A wide variety of living organisms including plants, animals and micro-organisms with whom we share this planet earth makes the world a beautiful place to live in. Living organisms exist almost everywhere from mountain peaks to the ocean depths; from deserts to the rainforests. They vary in their habit and behaviour, shapes, sizes and colour. The remarkable diversity of living organisms form an inseparable and significant parts of our planet however, the ever increasing human population is posing serious threats to bio-diversity.
WHAT IS BIOLOGICAL DIVERSITY
Sum total of all the variety of living organisms on earth constitute biodiversity. Biological diversity is usually considered at three different levels –
a) genetic diversity i.e. at genetic level ,
b) species diversity i.e. at the level of species, and
c) ecosystem diversity i.e. at the level of ecosystem.
a) Genetic Diversity : With the above background, genetic diversity refers to the variety of genes contained within species of plants, animals and micro-organisms. New genetic variation in individuals occurs by gene and chromosomal mutation, and in organisms with sexual reproduction may be spread across the population by recombination. For instance, two brothers differ in their structure, although their parents are the same. The differences could be in alleles (different variants of the same gene), in entire gene (the traits determining particular characteristics) or in chromosomal structure. The amount of genetic variation (gene pool) present in an inter-breeding population is shaped or decided by the process of natural selection. Selection leads to certain genetic attributes being preferred and results in changes in the frequency of genes within this pool. This forms the basis of adaptation among the living organisms. India has high genetic diversity and is regarded as a Vavilov’s centre of high crop genetic diversity – so named after the Russian agro-botanist N I Vavilov, who identified eight such centres of origin of cultivated plants around the world in the 1950s
b) Species diversity : Species diversity refers to the variety of species within a geographical area. Species diversity can be measured in terms of:
(a) Species richness – refers to the number of various species in a defined area
(b) Species abundance – refers to the relative numbers among species. For example, the number of species of plants, animals and microorganisms may be more in an area than that recorded in another area.
(c) Taxonomic or phylogenetic diversity – refers to the genetic relationships between different groups of species.
Ecosystem diversity : It refers to the presence of different types of ecosystems. For instance, the tropical south India with rich species diversity will have altogether different structure compared to the desert ecosystem which has far less number of plant and animal species. Likewise, the marine ecosystem although has many types of fishes, yet it differs from the freshwater ecosystem of rivers and lakes in terms of its characteristics. So such variations at ecosystem level are termed as ecosystem diversity.
Hot spots of biodiversity : Biodiversity is not uniformly distributed across the geographical regions of the earth. Certain regions of the world are very rich in biodiversity. We call such areas as “mega diversity zones”. We also refer to them as “hot-spots”. For example, India accounts for only 2.4 % of the land area of the world; but it contributes approximately 8% species to the global diversity due to existence of such pockets.
Norman Myers, a British Ecologist, developed the concept of hot spots in 1988 to designate priority areas for in situ conservation. According to him, the hot spots are the richest and the most threatened reservoirs of biodiversity on the earth.
The criteria for determining a hot spot are:
i) The area should support >1500 endemic species,
ii) It must have lost over 70 % of the original habitat Twenty-five biodiversity hot spots have been identified in the world. These hot spots are characterized by posing exceptionally high biodiversity. For example the total area of these 25 hot spots cover 1.4% of the total land area, support 44% of plant and 35% terrestrial vertebrates
WHY IS BIOLOGICAL DIVERSITY IMPORTANT : Humans depend for their sustenance, health, wellbeing and cultural growth on nature. Biotic resources provide food, fruit, seed, fodder, medicines and a host of other goods and services. The enormous diversity of life is of immense value, imparting resilience to ecosystems and natural processes. Biodiversity also has enormous social and cultural importance.
The value of biological diversity The various benefits of biological diversity can be grouped under three categories:
a) ecosystem services,
b) biological resources,
c) social benefits.
