Pariksha SaathiLesson 2 of 10 · Environment and Ecology
Biodiversity: Levels, Hotspots, Megadiverse Countries and Conservation Methods
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What biodiversity means
Biodiversity is the variety of life at every level of biological organisation, from genes to whole ecosystems. The term was popularised by the American biologist Edward O. Wilson. It matters because species-rich ecosystems are more productive and recover better from disturbance, and because people depend on biodiversity for food, medicine, fibre, timber and clean water. The ecologist Paul Ehrlich compared species to the rivets of an aeroplane: losing a few may go unnoticed, but every loss weakens the whole, and losing a key rivet can bring the plane down. This is called the rivet popper hypothesis.
Three levels of diversity
Genetic diversity is variation within one species. The NCERT textbook gives three examples: India has more than 50,000 genetically different strains of rice and about 1,000 varieties of mango, and the medicinal plant Rauwolfia vomitoria growing in different Himalayan ranges differs in the strength of its drug reserpine. Species diversity is the variety of species in a region; the Western Ghats, for example, have more amphibian species than the Eastern Ghats. Ecological or ecosystem diversity is the variety of habitats: India's deserts, rainforests, mangroves, coral reefs, wetlands, estuaries and alpine meadows give it far more ecosystem diversity than a country such as Norway. Ecologists also speak of alpha diversity (within one community), beta diversity (change between communities) and gamma diversity (over a whole region). Diversity is highest in the tropics and falls towards the poles; the Amazon rainforest is the richest region on Earth.
India's share and endemic species
By the NCERT textbook figure, India has only 2.4 per cent of the world's land area but about 8.1 per cent of its recorded species. An endemic species is one found naturally in a single region and nowhere else in the wild. Indian examples are the Asiatic lion (wild only in and around Gir in Gujarat), the Nilgiri tahr and lion-tailed macaque of the Western Ghats, the sangai deer of Manipur and the pygmy hog of Assam. Endemic species are especially at risk because one habitat loss can wipe them out. The main threats are summed up as the 'evil quartet': habitat loss and fragmentation, over-exploitation, invasion by alien species, and co-extinction. Alien invaders in India include water hyacinth, Lantana and Parthenium (carrot grass), while the Nile perch introduced into Lake Victoria in Africa led to the extinction of more than 200 species of cichlid fish.
Biodiversity hotspots
The British ecologist Norman Myers gave the hotspot concept in 1988, and Conservation International later adopted it. A region qualifies if it has at least 1,500 species of endemic vascular plants (more than 0.5 per cent of the world's total) and has already lost at least 70 per cent of its original vegetation. Hotspots cover only a small part of the Earth's land yet hold a very large share of its endemic species, so protecting them saves many species at once. India includes parts of four hotspots: the Himalaya, Indo-Burma (the north-east), the Western Ghats and Sri Lanka, and Sundaland (the Nicobar Islands). The Western Ghats were also inscribed as a UNESCO World Heritage Site in 2012.
Megadiverse countries
In 1998 Conservation International identified 17 megadiverse countries which together hold most of the world's species; India is one of them, along with countries such as Brazil, Indonesia, China, Mexico and Australia. In 2002 the Cancun Declaration, signed in Mexico, created the Group of Like-Minded Megadiverse Countries, which speaks together on access to genetic resources and the sharing of benefits from them.
In-situ conservation
In-situ means 'on site': species are protected in their natural home together with their whole ecosystem, which also lets evolution continue. National parks, wildlife sanctuaries, biosphere reserves, conservation reserves and community reserves are its legal forms. India also has an old tradition of sacred groves, forest patches protected by communities for religious reasons, found in the Khasi and Jaintia Hills of Meghalaya, the Aravalli hills of Rajasthan, the Western Ghats of Karnataka and Maharashtra, and the Sarguja, Chanda and Bastar areas of central India; many of them shelter rare species.
Ex-situ conservation
Ex-situ means 'off site': threatened plants and animals are protected outside their natural habitat. Zoos, botanical gardens, wildlife safari parks and captive breeding centres are its familiar forms; the Indian Botanic Garden at Howrah, founded by Robert Kyd in 1787, is famous for its Great Banyan tree. Seed banks store seeds at low temperature and humidity, and gene banks keep pollen, tissue cultures and DNA. Gametes and embryos can be kept for long periods by cryopreservation in liquid nitrogen at minus 196 degrees Celsius. India's National Gene Bank is maintained by the National Bureau of Plant Genetic Resources (NBPGR) in New Delhi, and the Svalbard Global Seed Vault, opened in Norway's Arctic in 2008, keeps back-up seeds from gene banks all over the world. Ex-situ methods are a safety net; in-situ protection remains the main strategy because it saves species together with their habitats.
Key facts
- Biodiversity: term popularised by Edward O. Wilson; three levels are genetic, species and ecological (ecosystem) diversity.
- Genetic diversity in India (NCERT): more than 50,000 strains of rice and about 1,000 varieties of mango.
- Rivet popper hypothesis: Paul Ehrlich compared species to rivets in an aeroplane; each extinction weakens the ecosystem.
- Hotspot (Norman Myers, 1988): at least 1,500 endemic vascular plant species and at least 70 per cent of original vegetation lost.
- India's four hotspots: Himalaya, Indo-Burma, Western Ghats and Sri Lanka, Sundaland (Nicobar Islands).
- Megadiverse countries: 17 identified by Conservation International in 1998, India among them; Like-Minded Megadiverse Countries group formed by the Cancun Declaration, 2002.
- Evil quartet of threats: habitat loss and fragmentation, over-exploitation, alien species invasion, co-extinction; Nile perch wiped out over 200 cichlid species in Lake Victoria.
- In-situ: national parks, sanctuaries, biosphere reserves, sacred groves (Khasi and Jaintia Hills, Aravallis, Bastar). Ex-situ: zoos, botanical gardens, seed banks, cryopreservation.
- Cryopreservation stores gametes and embryos in liquid nitrogen at minus 196 degrees Celsius; NBPGR, New Delhi, keeps India's National Gene Bank.
- Svalbard Global Seed Vault in Norway opened in 2008; the Indian Botanic Garden, Howrah, was founded by Robert Kyd in 1787.
Quick revision
Biodiversity term popularised by E.O. Wilson; genetic, species and ecosystem diversity; India 2.4 per cent of land, about 8.1 per cent of species (NCERT); hotspot concept Norman Myers 1988 (1,500 endemic plants, 70 per cent habitat lost); India in 4 hotspots; 17 megadiverse countries (1998); evil quartet; in-situ: parks, sanctuaries, sacred groves; ex-situ: zoos, seed banks, cryopreservation at minus 196 C; Svalbard vault 2008.