Chapter 3 · Topic 3.1 · Prelims + Mains1 of 3
Biodiversity: Levels, hotspots and threats
Key points
- Three levels: genetic, species, ecosystem diversity. Term coined by Walter G. Rosen in 1985.
- Biodiversity is higher at low latitudes and low altitudes.
- India: 2.4% of Earth's land, 7–8% of known species, one of 17 megadiverse countries.
- Hotspot: at least 1,500 endemic vascular plants and 70% habitat lost. Conservation International lists 36.
- India's hotspots: Himalaya, Indo-Burma, Western Ghats and Sri Lanka, Sundaland (Nicobar).
- Asiatic lion moved from Critically Endangered to Endangered in 2008.
9 PYQs 2011–2026
Prelims box: facts and traps
| Item | Fact |
|---|---|
| Hotspot endemism test | At least 1,500 endemic vascular plant species |
| Hotspots worldwide | 36 (Conservation International), older lists 34 |
| Megadiverse countries | 17, India one of them |
| India's land share | 2.4% |
- Trap: Red Data Books list threatened species, not endemic ones only.
On this page (3 sections)
What biodiversity means
Biodiversity is the variety of life at all levels, from genes to ecosystems. Think of a fruit market: many kinds of mangoes (genes), many fruits (species), many farms (ecosystems). The word was coined as ‘BioDiversity’ by Walter G. Rosen in 1985 and made popular by the biologist E. O. Wilson.
| Level | Meaning | Example |
|---|---|---|
| Genetic diversity | Variation in genes within a species | Thousands of rice and mango varieties in India |
| Species diversity | Variety of species in an area | Western Ghats amphibians |
| Ecosystem diversity | Variety of habitats and ecosystems | Deserts, rainforests, mangroves, coral reefs, alpine meadows |
Ecologists also measure alpha diversity (within one community), beta diversity (the change from one community to the next) and gamma diversity (across a whole region).
Biodiversity is normally greater in the lower latitudes, near the equator, than in the higher latitudes. It is also greater at lower altitudes than at higher ones on mountain slopes (Prelims 2011: Both 1 and 2).
Consider the following statements : 1. Biodiversity is normally greater in the lower latitudes as compared to the higher latitudes. 2. 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 ?
- 1 only
- 2 only
- Both 1 and 2
- Neither 1 nor 2
Show answer
Answer: (c) · UPSC official key
| India’s biodiversity | Figure (source) |
|---|---|
| Share of Earth’s land | 2.4% (PIB, 3 March 2025) |
| Share of known species | 7–8%: over 45,000 plants and 91,000 animals (PIB, 3 March 2025) |
| Megadiverse status | One of the 17 megadiverse countries (PIB, 12 October 2021) |
| Crop origins | One of the 8 centres of origin of cultivated plants (PIB, 12 October 2021) |
Mains 2018 asked how biodiversity varies in India and how the Biological Diversity Act, 2002 helps conserve plants and animals. Use the ten biogeographic zones, the hotspots and the three-tier NBA–SBB–BMC structure (National Biodiversity Authority, State Biodiversity Boards and local Biodiversity Management Committees).
How does biodiversity vary in India? How is the Biological Diversity Act, 2002 helpful in conservation of flora and fauna?
Hotspots, megadiversity and endemism
| Hotspot criterion (Conservation International) | Threshold |
|---|---|
| Endemism | At least 1,500 endemic vascular plant species |
| Threat | Has lost at least 70% of its original natural vegetation |
A hotspot is a place that is both very rich in unique species and under heavy threat. The ecologist Norman Myers proposed the idea, and Conservation International formalised it. It now lists 36 hotspots covering about 2.5% of Earth’s land. Older lists, still quoted by PIB, count 34.
| Hotspots in India | Indian part |
|---|---|
| Himalaya | Himalayan states from Ladakh to Arunachal Pradesh |
| Indo-Burma | Most of North-east India |
| Western Ghats and Sri Lanka | Western Ghats from Gujarat to Kerala |
| Sundaland | Nicobar Islands |
A megadiverse country holds a very large share of the world’s species. India is one of the 17 megadiverse countries and a member of the Like-Minded Megadiverse Countries group formed at Cancún in 2002.
