There is fascinating variety in organism’s complex ecological relationship among organisms, genetic diversity within species and a great variety of ecological systems. Biodiversity consists of three hierarchical levels:
1. Genetic diversity; 2. Species diversity 3. Community and ecosystem diversity
Every species, varying from bacteria to higher plants and animals, stores an immense amount of genetic information. For example, the number of genes is about 450-700 in mycoplasma, 4000 in E. coli, 13000 in Drosophila melanogaster, 32000 to 50000 in Oryza sativa, and 35000 to 45000 in Homo sapiens. The genetic diversity enables a population to adapt to its environment and to respond to natural selection. If a species has more genetic diversity, it can adapt better to the changed environmental conditions.
Species diversity refers to the variety of species within a region. The simplest measure of species diversity is species richness, i.e. number of species per unit area. The number of species increases with the area of the site. Generally, the greater the species richness, the greater is the species diversity.
Diversity at the level of community and ecosystem has three perspectives, alpha diversity, beta diversity and gamma diversity.
(i) Alpha diversity is the diversity of organism sharing the same community/habitat. A combination of species richness and equitability/evenness is used to represent diversity within a community habitat.
(ii) Beta diversity is the rate of replacement of species along a gradient of habitats or communities.
(iii) Gamma diversity refers to the diversity of the habitats over the total landscape or geographical areas. Ecosystem diversity describes the number of niches, tropic levels and various ecological processes that sustain energy flow, food webs and recycling of nutrients.
Biodiversity varies with change in latitude or altitude. As we move from high to low latitudes, the biological diversity increases. While in temperate region the climate is severe with short growing period for plants in tropical rain forest, the conditions are favourable for growth throughout the year. Favourable environmental conditions favour speciation and make it possible for a larger number of species to occur and grow. A correlation is also found for a wide variety of taxonomic groups such as ants, birds, butterflies and moths.
Human derive severe direct and indirect benefits from living world. Biodiversity is the source of food, medicines, pharmaceutical drugs, fibres, rubber and timber. The biological resources contain potentially useful resource as well. The diversity of organisms also provides many ecological services free of charge that are responsible for maintaining ecosystem health.
Of the several thousand species of edible plants, about 20 plant species are cultivated to produce around 85 per cent of the world’s food. Wheat, corn and rice, the three major carbohydrate crops yield nearly two-thirds of food sustaining the human population. Fats, oils, fibres, etc. are other uses for which more and more new species need to be investigated.
Biodiversity is a rich source of substances with therapeutic properties. Several important pharmaceuticals have originated as plant based substances developed into valuable drug are as follows:
(a) Morphine (Ppaver seminiferous), used as an analgesic.
(b) Quinine (Chinchena ledgeriana) used for the treatment of malaria.
(c) Taxol, an anti-cancer drug obtained from the bark of the yew tree (Taxus brevifolia, T. baccata).
Biodiversity has also great aesthetic value. Examples of aesthetic rewards include eco-tourism, bird watching, wildlife, pet-keeping, gardenings, etc. People have always related biodiversity to the very existence of human race through cultural and religious beliefs.In majority of Indian villages and towns, plants like Osmium sanctum (tulsi) Ficus religiosa (peepal) and Prosopis cineraria (khejri) and various other trees are planted, which are considered sacred and worshipped by the people. Several birds, and even snakes, have been considered sacred. Plants and animals are also recognised as symbol of national pride and cultural heritage.
Biodiversity is essential for maintenance and sustainable utilisation of goods and services from ecological systems as well as form individual species. These services include maintenance of gaseous composition of the atmosphere, climate control by forests, ocean systems, natural pest control, and pollination of plants by insects and birds, formation and protection of soil, conservation and purification of water and nutrient cycling.
Human activities are the major threat to biodiversity as they alter the natural habitat, which protects the natural flora and fauna. Some are the main factors to extinction of species are consequent loss of biodiversity are discussed below:
(i) Habitat Loss and Fragmentation: The destruction of habitats is the main reason for the loss of biodiversity. When people cut down trees, fill a well, and plough grassland or burn a forest, the natural habitat of a species is changed or destroyed. Deforestation deprives animal life of shelter and food. This results in decrease in population of many species. Deforestation also affects migrating animals because it disturbs their habitat.
