Biodiversity and Its Conservation
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CHAPTER BIODIVERSITY AND 15 ITS CONSERVATION The term Biodiversity is a concise term used for 'Biological diversity'. Biodiversity means the variability among living organisms from all sources, such as terrestrial, marine, other ecosystems and the ecological complexes of which they are part. This includes diversity within the species, between the species and of the ecosystems. The term biodiversity describes all aspects of diversity but especially the richness of species within a specified region or the world, the complexity of ecosystems and genetic diversity. Diversity differs from place to place as each habitat has its own distinct biota. The major factors that tend to decrease biodiversity are increasing human population, higher resource consumption and pollution. Loss of biodiversity reduces gene pool of species, number of interactions in the biota and ability of species to adapt themselves to change in the environment. India is one of the 12 mega biodiversity countries in the world. The country is divided into 10 biogeographic regions. Endemism of Indian biodiversity is significant about 5150 species of flowering plants (30% of the world's endemic flora) are endemic to the country. These are distributed over 141 genera belonging to 47 families. These are concentrated in the floristically rich areas of North-East India, Western Ghats, North-West Himalayas and the Andaman and Nicobar Islands. These areas constitute 2 of the 18 hot spots identified in the world. It is estimated that 62% of the known amphibian species are endemic to India of which a majority is found in Western Ghats. BIODIVERSITY IN INDIA India with 2.4% of the world's land area share 8.1% of the global species diversity. It is among 12 mega diversity countries of the world. Nearly 45,000 species of plants and twice as many of animals have been recorded from India. It is estimated that probably more than 1,00,000 plant species and more than 3,00,000 animal species yet to be discovered and described. LEVELS OF BIODIVERSITY The biological diversity includes following three hierarchical levels: 1. Genetic diversity 2. Species diversity 3. Community and ecosystem diversity GENETIC DIVERSITY It is the diversity in the number and types of genes as well as chromosomes present in different species and the variations in the genes and their alleles in the same species. Variations in the genes of a species increases with the increase in size and environmental parameters of the habitat. Ecotype formation depends upon it. Genetic diversity is useful in adaptation to changes in the environmental condition. It helps in speciation or new species evolution. India has more than 50,000 genetically different strains of rice, and 1,000 varieties of mango. SPECIES DIVERSITY It means the species richness in any habitat. Greater the species richness, greater will be their diversity. However, it should not be confused with the species abundance. It is the diversity at the species level. For example, the Western ghats have a greater amphibian species diversity than Eastern ghats. ECOSYSTEM DIVERSITY Ecological or ecosystem diversity is the diversity at the ecosystem level. For example, India with its deserts, rainforests, mangroves, coral reefs, wetlands, estuaries and alpine meadows has a greater ecosystem diversity than a Scandinavian country-like Norway. Diversity at the level of community and ecosystem has three perspectives, i.e., , and - diversity (Whittaker; 1965). (i) -diversity (within community diversity) It is also called local diversity and is a diversity within a community, (ii) -diversity (between community diversity) It is calculated by dividing gamma ( ) by a diversity and is a diversity between two community. (iii) -diversity Also called regional diversity. It represents the total richness of species in all the habitats found within a region, geographical area or landscape. PATTERNS OF BIODIVERSITY All over the Earth, biodiversity shows following pattern: LATITUDINAL GRADIENT The diversity of plants and animals is not uniform throughout the world. It shows an uneven distribution. In general, species diversity decreases as we move away from the equator towards the poles. Usually, tropics (latitudinal. range of 23.5°N to 23.5°S) harbour more species than temperate or polar areas. Columbia located near the equator has nearly 1,400 species of birds, while New York at 41°N has 105 species and Greenland at 71°N only 56 species. India, with much of its land area in the tropical latitudes, has more than 1,200 species of birds. The largely tropical Amazonian rainforest in South America has the greatest biodiversity on the Earth. There are about 40,000 species of plants, 3,000 of fishes, 1,300 of birds, 427 of mammals, 427 of amphibians, 378 of reptiles and more than 1,25,000 invertebrates. SPECIES/AREA RELATIONSHIP The great German naturalist and geographer Alexander von Humboldt observed that within a region, species