Unit 3: Biodiversity and conservation

Biodiversity, coined by Walter Rosen (1985) and popularized by E.O. Wilson, is the variety and variability of life at all levels of organization. The 1992 Convention on Biological Diversity (CBD, Rio Earth Summit) defines it as variability among living organisms from all sources, including terrestrial, marine and other aquatic ecosystems. Roughly 1.7 million species are described; total estimates range from 5 to 30 million.

• Scope: covers genes, species and ecosystems, plus the ecological processes that sustain them.
• Distribution: uneven, richest near the equator (tropical rainforests hold over 50% of species on ~7% of land) and declining toward the poles (latitudinal gradient).
• Dynamism: shaped continuously by speciation, extinction, migration and environmental change.
• Measurement scales: alpha (within a habitat), beta (between habitats), gamma (regional/landscape) diversity.

II. Levels of Biological Diversity

A. Levels of biological diversity

Biodiversity is expressed at three hierarchical, interdependent levels.

• Continuum: genes build species, species assemble into ecosystems; loss at one level erodes the others.

B. Genetic diversity

The variation of genes within a single species across its individuals and populations.

• Basis: differences in alleles, gene frequencies and chromosome structure; e.g. India has over 50,000 genetically distinct rice varieties.
• Function: provides raw material for adaptation and evolution; high diversity resists disease and environmental stress.
• Concern: inbreeding and small populations lower fitness (genetic drift, bottleneck effect).

C. Species diversity

The variety of species within a region, measured by richness and evenness.

• Richness: total number of species in an area.
• Evenness: relative abundance of each species.
• Example: the Western Ghats show high species diversity with many endemics like the lion-tailed macaque.

D. Ecosystem diversity

The variety of habitats, biotic communities and ecological processes in the biosphere.

• Range: forests, grasslands, wetlands, deserts, mangroves, coral reefs, each with distinct food webs.
• Value: diverse ecosystems stabilize nutrient cycling and energy flow.
• India example: from the cold deserts of Ladakh to the Sundarbans mangroves.

III. Importance of Biodiversity

A. Ecosystem services

The benefits ecosystems provide to humanity, grouped by the Millennium Ecosystem Assessment (2005).

• Provisioning: food, fresh water, timber, fibre, medicines.
• Regulating: climate regulation, pollination, flood and disease control, water purification.
• Supporting: soil formation, nutrient cycling, primary production, oxygen release.
• Cultural: recreation, spiritual and educational value.

B. Ecological value

Diversity keeps ecosystems functional and resilient.

• Stability: more species means more redundancy, so function persists if one is lost.
• Processes: decomposers recycle nutrients; predators control prey populations.
• Keystone role: species like the fig or tiger sustain many dependents disproportionate to their number.

C. Economic value

Biodiversity underpins direct and indirect economic returns.

• Direct (consumptive): fuelwood, meat, fish consumed locally without market.
• Direct (productive): timber, silk, honey, drugs traded in markets; ~25% of medicines derive from plants.
• Indirect: photosynthesis, watershed protection, carbon storage worth billions annually.

D. Social value

Communities depend on and revere biodiversity through customs.

• Livelihoods: tribal and rural life tied to forest produce.
• Cultural-religious: sacred groves, worship of species like tulsi, peepal and cow.

E. Aesthetic value

The intrinsic beauty of nature that enriches human experience.

• Ecotourism: national parks and sanctuaries draw visitors; "charismatic" species like tigers and peacocks.
• Inspiration: landscapes and wildlife influence art, photography and recreation.

F. Informational value

Biodiversity is a genetic and scientific library.

• Research: wild relatives supply genes for crop and livestock improvement.
• Bioprospecting: undiscovered molecules for future drugs and industry.
• Knowledge: each species carries evolutionary and ecological information.

IV. Hot spots of biodiversity

Regions with exceptional endemism under severe threat, a concept given by Norman Myers (1988).

• Criteria: must contain at least 1,500 endemic vascular plant species and have lost 70% or more of its original habitat.
• Global count: around 36 recognized hotspots covering ~2.4% of land but holding a large share of endemics.
• Indian hotspots: Western Ghats–Sri Lanka, Indo-Burma, Himalaya, and Sundaland (Nicobar Islands).
• Purpose: targets scarce conservation funds where impact is greatest.

V. Threats to biodiversity

A. Overview

The main drivers are summarized by the acronym HIPPO (Habitat loss, Invasives, Pollution, Population, Overharvesting).

• Rate: current extinction is estimated 100–1,000 times the natural background rate.

B. Habitat loss

The destruction, fragmentation or degradation of natural habitats, the leading cause of extinction.