Endemism, species found nowhere else, is high where areas are isolated: the Western Ghats (many amphibians, the Nilgiri tahr and the lion-tailed macaque), the North-east, the Himalaya and the Andaman and Nicobar Islands.
Threats and the IUCN Red List
| Threat (HIPPO + climate) | Example |
|---|---|
| Habitat loss and fragmentation | Roads, mines and farms cutting forests into patches |
| Invasive alien species | Lantana, Prosopis, water hyacinth |
| Pollution | Pesticides, plastics, nutrient run-off |
| Human population pressure | Encroachment, fuelwood demand |
| Overexploitation | Poaching, overfishing, wildlife trade |
| Climate change | Coral bleaching, shifting ranges up mountains |
The term ‘sixth mass extinction’ is discussed in the context of mankind’s over-exploitation and misuse of natural resources, loss and fragmentation of natural habitats, destruction of ecosystems, pollution and global climate change (Prelims 2018).
The term “sixth mass extinction/sixth extinction” is often mentioned in the news in the context of the discussion of
- Widespread monoculture practices in agriculture and large-scale commercial farming with indiscriminate use of chemicals in many parts of the world that may result in the loss of good native ecosystems.
- Fears of a possible collision of a meteorite with the Earth in the near future in the manner it happened 65 million years ago that caused the mass extinction of many species including those of dinosaurs.
- Large scale cultivation of genetically modified crops in many parts of the world and promoting their cultivation in other parts of the world which may cause the disappearance of good native crop plants and the loss of food biodiversity.
- Mankind’s over-exploitation/misuse of natural resources, fragmentation/loss of natural habitats, destruction of ecosystems, pollution and global climate change.
Show answer
Answer: (d) · UPSC official key
| IUCN Red List category | Meaning |
|---|---|
| Extinct (EX) | No individual left |
| Extinct in the Wild (EW) | Survives only in captivity or cultivation |
| Critically Endangered (CR), Endangered (EN), Vulnerable (VU) | The three ‘threatened’ categories, from highest to lowest risk |
| Near Threatened (NT), Least Concern (LC) | Not threatened now |
| Data Deficient (DD), Not Evaluated (NE) | Too little information, or not yet assessed |
The Red Data Books published by IUCN contain lists of threatened plant and animal species (Prelims 2011: 2 only).
The “Red Data Books” published by the International Union for Conservation of Nature and Natural Resources (IUCN) contain lists of 1. Endemic plant and animal species present in the biodiversity hotspots. 2. Threatened plant and animal species. 3. Protected sites for conservation of nature and natural resources in various countries. Select the correct answer using the codes given below :
- 1 and 3
- 2 only
- 2 and 3
- 3 only
Show answer
Answer: (b) · UPSC official key
An example of recovery: IUCN moved the Asiatic lion from Critically Endangered to Endangered in 2008 (PIB, March 2025).
What UPSC asks: Prelims: hotspots, Red List. Mains: India’s biodiversity, BD Act, 2002.
Mains box: analysis and answer points
- Variation in India: ten biogeographic zones, hotspots.
- BD Act, 2002: NBA, SBB, BMC structure.
- Threats: HIPPO plus climate, sixth mass extinction.
Practice
Practice MCQs (8)
A species that occurs naturally only in a particular geographical region, such as a single island, mountain range or country, and nowhere else in the world is called
Answer (a) & explanation
An endemic species is one confined in nature to a particular geographical area. High endemism is one of the two criteria for a biodiversity hotspot, and regions such as the Western Ghats and the islands of India are rich in endemics. An exotic species is one introduced from elsewhere; a cosmopolitan species is found across most of the world; and a keystone species is defined by its large effect on its community, not by its range.
The term 'biodiversity' was popularised by which one of the following scientists, who used it to describe the combined diversity at all levels of biological organisation?
