Biodiversity and Conservation

🎯 Key Points

• Three levels: genetic diversity (within species — allelic variation), species diversity (richness/evenness within a community), ecological diversity (number of niches/ecosystems in a region)
• India: 12 mega-diversity countries; ~45,000 plant species (7% of world) + ~91,000 animal species (6.5%)
• Latitudinal gradient: biodiversity highest near equator, decreases toward poles — due to higher solar energy, longer evolution time, greater habitat stability in tropics
• Species-area relationship: log S = log C + Z log A (Z = 0.1–0.2 for smaller areas; 0.6–1.2 across continents)
• HIPPO acronym for biodiversity threats: Habitat loss, Invasive species, Pollution, Population (human), Overexploitation
• Biodiversity hotspots (Norman Myers): criteria = >1500 endemic vascular plant species + >70% original habitat lost; 34 hotspots globally; India has 4 (Western Ghats–Sri Lanka, Indo-Burma, Himalaya, Sundaland)
• In-situ conservation: protect in natural habitat — national parks, wildlife sanctuaries, biosphere reserves, sacred groves
• Ex-situ conservation: outside natural habitat — zoos, botanical gardens, cryopreservation, seed banks, pollen banks
• IUCN Red List categories: Extinct (EX) → Extinct in Wild (EW) → Critically Endangered (CR) → Endangered (EN) → Vulnerable (VU) → Near Threatened (NT) → Least Concern (LC)

Biodiversity Patterns

• Species richness: total number of species in an area; higher in tropics (Amazon: 40,000 plant species; Western Ghats: 15,000)
• Why tropics are richer: (1) more solar energy → more NPP → more species supported; (2) greater evolutionary time without ice-age disruption; (3) more stable environment; (4) more spatial heterogeneity → more niches
• Alexander von Humboldt: first quantified latitudinal gradient; species richness vs latitude graph
• Rivet popper hypothesis (Paul Ehrlich): each species = rivet in an airplane; a few rivets removed → OK, but cumulative loss → crash (ecosystem collapse)

Threats to Biodiversity

• Habitat loss: #1 cause globally; tropical deforestation most damaging; fragmentation creates isolated "islands" → edge effects + small populations + inbreeding
• Invasive species: Nile perch in Lake Victoria → eliminated 200 native cichlid species; water hyacinth (Eichornia crassipes) in Indian rivers; Lantana + Parthenium in India
• Co-extinction: host plant extinction → dependent insect extinct; pollinator extinction → plant extinction
• Sixth mass extinction: current rate 100–1000× background rate; driven by humans

Conservation Strategies

• Biosphere reserves: UNESCO MAB programme; core zone (no human activity) + buffer zone (limited research) + transition/manipulation zone (human activity allowed); 18 in India
• Sacred groves: forest patches protected by local communities for religious/cultural reasons; rich in endemic species; Meghalaya, Rajasthan
• India's Protected Areas: 104 national parks + 543 wildlife sanctuaries + 18 biosphere reserves
• Project Tiger (1973): India's flagship conservation program; tiger population increased from 1827 (1972) to >3000 (2022)
• Cryopreservation: seeds/gametes stored at −196 °C in liquid N₂; used for ex-situ gene banking

Levels of Biodiversity

• Genetic diversity: variation in genes (alleles) within a single species; e.g. the medicinal plant Rauwolfia vomitoria shows genetic variation in the potency of the drug reserpine across its range, and India has over 50,000 genetically different strains of rice
• Species diversity: diversity at the level of species within a region; e.g. the Western Ghats have a greater amphibian species diversity than the Eastern Ghats
• Ecological (ecosystem) diversity: diversity at the ecosystem level; India — with deserts, rainforests, mangroves, coral reefs, wetlands, estuaries and alpine meadows — has far greater ecosystem diversity than a country like Norway

Importance of Biodiversity

• Narrowly utilitarian: direct economic benefits humans obtain from nature — food, firewood, fibre, medicines and industrial products (bioresources)
• Broadly utilitarian: ecosystem services such as oxygen production (the Amazon forest is estimated to contribute a large share of atmospheric oxygen), pollination by bees and birds, and aesthetic and recreational value
• Ethical/moral: every species has intrinsic value, and we have a moral responsibility to pass on our biological legacy in good order to future generations

The Evil Quartet — Causes of Biodiversity Loss

• Habitat loss and fragmentation: the most important cause; e.g. clearing of tropical rainforests such as the Amazon ("lungs of the planet"); fragmentation particularly harms animals needing large territories
• Over-exploitation: over-harvesting of species for human use has driven extinctions (e.g. Steller's sea cow, passenger pigeon) and threatens many marine fish stocks
• Alien (invasive) species invasions: introduced species turn invasive and displace natives; e.g. the Nile perch introduced into Lake Victoria wiped out over 200 native cichlid fish; water hyacinth (Eichhornia) and Parthenium in India
• Co-extinctions: extinction of one species causes the extinction of others obligately associated with it (e.g. a host and its specific parasite, or a plant and its obligate pollinator)

Ex-situ Conservation (Expanded)

• Ex-situ conservation protects threatened species outside their natural habitat under specially managed conditions
• Methods include zoological parks (zoos), botanical gardens and wildlife safari parks, where endangered animals and plants are maintained and bred
• Seed banks, gene banks, pollen banks and cryopreservation: gametes and seeds are preserved for long periods, often at very low temperature (−196 °C in liquid nitrogen)
• Using in-vitro fertilisation and tissue culture, species on the verge of extinction can be propagated and later reintroduced into the wild

Global Conservation Efforts

• The Earth Summit (Rio de Janeiro, 1992): the historic Convention on Biological Diversity (CBD) was signed, calling on nations to conserve biodiversity and use its benefits in a sustainable and equitable manner
• World Summit on Sustainable Development (Johannesburg, 2002): 190 countries pledged to significantly reduce the rate of biodiversity loss at global, regional and local levels
• These agreements promote fair sharing of the benefits arising from commercial use of genetic resources with the host countries and communities, discouraging biopiracy