Chapter 13: Biodiversity and Conservation

In the figure : Conservation aims to protect all three levels.

In the figure : Only about 22 per cent of the estimated species have been described.

Rule 1: Levels with examples — Genetic diversity: the medicinal plant Rauwolfia vomitoria shows variation in the potency of its chemical (reserpine) in different Himalayan ranges; India has over 50,000 genetically different strains of rice and 1,000 of mango. Species diversity: the Western Ghats have more amphibian species than the Eastern Ghats. Ecological diversity: India, with deserts, rain forests, mangroves, coral reefs, wetlands, estuaries and alpine meadows, has a greater ecosystem diversity than a Scandinavian country such as Norway.

• Easy : Many rice varieties show genetic diversity.
• Medium : Western Ghats vs Eastern Ghats amphibians show species diversity.
• Exam-type : Q: What type of diversity is shown by 1,000 varieties of mango? A: Genetic diversity.

Rule 2: How many species? — More than 70 per cent of the described species are animals, and about 70 per cent of those are insects. Fungi have more species than all vertebrates together. India has about 45,000 plant species and about twice as many animal species, and is one of the 12 mega-diversity countries. Many tropical species are still unknown; prokaryote counts are very uncertain.

• Easy : Insects are the largest group of animals.
• Medium : India is a mega-diversity country.
• Exam-type : Q: What per cent of the estimated species is described? A: About 22 per cent.

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In the figure : Bird species fall sharply with latitude.

In the figure : Larger areas show a steeper slope.

Rule 1: Why are the tropics richer? — Three main ideas: (a) tropics had more evolutionary time, since temperate areas were repeatedly glaciated; (b) tropical environments are less seasonal and more constant and predictable, which promotes niche specialisation; (c) more solar energy gives higher productivity and so supports more species.

• Easy : Tropical climate is more stable.
• Medium : Glaciation affected temperate regions.
• Exam-type : Q: Name two reasons for high tropical diversity. A: More evolutionary time and constant environment (or more solar energy).

Rule 2: Species-area relationship — Humboldt found that within a region species richness increases with area, up to a limit. On a log-log graph it is a straight line. For small regions Z is about 0.1 to 0.2 whatever the group or region. For very large areas such as whole continents, Z is steeper, 0.6 to 1.2.

• Easy : Larger area: more species.
• Medium : On a log scale the graph is a straight line.
• Exam-type : Q: What is the usual range of Z for small regions? A: 0.1 to 0.2.

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In the figure : Amphibians and gymnosperms are the most threatened groups.

Rule 1: Why diversity matters — Biodiversity loss in a region may cause (a) a decline in plant production, (b) lower resistance to drought and other disturbances and (c) more variability in processes such as water use and pest and disease cycles.

• Easy : More species: more stability.
• Medium : Fewer species: lower resistance.
• Exam-type : Q: State the rivet popper hypothesis. A: Loss of a few species is tolerable, but the loss of many weakens an ecosystem like removing rivets from an aircraft.

Rule 2: Extinction facts — IUCN Red List (2004): 784 species became extinct in 500 years. Examples: dodo (Mauritius), quagga (Africa), thylacine (Australia), Steller's sea cow (Russia), and three tiger subspecies (Bali, Javan, Caspian). Over 15,500 species face extinction. Past mass extinctions numbered five. At present trends, nearly half of all species could be lost in 100 years.

• Easy : Dodo is an extinct bird of Mauritius.
• Medium : The thylacine lived in Australia.
• Exam-type : Q: How many mass extinctions occurred earlier? A: Five.

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In the figure : Habitat loss is the most important cause.

Rule 1: The four causes — Habitat loss: rain forests once covered 14 per cent of the land and now cover about 6 per cent; the Amazon is cleared for soya and cattle. Fragmentation harms animals needing large territories and migratory animals. Over-exploitation: Steller's sea cow and passenger pigeon; over-fishing. Alien species: Nile perch in Lake Victoria wiped out over 200 cichlid species; Parthenium, Lantana and water hyacinth are weeds in India; African catfish Clarias gariepinus threatens native catfish. Co-extinction: parasites of an extinct host and the plant–pollinator pair.

• Easy : Passenger pigeon: over-exploitation.
• Medium : Nile perch: alien species.
• Exam-type : Q: Which is the most important cause? A: Habitat loss and fragmentation.

Rule 2: Linking to causes — Identify the cause by the story. Forest broken into patches → fragmentation. Fish stock collapses from heavy catch → over-exploitation. An introduced weed spreading → invasion. An orchid vanishes after its only pollinator disappears → co-extinction.

• Easy : Weed spreading over fields is invasion.
• Medium : Orchid and its pollinator is co-extinction.
• Exam-type : Q: Fish parasites vanish after the host dies. Which cause? A: Co-extinction.

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In the figure : Each reason adds a different kind of value.

Rule 1: Utilitarian arguments — More than 25 per cent of drugs sold worldwide come from plants, and 25,000 plant species are used in traditional medicines. Bioprospecting explores biodiversity for economically useful products. The Amazon forest produces about 20 per cent of the oxygen in the atmosphere. Pollinators (bees, birds, bats) enable fruit and seed formation. Aesthetic pleasure is an intangible benefit.

• Easy : Plant-based drugs are a direct benefit.
• Medium : Pollination is an ecosystem service.
• Exam-type : Q: What is bioprospecting? A: Exploring molecular, genetic and species diversity for products of economic value.

Rule 2: Ethical argument — Species have a right to exist regardless of their use to humans. We share the planet with millions of plants, animals and microbes and owe them care.

• Easy : A species without economic use still matters.
• Medium : It is a moral duty.
• Exam-type : Q: What is the ethical argument? A: Every species has an intrinsic value and we must protect it.

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In the figure : In situ keeps the whole ecosystem safe; ex situ is for species at very high risk.

Rule 1: Hotspots and in situ — There are 34 hotspots in the world (initially 25, then 9 more). Three cover India: Western Ghats and Sri Lanka, Indo-Burma and Himalaya. They cover less than 2 per cent of the land, yet strict protection could cut the ongoing mass extinctions by almost 30 per cent. India has 14 biosphere reserves, 90 national parks and 448 sanctuaries, plus sacred groves in Meghalaya (Khasi and Jaintia Hills), Aravalli Hills, the Western Ghats and Madhya Pradesh.

• Easy : Hotspots: less than 2 per cent of land.
• Medium : Sacred groves are in Meghalaya.
• Exam-type : Q: Name the three hotspots of India. A: Western Ghats and Sri Lanka, Indo-Burma, Himalaya.

Rule 2: Ex situ and international efforts — Ex situ methods: zoological parks, botanical gardens, wildlife safari parks, cryopreservation of gametes, in vitro fertilisation, tissue culture and seed banks. The Convention on Biological Diversity (Earth Summit) was held at Rio de Janeiro in 1992. The 2002 World Summit on Sustainable Development in Johannesburg: 190 countries pledged a major reduction in biodiversity loss by 2010.

• Easy : Seed bank is an ex situ method.
• Medium : Earth Summit: Rio, 1992.
• Exam-type : Q: Where and when was the Earth Summit? A: Rio de Janeiro, 1992.

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