Answer (b) & explanation
NCERT states that the term biodiversity was popularised by the sociobiologist Edward Wilson to describe the combined diversity at all levels of biological organisation, from genes to ecosystems. The other names belong to related ideas: Norman Myers proposed the hotspot concept in 1988, Paul Ehrlich gave the rivet popper hypothesis, and Alexander von Humboldt described the species-area relationship.
With reference to the Group of Like-Minded Megadiverse Countries (LMMC), consider the following statements:
1. The group was established through the Cancun Declaration of 2002.
2. India was one of its founding members.
3. The status of a 'megadiverse country' is formally conferred on a nation by a decision of the Conference of the Parties to the Convention on Biological Diversity.
Which of the statements given above is/are correct?
Answer (c) & explanation
Statements 1 and 2 are correct. The Like-Minded Megadiverse Countries group was set up by the Cancun Declaration of 18 February 2002; the founding meeting brought together twelve countries, including India, Brazil, China, Mexico, Indonesia and South Africa, and the group later grew to about seventeen members. It is a consultation and cooperation mechanism for promoting the interests of biodiversity-rich nations, especially on access and benefit sharing. 'Megadiverse' is not a legal status conferred by the CBD; the term comes from a scientific identification of the most species-rich countries, popularised by Conservation International.
With reference to biodiversity hotspots, consider the following statements:
1. To qualify as a hotspot, a region must contain at least 1,500 species of vascular plants found nowhere else on Earth.
2. To qualify as a hotspot, a region must have retained at least 70 per cent of its primary native vegetation.
3. The hotspot concept was first put forward by the British ecologist Norman Myers.
Which of the statements given above are correct?
Answer (b) & explanation
Statements 1 and 3 are correct. A biodiversity hotspot must meet two criteria: it must hold at least 1,500 endemic vascular plant species, and it must have lost at least 70% of its primary native vegetation. Statement 2 inverts the second criterion; a hotspot is both irreplaceable and threatened, so a region that still retains most of its vegetation does not qualify. Norman Myers identified the first ten tropical forest hotspots in 1988, and Conservation International adopted the idea in 1989; there are 36 hotspots today.
Consider the following global biodiversity hotspots:
1. Himalaya
2. Western Ghats and Sri Lanka
3. Sundaland
4. Mountains of Southwest China
How many of the above include some part of Indian territory?
Answer (c) & explanation
Only three: the Himalaya, the Western Ghats and Sri Lanka, and Sundaland (through the Nicobar Islands). The fourth hotspot that India is usually credited with is Indo- Burma, which is not in this list. The Mountains of Southwest China hotspot lies in south-east Tibet, western Sichuan and northern Yunnan; it adjoins the eastern Himalaya but does not extend into India.
The Nicobar Islands of India form a part of which one of the following global biodiversity hotspots?
Answer (a) & explanation
According to the Critical Ecosystem Partnership Fund, the Sundaland hotspot covers the western half of the Indonesian archipelago (dominated by Borneo and Sumatra), nearly all of Malaysia, Singapore, Brunei and a small part of southern Thailand, and it also includes the Nicobar Islands under Indian jurisdiction. India's other hotspots are the Himalaya, Indo-Burma and the Western Ghats and Sri Lanka. Wallacea lies further east, in central Indonesia and Timor-Leste.
Consider the following statements:
1. Amazonia, though extremely rich in species, is not classed as a biodiversity hotspot because most of its original vegetation is still intact.
2. All the currently recognised biodiversity hotspots are terrestrial regions.
3. Biodiversity hotspot status is conferred on a region by IUCN through its Red List of Threatened Species.
Which of the statements given above is/are correct?
Answer (a) & explanation
Statements 1 and 2 are correct. Hotspots combine high plant endemism with severe habitat loss. Vast species-rich forests that remain largely intact, such as Amazonia, the Congo forests and New Guinea, are treated by Conservation International as high-biodiversity wilderness areas, not hotspots. CEPF describes the 36 hotspots as Earth's most biologically rich yet threatened terrestrial regions. The hotspot framework comes from Norman Myers and Conservation International and is applied by CEPF; the IUCN Red List assesses the extinction risk of species, not regions, so statement 3 is wrong.
