Biodiversity: levels, hotspots & India's bio-geographic zones

Defining Biodiversity

Biodiversity, a term popularised by entomologist E.O. Wilson and Walter G. Rosen in 1985, denotes the variability among living organisms from all sources. The Convention on Biological Diversity (CBD), opened for signature at the Rio Earth Summit on 5 June 1992 and in force from 29 December 1993, formally defines it in Article 2 and recognises three hierarchical levels.

The Three Levels

Genetic diversity is the variation of genes within a single species. India holds enormous crop and livestock genetic wealth — an estimated 50,000 rice landraces and 27 indigenous cattle breeds. The 30,000-rice-variety collection associated with R.H. Richharia and the diversity conserved at the National Bureau of Plant Genetic Resources (NBPGR, New Delhi) illustrate the point. High genetic diversity confers adaptability and disease resistance; its erosion underlies vulnerabilities like the 1970 US corn-leaf-blight epidemic.

Species diversity is the variety of species in a region, measured by richness (count) and evenness (relative abundance). The Western Ghats and the Eastern Himalaya host exceptionally high species diversity. India, with about 2.4% of the world's land area, holds roughly 7–8% of all recorded species — over 45,000 plant and 91,000 animal species per the Botanical and Zoological Surveys of India.

Ecosystem diversity is the variety of habitats, biotic communities and ecological processes — India spans deserts, mangroves (Sundarbans), coral reefs (Gulf of Mannar, Lakshadweep), alpine meadows and rainforests.

Patterns and Measurement

Species diversity is measured at three spatial scales defined by R.H. Whittaker (1972): alpha (within-habitat), beta (between-habitat turnover) and gamma (landscape-level) diversity. Latitudinal gradients explain why tropical regions like India are richer than temperate zones — greater solar energy, evolutionary time, and lack of glacial disruption.

India is one of 17 megadiverse countries identified by Conservation International (1998) and the UNEP-WCMC, a group that collectively holds about 70% of global biodiversity. The others in Asia include China, Indonesia, Malaysia, the Philippines and Papua New Guinea. Megadiverse status is a high-yield Prelims fact: candidates must know India is megadiverse AND a hotspot host — the two concepts are distinct.

Biodiversity Hotspots

The biodiversity-hotspot concept was articulated by British ecologist Norman Myers in 1988 and refined in the 2000 Nature paper. To qualify, a region must satisfy two strict criteria: (1) contain at least 1,500 endemic vascular plant species (>0.5% of the world total), and (2) have lost at least 70% of its original primary vegetation. There are 36 recognised global hotspots; four extend into India:

• The Himalaya — the entire Indian Himalayan arc, including the Eastern Himalaya.
• Indo-Burma — the Northeast (excluding Assam plains), covering Manipur, Mizoram and beyond.
• The Western Ghats and Sri Lanka — the 1,600-km escarpment, a UNESCO World Heritage Site (2012).
• Sundaland — reaching India only through the Nicobar Islands.

Retain the count precisely: four hotspots touch India. A frequent PYQ trap conflates hotspots with megadiverse status or with the number of biosphere reserves.

India's Ten Bio-geographic Zones

The Wildlife Institute of India (WII), under Rodgers and Panwar (1988, updated 2002), classified India into ten bio-geographic zones and 27 provinces, a framework that guides protected-area planning:

1. Trans-Himalaya — Ladakh, cold desert; snow leopard, Tibetan antelope.
2. Himalaya — alpine and temperate; the richest mammalian zone.
3. Desert — Thar (Rajasthan) and Rann of Kutch; Great Indian Bustard.
4. Semi-Arid — Gujarat-Rajasthan; Gir's Asiatic lions.
5. Western Ghats — high endemism; lion-tailed macaque.
6. Deccan Peninsula — largest zone by area; dry deciduous forests.
7. Gangetic Plain — alluvial; high human density, low natural cover.
8. North-East India — transition between Indian and Indo-Malayan biotas.
9. Islands — Andaman, Nicobar and Lakshadweep; high endemism, coral reefs.
10. Coasts — long coastline with mangroves and estuaries.

Distinguish carefully: bio-geographic zones are a national classification by WII; biodiversity hotspots are a global conservation-priority concept by Myers/Conservation International. Examiners routinely test whether candidates can keep the two frameworks apart.

Endemism

Endemism — species confined to a defined geography — drives hotspot designation. The Western Ghats harbour the purple frog (Nasikabatrachus sahyadrensis, described 2003) and over 1,500 endemic plants; the Northeast hosts Hoolock gibbons, India's only ape. Island endemism is extreme: the Nicobar megapode and Narcondam hornbill occur nowhere else on Earth.

Why This Matters for the Exam

This lesson directly serves Prelims General Studies Paper I (Environment is a standalone high-weight area since 2011) and Mains GS-3 under the syllabus head 'Conservation, environmental pollution and degradation'. Biodiversity is among the three or four most reliably tested environment sub-topics, with the UPSC asking 8–15 environment questions in most recent Prelims.

How It Is Tested

Prelims favours precise, factual recall and discrimination between near-identical options. Recurrent question patterns include: the number of hotspots in India (answer: four), the criteria for hotspot status (Myers' twin tests of endemism and habitat loss), matching species to zones, and distinguishing megadiverse status from hotspots. In 2017 UPSC asked which factors make India biodiversity-rich; in 2019 a statement-based question tested the Western Ghats. Memorise: 17 megadiverse countries, 36 global hotspots, 4 in India, 10 bio-geographic zones, 27 provinces.

Mains demands analytical synthesis. A typical GS-3 prompt asks you to explain why the Western Ghats and Eastern Himalaya are hotspots and link this to conservation policy — the Gadgil Committee (2011) and Kasturirangan Committee (2013) Ecologically Sensitive Area reports are the natural bridge. Connect biodiversity to the National Biodiversity Action Plan (2008), the Biological Diversity Act 2002, and the Aichi/Kunming-Montreal Global Biodiversity Framework (2022) target of protecting 30% of land and sea by 2030 (30x30).

High-Yield Retention List

• Three levels: genetic, species, ecosystem (CBD Article 2).
• Whittaker's alpha, beta, gamma diversity.
• Hotspot criteria: ≥1,500 endemic vascular plants AND ≥70% habitat loss.
• Four Indian hotspots: Himalaya, Indo-Burma, Western Ghats–Sri Lanka, Sundaland.
• Ten WII bio-geographic zones — be able to place flagship species in each.
• India = 1 of 17 megadiverse countries; ~2.4% land, ~7–8% of species.

The single most common error is conflating frameworks. Keep three vocabularies separate: WII's zones (national planning), Myers' hotspots (global priority), and CBD's levels (definitional). Answers that cite the correct authority by name — Rodgers & Panwar 1988, Myers 2000, CBD 1992 — read as authoritative and score higher in Mains.