Escalating scourge of biodiversity degeneration: Conservation is the need of the hour
What is Biodiversity?
Biodiversity (short form of Biological diversity) refers to the variability among living organisms which includes diversity within species, between species and of their ecosystem (Biodiversity Convention, Rio de Janeiro June 1992). The term biodiversity was coined by Walter G. Rosen in 1985. There are three levels of biodiversity as follows:
1. Genetic diversity
This includes the genetic variation within species, both among geographically separated populations and among individuals within single population. This genetic diversity is the result of different modes of adaptation in different habitats, which provides organisms and ecosystems with capacity to recuperate after change has occurred. Thus genetic diversity can be viewed and compared at three levels.
(i) Genetic variability between individuals within population.
(ii) Genetic variability among population within species; and
(iii) Diversity among species.
2. Species diversity
It denotes the variety of species on earth from acellular viruses to single celled microorganisms like bacteria, mycoplasmas, actinomycetes etc. to multicellular plants and animals. For proper functioning of particular community or ecosystem the species diversity is very essential. In a community the survival of all species are interrelated to the existence of other living organisms.
3. Ecosystem diversity
It refers to variations in the biological communities in which species live, the ecosystem in which communities exist and interactions among these levels. Ecosystem diversity is reflected in diverse biogeographic zones such as lakes, deserts, coasts, estuaries etc.
Why Tropical and Subtropical Regions are Rich in Biodiversity?
Most of the world's biodiversity is concentrated in the tropical and subtropical forests. The tropics remained stable during the geological periods and did not face any major loss of biodiversity. On the other hand, the temperate and other regions were affected because of several episodes of glaciations. Thus, biota (flora and fauna of an area) from the Northern and Southern hemispheres moved (south or north, respectively) to the tropics and the subtropics.
In this process, there was often a virtual destruction of entire species of flora and fauna. However, the movement to, and the recolonization of, the temperate areas took place after the recession of each glaciation. During such to-and-fro migrations, many species were completely lost, many new ones arose, and only those species survived which had some inherent competitive advantage over the others.
The warm temperatures and high humidity levels in the tropics are conducive to greater survival rates than are the harsh temperatures in the winter in the temperate regions. Special features such as dormancy, hibernation, or migration are required to survive or escape the harsh winter conditions. Such adaptations are normally difficult to achieve. This led to a decrease in the overall number of species in the temperate regions, as compared to the tropical regions.
With greater solar energy received in the tropics, there is greater biomass production. This allows higher productivity and a wider resource base. Thus, there is greater biodiversity in the tropics.
A major difference between the temperate and the tropical flora is that, in the former, large populations of a very small number of species dominate, whereas in the tropics there are very small populations (often single and isolated individuals) of a large number of species, correlated with greater pressure from pests, disease, and parasites. In the temperate regions, these are eliminated by harsh winters. The tropical biota counters the danger from these diseases, pests and parasite by developing a greater heterogeneity of biota. In temperate conditions, the evolutionary trend has been towards a reduced number of species but with large populations. This has led to a greater number of endemic or rare species in the tropics than in the temperate regions.
The tropical biota is older than temperate biota which had got much more time to evolve local adaptations with increasing specialization, including reproductive biology. Thus there is, far more biodiversity in the tropics and subtropics than in the temperate regions of the world.
How Biodiversity is described?
Biodiversity is described by three parameters which are as follows:
(i) Alpha diversity: It refers to intra community diversity. It is in fact number of species in a single community. This can be used for the comparison of the number of species in different ecosystem types.
(ii) Beta diversity: In refers to inter community diversity. It is degree to which species composition changes along an environmental gradient. It is normally represented in terms of the similarity index or of a species turnover rate.
(iii) Gamma diversity: It refers to inter continental diversity. Therefore, this applies to larger geographical scales and defined as "the rate at which additional species are encountered as geographical replacements within a habitat type in different localities."
Why Biodiversity is Important?
Biodiversity plays important role in the life of man. Without biodiversity existence of human life is not possible on this earth. The various benefits of biodiversity are described as follows:
1. Plants are source of medicines. It is estimated that more than 25 per cent of all the medicines available today are derived from tropical plants. The plant Rauvolfia serpentina is source of alkaloid reserpine used in treatment of hypertension. The dried ripe seeds of tree Strychnos nux-vomica are source of alkaloid nuxvomica which is used in the treatment of paralysis and nervous disorders.
The bark of Gymnospermic shrub Ephedra gerardiana is source of alkaloid ephedrine used in the treatment of asthma. Similarly the bark of Gymnospermic tree Taxus baccata is source of alkaloids taxol and baccatinused in the treatment of cancer. The gum obtained from the plant Commiphora wightii is used in the treatment rheumatic arthritis.
The alkaloid Dioscorin obtained from the plant Dioscorea delatoides is used as contraceptive. The roots ofAtropa acuminata is used as an anodyne of rheumatism, neuralgia and local inflammations. The plantsCoptis teeta and Colchicum luteum are used in the treatment of malaria and gout, respectively. However, according to Red Data Book all the aforesaid medicinal plant species belongs to endangered category of plant species in India.
