Biodiversity & Conservation

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1. Biodiversity Definition: The occurrence of different types of genes, gene pools, species, habitats and ecosystems in a particular place and various parts of the Earth. Term "biodiversity" was given by Edward Wilson . Biodiversity is divided into three levels: (i) Genetic diversity: Is the measure of variety in genetic information contained in the organism over its distributional range. It enables a population to adapt to its environment. Example: Medicinal plant Rauwolfia vomitoria growing in Himalayan ranges shows variation in potency and concentration of the active chemical reserpine that it produces. There are more than 50,000 genetically different strains of rice and 1,000 varieties of mango in India. (ii) Species diversity: Is a measure of the variety of species and their relative abundance present within a region. Example: The Western Ghats have a greater amphibian species diversity than the Eastern Ghats. (iii) Ecological diversity: Is a measure of the diversity at community and ecosystem levels. They represent the local, unique, habitat and regional components of species diversity. Example: India has a Scandinavian country like Norway due to presence of large number of ecosystems like deserts, rainforests, coral reefs, wetlands, estuaries and alpine meadows. 2. Global Species Diversity According to the International Union for Conservation of Nature and Natural Resources (IUCN 2004), the total number of plant and animal species is over 1.5 million. A more conservative and scientifically sound estimate made by Robert May, places the global species diversity at about 7 million. More than 70% of all the species are animals, while plants account for about 22% of the total. Among animals, insects are the most species-rich taxonomic group, making up more than 70% of the total. Of the total, only 25% of species have been recorded from India. India has 2.4% of the world's land area and 8.1% of the global species diversity. Nearly 45,000 species of plants and twice as many of animals have been recorded from India. 3. Patterns of Biodiversity (i) Latitudinal gradients: Species diversity decreases as we move away from the equator towards the poles. Tropics (latitudinal range of $23.5^\circ$ N to $23.5^\circ$ S) harbor more species than temperate or polar areas. Example: Colombia (near the equator) has about 1,400 species of birds, while New York (41$^\circ$ N) has 105 species, and Greenland (71$^\circ$ N) has only 56 species. Amazonian rainforests (South America) have the greatest biodiversity on Earth. Reasons for greater diversity in tropics: Tropical latitudes have remained undisturbed for millions of years, leading to longer evolutionary time for species diversification. Tropical environments are less seasonal, more constant and predictable, promoting niche specialization and greater species diversity. There is more solar energy available in the tropics, which contributes to higher productivity and indirectly to greater diversity. (ii) Species-Area relationships: Within a region, species richness increases with increasing explored area, but only up to a limit. Alexander von Humboldt observed that within a region, species richness increased with increasing explored area, but only up to a limit. The relationship between species richness and area for a wide variety of taxa (angiosperm plants, birds, bats, freshwater fishes) turns out to be a rectangular hyperbola. On a logarithmic scale, the relationship is a straight line: $\log S = \log C + Z \log A$. $S$ = Species richness $A$ = Area $Z$ = Slope of the line (regression coefficient) $C$ = Y-intercept The value of $Z$ lies in the range of 0.1 to 0.2 for small areas. For very large areas like entire continents, the slope of the line is much steeper ($Z$ values in the range of 0.6 to 1.2). 4. Importance of Species Diversity to the Ecosystem Ecologists believe that communities with more species are more stable than those with fewer species. A stable community should not show much variation in productivity from year to year. It must be resistant to occasional disturbances (natural or man-made). It must be resistant to invasions by alien species. David Tilman's long-term ecosystem experiments showed that plots with more species showed less year-to-year variation in total biomass and had higher productivity. 5. Loss of Biodiversity The world is facing accelerated rates of species extinctions due to human activities. The colonization of tropical Pacific Islands by humans has led to the extinction of more than 2,000 species of native birds. The IUCN Red List (2004) documents the extinction of 784 species (338 vertebrates, 359 invertebrates, and 87 plants) in the last 500 years. Some recent extinctions: Steller's sea cow (Russia) Thylacine (Australia) Dodo (Mauritius) Quagga (Africa) Three subspecies of Tiger (Bali, Javan, Caspian) In the past 20 years, 27 species have disappeared. General impacts of biodiversity loss: (i) Decline in plant production (ii) Lowered resistance to environmental disturbances such as drought (iii) Increased variability in ecosystem processes like plant productivity, water use, and pest and disease cycles. 6. Causes of Biodiversity Losses ('The Evil Quartet') (i) Habitat loss and fragmentation: This is the primary cause of extinction of species. Tropical rainforests initially covered 14% of the land surface; now cover only 6%. The Amazon rainforest ('lungs of the planet') is being cut and cleared for cultivation of soya beans and for conversion into grasslands for raising beef cattle. When large habitats are broken into small fragments due to human settlements, building of roads, digging of canals, etc., the population of animals requiring large territories and some animals with migratory habits declines. (ii) Over-exploitation: When biological system is over-exploited by man for the natural resources, it results in degradation and extinction of the resources. Example: Steller's sea cow, passenger pigeon, and many marine fishes have become extinct due to over-exploitation by man. (iii) Alien (exotic) species invasions: When alien species are introduced unintentionally or deliberately, they cause decline or extinction of indigenous species. Example: The Nile perch introduced into Lake Victoria (East Africa) caused the extinction of an ecologically unique assemblage of more than 200 species of cichlid fish in the lake. Parthenium (carrot grass), Lantana , and Eichhornia (water hyacinth) are invasive weed species that pose a threat to our native species. African catfish ( Clarias gariepinus ) for aquaculture purposes is posing a threat to the indigenous catfishes of Indian rivers. (iv) Co-extinctions: When a species becomes extinct, the plant and animal species associated with it in an obligatory manner, also become extinct. Example: When a host fish species becomes extinct, all those parasites exclusively dependent on it, will also become extinct. In plant-pollinator mutualism also, extinction of one results in the extinction of the other. 