UPSC Biology Biodiversity Conservation And Wild Life / जैव विविधता संरक्षण और वन्य जीवन Biodiversity and Conservation

 Biodiversity and Conservation

1.           Biodiversity

• Biodiversity is the term popularised by the sociobiologist Edward Wilson to describe the combined diversity at all the levels of biological organisation. The most important of them are:
• Genetic diversity: A single species might show high diversity at the genetic level over its distributional range. The genetic variation shown by the medicinal plant Rauwolfia vomitoria growing in different Himalayan ranges might be in terms of the potency and concentration of the active chemical (reserpine) that the plant produces. India has more than 50,000 genetically different strains of rice, and 1,000 varieties of mango.
• Species diversity: The diversity at the species level. For example, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats.
• Ecological diversity: At the ecosystem level, India, for instance, with its deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows has a greater ecosystem diversity than a Scandinavian country like Norway.
• It has taken millions of years of evolution, to accumulate this rich diversity in nature, but we could lose all that wealth in less than two centuries if the present rates of species losses continue.

2.           Species on the Earth and in India

• More than 70 per cent of all the species recorded are animals, while plants (including algae, fungi, bryophytes, gymnosperms and angiosperms) comprise no more than 22 per cent of the total.
• Among animals, insects are the most species-rich taxonomic group, making up more than 70 per cent of the total. That means, out of every 10 animals on this planet, 7 are insects. Again, how do we explain this enormous diversification of insects?
• The number of fungi species in the world is more than the combined total of the species of fishes, amphibians, reptiles and mammals.
• It should be noted that these estimates do not give any figures for prokaryotes. Biologists are not sure about how many prokaryotic species there might be. The problem is that conventional taxonomic methods are not suitable for identifying microbial species and many species are simply not culturable under laboratory conditions. If we accept biochemical or molecular criteria for delineating species for this group, then their diversity alone might run into millions.
• Although India has only per cent of the world's land area, its share of the global species diversity is an impressive per cent. That is what makes our country one of the 12 mega diversity countries of the world. Nearly species of plants and twice as many of animals have been recorded from India.
• However living species are actually there waiting to be discovered and named?
• If we accept May's global estimates, only 22 per cent of the total species have been recorded so far. Applying this proportion to India's diversity figures, we estimate that there are probably more than plant species and more than animal species yet to be discovered and described.
• A large fraction of these species faces the threat of becoming extinct even before we discover them.

3.            Patterns of Biodiversity

• Latitudinal gradients: The diversity of plants and animals is not uniform throughout the world but shows a rather uneven distribution. For many group of animals or plants, there are interesting patterns in diversity, the most well-known being the latitudinal gradient in diversity.                                
• In general, species diversity decreases as we move away from the equator towards the poles. With very few exceptions, tropics (latitudinal range of N to S) harbour more species than temperate or polar areas. Colombia located near the equator has nearly species of birds while New York at N has species and Greenland at N only                                                           
• India, with much of its land area in the tropical latitudes, has more than species of birds. A forest in a tropical region like Equador has up to 10 times as many species of vascular plants as a forest of equal area in a temperate region like the Midwest of the USA.
• The largely tropical Amazonian rain forest in South America has the greatest biodiversity on earth.
• What is so special about tropics that might account for their greater biological diversity? Ecologists and evolutionary biologists have proposed various hypotheses; some important ones are :
• Speciation is generally a function of time, unlike temperate regions subjected to frequent glaciations in the past, tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification
• Tropical environments, unlike temperate ones, are less seasonal, relatively more constant and predictable. Such constant environments promote niche specialization and lead to a greater species diversity.
• There is more solar energy available in the tropics, which contributes to higher productivity; this in turn might contribute indirectly to greater diversity.