richness increases with increasing explored area, but only up to a limit. In fact, the relation between species richness and area for a wide variety of taxa (angiosperms, birds, bats, freshwater fishes) turn out to be a rectangular hyperbola as described by following figure15.1. On a logarithmic scale, the relationship is a straight line described by the following equation: log S = log C + Z log A where, S = Species richness A = Area Z = Slope of the line (regression coefficient) C = Y-intercept Figure 15.1 Showing species area relationship. (Note that on log scale, the relationship becomes linear) Ecologists have discovered that the value of Z-lines in the range of 0.1 to 0.2, regardless of the taxonomic group or the region whether it is the plants in Britain, birds in California or molluscs in New York state, the slopes of the regression line are amazingly similar. LOSS OF BIODIVERSITY The loss of biological diversity is a global crisis. Out of the 1.6 million species known to 1 1 inhabit the Earth, about to is likely to get extinct within the next few decades. Biological 4 3 extinction has been a natural phenomenon in geological history. The destruction of the world's tropical forests, which are disappearing at an alarming rate, is one of the most urgent global environmental issues. Tropical forests are estimated to contain 50 to 90% of the world's total biodiversity. The biological wealth of our planet has been declining rapidly and the accusing finger is clearly pointing towards the human activities. The colonization of tropical Pacific Islands by humans is said to have led to the extinction of more than 2,000 species of native birds Adding to the grim scenario of extinctions, the fact is that more than 15,500 species worldwide are facing the threat of extinction. Presently, 12 percent of all bird species, 23 percent of all mammal species, 32 percent of all amphibian species and 31 percent of all gymnosperm species in the world face the threat of extinction. The current species extinction rates are estimated to be 100 to 1,000 times faster than in the pre-human times and our activities are responsible for the faster rates. In general, loss of biodiversity in a region may lead to (a) Decline in plant production, (b) Lowered resistance to environmental perturbations such as drought and (c) Increased variability in certain ecosystem processes, such as plant productivity, water use and pest and disease cycles. CAUSES OF BIODIVERSITY LOSS The accelerated rates of species extinctions that the world is facing now are largely due to human activities. There are following four major causes of biodiversity reduction. (i) HABITAT LOSS AND FRAGMENTATION This is the most important cause of driving animals and plants to extinction. The most dramatic examples of habitat loss come from the tropical rainforests. Once covering more than 14 percent of the Earth's land surface, these rainforests now cover not more than 6 percent. They are being destroyed fast. By the time you finish reading this chapter, 1,000 more hectares of rainforest would have been lost. The Amazon rainforest (it is so huge that it is called the lungs of the planet), harbouring probably millions of species is being out and cleared for cultivating soyabeans or for the conversion to grasslands for raising beef cattle. (ii) OVER-EXPLOITATION Humans have always depended on nature for food and shelter, but when 'need' turns to 'greed', it leads to over-exploitation of natural resources. Many species extinctions in the last 500 years (Steller's sea cow, passenger pigeon), were due to over-exploitation by humans. Presently, many marine fish populations around the world are over harvested, endangering the continued existence of some commercially important species. (iii) ALIEN SPECIES INVASION When alien species are introduced unintentionally or deliberately for whatever purpose, some of them turn invasive, and cause decline or extinction of indigenous species. The Nile perch introduced into Lake Victoria in East Africa led eventually to the extinction of an ecologically unique assemblage of more than 200 species of cichlid fish in the lake. Another example of environmental damage caused and threat posed to our native species by invasive weed species like carrot grass (Parthenium), Lantana and water hyacinth (Eichhornia). The recent illegal introduction of the African catfish Clarias gariepinus for aquaculture purposes is posing a threat to the indigenous catfishes in our rivers. (iv) CO-EXTINCTION When a species becomes extinct, the plant and animal species associated with it in an obligatory way also become extinct. When a host fish species becomes extinct, its unique assemblage of parasites also meets the same fate. Another example is the case of a coevolved plant-pollinator mutualism where extinction of one invariably leads to the extinction of the other. RED DATA BOOK AND IUCN IUCN is International Union of Conservation of Nature and Natural Resources which is now called World Conservation Union (WCU).