Biodiversity and Conservation — Short Notes

Biodiversity — variety and variability of life on Earth. Term popularised by Edward Wilson.

Levels of Biodiversity

1. Genetic diversity — variation of genes within a species (e.g. Rauwolfia vulgaris has different chemical concentrations across ranges).
2. Species diversity — variety of species in an area (Western Ghats amphibians > Eastern Ghats).
3. Ecosystem diversity — variety of ecosystems (deserts, forests, wetlands, mangroves).

How Much Biodiversity Exists?

• ~1.5 million species described so far.
• Robert May estimates ~7 million species globally.
• Animals dominate: ~70% animals, ~22% plants, rest microbes.
• Insects account for 70% of animal species.
• India — hosts 2.4% of world species despite being 2.4% of land area (mega-diverse country).
• Number of prokaryotes underestimated (culturability issue).

Patterns of Biodiversity

Latitudinal Gradient

• Species diversity decreases from equator to poles.
• Colombia (~4°N): ~1400 bird species; New York (41°N): ~105; Greenland (71°N): ~56.
• Reasons: tropics are climatically stable, energy-rich; had longer evolutionary time; niche specialisation.

Species-Area Relationship

• Species richness increases with area, then plateaus (log-log line).
• Alexander von Humboldt formulated it.
• S = CA^Z: log S = log C + Z log A.
• Z (slope) = 0.1–0.2 for smaller areas; ~0.6–1.2 for very large areas (continents).

Importance of Species Diversity

• Stable communities have:
• Low variation in productivity year-to-year.
• Greater resistance to disturbance (invasions, diseases).
• Ecosystem services.
• David Tilman's experiments: more species → less variation in productivity.
• Rivet-popper hypothesis (Paul Ehrlich) — species are like rivets on an aeroplane; losing many risks catastrophic failure.

Loss of Biodiversity

• Current extinction rate is 100-1000× the natural rate.
• We're in the sixth mass extinction.
• ~700 species have gone extinct in recent times; IUCN Red List (2004) lists ~15,500 as threatened.
• Since 1500 AD: 338 vertebrates, 361 invertebrates, and 87 plants documented as extinct.

Causes (mnemonic: HIPPO)

1. Habitat loss & fragmentation — biggest cause; e.g. Amazon deforestation.
2. Invasive alien species — Lantana, water hyacinth (Eichhornia), African catfish.
3. Pollution — chemical, plastic, noise.
4. Population — human population pressure.
5. Overexploitation — fisheries collapse, poaching.

Why Conserve Biodiversity?

Narrowly utilitarian

• Food, firewood, fibre, medicines (e.g. anti-cancer taxol from Taxus, quinine from Cinchona).

Broadly utilitarian

• Ecosystem services — 20% of O₂ from Amazon, climate regulation.
• Pollination, water cycles.

Ethical

• Moral duty to protect other species.

Conservation Strategies

In-situ (in the natural habitat)

• Biosphere reserves — 18 in India (e.g. Nilgiri, Sundarbans, Nanda Devi).
• National parks — over 100 (Jim Corbett, Kanha).
• Wildlife sanctuaries — 500+.
• Sacred groves — Meghalaya's Khasi/Jaintia hills; Kerala's Sarpakavus.
• Hotspots — biodiversity-rich areas with high endemism + severe threat.
• 34 global hotspots; India has 3: Western Ghats + Sri Lanka, Eastern Himalayas, Indo-Burma.

Ex-situ (outside natural habitat)

• Zoos, botanical gardens, seed banks, gene banks, tissue culture, cryopreservation (−196°C).
• Useful for critically endangered species.

International Efforts

• Earth Summit 1992 (Rio de Janeiro) — Convention on Biological Diversity.
• World Summit 2002 (Johannesburg) — 190 countries pledged to reduce biodiversity loss.

Take-aways

• Biodiversity spans genes → species → ecosystems.
• Tropics are richest; areas act as "living libraries" of evolution.
• Threats are dominated by human activity (HIPPO).
• Conservation combines in-situ (parks, hotspots) and ex-situ (zoos, gene banks) methods.