communities.
- Climate link: warming shifts species ranges upslope in the Himalaya and Western Ghats and bleaches coral, so conservation must be climate-smart.
- Global frame: the Kunming-Montreal Global Biodiversity Framework (2022) aims to protect 30% of land and sea by 2030, and India’s targets under it are an active topic.
Likely mains framings: discuss India’s biodiversity hotspots and the threats they face; examine how habitat fragmentation reduces species richness; explain the role of local communities in conserving biodiversity; assess the importance of invasive species management.
Biodiversity in Odisha: Simlipal, Bhitarkanika and Chilika
- Position: Odisha has no hotspot of its own, but its hills, deltas, coast and lakes hold rich biodiversity. The Eastern Ghats, which extend into the state, are not a designated hotspot.
- Simlipal: a national park, tiger reserve and UNESCO biosphere reserve (2009) in Mayurbhanj, known for sal forests and pseudo-melanistic tigers. It is also part of the Mayurbhanj Elephant Reserve.
- Bhitarkanika: mangroves in the Brahmani-Baitarani delta, Kendrapara district, the second largest mangrove ecosystem in India and a Ramsar site (2002), with saltwater crocodiles and many birds.
- Gahirmatha: a marine sanctuary off the Kendrapara coast, one of the largest olive ridley nesting beaches in the world. Rushikulya in Ganjam is another mass-nesting site.
- Chilika: India’s first Ramsar site (1981), the largest brackish water lagoon in Asia, with the Irrawaddy dolphin, a wintering ground for lakhs of migratory waterfowl, and the Nalabana bird sanctuary.
- Satkosia: a tiger reserve on the Mahanadi gorge and a gharial habitat.
- Threats in Odisha: mining in forest areas, elephant corridors fragmented by infrastructure, coastal erosion and mangrove loss, shifting (Podu) cultivation pressure, and cyclones.
Odisha’s coast shows how one landscape holds three ecosystem types: mangroves at Bhitarkanika, a brackish lagoon at Chilika and sandy nesting beaches at Gahirmatha. This is ecosystem diversity in practice, and each type protects a different group of species.
Biodiversity Practice Questions and PYQs
Consider the following statements. I. Biodiversity is normally greater in the lower latitudes as compared to the higher latitudes. II. Along the mountain gradients, biodiversity is normally greater in the lower altitudes as compared to the higher altitudes. Which of the statements given above is/are correct?
- Only I
- Only II
- Both I and II
- Neither I nor II
Show answer
(c) - richness falls with both latitude and altitude. UPSC 2011
Which of the following can be threats to the biodiversity of a region? I. Global warming II. Fragmentation of habitat III. Invasion of alien species IV. Promotion of vegetarianism
- II and III only
- I, III and IV
- I, II and III
- I and IV
Show answer
(c) - vegetarianism is not a recognised threat. UPSC 2012
Consider the following statements. I. Biodiversity hotspots are located only in tropical regions. II. India has four biodiversity hotspots, namely Eastern Himalayas, Western Himalayas, Western Ghats and Andaman and Nicobar Islands. Which is/are correct?
- Only I
- Only II
- Both I and II
- Neither I nor II
Show answer
(d) - hotspots also occur in temperate regions, and India’s four are the Himalaya, Indo-Burma, Western Ghats and Sri Lanka, and Sundaland. UPSC 2010
The Himalayan Range is very rich in species diversity. Which one among the following is the most appropriate reason for this phenomenon?
- It has a high rainfall that supports luxuriant vegetative growth.
- It is a confluence of different biogeographical zones.
- Exotic and invasive species have not been introduced in this region.
- It has less human interference.
Show answer
(b) - the Himalaya meets several biogeographic realms and spans a wide altitude range. UPSC 2011
Biodiversity forms the basis for human existence in the following ways. I. Soil formation II. Prevention of soil erosion III. Recycling of waste IV. Pollination of crops
- I, II and III
- II, III and IV
- I and IV
- I, II, III and IV
Show answer
(d) - all four are ecosystem services supported by biodiversity. UPSC 2011
Which of the following have coral reefs? I. Andaman and Nicobar Islands II. Gulf of Kachchh III. Gulf of Mannar IV. Sundarbans
- I, II and III only
- II and IV only
- I and III only
- I, II, III and IV
Show answer
(a) - the Sundarbans have mangroves, not coral reefs. UPSC 2014
Which one among the following regions of India is a confluence of Mangrove forest, Evergreen forest and Deciduous forest?
- North Coast of Andhra Pradesh
- South-Western Bengal
- Southern Saurashtra
- Andaman and Nicobar Islands
Show answer
(d) - the Andamans hold all three forest types. UPSC 2015
Consider the following statements about Odisha’s biodiversity. 1. Simlipal is a UNESCO biosphere reserve. 2. Chilika was India’s first Ramsar site. 3. The Eastern Ghats are a recognised biodiversity hotspot. How many are correct?
- Only one
- Only two
- All three
- None
Show answer
(b) - statements 1 and 2 are correct, while the Eastern Ghats are not a designated hotspot.