Ecosystem services Living organisms provide many ecological services free of cost that are responsible for maintaining ecosystem health. Thus biodiversity is essential for the maintenance and sustainable utilization of goods and services from ecological system as well as from individual species.
i) Protection of water resources: Natural vegetation cover helps in maintaining hydrological cycles, regulating and stabilizing water run-off and acting as a buffer against extreme events such as floods and droughts. Vegetation removal results in siltation of dams and waterways. Wetlands and forests act as water purifying systems, while mangroves trap silt thereby reducing impacts on marine ecosystems.
ii) Soil protection: Biological diversity helps in the conservation of soil and retention of moisture and nutrients. Clearing large areas of vegetation cover has been often seen to accelerate soil erosion, reduce its productivity and often result in flash floods. Root systems allows penetration of water to the sub soil layer. Root system also brings mineral nutrients to the surface by nutrient uptake.
iii) Nutrient storage and cycling: Ecosystem perform the vital function of recycling nutrients found in the atmosphere as well as in the soil. Plants are able to take up nutrients, and these nutrients then can form the basis of food chains, to be used by a wide range of life forms. Nutrients in the soil, in turn, is replenished by dead or waste matter which is transformed by micro-organisms; this may then feed others such as earthworms which also mix and aerate the soil and make nutrients more readily available.
iv) Pollution reduction: Ecosystems and ecological processes play an important role in maintenance of gaseous composition of the atmosphere, breakdown of wastes and removal of pollutants. Some ecosystems, especially wetlands have the ability to breaking down and absorb pollutants. Natural and artificial wetlands are being used to filter effluents to remove nutrients, heavy metals, suspended solids; reduce the BOD (Biological Oxygen Demand) and destroy harmful micro-organisms. Excessive quantities of pollutants, however, can be detrimental to the integrity of ecosystems and their biota.
v) Climate stability: Vegetation influences climate at macro as well as micro levels. Growing evidence suggests that undisturbed forests help to maintain the rainfall in the vicinity by recycling water vapor at a steady rate back into the atmosphere. Vegetation also exerts moderating influence on micro climate. Cooling effect of vegetation is a common experience which makes living comfortable. Some organisms are dependent on such microclimates for their existence.
vi) Maintenance of ecological processes: Different species of birds and predators help to control insect pests, thus reduce the need and cost of artificial control measures. Birds and nectar–loving insects which roost and breed in natural habitats are important pollinating agents of crop and wild plants. Some habitats protect crucial life stages of wildlife populations such as spawning areas in mangroves and wetlands. Without ecological services provided by biodiversity it would not be possible to get food, pure air to breathe and would be submerged in the waste produced.
Biological resources of economic importance
i) Food, fibre, medicines, fuel wood and ornamental plants: Five thousand plant species are known to have been used as food by humans. Presently about 20 species feed the majority of the world’s population and just 3 or 4 only are the major staple crops to majority of population in the world.
ii) Breeding material for crop improvement: Wild relatives of cultivated crop plants contain valuable genes that are of immense genetic value in crop improvement programmes. Genetic material or genes of wild crop plants are used to develop new varieties of cultivated crop plants for restructuring of the existing ones for improving yield or resistance of crops plants. For example: rice grown in Asia is protected from four main diseases by genes contributed by a single wild rice variety.
iii) Future resources: There is a clear relationship between the conservation of biological diversity and the discovery of new biological resources. The relatively few developed plant species currently cultivated have had a large amount of research and selective breeding applied to them. Many presently under-utilised food crops have the potential to become important crops in the future.Knowledge of the uses of wild plants by the local people is often a source for ideas on developing new plant products.
Social benefits
i) Recreation: Forests, wildlife, national parks and sanctuaries, garden and aquaria have high entertainment and recreation value. Ecotourism, photography, painting, film making and literary activities are closely related.
ii) Cultural values: Plants and animals are important part of the cultural life of humans. Human cultures have co-evolved with their environment and biological diversity can be impart a distinct cultural identity to different communities. The natural environment serves the inspirational, aesthetic, spiritual and educational needs of the people, of all cultures. In a majority of Indian villages and towns, plants like Tulsi (Ocimum sanctum), Peepal (Ficus religiosa), Khejri (Prosopis cineraria) are planted and considered sacred and worshipped.
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