• Deforestation: clearing for agriculture, mining, dams and urban growth.
• Fragmentation: breaks large habitats into isolated patches, cutting gene flow (e.g. elephant corridors severed).
• Degradation: pollution and overgrazing lower habitat quality.

C. Poaching of wildlife

Illegal hunting and trade of species for commercial gain.

• Products: tiger skins and bones, rhino horn, elephant ivory, musk, furs.
• Impact: pushed the cheetah to extinction in India (1952) and threatens the one-horned rhino.
• Scale: wildlife trafficking is among the largest illegal trades globally.

D. Biological invasions

The spread of non-native species that outcompete native ones.

• Mechanism: invasives lack natural predators, multiply rapidly and dominate.
• Examples: water hyacinth (Eichhornia, "terror of Bengal"), Lantana camara, Parthenium, African catfish.
• Effect: displace natives, alter habitats and reduce local diversity.

E. Human-wildlife conflicts

Negative interactions where wildlife and humans compete for space and resources.

• Causes: shrinking habitat forces animals into farmland and settlements.
• Instances: elephant crop raids and railway deaths, leopard attacks in urban fringes, man-eating tigers in the Sundarbans.
• Consequence: retaliatory killing of wildlife and loss of human life and property.

VI. Species of conservation concern

A. IUCN Red List categories

The IUCN classifies species by extinction risk to guide protection.

• Assessment basis: population size, decline rate, geographic range and fragmentation.

B. Extinct species

Species with no surviving individuals anywhere.

• Definition: no reasonable doubt the last individual has died.
• Examples: dodo, Indian cheetah (regionally extinct), passenger pigeon.

C. Endangered species

Species facing very high risk of extinction in the near future.

• Trigger: severe population decline or very small numbers.
• Examples: Bengal tiger, Asiatic lion (Gir), one-horned rhinoceros.

D. Vulnerable species

Species facing high risk of extinction in the medium-term future.

• Status: less critical than endangered but declining.
• Examples: sloth bear, blue whale, Gangetic dolphin.

E. Rare species

Species with small or localized populations, not yet threatened but at potential risk.

• Feature: low abundance or restricted range; any disturbance can threaten them.
• Examples: Hangul (Kashmir stag), musk deer.

F. EDGE species

Evolutionarily Distinct and Globally Endangered species prioritized by the Zoological Society of London.

• Concept: combines unique evolutionary history (few close relatives) with high extinction risk.
• Value: their loss erases irreplaceable branches of the tree of life.
• Examples: gharial, pygmy hog, purple frog of the Western Ghats.

VII. Conservation Strategies

A. Two approaches

Conservation is pursued either within or outside natural habitats.

1. In-situ conservation: protects species in their natural habitat, conserving whole ecosystems and evolutionary processes.
   • Protected areas: national parks (e.g. Jim Corbett), wildlife sanctuaries, biosphere reserves (e.g. Nilgiri).
   • Advantages: species adapt naturally; large populations conserved cheaply in situ.
   • Special programmes: Project Tiger (1973), Project Elephant.
2. Ex-situ conservation: protects species outside their natural habitat under human care.
   • Facilities: zoos, botanical gardens, gene banks, seed banks, cryopreservation, tissue culture.
   • Advantages: enables captive breeding and reintroduction of critically endangered species.
   • Limitation: limited numbers, loss of wild adaptations, high cost.

VIII. Biogeographic zones of India

India is divided into ten biogeographic zones based on climate, geography and biota (Rodgers and Panwar, 1988).

• The zones:
  • Trans-Himalaya: cold, arid Ladakh plateau; wild yak, snow leopard.
  • Himalaya: alpine to temperate ranges; high altitudinal diversity.
  • Desert: Thar and Kutch; adapted xeric species.
  • Semi-Arid: transition belt of Gujarat, Rajasthan; the Gir lion.
  • Western Ghats: wet, high-endemism mountain chain.
  • Deccan Peninsula: largest zone, dry deciduous forests.
  • Gangetic Plain: fertile alluvial belt.
  • North-East India: rich rainforests, gateway of Indo-Malayan biota.
  • Islands: Andaman, Nicobar and Lakshadweep; coral and endemics.
  • Coasts: long shoreline with mangroves and beaches.

IX. India as a mega-diversity nation

India is one of the world's 17 megadiverse countries, hosting a disproportionate share of global species.

• Share: ~2.4% of land area but 7–8% of recorded species, including ~45,000 plant and ~91,000 animal species.
• Endemism: about 33% of plants and many animals are found nowhere else.
• Hotspots: four of the global hotspots lie fully or partly within India.
• Agro-diversity: a Vavilov centre of origin for crops like rice, mango, sugarcane and many spices.
• Cultural link: long tradition of conservation through sacred groves and reverence for nature.