BIODIVERSITY & CONSERVATION:
CHAPTER AT A GLANCE
Edward Wilson popularized the term biodiversity.
LEVELS OF BIODIVERSITY
- Genetic diversity: Diversity shown by a single species at genetic level. E.g. Rauwolfia vomitoria shows genetic variation in reserpine.
- Species diversity: Diversity at species level. E.g. Western Ghats have greater amphibian species than Eastern Ghats.
- Ecological diversity: Diversity at ecosystem level. E.g. deserts, rain forests, mangroves etc.
TOTAL NUMBER OF SPECIES ON EARTH (GLOBAL SPECIES DIVERSITY)
Biologists are not sure about No. of prokaryotic species because
i. Latitudinal gradients:
Species diversity decreases from the equator to the poles.
Biodiversity (species richness) is highest in tropics because
Study of Alexander von Humboldt: Within a region, species richness increases with increasing explored area, but only up to a limit.
S= CAz
S= Species richness A= Area
C= Y-intercept Z= slope of the line (regression co-efficient)
- Conventional taxonomic methods are not suitable to identify microbial species.
- In laboratory, many species cannot be cultured.
PATTERNS OF BIODIVERSITY
i. Latitudinal gradients:
Species diversity decreases from the equator to the poles.
Biodiversity (species richness) is highest in tropics because
- It had more evolutionary time.
- Relatively constant environment.
- It receives more solar energy.
Study of Alexander von Humboldt: Within a region, species richness increases with increasing explored area, but only up to a limit.
S= CAz
S= Species richness A= Area
C= Y-intercept Z= slope of the line (regression co-efficient)
For small areas, Z value= 0.1 to 0.2.
For large areas (e.g. entire continents), Z value= 0.6 to 1.2.
IMPORTANCE OF SPECIES DIVERSITY
Rivet popper hypothesis: Proposed by Paul Ehrlich. In an airplane (ecosystem), if passengers pop a rivet (extinction of a species), it may not affect flight safety (functioning of ecosystem). But as more rivets are removed, plane becomes dangerously weak.
LOSS OF BIODIVERSITY
IUCN Red List (2004): E.g. Dodo, Quagga, Thylacine, Stellar’s sea cow etc.
Causes of Biodiversity losses (‘The Evil Quartet’)
- Habitat loss & fragmentation: Most important cause.
- Over-exploitation: Stellar’s sea cow, Passenger pigeon etc. extinct due to over exploitation.
- Alien species invasions: Cause extinction of indigenous species. E.g. Nile Perch introduced in Lake Victoria caused extinction of cichlid fish, African Catfish is a threat to indigenous catfishes in our rivers.
- Co-extinction: When a species extinct, the species associated with it also extinct. E.g. Parasites – host, Plant – pollinator.
BIODIVERSITY CONSERVATION
There are 3 categories of reasons for conservation.
a. In situ conservation (on site):
- Narrowly utilitarian arguments: Human derive economic benefits from nature such as food, firewood, industrial products and medicines.
- Broadly utilitarian arguments: Biodiversity has ecosystem services. E.g. production of O2, Pollination, Aesthetic pleasures.
- Ethical arguments: Every species has an intrinsic value. We have a moral duty to care for their well-being.
a. In situ conservation (on site):
Conservation of organisms within natural or human-made ecosystems. E.g.
- National Park: Reserved for the welfare of wildlife where private ownership, cultivation, grazing etc. are prohibited. E.g. Eravikulam National Park.
- Sanctuary: Protection only to the animals. Collection of timbers, minor forest products and private ownership are allowed. E.g. Periyar wildlife sanctuary.
- Biosphere Reserves: Areas of land or coastal ecosystems for conservation and sustainable use.
- Sacred forests (Sacred groves): Forest fragments which are communally protected based on religious beliefs.
- Conservation of organisms outside their habitats.
- E.g. genetic resource centres, zoological parks, wildlife safari parks, botanical gardens, gene banks, cryopreservation etc.
- The regions with very high species richness, high endemism but most threatened.
- There are 34 hotspots in the world.
- 3 hotspots cover India’s biodiversity regions- Western Ghats & Sri Lanka, Indo-Burma and Himalaya.