Biodiversity and Conservation - Quick Revision
Levels of biodiversity (Edward Wilson popularised the term)
- Genetic diversity: variation within a species, e.g. >50,000 rice strains and 1,000 mango varieties in India; reserpine potency in Rauwolfia vomitoria across Himalayan ranges.
- Species diversity: variety of species, e.g. Western Ghats richer in amphibians than Eastern Ghats.
- Ecological (ecosystem) diversity: variety of ecosystems, e.g. India (deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, alpine meadows) > Norway.
How many species
- IUCN (2004): >1.5 million described. Robert May's estimate of global diversity: ~7 million.
- >70% of recorded species are animals; plants <=22%. Insects = most species-rich (>70% of animals; 7 of every 10 animals). Fungi species > fishes + amphibians + reptiles + mammals combined.
- India: 2.4% of land area but 8.1% of global species diversity; one of 12 mega diversity countries; ~45,000 plant species and twice as many animals.
Patterns
- Latitudinal gradient: diversity decreases from equator (tropics, 23.5N-23.5S) to poles. Reasons: tropics had long evolutionary time (less glaciation), constant/predictable environment, more solar energy (productivity).
- Species-area relationship (Alexander von Humboldt): rectangular hyperbola; on log scale log S = log C + Z log A. Z (slope) = 0.1-0.2 for small areas, 0.6-1.2 for continents.
- Importance: more species = more stable, more productive (David Tilman); rivet popper hypothesis (Paul Ehrlich).
Loss of biodiversity
- Sixth Extinction: present rates 100-1,000x pre-human, driven by humans; 5 past mass extinctions.
- The Evil Quartet: (i) Habitat loss & fragmentation (most important), (ii) Over-exploitation, (iii) Alien species invasions, (iv) Co-extinctions.
Conservation
- Why: narrowly utilitarian, broadly utilitarian, ethical.
- In situ: 34 biodiversity hotspots (3 in India: Western Ghats-Sri Lanka, Indo-Burma, Himalaya); India has 14 biosphere reserves, 90 national parks, 448 wildlife sanctuaries, plus sacred groves.
- Ex situ: zoos, botanical gardens, seed banks, in vitro fertilisation, tissue culture, cryopreservation (-196 C).
- Global: Rio Earth Summit / Convention on Biological Diversity (1992); Johannesburg World Summit (2002, target 2010).