4.           The importance of Species Diversity to the Ecosystem

• Does the number of species in a community really matter to the functioning of the ecosystem? This is a question for which ecologists have not been able to give a definitive answer. For many decades, ecologists believed that communities with more species. generally, tend to be more stable than those with less species,
• At a time when we are losing species at an alarming pace, one might ask-Does it really matter to us if a few species become extinct? Would Western Ghats ecosystems be less functional if one of its tree frog species is lost forever? How is our quality of life affected if, say, instead of we have only species of ants on earth?
• There are no direct answers to such naive questions but we can develop a proper perspective through an analogy (the 'rivet popper hypothesis') used by Stanford ecologist Paul Ehrlich. In an airplane (ecosystem) all parts are joined together using thousands of rivets (species). If every passenger travelling in it starts popping a rivet to take home (causing a species to become extinct), it may not affect flight safety (proper functioning of the ecosystem) initially, but as more and more rivets are removed, the plane becomes dangerously weak over a period of time.
• Furthermore, which rivet is removed may also be critical. Loss of rivets on the wings (key species that drive major ecosystem functions) is obviously a more serious threat to flight safety than loss of a few rivets on the seats or windows inside the plane.

5.           Loss of Biodiversity

• The biological wealth of our planet has been declining rapidly and the accusing finger is clearly pointing to human activities.
• Causes of biodiversity losses: The accelerated rates of species extinctions that the world is facing now are largely due to human activities. There are four major causes ('The Evil Quartet' is the sobriquet used to describe them).
• Habitat loss and fragmentation
• This is the most important cause driving animals and plants to extinction. The most dramatic examples of habitat loss come from tropical rain forests. Once covering more than 14 per cent of the earth's land surface, these rain forests now cover no more than 6 per cent.
• The Amazon rain forest (it is so huge that it is called the 'lungs of the planet') harbouring probably millions of species is being cut and cleared for cultivating soya beans or for conversion to grasslands for raising beef cattle.
• Besides total loss, the degradation of many habitats by pollution also threatens the survival of many species. When large habitats are broken up into small fragments due to various human activities, mammals and birds requiring large territories and certain animals with migratory habits are badly affected, leading to population declines.

• 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 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.

• Alien species invasions

 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 m east Africa led eventually to the extinction of an ecologically unique assemblage of more than species of cichlid fish in the lake.

We must be familiar with the environmental damage caused and threat posed to our native species by invasive weed species like carrot grass (Parthemum) Lantana and water hyacinth (Eicchomia). The recent illegal introduction of the African catfish Clarias  gariepinus  for aquaculture purposes is posing a threat to the indigenous catfishes in our rivers.

• Co-extinctions
• 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.

6.         Why Should We Conserve Biodiversity?

• The narrowly utilitarian arguments for conserving biodiversity are obvious; humans derive ' countless direct economic benefits from naturefood (cereals, pulses, fruits), firewood, fibre, construction material, industrial products (tannins, lubricants, dyes, resins, perfumes) and products of medicinal importance.
• More than per cent of the drugs currently sold in the market worldwide are derived from plants and species of plants contribute to the traditional medicines used by native peoples around the world.
• Nobody knows how many more medicinally useful plants there are in tropical rain forests waiting to be explored. With increasing resources put into 'bioprospecting' (exploring molecular, genetic and species-level diversity for products of economic importance), nations endowed with rich biodiversity can expect to reap enormous benefits.
• The broadly utilitarian argument says that biodiversity plays a major role in many ecosystem services that nature provides. The fast-dwindling Amazon forest is estimated to produce, through photosynthesis, 20 per cent of the total oxygen in the earth's atmosphere. Can we put an economic value on this service by nature? We can get some idea by finding out how much your neighborhood hospital spends on a cylinder of oxygen.
• Pollination (without which plants cannot give us fruits or seeds) is another service, ecosystems provide through pollinators layer - bees, bumblebees, birds and bats. What will be the costs of accomplishing pollination without help from natural pollinators? There are other intangible benefits - that we derive from nature-the aesthetic pleasures of walking through thick woods, watching spring flowers in full bloom or waking up to a bulbul’s song in the morning. Can we put a price tag on such things?
• The ethical argument for conserving biodiversity relates to what we owe to millions of plant, animal and microbe species with whom we share this planet. Philosophically or spiritually, we need to realise that every species has an intrinsic value, even if it may not be of current or any economic value to us. We have a moral duty to care for their well-being and pass on our biological legacy in good order to future generations.

