Unit 3: Biodiversity and conservation

I. Orientation: What Biodiversity Means

Biodiversity ("biological diversity", a term popularised by Walter G. Rosen and E.O. Wilson in the mid-1980s) is the total variety of life at every level of biological organisation. Its authoritative legal definition comes from Article 2 of the Convention on Biological Diversity (Rio de Janeiro, 5 June 1992), which describes it as "the variability among living organisms from all sources... this includes diversity within species, between species and of ecosystems." Roughly 1.7–1.9 million species have been formally described against an estimated global total of 8.7 million eukaryotes, so the subject is studied through samples, indices and proxies rather than complete inventories.

Defining properties and conventions used throughout this unit:

• Hierarchical: diversity is measured at three nested levels — genetic (within species), species (between species), ecosystem (between habitats).
• Unevenly distributed: species richness rises towards the equator and falls with altitude and latitude; the tropics hold ~50% of species on ~7% of land area.
• Measurable: species richness (count of species), Simpson's and Shannon's indices (richness weighted by abundance), and α (within-habitat), β (between-habitat) and γ (landscape) diversity.
• Dynamic yet finite: current extinction rates are estimated at 100–1,000 times the background rate of ~1 species per million species-years.
• Managed by instruments: CBD (1992), India's Biological Diversity Act (2002), Wildlife (Protection) Act (1972), CITES (1973), IUCN Red List.

II. Levels of Biological Diversity

The three levels are complementary: losing any one erodes the others, since genes reside in species and species compose ecosystems.

A. Genetic diversity

• Definition: variation in alleles, genes and genotypes within and between populations of one species.
• Anchor: India holds ~50,000 landraces of rice (Oryza sativa) and ~1,000 mango varieties — a single-species genetic library.
• Function: raw material of adaptation; low diversity causes inbreeding depression, as in Asiatic lions of Gir (all descended from ~20 individuals in 1900).
• Measure: heterozygosity (H), allelic richness, nucleotide diversity (π).

B. Species diversity

• Definition: variety of species in a defined region, combining richness (number) and evenness (relative abundance).
• Anchor: the Western Ghats support ~5,000 flowering plants with ~1,700 endemics; the Amazon may hold 40,000 plant species.
• Endemism: species restricted to one area — e.g. Nasikabatrachus sahyadrensis (purple frog), Western Ghats only.

C. Ecosystem diversity

• Definition: variety of habitats, biotic communities and ecological processes across a landscape or biosphere.
• Anchor: India spans mangroves (Sundarbans, ~10,000 km² with Bangladesh), cold deserts (Ladakh), coral reefs (Gulf of Mannar), alpine meadows and rainforests.
• Also called: community or landscape diversity; captured by β-diversity between adjacent habitats.

III. Importance of Biodiversity

Diversity is valued both instrumentally (what it does for humans) and intrinsically (its worth independent of use).

A. Ecosystem services

• Millennium Ecosystem Assessment (2005) fourfold scheme:
  • Provisioning: food, fuelwood, fibre, fresh water, medicines.
  • Regulating: climate regulation, flood control, pollination, disease and pest control.
  • Cultural: recreation, spiritual and educational value.
  • Supporting: soil formation, nutrient cycling, primary production.
• Anchor: insect pollination underpins ~35% of global crop production by volume; mangroves reduce cyclone storm-surge height and wave energy.

B. Ecological value

• Stability–diversity link: diverse communities resist invasion and recover faster after disturbance (Tilman's Minnesota grassland plots showed diverse plots retained productivity through drought).
• Keystone species: disproportionate control over community structure — the tiger regulates ungulate grazing pressure; fig trees sustain frugivores in lean seasons.

C. Economic value

• Direct: timber, fisheries (marine capture ~90 million tonnes/year), crops, silk, lac, honey.
• Bioprospecting: Rauvolfia serpentina → reserpine (hypertension); Catharanthus roseus → vincristine/vinblastine (leukaemia); ~25% of prescription drugs derive from plants.
• Option value: the yet-unknown future worth of untested species — the reason gene banks are maintained.

D. Social value

• Livelihood dependence: ~275 million people in India depend partly on forests for fuel, fodder and non-timber forest produce.
• Traditional knowledge: tribal pharmacopoeias and agro-biodiversity practices; protected in India via People's Biodiversity Registers under the Biological Diversity Act, 2002.

