Biodiversity and Conservation

Key Concepts

What is Biodiversity?

Immense heterogeneity exists at all levels of biological organisation. The term was popularised by sociobiologist Edward Wilson.

• Genetic Diversity: Variation within a species (e.g., 50,000 strains of rice in India; Rauwolfia vomitoria producing different concentrations of reserpine).
• Species Diversity: Diversity at the species level (e.g., Western Ghats have more amphibians than Eastern Ghats).
• Ecological Diversity: Diversity at ecosystem levels (e.g., India has deserts, rain forests, mangroves, coral reefs).

Global and Indian Biodiversity

• Robert May’s Estimate: Global species diversity is about 7 million.
• Named Species: ~1.5 million. > 70% are animals, 22% are plants. Among animals, > 70% are insects.
• India: Has 2.4% of world's land but 8.1% of global species diversity. One of the 12 mega diversity countries. ~45,000 plant and ~90,000 animal species recorded.

Patterns of Biodiversity

1. Latitudinal Gradients: Species diversity decreases from equator to poles.
   • Tropics (23.5° N to 23.5° S): Harbour more species. e.g., Amazon rain forest (greatest biodiversity).
   • Reasons for Tropical Richness: (a) More evolutionary time (undisturbed by glaciations). (b) Constant, predictable environment (promotes niche specialisation). (c) More solar energy (higher productivity).
2. Species-Area Relationship: Popularised by Alexander von Humboldt.
   • Species richness increases with explored area but up to a limit (Rectangular Hyperbola).
   • Equation: log S = log C + Z log A.
   • Slope (Z) is usually 0.1 to 0.2, but steeper (0.6 to 1.2) for very large areas like continents.

Importance of Species Diversity

• Ecosystem Stability: Diverse communities are more productive and resistant to invasions/disturbances (Tilman's experiments).
• Rivet Popper Hypothesis (Paul Ehrlich): Analogizes species to rivets in an airplane. Losing 'wing rivets' (key species) is catastrophic for ecosystem functioning.

Loss of Biodiversity

• The Sixth Extinction: Currently in progress; 100 to 1,000 times faster than pre-human rates.
• The Evil Quartet (Causes):
  1. Habitat Loss and Fragmentation: Most important cause (e.g., Amazon forest being cleared for soya beans).
  2. Over-exploitation: e.g., Steller's sea cow, passenger pigeon.
  3. Alien Species Invasions: e.g., Nile perch in Lake Victoria; Lantana, Water hyacinth in India.
  4. Co-extinctions: Extinction of host leads to extinction of obligatory parasites/mutualists.

Biodiversity Conservation

• Why Conserve?
  • Narrowly Utilitarian: Direct economic benefits (food, medicine, fiber).
  • Broadly Utilitarian: Ecosystem services (20% O2 from Amazon, pollination, aesthetic value).
  • Ethical: Moral duty to protect every species.
• How to Conserve?
  1. In Situ (On site): Protecting the whole ecosystem.
     • Biodiversity Hotspots: Regions with high species richness and endemism (34 globally; 3 in India: Western Ghats-Sri Lanka, Indo-Burma, Himalaya).
     • Protected Areas: 14 Biosphere Reserves, 90 National Parks, 448 Wildlife Sanctuaries.
     • Sacred Groves: Veneration of forest patches (e.g., Khasi/Jaintia Hills).
  2. Ex Situ (Off site): Threatened species kept in special settings.
     • Zoological parks, Botanical gardens, Wildlife safari parks.
     • Cryopreservation (gametes), Tissue culture, Seed banks.
• Global Efforts: The Earth Summit (Rio, 1992) and World Summit (Johannesburg, 2002).