7.           How do we conserve Biodiversity?

• When we conserve and protect the whole ecosystem, its biodiversity at all levels is protected-we save the entire forest to save the tiger. This approach is called in situ (on site) conservation.
• However, when there are situations where an animal or plant is endangered or threatened and needs urgent measures to save it from extinction, ex situ (off site) conservation is the desirable approach.
• In situ conservation
• 'Biodiversity hotspots' regions are very high levels of species richness and high degree of endemism (that is, species confined to that region and not found anywhere else).
• The total number of biodiversity hotspots in the world to 34. These hotspots are also regions of accelerated habitat loss. Three of these hotspots - Western Ghats and Sri Lanka, Indo-Burma and Himalaya - cover our country's exceptionally high biodiversity regions.
• Although all the biodiversity hotspots put together cover less than 2 per cent of the earth's land area, the number of species they collectively harbour is extremely high and strict protection of these hotspots could reduce the ongoing mass extinctions by almost 30 per cent.
• In India, ecologically unique and biodiversity-rich regions are legally protected as biosphere reserves, national parks and sanctuaries. India now has 14 biosphere reserves, 90 national parks and 448 wildlife sanctuaries. India has also a history of religious and cultural traditions that emphasised protection of nature.

• Ex situ Conservation

• In this approach, threatened animals and plants are taken out from their natural habitat and placed in special setting where they can be protected and given special care. Zoological parks, botanical gardens and wildlife safari parks serve this purpose. There are many animals that have become extinct in the wild but continue to be maintained in zoological parks. In recent years ex situ conservation has advanced beyond keeping threatened species in enclosures.
• Now gametes of threatened species can be preserved in viable and fertile condition for long periods using cryopreservation techniques, eggs can be fertilised in vitro, and plants can be propagated using tissue culture methods. Seeds of different genetic strains of commercially important plants can be kept for long periods in seed banks.
• Biodiversity knows no political boundaries and its conservation is therefore a collective responsibility of all nations. The historic Convention on Biological Diversity ('The Earth Summit') held in Rio de Janeiro in 1992, called upon all nations to take appropriate measures for conservation of biodiversity and sustainable utilisation of its benefits. In a follow-up, the World Summit on Sustainable Development held in 2002 in Johannesburg, South Africa, 190 countries pledged their commitment to achieve by 2010, a significant reduction in the current rate of biodiversity loss at global, regional and local levels.
• The green plants in a terrestrial ecosystem capture about 1 per cent of the energy of sunlight that falls on their leaves and convert it into food energy.
• When green plants are eaten by primary consumers, a great deal of energy is lost as heat to the environment, some amount goes into digestion and in doing work and the rest goes towards growth and reproduction. An average of 10 per cent of the food eaten is turned into its own body and made available for the next level of consumers.
• Therefore, 10 per cent can be taken as the average value for the amount of organic matter that is present at each step and reaches the next level of consumers.
• Since so little energy is available for the next level of consumers, food chains generally consist of only three or four steps. The loss of energy at each step is so great that very little usable energy remains after four trophic levels.
• There are generally a greater number of individuals at the lower trophic levels of an ecosystem, the greatest number is of the producers.
• The length and complexity of food chains vary greatly. Each organism is generally eaten by two or more other kinds of organisms which in turn are eaten by several other organisms.
• The flow of energy is unidirectional. The energy that is captured by the autotrophs does not revert back to the solar input and the energy which passes to the herbivores does not come back to autotrophs. As it moves progressively through the various trophic levels it is no longer available to the previous level.
• Another interesting aspect of food chain is how unknowingly some harmful chemicals enter our bodies through the food chain. One of the reasons is the use of several pesticides and other chemicals to protect our crops from diseases and pests. These chemicals are either washed down into the soil or into the water bodies. From the soil, these are absorbed by the plants along with water and minerals, and from the water bodies these are taken up by aquatic plants and animals.
• This is one of the ways in which they enter the food chain. As these chemicals are not degradable, these get accumulated progressively at each trophic level. As human beings occupy the top level in any food chain, the maximum concentration of these chemicals get accumulated in our bodies. This phenomenon is known as biological magnification. This is the reason why our food grains such as wheat and rice, vegetables and fruits, and even meat, contain varying amounts of pesticide residues. They cannot always be removed by washing or other means.
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