E. Aesthetic value

• Amenity and eco-tourism: landscape beauty converted into income — Kaziranga, Periyar and Ranthambhore tourism revenues.
• Cultural expression: sacred groves (devrai in Maharashtra, sarna in Jharkhand) preserve forest patches for religious, not utilitarian, reasons.

F. Informational value

• Biology as data: each species is a record of evolutionary problem-solving; loss is irreversible information loss.
• Anchor: biomimicry — Velcro from Xanthium burs, lotus-effect self-cleaning surfaces; wild relatives supply disease-resistance genes to crops.

IV. Hot Spots of Biodiversity

A hotspot is a small area with exceptional endemism that is simultaneously under severe threat — a strategy for prioritising limited conservation funds.

A. Concept and criteria

• Origin: Norman Myers, 1988; refined with Conservation International (2000).
• Two qualifying criteria: ≥1,500 endemic vascular plant species, and ≥70% of original primary vegetation already lost.
• Scale: 36 recognised hotspots covering ~2.4% of Earth's land surface, holding well over half of all endemic plant species.

B. Indian hotspots

• Himalaya: Eastern Himalayan flank; Rhododendron radiation, snow leopard, red panda.
• Indo-Burma: north-east India and Andaman Islands; hoolock gibbon, freshwater turtles.
• Western Ghats–Sri Lanka: high amphibian endemism (>75% of Ghats amphibians endemic); lion-tailed macaque, Nilgiri tahr.
• Sundaland: represented in India by the Nicobar Islands; Nicobar megapode.

V. Threats to Biodiversity

Drivers are often summarised as HIPPO — Habitat loss, Invasives, Pollution, Population, Overharvesting; the syllabus treats four.

A. Habitat loss

• Forms: outright destruction, fragmentation, and degradation.
• Fragmentation effect: small fragments suffer edge effects and lose area-sensitive species; species–area relationship S = cA^z where S = species number, A = area, c = constant, z ≈ 0.15–0.35 — a 90% habitat loss costs roughly 50% of species.
• Anchors: tropical forests cleared at ~10 million ha/year; India's wetlands and mangroves lost to aquaculture, dams and urban expansion.

B. Poaching of wildlife

• Definition: illegal killing or capture for trade in body parts, pets or curios.
• Anchors: tiger bone and skin, rhino horn (Kaziranga poaching), pangolin scales (world's most trafficked mammal), Shahtoosh wool from Tibetan antelope.
• Control instruments: Wildlife (Protection) Act, 1972 Schedule I (absolute protection); CITES Appendix I bans commercial international trade; Wildlife Crime Control Bureau (2007).

C. Biological invasions

• Mechanism: alien species freed of natural enemies out-compete natives; second largest cause of extinctions on islands.
• Anchors: Eichhornia crassipes (water hyacinth, "Bengal terror") deoxygenating Indian water bodies; Lantana camara and Parthenium hysterophorus in dry forests; Prosopis juliflora in semi-arid zones; Nile perch introduction into Lake Victoria extirpated ~200 endemic cichlids.

D. Human wildlife conflict

• Cause: shrinking habitat, blocked migration corridors and crop-raiding at forest edges.
• Anchors: ~400–500 human deaths per year in India from elephant encounters, with elephant deaths from train collisions and electrocution; leopards in Sanjay Gandhi National Park bordering Mumbai; crop damage by nilgai and wild boar.
• Mitigation: elephant corridors and underpasses, solar fencing, ex-gratia compensation, early-warning SMS systems.

VI. Species of Conservation Concern

The IUCN Red List (categories revised 1994, criteria 2001) grades extinction risk using quantitative thresholds on population decline, population size, range and modelled probability of extinction.

A. Extinct species

• Criterion: no reasonable doubt that the last individual has died.
• Anchors: dodo (Raphus cucullatus, Mauritius, c. 1681); Indian cheetah declared extinct in India in 1952; Extinct in the Wild is separate — surviving only in cultivation/captivity.

B. Endangered species

• Criterion (illustrative): ≥50% population reduction over 10 years or 3 generations, or fewer than 250 mature individuals.
• Anchors: Asiatic lion, Bengal tiger, snow leopard, Nilgiri tahr.

C. Vulnerable species

• Criterion: high risk in the medium-term future — e.g. fewer than 1,000 mature individuals, or ≥10% probability of extinction within 100 years.
• Anchors: sloth bear, gaur, dugong.