2. Biodiversity helps in increasing agricultural productivity and also in developing disease resistant varieties. It was evident in the early 1970s when epidemic called grassy stunt disease of rice caused by virus destroyed more than 160,000 hectares of the crop in Asia. A resistance gene borrowed from wild rice variety of Central India named Oryza nivara controlled the disease. It was the only known genetic source of resistance to the grassy stunt disease. The cultivar IR 36 was developed with help of Oryza nivara.
Today 20 major genes from wild rice for disease and pest resistant are used in rice improvement programme. A wild barley plant from Ethopia provided a gene that protected California from lethal yellow dwarf virus. A wild tomato discovered in the Andes has been used to increase the sugar content of cultivated varieties, increasing their commercial value by millions of dollars per year.
The Solanum tuberosum (Potato) has been greatly benefitted from its several wild relatives. For instance,Solanum acaule has conferred resistance to Solanum tuberosum against potato virus X and potato leaf roll virus. Similarly Solanum spegazzini another wild relative of potato has been source of resistant genes against five races of cyst rematode (Globodera) and the fungus Fusarium coeruleum. The Solanum vernei has also been the source of resistant gene against cyst nematode (Globodera).
The Solanum stoloniferum has contributed a gene that gives resistance to potato virus Y. The Solanum demissum has been source of resistant gene against Phytopthora infestans (the fungus causing late blight of potato). The grass Saccharum spontaneum (Kans) has been source of resistance gene to the red rot disease of sugarcane (Saccharum officinarum)
3. Biodiversity play a role in the maintenance of productivity in the face of natural and human induced change (e.g. drought, disturbance, climate change, toxins etc.) and changes in landscape configuration can have large and long lasting effects on regional productivity.
4. Biodiversity fulfils the need of food, fodder, fuel, fibre, timber and ornamentation. Plants are important source of grazing for cattle and other herbivores. Flesh of animals is an important source of food for human beings. A conservative estimate is that a lower middle-class Indian uses at least 75 species daily as food, drink, condiments, clothing, shelter, recreation, ornamentation and so on.
5. Forests comprising diverse group of plant species are the major sinks of carbon dioxide which serve as a green house gas causing global warming, thus biologically diverse forest ecosystem helps in abatement of global warming.
6. Biodiversity plays an important role in protecting the water resources. The natural vegetation cover in water catchment helps in maintaining hydrological cycles, regulating and stabilizing water runoff and acts as buffer against natural disasters like flood and drought. Vegetation facilitates the percolation of water into the ground, thus helping in maintenance of ground water table. Deforestation has been the major cause of the lowering of ground water table.
7. The standing mangrove vegetation along the coastal areas serves as a shield against natural disasters like cyclone and tsunami. In addition to this, mangroves play an important role in controlling shoreline erosion. Degeneration of mangrove diversity along coast may lead to lessening of production in unmanaged fisheries.
8. Biodiversity plays significant role in soil formation and its conservation. The vegetation improves the soil structure, increase the water holding capacity of the soil and also raise the nutrient level of the soil.
9. Biological diversity plays important role in nutrient recycling. It is the sink and source of nutrients. Microbes decompose the dead plant parts and animals in the soil thus facilitating the nutrient return to the soil
10. Biodiversity helps in elimination of environmental pollution. Breakdown of the pollutants and its absorption is feature of many plants. The plant Cathranthus roseus has the ability to degrade Trinitrotoluene (TNT) like explosive. Several strains of micro-organisms have been found useful for the purpose of cleaning up toxic wastes. The bacteria like Pseudomonas putida, Arthrobacter viscosus andCitrobacter spp. have the ability to remove several toxic heavy metals from industrial effluents. Radioactive toxic metals as uranium and thorium are removed by Rhizopus arrhizus, however, the Penicillium crysogenium has the ability to accumulate radium.
Some plant species thrive on soils that are rich in heavy metals. These plants possess biochemical mechanisms that enable them to extract those metals from the soil and accumulate them to very high levels in their tissues. Several plants have the ability to hyper accumulate metals like copper, nickel, cadmium, chromium, cobalt and mercury. They can be planted on toxic waste sites where they can remove the toxic metals from the soil.
The Brassica juncea (Indian mustard) has the capability of absorbing cadmium and chromium from the soil. Aquatic plants like Eichhornia crassipes, Salvinia molesta and Lemna minor are used for disposition and extraction of metals like copper, cadmium, iron and mercury from water.
11. Biodiversity plays important role in maintenance of human health. Alterations in biodiversity can affect disease transmission either through their influence on vectors of disease, or more directly on their influence on the disease causing organisms themselves. Changes in landscape diversity, due to agriculture, have resulted in the spread of human diseases. For instance, the introduction of jhum cultivation (slash-and-burn agriculture) into wet tropical Africa resulted in an increase in malaria which in turn increased the occurrence of sickle-cell anaemia. Physically damaged reefs are often invaded by the dinoflagllateGambierdiscus toxicus, which is responsible for ciguatera in human beings.