7. Biodiversity Conservation Biodiversity is important for ecosystem health and for survival of human race on Earth. Reasons for conserving biodiversity: (i) Narrowly utilitarian arguments: Human beings derive direct economic benefits from nature like food, firewood, fibre, construction material, industrial products (resins, gums, dyes, tannins, etc.) and medicinally important products. More than 25% of the drugs are derived from plants and about 25,000 species of plants are used by native people as traditional medicines. (ii) Broadly utilitarian arguments: Biodiversity plays a major role in maintaining and sustaining supply of goods and services from various species as well as ecological systems. The different ecological services provided are: (a) Amazon forest is estimated to contribute 20% of the total oxygen in the atmosphere on Earth by photosynthesis. (b) Ecosystem provides pollinators like bees, bumble bees, birds and bats which pollinate plants to form fruits and seeds. (c) Aesthetic pleasures like bird watching, spring flowers in full bloom, walking through the thick forest, waking up to a bulbul's song, etc. are some other benefits of the ecosystem. (iii) Ethical reasons: There are thousands of plants, animals and microbes on this Earth which are not useless. Every one has some intrinsic value even if it is not of any economic value to us. It is, therefore, our moral duty to ensure well-being of all the living creatures for the utilisation of future generations. 8. Conservation of Biodiversity Biodiversity can be conserved by protecting its whole ecosystem. There are two basic approaches for conservation of biodiversity: (i) In situ conservation (On-site conservation): This approach involves protection of species in their natural habitat. (a) Biodiversity hotspots: These are regions of high levels of species richness and high degree of endemism (species found only in a particular region and nowhere else). There are 34 hotspots in the world. In India, the three hotspots are: Eastern Ghats and Sri Lanka, Indo-Burma and Himalaya. Biodiversity hotspots cover less than 2% of Earth's land area, but they harbour large number of species. Thus, they could reduce mass extinction by 30%. (b) Protected areas: India has 14 biosphere reserves, 90 national parks and 448 wildlife sanctuaries. Jim Corbett National Park was the first to be established in India. (c) Ramsar sites: Ramsar sites are wetlands which are considered to be of international importance. Ramsar Convention (1971) is an international treaty for the conservation and sustainable utilisation of wetlands. Ramsar convention works for the conservation and use of wetlands, the recognition of fundamental ecological functions of wetlands and their cultural, economic, scientific and recreational value. There are 26 Ramsar sites in India. Some of these are Ashtamudi wetland (Kerala), Sambhar lake, Kolleru lake, Chilika lake, Bhitarkanika wetland (Odisha). Wetlands include marshes, lakes, coral reefs, etc. (d) Sacred groves: These are forest patches set aside for worship. All the trees and wildlife within are given total protection by tribal people. Large number of rare and threatened plants can be found in these regions. Some of the sacred groves in India are as follows: Khasi and Jaintia Hills in Meghalaya. Western Ghat regions of Karnataka and Maharashtra. Aravalli Hills of Rajasthan. Sarguja, Chanda and Bastar areas of Madhya Pradesh. (ii) Ex situ conservation (Off-site conservation): This approach involves placing threatened animals and plants in special care units for their protection. In India, botanical gardens and zoological parks are where animals which have become extinct are maintained. Cryopreservation (preservation at $-196^\circ$C) techniques, sperm, eggs, animal cells, tissues and embryos can be stored for long period in gene banks, seed banks. Plants are propagated in in vitro cloning tissue culture methods (micropropagation). It is the desirable approach when urgent measures to save extinction are required. 9. Conventions on Biodiversity The Earth Summit was held in Rio de Janeiro in 1992, which called upon all nations to take appropriate measures for conservation of biodiversity and sustainable utilisation of its benefits. The World Summit on Sustainable Development was held in Johannesburg, South Africa in 2002 in which 190 countries pledged to reduce the current rate of biodiversity loss at global, regional and local levels by 2010. Table: Differences between in situ conservation and ex situ conservation S. No. In situ conservation Ex situ conservation (i) It is the conservation and protection of biodiversity in its natural habitat. It is the conservation of selected threatened plants and animal species in places outside their natural habitat. (ii) Population is conserved in the surroundings where they have developed their distinctive features. Population is conserved under simulated conditions that closely resemble their natural habitat. (iii) E.g., national parks, biosphere reserves, wildlife sanctuaries, etc. E.g., botanical gardens, zoological parks, wildlife safari, gene banks, etc. (iv) Protection of entire ecosystem, allowing species to evolve in their natural environment. Protection of individual species, often through captive breeding programs or seed banks. (v) Cost-effective and preserves interactions between species. Often expensive and requires intensive management. (vi) Larger number of species can be conserved, including microorganisms. Limited number of species can be conserved, mainly those that are easily manageable.