In the biogeographic classification of India prepared by the Wildlife Institute of India (Rodgers and Panwar), the country is divided into ten biogeographic zones. Which one of the following zones is the largest by area?
Answer (d) & explanation
The Rodgers and Panwar classification (later revised with Mathur) divides India into 10 biogeographic zones and 27 provinces: Trans-Himalaya, Himalaya, Desert, Semi-arid, Western Ghats, Deccan Peninsula, Gangetic Plain, Coasts, North-East and Islands. The Deccan Peninsula is by far the largest, covering about 42% of the country's area. The Semi-arid zone is second at roughly 16%, while the Western Ghats, despite its biological richness, covers only about 4%.
0 / 0 correct
Prelims PYQs on this topic (8)
Three of the following criteria have contributed to the recognition of Western Ghats-Sri Lanka and Indo-Burma regions as hotspots of biodiversity :
- 1. Species richness
- 2. Vegetation density
- 3. Endemism
- 4. Ethno-botanical importance
- 5. Threat perception
- 6. Adaptation of flora and fauna to warm and humid conditions
Which three of the above are correct criteria in this context ?
Answer (c) & explanation
Criteria 1, 3 and 5 are correct (c). A biodiversity hotspot, a concept from Norman Myers (1988) later adopted by Conservation International, must meet two strict tests: it must have at least 1,500 endemic vascular plant species (endemism), and it must have lost at least 70% of its original habitat (threat). Such places also have high species richness. So 1, 3 and 5 are the criteria. Vegetation density (2), ethno-botanical importance (4) and adaptation to warm humid conditions (6) are not hotspot criteria, so options (a), (b) and (d) fail.
Notice the numbers: there are 36 hotspots worldwide, covering about 2.5% of land but holding over half of plant species as endemics. India has parts of four: the Himalaya, Indo-Burma, Western Ghats-Sri Lanka and Sundaland (Nicobar Islands). Trap: dense forest alone does not make a hotspot.
Answer as per the official UPSC answer key.
The “Red Data Books” published by the International Union for Conservation of Nature and Natural Resources (IUCN) contain lists of
- 1. Endemic plant and animal species present in the biodiversity hotspots.
- 2. Threatened plant and animal species.
- 3. Protected sites for conservation of nature and natural resources in various countries.
Select the correct answer using the codes given below :
Answer (b) & explanation
Statement 2 only is correct (b). The Red Data Book, now the IUCN Red List, records species at risk of extinction, sorted into categories: Critically Endangered, Endangered and Vulnerable (together 'threatened'), plus Near Threatened, Least Concern, Extinct in the Wild and Extinct. Statement 1 is wrong: it does not list endemic species of hotspots as such; endemics appear only if they are assessed for risk. Statement 3 is wrong: protected sites are listed in the World Database on Protected Areas, not the Red List. So (a), (c) and (d) fail.
Notice the colour code: the old books used pink pages for critically endangered species and green pages for those once endangered but now safe. Trap: hotspots and protected areas are different conservation lists.
Answer as per the official UPSC answer key.
With reference to an organization known as ‘BirdLife International’, which of the following statements is/are correct?
- 1. It is a Global Partnership of Conservation Organizations.
- 2. The concept of ‘biodiversity hotspots’ originated from this organization.
- 3. It identifies the sites known/referred to as ‘Important Bird and Biodiversity Areas’.
Select the correct answer using the code given below.
Answer (c) & explanation
Statements 1 and 3 are correct (c). BirdLife International is a global partnership of national conservation organisations; its Indian partner is the BNHS (1). It identifies Important Bird and Biodiversity Areas (IBAs), sites vital for birds and wider biodiversity (3). Statement 2 is wrong: the biodiversity hotspot idea came from the British ecologist Norman Myers in 1988 and was later adopted by Conservation International.
BirdLife is also the Red List authority for birds within IUCN. India has four hotspots: the Himalaya, Indo-Burma, the Western Ghats–Sri Lanka and Sundaland (Nicobar). Notice how birds act as indicators of ecosystem health.
Hotspots are Myers' idea. BirdLife is known for IBAs.