Changes in plant species composition can result in changes in the emissions of volatile organic compounds by plants which can lead, along with industrial pollutants, to increases in tropospheric ozone that can indirectly affect human health. Rooting depth changes as a result of replacing species when forests are converted to agricultural systems. These changes in rooting depth affect the amount of water percolating through the soil and may increase the levels of nitrate in ground water.
12. Vegetation influences climate both at the micro and macro levels. Forests maintain rainfall by recycling water vapour stability into atmospheric turbulence. Change in species composition affects atmospheric interaction and local weather through changes in evapo-transpiration and albedo. In desert and grassland systems, the amount of water transpired and hence the local climate depends very strongly on the particular complement of species present and the way in which they partition water. In marine systems, planktonic algae emit considerable amount of dimethyl sulphide, which subsequently have a strong influence on cloud formation.
13. Biodiversity provide stability to the ecosystem and maintains the ecological balance. Plants and animals in ecosystem are linked to each other through food chain and food web. The loss of one species in the ecosystem affects the survival of other species. Thus the ecosystem becomes fragile.
14. There are various social benefits of biodiversity. Nature is the best laboratory for studies. The research, education and extension works can progress only with the help of nature and its inherent biodiversity. There are evidences to prove that human culture has co-evolved with the environment. For this reason itself, conservation of biodiversity is important for his cultural identity.
15. Biologically diverse forest ecosystems are home of wild-life and tribals. The forest of surrounding areas fulfils all the needs of the tribals. Due to constant association with the forest environment tribals have evolved a curious knowledge of plants and their utility for them. Many of the uses for which plant tribals employ products are not known outside their restricted community.
16. Biodiversity has aesthetic value as well. In provides beauty to the landscapes. Wild animals and plants provide inspiration not only to biologists but also to naturalists, explorers, painters, photographers, poets, writers and musicians. More over some of the interesting aspects of animal life (social, behavior, migration etc.) occur only in wild not in zoos.
Global Biodiversity Degeneration:
Among the six major environmental threats facing humanity, the degeneration of biodiversity is a serious one. The other five threats are population explosion, land degradation, shrinking forest cover, climate change and the AIDS epidemic.
Biodiversity, the earth's biological wealth is the entire complement of life that has survived nearly 4 billion years of evolution. The ever increasing degeneration of this bio-wealth has posed serious threat to the very existence of mankind. The degeneration of biodiversity is a matter of serious concern in developing and underdeveloped nations of the world. The North America (Neo-tropical regions), South America, Africa and Asia have fabulous wealth of flora and fauna. However, prevailed illiteracy, poverty, lack of scientific advancement, population explosion are the major factors responsible for the degeneration of biodiversity in these continents.
Exactly how many species of life exist on earth is not known to anybody. Estimate range from 3 million to 100 million. There are 1,435,662 identified species all over the world. However, a large number of species are still unidentified. The identified species includes 751,000 species of insects, 250,000 of flowering plants, 281,000 of animals, 68,000 of fungi, 30,000 of Protists (unicellular and colonial eucaryotes) 26,900 of algae, 4,800 of bacteria and other similar forms and 1,000 of viruses. Disappearance of ecosystems is leading to loss of habitat for several species. Approximately 27,000 species become extinct every year. Majority of them are small tropical organisms. Extinction of species leads to further destruction of fragile ecosystem. If this trend of biodiversity depletion continues, 25 per cent of the world's species may be gone by the year 2050.
In the last half billion years of the history of Earth's life, six great waves of extinction have already destroyed variety of living organisms including the mammoth reptile dinosaurs. The first was in Ordovician period (500 million years ago), the second in the Devonian (400 million years ago), the third in the Permian (250 million years ago), the fourth in the Triassic (180 million years ago), fifth in the Cretaceous (65 million years ago) and sixth in the Pleistocene period (1 million years ago). In Ordovician period 50 per cent animal families including many tribolites were eliminated.
However, Devonian period saw the extinction of 30 per cent of animal’s families agnathan and placoderm fishes and tribolites as well. In Permian period 50 per cent of animal families, including over 95 per cent of marine species, many trees, amphibians, most bryozoans and brachiopods and all tribolites were eliminated, while in Triassic period 35 per cent of animal families, including many reptiles and marine molluscs eliminated. The Cretaceous period saw the extinction of the giant dinosaurs and many marine species, including many foraminiferans and molluscs. In Pleistocene period large mammals and birds became extinct. All these episodes of extinctions were the result of major changes occurring on Earth. However, the present day extinctions are caused entirely by the activity of human beings. Scientists have estimated that human activities are likely to eliminate approximately 10 million species by year 2050.
Tropical rain forest are the store house of biodiversity covering only 7 per cent of the earth's geographical area but supports more than half of the world's identified species. Since most of the rain forests are located in developing countries, therefore, increasing pressure of population is leading to rapid depletion of forest. In ten years from 1980-1990, the tropical forest cover went down from 1.91 billion hectares to 1.75 billion hectares. If rational conservation measures are not undertaken soon, 90 per cent of these habitats could be destroyed in the near future.