Construction of dams, blocks spawning and migration of fishes by inundating the habits and by changing the physical environment sometimes human cleanliness destroys the habitat of scavengers such as vultures, kites, dogs and even insets, etc. (ii) Introduction of Exotic or Non-native Species: New species entering a geographical region are called exotic or alien species. Introduction of such invasive species may cause disappearance of native species through changed biotic interactions.
Invasive species are considered second only to habitat destruction as a major cause of extinction of species. (iii) Over-exploitation: Over-exploitation of a particular species reduces the size of its population to an extent that it becomes vulnerable to extinction. (iv) Pollution: Soil, water and atmospheric pollution as also communities are affected by natural disturbances such as fire, free fall and defoliation by insects Man-made disturbances in intensity rate and spatial extent. For example, by using fire man may more frequently change species richness of a community. Some human impacts are new and never faced before biota, the vast number of synthetic compounds massive releases of radiations or spillover of oil in sea. Pollution may reduce and eliminate population of sensitive.
We should not deprive future generations from the economic and aesthetic benefits that they can derive from biodiversity. We require more knowledge to conserve biodiversity in reduced space and under increased pressure of human activities. Some measures have been taken for conversation of biodiversity these are:
(a) Protected Areas: India is very rich with various biographical provinces. It ranges from the cold desert of Ladakh and Spiti to hot desert of the Thar, the temperate forest in the Himalayas to the lush green tropical rain forests of lowlands. To protect, preserve and propagate this varied gift of Nature, the Government of India passed the Wild Life Protection Act in 1972, under which natural parks and wildlife sanctuaries could be created. Creation of biosphere reserves had also been put into practice since 1986. Protected areas are national parks and wildlife sanctuaries.
National Parks are areas which are strictly reserved for the betterment of the wildlife and where activities such as cultivation, grazing and forestry or plantation are not permitted and no private ownership right is allowed.
Wildlife Sanctuary protection is given only to the fauna and operations such as harvesting of timber, collection of minor forest products and private ownership rights are permitted as long as they do not interfere with the well-being of the animals. (b) Biosphere Reserves: Biosphere reserves are special category of protected areas of land and/or coastal environments, wherein people are an integral component of the system. In biosphere reserves, wild populations as well as traditional lifestyles of tribals and different domesticated plants and animals and genetic resources are protected.
The Earth Summit held in 1992 at Rio de Janeiro, Brazil resulted into a convention on biodiversity, which came into force on 29 December 1993. The convention had three key objectives:
(a) Conservation of biological diversity;
(b) Sustainable use of biodiversity; and
(c) Fair and equitable sharing of benefits arising out of the utilisation of genetic resources.
The World Conservation Union and the World Wide Fund for Nature (WWF) support projects worldwide to promote conservation and appropriate development of biosphere reserves.
The Indian region has contributed significantly to the global biodiversity. India is a homeland of 170 cultivated species and 325 wild relatives of crop plants. It is centre of diversity of animal species (zebu, chicken, mithun, water buffalo, camel); fruit plants and vegetables (mango, jackfruit, cucurbits), edible diascoreas, cococasia, alocasia; species and condiments (cardamom, ginger, black pepper, turmeric); and brassica, and bamboos. India also represents a secondary centre of domestication for some animals (horse, sheep, goat, cattle, yak and donkey) and plants (tobacco, potato and maize).
The in situ conversation of biodiversity in India is being carried out through biosphere reserves, national parks, wildlife sanctuaries and other protected areas by the Ministry of Environment and Forests. The joint forest management systems involve forest departments and local communities. This enables the tribal people and local communities to have access to non- wood forest products, and at the same time protect the forest resources.
The National Bureau of Plant, Animal and Fish Genetic Resources has a number of programmes to collect and conserve the germplasm of plants and animals in seed gene banks, and field gene banks for in vitro conservation. Botanical and zoological gardens have large collection of plant and animal species in different climatic regions of India.
The diverse varieties of food available through plants and animals have sustained human life ever since man came into existence. It is our principle duty to conserve all these species. We must adopt environment-friendly practices which do not harm natural ecosystems. The conservation of agrobiodiversity is particularly important at a tin e when our food security is under threat. Local knowledge, research and informal innovations relating to genetic resources and natural resources management hold the key to preserving biodiversity.