Answer as per the official UPSC answer key.
Which of the following can be threats to the biodiversity of a geographical area?
- 1. Global warming
- 2. Fragmentation of habitat
- 3. Invasion of alien species
- 4. Promotion of vegetarianism
Select the correct answer using the codes given below :
Answer (a) & explanation
Items 1, 2 and 3 are correct (a). The main threats to biodiversity are habitat loss and fragmentation (2), invasive alien species such as Lantana and Prosopis in India (3), climate change (1), pollution and over-exploitation. Item 4 is wrong: vegetarianism needs less land and water than meat-heavy diets, so it reduces pressure on habitats; it is not a threat. So (b), (c) and (d) fail.
Notice the framework: E.O. Wilson's 'HIPPO' (habitat loss, invasive species, pollution, population, over-harvesting). The IPBES assessment (2019) said about 1 million species face extinction. India's National Biodiversity Strategy and Action Plan (2024) aligns with the Kunming-Montreal 30x30 target. Trap: item 4 is a lifestyle choice dressed up as a threat.
Answer as per the official UPSC answer key.
Which organization has enacted the Nature Restoration Law (NRL) to tackle climate change and biodiversity loss?
Answer (a) & explanation
The European Union enacted the Nature Restoration Law (a). The European Union adopted its Nature Restoration Law in 2024. It requires member states to restore at least 20% of the EU's damaged land and sea areas by 2030, and all ecosystems in need by 2050. Options (b), (c) and (d) are wrong: only a body that makes laws can "enact" one. The World Bank, OECD and FAO give loans, advice or technical help, but cannot pass binding laws.
Notice the link to the Kunming-Montreal Global Biodiversity Framework (2022), whose "30 by 30" target asks for 30% of land and sea to be protected by 2030. The EU law faced strong protests from farmers before it passed narrowly.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. In India, the Biodiversity Management Committees are key to the realization of the objectives of the Nagoya Protocol.
- 2. The Biodiversity Management Committees have important functions in determining access and benefit sharing, including the power to levy collection fees on the access of biological resources within its jurisdiction.
Which of the statements given above is/are correct?
Answer (c) & explanation
Both statements are correct (c). Statement 1 is right: under the Biological Diversity Act, 2002, every local body, such as a panchayat or municipality, sets up a Biodiversity Management Committee. BMCs are key to the Nagoya Protocol's aim of fair and equitable sharing of benefits from biological resources and traditional knowledge, because they bring it down to villages. Statement 2 is right: BMCs keep the People's Biodiversity Register, are consulted on access to local resources, and may levy collection fees on those who take resources from their area.
Notice the three-tier structure: the National Biodiversity Authority in Chennai, State Biodiversity Boards and BMCs. The Act was amended in 2023 to ease rules for AYUSH practitioners and research.
Answer as per the official UPSC answer key.
Mains PYQs on this topic (1)
Write an answer
In 150 words, explain the significance of Biodiversity with one recent example.
Flashcards (14)
Three levels of biodiversity?
Genetic, species, ecosystem.
Who popularised the word biodiversity?
E. O. Wilson (coined by W. G. Rosen, 1985).
Biodiversity vs latitude?
Greater at lower latitudes.
India's share of Earth's land?
2.4%.
India's share of known species?
7–8%.
Number of megadiverse countries?
17, including India.
Hotspot endemism threshold?
At least 1,500 endemic vascular plants.
Hotspot habitat-loss threshold?
At least 70% of original vegetation lost.
Hotspots worldwide (CI)?
36.
India's four hotspots?
Himalaya, Indo-Burma, Western Ghats–Sri Lanka, Sundaland.
Nicobar Islands fall in which hotspot?
Sundaland.
HIPPO stands for?
Habitat loss, Invasives, Pollution, Population, Overexploitation.
Red Data Books list?
Threatened plant and animal species.
Three 'threatened' IUCN categories?
CR, EN, VU.
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Next topic · 3.2 →Biodiversity: Value and in-situ conservationSyllabus: GS-III · Conservation, environmental pollution and degradation, environmental impact asse…