This would amount to a potential loss of 15,000 to 50,000 species per year or 50 to 150 species per day. Tropical deforestation will be the single greatest cause of species extinction in the next half century. A virtual "Extinction Epidemic" seems to be looming large threatening to disturb the normal evolutionary process.
All over the world about 60,000 species of plants and about 4,000 species of animals are on verge of extinction. Though the great majority of the species are plants, however, there are also species of animals as well. This includes fishes (343), amphibians (50), reptiles (170), invertebrates (1355), birds (1037) and mammals (497).
The disappearance of genes/alleles from gene pool and reduction in the genetic resources of the earth is known as genetic erosion. Twentieth century has witnessed a loss of 75 per cent of genetic diversity of crop plants. Genetic erosion occurs due to crop number and crop varieties. Originally a large number of plants were utilized for different uses but gradually the number of exploitable plants has decreased. For instance, out of 3000 food plant species only 150 were commercialized.
Agriculture is dominated by only 12 species out of which four yields more than 50 per cent of the total (rice, wheat, maize, potato). In recent times there is a tendency to incorporate the maximum good characters in a single variety. As soon as better variety is developed the same is distributed far and wide and brought in use consequently the local indigenous varieties are discarded and their specific alleles are lost forever.
The genetic erosion is a matter of serious concern as it would hamper the crop improvement programme. The traditional varieties of crops and their wild relatives possess several useful genes, which may be exploited for the improvement of crop varieties through crop breeding. Thus the maintenance of a diversity of crops with different characteristics gives the community a buffer stock of food, if droughts or floods or pest attack occurs.
India as megadiversity nation:
The Earth's biological diversity is distributed in specific ecological regions. There are over a thousand major 'ecoregions' in the world. Of these, 200 are known to be richest, rarest and most distinctive natural areas. These areas are referred to as the 'Global 200'.
It has been estimated that 50,000 endemic plants, which comprise 20 per cent of global plant life, possibly occur in only 18 'hot spots' of the world. Countries, which have a relatively large proportion of these biodiversity hot spots, are referred to as 'megadiversity nation'.
With 2.4 per cent of the world's land, India contributes 8 per cent to the world diversity. It has, therefore, been designated as one of the 12 megadiversity regions of the world. India is recognized as a country uniquely rich in biodiversity because of its tropical location, varied physical features and climate. Indian biodiversity is estimated to be over 45,000 plant species contributing 8 per cent of the world's flora and about 80,000 animal species constituting 7 per cent of the world's fauna of which 33 per cent flora and 62 per cent fauna are endemic to India. Of the estimated 45,000 species of plants about 5,000 species of algae, 20,000 of fungi, 1,600 of lichens, 2,700 of bryophytes, 600 of pteridophytes and 15,000 of flowering plants have been identified and described so far. Indian flowering plants represent15 per cent of the flowering plants of the world. Among flowering plants orchids have high species diversity (1,082) found mainly in North-eastern Himalaya.
Among the larger animals 79 mammals, 44 birds, 15 reptiles and 3 amphibians are threatened today and 1,500 plant species belong to endangered category.
As far as faunal diversity is concerned, India is home for 67,000 species of insects, 1,000 of molluscs, 6,500 other invertebrates 1,700 of fishes, 1,200 of birds, 453 of reptiles, 182 of amphibians, and 350 of mammals, in which 62 per cent amphibians and 32 per cent reptiles are endemic to India. Among lizards, of the 153 species recorded 50 per cent are endemic. India sub-continent alone has given the world nearly 320 species of wild animals, whose centre of origin lies in India.
Apart from the high biodiversity in Indian wild plants and animals there is also a great diversity of cultivated crops and breeds of domestic livestock. Livestock diversity of India includes 27 breeds of cattle, 40 breeds of sheep, 22 breeds of goats and 8 breeds of buffaloes. India has contributed 167 species of cultivated plants along with their wild relatives and land races. Rice, sugarcane, mango, jute, jackfruit, ginger, black pepper, turmeric, bamboos, cucurbits, betel nut, Asiatic vignas, egg plant, citrus fruits, banana, cardamom, minor millets vegetable amaranths, amorphophallus, colocasia, alocasia, edible dioscoreas have originated in India. India has also been a secondary centre of domestication for the horse, goat, sheep, cattle, yak, donkey, tobacco, potato, red pepper, grain amaranths, maize, soyabean and oil palm. Some of these species were very early introduction into India.
These species have undergone evolution in the Indian region and have been selected over a period of time to meet human needs suitable to Indian conditions. India has also contributed very important genes to world agriculture and animal husbandry that have made a significant difference to human welfare. The traditional cultivars of India included 30,000 to 50,000 varieties of rice and a number of cereals, vegetables and fruits. The highest diversity of cultivars is concentrated in the high rainfall areas of the Western Ghats, Eastern Ghats, Northern Himalayas and the North-eastern hills. Gene banks have collected over 34,000 cereals and 22,000 pulses grown in India.