D. Rare species

• Definition: naturally low in numbers, narrowly endemic or thinly scattered, and therefore at risk even without decline; a pre-1994 IUCN category retained in Indian usage.
• Anchor: Rafflesia; many single-locality Western Ghats amphibians.

E. EDGE species

• Definition: Evolutionarily Distinct and Globally Endangered — ZSL programme launched 2007, prioritising species with few close relatives, whose loss removes disproportionate evolutionary history.

EDGE = ln(1 + ED) + GE × ln(2)
ED = evolutionary distinctness (share of phylogenetic branch length)
GE = Red List category score: LC=0, NT=1, VU=2, EN=3, CR=4

• Anchors: gharial, purple frog, Chinese giant salamander, aye-aye.

VII. Conservation of Biodiversity

A. In-situ conservation

• Principle: protect species in their natural habitat, conserving the whole community and its processes.
• Instruments in India: ~106 national parks; ~570 wildlife sanctuaries; 18 biosphere reserves (core–buffer–transition zoning, UNESCO MAB); conservation and community reserves; sacred groves.
• Species projects: Project Tiger (1973, now ~55 tiger reserves), Project Elephant (1992), Crocodile Breeding and Management Project (1975).
• Merit and limit: evolution continues in situ, but reserves are vulnerable to encroachment, fire and poaching.

B. Ex-situ conservation

• Principle: maintain organisms or their propagules outside natural habitat as insurance and for reintroduction.
• Instruments: zoos and safari parks; botanical gardens; seed and gene banks (National Bureau of Plant Genetic Resources, New Delhi); cryopreservation of gametes and embryos in liquid nitrogen at −196 °C; tissue culture; DNA libraries.
• Anchors: vulture breeding centre at Pinjore following the diclofenac-induced crash (>97% decline in Gyps populations); gharial hatchlings released into the Chambal.
• Limit: small captive populations lose genetic variation; behaviour needed for wild survival may not be learned.

VIII. Biogeographic Zones of India

Rodgers and Panwar (1988), for the Wildlife Institute of India, divided the country into 10 biogeographic zones to guide protected-area planning; they combine geology, climate and biotic assemblage rather than political boundaries.

• Trans-Himalaya: cold arid Ladakh–Spiti plateau; wild ass, Tibetan antelope.
• Himalaya: young folded mountains; altitudinal zonation from sal forest to alpine meadow.
• Desert: Thar and Kutch; Prosopis, great Indian bustard.
• Semi-arid: Punjab–Gujarat–Rajasthan transition; blackbuck, Asiatic lion at Gir.
• Western Ghats: ~1,600 km hill chain; evergreen shola–grassland mosaic.
• Deccan Peninsula: the largest zone (~42% of land area); dry deciduous teak forests.
• Gangetic Plain: alluvial, densely farmed; Terai grasslands with rhino at Dudhwa.
• Coasts: ~7,500 km coastline; mangroves, mudflats, sandy beaches.
• North-East: Brahmaputra valley and hills; wettest region, highest floristic richness.
• Islands: Andaman, Nicobar and Lakshadweep; coral reefs and high island endemism.

IX. India as a Mega Diversity Nation

Megadiverse countries are the 17 states identified by UNEP-WCMC (2002) that together contain ~70% of global species; India qualifies on richness, endemism and cultural-agricultural diversity.

• Share: ~2.4% of the world's land area supporting ~7–8% of all recorded species.
• Inventory: ~47,000 plant species and ~1,00,000 animal species described, including ~1,300 bird species.
• Endemism: ~33% of Indian flowering plants and a high proportion of Western Ghats amphibians and reptiles are endemic.
• Hotspots and zones: 4 of the world's 36 hotspots; 10 biogeographic zones; all major biome types except true tundra.
• Agro-biodiversity: a Vavilovian centre of origin/diversity for rice, brinjal, black pepper, cardamom, mango, banana and pulses, with ~166 crop species and ~320 wild crop relatives.
• Cultural diversity: ~4,600 ethnic communities, sacred groves and traditional medicinal systems (Ayurveda, Siddha, Unani) tied directly to plant diversity.
• Governance: the three-tier structure of the Biological Diversity Act, 2002 — National Biodiversity Authority (Chennai), State Biodiversity Boards and local Biodiversity Management Committees — regulates access and benefit-sharing over this endowment.