India is extremely rich in Ecosystem diversity as well. According to Wildlife Institute of India the country has 10 bio-geographic zones:
(v) Western Ghats
(vii) Gangetic Plain
(viii) North-East India
(ix) Islands; and
The North-East, the Western Ghats, Western and North-Western Himalayas are rich in endemism. At least 200 endemic species are found in the Andaman and Nicobar islands.
Of the 18 biodiversity hot spots of the world 2 of them belongs to India. Western Ghat and Eastern Himalayas are the hot spots of biodiversity in India.
The Andaman and Nicobar islands are extremely rich in species, and many sub-species of different animals and birds evolved. The islands alone have as many as 2,200 species of flowering plants and 120 species of ferns. Out of 135 genera of land mammals in India 85 (63%) are found in North-east. The North-eastern states also have 1,500 endemic plant species.
A major proportion of amphibian and reptile species, especially snakes, is concentrated in Western Ghats, which is also habitat for 1,500 endemic plant species.
Coral reefs in Indian waters surround the Andaman and Nicobar islands, the Lakshadweep islands and the Gulf areas of Gujarat and Tamil Nadu. Coral reefs are biologically diverse ecosystems often called as 'Tropical rain forest' of the ocean.
There is an intimate connection between high biodiversity and high cultural diversity. The term culture is used here in a composite sense to denote the history, culture, religion, philosophy, languages and indigenous systems of medicine prevalent in a society. Besides India the other counties that are rich in culture and biodiversity includes Indonesia, Mexico, Zaire, Brazil and Australia. All these countries are known as megadiversity of the world. Thus it is evident that cultural and biological diversities have been mutually reinforcing and supportive.
What are the Causes of Biodiversity Degeneration?
The threats to biodiversity emanate from human activities such as the clearing of land for the purpose of agriculture, housing, industries, roads, railways and airports. The overgrazing of grasslands, the cutting and burning of forests, the unsustainable logging and collection of wood for fuel, the indiscriminate use of fertilizers, the over watering of crops, the over-exploitation of fisheries in fresh and marine waters, the draining and filling of wetlands, the poor water management, urbanization and the pollution of air and water activities which threaten biodiversity.
The chief causes of biodiversity degeneration are as follows:
1. Destruction of habitat: The factors causing habitat destruction is expansion of human populations and human activities associated with global economy, such as mining, cattle ranching, forestry, agriculture, and establishment of multi-purpose projects etc. initiated with goal of making profit. Habitat loss is the primary threat to majority of vertebrates currently facing extinction. In many countries, especially on islands and when human population density is high, most of the original habitat has been decimated. More than 50 per cent of the wild life habitat has been destroyed in 49 out of 61 Old world tropical countries. Due to rapidly expanding human population the forest wetlands and mangroves are the threatened habitats in India.
2. Habitat fragmentation:
Habitat fragmentation is the process where a large, continuous area of habitat is both reduced in areas and divided into two or more fragments. When habitat is destroyed, the fragments are often isolated from one another by highly modified or degraded landscapes. Habitat fragmentation may limit the potential of species for dispersal and colonization. It also reduces the foraging ability of animals. Habitat fragmentation causes such edge effects as microclimatic changes in light, temperature, wind etc.
3. Environmental pollution:
The subtlest form of habitat degradation is environmental pollution, the most common causes of which are pesticides, industrial chemicals and wastes emissions from factories and automobiles, and sediment deposits from eroded hillsides. Thermal pollution has wiped out some species of fish such as the humpbacked chub in local areas. Trout and Salmon like aquatic animals fail to reproduce due to thermal pollution. Pesticide pollution kills the microbial flora and fauna of soil.
Besides this, pesticides drained by rain water to aquatic body kill the aquatic flora and fauna. Pesticides like DDT are the major cause of drop in bird population e.g. Vulture, Bald eagle, Osprey etc. DDT is non-biodegradable pesticide, which enters the birds body through food chain, suppressing the activity of estrogen, the female sex hormone. Altered estrogen causes thinning of the eggshell. Consequently the premature hatching of egg takes place leading to the death of developing embryo. The problem of acidification of lakes and rivers due to acid rain is another threat to aquatic life on the earth.
4. Introduction and invasion of exotic species:
The introduction and invasion of exotic species is the cause of biodiversity degeneration. The successful exotic species may kill or eat native species to the point of extinction or may alter habitat by creating unfavourable conditions that did not allow the native species to persist. Disease causing microorganisms, if introduced to new virgin areas may cause epidemics and native species are eliminated completely. Invasion of the exotic plant species like Parthenium hysterophorus, Lantana camara, Prosopis juliflora, Eupatorium adenophorum, Eupatorium riparium, Eupatorium odoratum, Ageratum conyzoides, Mikania micrantha and Galinsoga parvifolia are posing serious threats to biological diversity in India.
5. Introduction of competing or predatory species:
Introduced species may affect other species by preying on them, competing with them for food, destroying their habitat or upsetting the ecological balance. One classic disaster was the deliberate introduction of mongooses into Hawaii in 1883 to control the rodent population, which was destroying much of the valuable sugarcane crop.
Increasing human population has led to tremendous exploitation of natural resources. Over-exploitation of resources is enhanced when a commercial market develops for a previously unexploited or locally used species. Over- exploitation threatens about one-third of the endangered vertebrates in the world, as well as other species. Growing rural poverty, increasingly efficient methods of harvesting and the globalization of the economy combine to exploit species to the point of extinction. Even if a species is not completely eliminated by over-exploitation the population size may become so low that species is unable to recover. A medicinal plant Boerhaavia diffusa (Punarnava) is an ideal example of over-exploitation in rural areas of eastern Uttar Pradesh. The plant is indiscriminately extracted for its roots, which is used in the treatment of jaundice.
Due to indiscriminate killing many animals have reached the verge of extinction. Animals are hunted for many precious commodities like ivory, skin, fur, horns and flesh. The populations of rhinos have declined considerably in the state of Assam in India as they are poached for their horns used as aphrodisiac. Similarly Tibetan Antelope (Chirus) are shot and then fleeced to make Shahtoosh shawls. Five chirus are slaughtered for making of one shawl. In 1960 the population of chirus in India was about 5 million. However, today due to hunting their population has shrunk to few thousands only. Since several decades valley of Kashmir and Tibet have been the chief centres of trade for wool of Tibetan Antelope. The shawl is very warm and is so soft that it can easily pass through a ring. In black market the cost of one shawl ranges between 7.5 lakh to 12.5 lakh rupees.
Development activity and expanding agriculture has led to large scale destruction of forest cover especially in tropics which has caused tremendous loss of biodiversity of tropical forest. Jhum cultivation or shifting cultivation or slash-and-burn agriculture practiced by tribals is major cause of deforestation in developing countries of tropical regions. Jhum cultivation has led to considerable decline in the forest cover of North eastern India resulting into the degeneration of the biodiversity.
It is also one of the major causes of degeneration of biodiversity especially in arid and semi-arid regions. Grazing by cattle, goats, sheep and wild herbivores cause immense damage to plant life. Complete destruction of the photosynthetic organs by over-grazing results in death of the plants particularly in the case of palatable species. The animals trample upon many weaker species. Thus heavy grazing eliminates species from the community. The increase in human population is accompanied by an increase in livestock population. Consequently the process of over-grazing and trampling is enhanced leading to degeneration of biodiversity.
Human activity may enhance the incidence of disease in wild species. The extent of the disease increases when animals are confined to a nature reserve rather than being able to dispense over a large area. Animals are more prone to infection when they are under stress. Animals held in captivity are also more prone to higher level of disease.
11. Collection for zoo and research:
Collecting wild animals for pets, scientific research, and zoos can also threaten certain species. An endangered animals such as Gila monster and various species of fish, lizards, parakeets and parrots are sold as pets, especially in pet loving nations. Medical Research is an important activity, but it is also a serious threat to endangered wild primates such as the Chimpanzee and Orangutan.
12. Control of pest and predators:
Pest and predatory control for protection of livestock and crops have also exterminated or nearly exterminated some species. In attempt to exterminate particular species by poisoning sometimes poisons their predators. This can upset the food chains in ecosystems and allow species whose populations were controlled naturally to become pests. For instance, poison campaigns against prairie dogs and pocket gophers in order to protect rangeland for grazing livestock have just about eliminated their natural predator, the black-footed ferret.
13. Other factors
(i) Distribution range: A species with narrow range of distribution is vulnerable to extinction.
(ii) Degree of specialization: Species specialized to grow in a particular habitat is prone to extinction.
(iii) Position of the organism in food chain: The higher the organism is in food chain, the more susceptible it becomes to extinction.
(iv) Reproductive rate: The species with lower reproductive rate is susceptible to extinction compared to species with higher reproductive rate.
How to Conserve Biodiversity?
Conservation of biodiversity is the planning and management of biological resources in a way so as to secure their wide use and continuous supply, maintaining their quality, value and diversity. The World Conservation Strategy has suggested the following steps for biodiversity conservation:
1. Efforts should be made to preserve the species that are endangered.
2. Prevention of extinction requires sound planning and management.
3. Varieties of food crops, forage plants, timber trees, livestock, animals and their wild relatives should be preserved.
4. Each country should identify habitats of wild relatives and ensure their protection.
5. Habitats where species feed, breed, nurse their young’s and rest should be safeguarded and protected.
6. International trade in wild plants and animals be regulated.
7. Efforts should be made to preserve the species that are endangered.
8. Prevention of extinction requires sound planning and management.
9. Varieties of food crops, forage plants, timber trees, livestock, animals and their wild relatives should be preserved.
10. Each country should identify habitats of wild relatives and ensure their protection.
11. Habitats where species feed, breed, nurse their youngs and rest should be safeguarded and protected.
12. International trade in wild plants and animals be regulated.
For the conservation of biodiversity the immediate task will be to devise and enforce time bound programme for saving plant and animal species as well as habitats of biological resources. Action plan for conservation, therefore must be directed to:
(i) Inventorization of biological resources in different parts of the country including the island ecosystems.
(ii) Conservation of biodiversity through a network of protected areas including National Parks, Sanctuaries, Biosphere reserves, Gene Banks, Wetlands, Coral reefs etc.
(iii) Restoration of degraded habitats to their natural state.
(iv) Reduction of anthropogenic pressure by cultivating the species elsewhere.
(v) Rehabilitation of the threatened and endangered species.
(vi) Protection and sustainable use of genetic resources/germplasm through appropriate laws and practices.
(vii) Conservation of microbes which help in reclamation and rehabilitation of wastelands and revival of biological potential of land.
(viii) Control of over-exploitation through Convention on International Trade in Endangered Species (CITES) and other agencies.
(ix) Rehabilitation of tribals displaced owing to creation of protected areas.
(x) Protection of domesticated plant and animal species in order to conserve indigenous genetic diversity.
(xi) Multiplication and breeding of threatened species through modern techniques of tissue culture and biotechnology.
(xii) Maintenance of corridors between different nature reserves for the possible migration of species in response to climate, or any other disturbing factor.
(xiii) Restriction on the introduction of exotic species without adequate investigation.
(xiv) Support for protecting traditional indigenous knowledge and skills for conservation.
(xv) Discouragement of monoculture plantations.
Concept of endemic species, high-impact species, conservation – focus species and indicator species in the conservation of biodiversity
Endemic species are those with restricted distributions. An endemic species is not necessarily rare or restricted to a small range. This is dependent on the area over which endemism is measured. Although plant endemics have been recognized and investigated extensively, less attention have been given to endemic animal taxa. Endemic species are, however, increasingly recognized as being an important focus for conservation attention as the threats to narrow-ranged species, become more apparent. Furthermore, endemic species are the major components of hot spots of diversity, and form the basis for selecting priority conservation areas.
Endemics may be categorized according to their spatial distribution, inferred evolutionary age and affinities, and abundance. Engler (1882) provided one of the first classification of endemics according to their evolutionary age as follows: (i) Neoendemics: Comprising clusters of closely related species and sub-species that have evolved relatively recently. For example, the hundreds of species of Cichlid fishes in Lake Malawi. (ii) Palaeoendemics: Comprising phylogenetically highly ranking taxa, usually monotypic sections, sub-genera or genera that may be regarded as evolutionary relicts. For example, Welwitchia mirabilis of the Namib Desert. Further on the basis of cytological data, Favarger and Constandripoulos (1961) categorized endemics into four categories according to taxonomic rank and ploidy level.
(i) Palaeoendemics: Ancient isolated taxa with a high ploidy level, whose diploid ancestors are extinct or unknown.
(ii) Schizoendemics: Vicariant species of equal ploidy level, resulting from either gradual or rapid divergence.
(iii) Patroendemics: Restricted, diploid species that have spawned younger, widespread polyploid species.
(iv) Apoendemics: Polyploid endemics that are derived from wide spread species of a lower ploidy level. Schizoendemics, patroendemics and apoendemics are further sub-division of neoendemics.
Some species have more influence on ecosystems than others. Their impact and abundance may change over time, with other species replacing them in their influential position. Two groups are especially relevant to biodiversity conservation i.e. keystone species and exotic invasives.
Keystone species are those species, which maintain the structure and organization of the community. These are in fact those species, which allow large number of other species to persist in the community. To protect keystone species is a priority for conservation efforts, because if a keystone species is lost from a conservation area, numerous other species might be lost as well.
Among the most obvious keystone species are top predators, since they are often important in controlling herbivore population. In many regions where man has hunted gray wolves to extinction, deer populations have exploded. Consequently enhanced grazing has led to elimination of many herbaceous plant species. The loss of these plants was detrimental to the deer and to other herbivores, including the insect community that fed on the plants.
Many tropical trees like Ficus religiosa (Peepal), Ficus benghalensis (Bargad), Ficus glomerata (Gular), Ficus carica (Anjeer) and Ficus racemosa (Pakar) serve as a keystone species in the functioning of vertebrate communities. The flowers of aforesaid tree species are pollinated by small highly specialized wasp (Blastophaga spp.), which mature inside the developing fruits. These tree species also provide a reliable source of food to primates, birds and other fruit-eating vertebrates, even during dry season. Thus Ficus spp. are the examples of keystone species. Therefore the identification and preservation of keystone species is important for the maintenance of biodiversity.
These are newly appearing species either in natural or human-influenced ecosystems. They may be almost any type of organism which becomes for example, a new pathogen, vector, weed or invasive animal. Monitoring the spread and impact of these invasives are a crucial component of biodiversity conservation.
Since biodiversity conservation is a pragmatic science with a management component, it is important to note those species that flag conservation efforts. There are two general categories threatened, and umbrella and flagship species.
Mace and Stuart (1994) and the International Union of Conservation of Nature and Natural Resources (IUCN 1994d) have categorized the dwindling species of plants and animals for conservation purposes. The following categories have been identified:
(1) Endangered species: The species which are in danger of extinction and whose survival is unlikely if the causal factors continue to be operating. Their number have been reduced to a critical level or whose habitats have been so drastically reduced that they are deemed to be in immediate danger of extinction.
(2) Critically Endangered species: The species is facing extremely high risk of extinction in the wild in the immediate future.
(3) Vulnerable species: The species likely to move into the endangered category in the near future if the causal factor continue to operate.
(4) Rare species: Rare species are those species which are at risk because of low number.
(5) Indeterminate species: These are those species which are in danger of extinction but the reason is not known.
(6) Threatened species: These are species that are, often genetically impoverished, of low fecundity, dependent on patchy or unpredictable resources, extremely variable in population density persecuted, or otherwise prone to extinction in human-dominated landscapes.
(7) Insufficiently known species: The species that are probably belong to one of the conservation categories but are not sufficiently known to be assigned to a species category.
(8) Extinct species: The species that are no longer known to exist in the wild. Searches of localities where they were once found and of other possible sites have failed to detect the species.
(9) Extinct species in the wild: These are those species known only to survive in cultivation, in captivity or as naturalized population (or populations) well outside the past range.
(10) Conservation Dependent species: These species are not Critically Endangered, Endangered or Vulnerable but is the focus of a continuing species specific or habitat-specific conservation programme targeted towards the species in question, the cessation of which would result in the species qualifying for one of the threatened categories above within a period of five years.
(11) Near Threatened species: The species is not Critically Endangered, Endangered, Vulnerable or Conservation Dependent but is close to qualifying for Vulnerable.
(12) Least concern species: The species is not Critically Endangered, Endangered or Vulnerable and does not qualify for Conservation Dependent or Near Threatened.
(13) Data deficient species: There is inadequate information to make a direct or indirect, assessment of the risk, of extinction based on the distribution and/or population status of the species. A species in this category may be well studied, and its biology well known, but appropriate data on abundance and/or distribution are lacking. Listing in this category indicates that more information is required and acknowledges the possibility that future research will show that threatened classification is appropriate.
(14) Not Evaluated species: The species has not yet been assessed against the criteria.
Umbrella and Flagship species
These are those species whose occupancy area (plants) or home range (animals) are large enough and whose habitat requirements are wide enough that, if they are given a sufficiently large area for their protection, will bring other species under that protection. Many of the world's nature or game reserves were created principally for large mammals or birds and have inadvertently become reserves for other species with smaller ranges, particularly invertebrates.
These are popular charismatic species that serve as symbols and rallying points to stimulate conservation awareness and action. At the larger scale these include animals such as condors, pandas, rhinos, large cats and large primates, while at the smaller scale they include orchids, cacti and invertebrates such as large butterflies and stick insects. Flagship species may serve as both indicators and /or umbrella species and also provide a highly visible reminder of the progress of a particular conservation management plan.
Certain species flag changes in biotic or abiotic conditions. It is important to inventory these sensitive species because they themselves can become the important monitors. Indicator species reflect the quality and changes in environmental conditions as well as aspects of community composition.
Biological indicators can be used in ecological evaluation, especially for communities indicating areas of conservation interest. Indicator species are also used in environmental assessments and in the preparation of environmental sensitivity maps. The five different types of biological indicators are as follows.
(i) Sentinels: Sensitive species introduced into atypical conditions as early-warning devices.
(ii) Detectors: Species occurring naturally in the area of interest which may show measurable response to environmental change.
(iii) Exploiters: Species whose presence indicates the probability of disturbance or pollution.
(iv) Accumulators: Species which accumulate chemicals in their tissues.
(v) Bioassay organism: Selected organisms sometimes used as laboratory reagents to detect the presence and/or concentration of pollutants.
There are two main categories of biodiversity conservation i.e. ex situ conservation and in situconservation
1. Ex situ conservation: This is conservation outside their habitats by perpetuating sample population in genetic resources centres, zoos, botanical gardens, culture collection etc. or in the form of gene pools, and gamete storage for fish; germplasm banks for seeds, pollen, semen, ova, cells etc. In this type of conservation, plants are maintained more easily than animals. Seed banks, botanical gardens, pollen storage, tissue culture and genetic engineering have been playing important role in ex situ conservation.
Ex situ technologies: A growing range of technologies and strategies are available to conserve species and genetic resources ex situ. For plants, botanical gardens and seed banks are the traditional forms of off-site conservation, and they maintain the bulk of the collections. Gene bank standards for conserving orthodox seeds (seeds which can withstand drying and freezing temperatures) have been established: however, for recalcitrant species (those having seeds that do not tolerate drying or freezing temperatures), live collections in field gene banks are one alternative. For animals, the maintenance of live collections of breeding stock (or breeding nuclei) has been the traditional strategy. More sophisticated techniques have been developed during the past 40 years. Biotechnology has provided many new conservation tools and in vitro culture for both plant and animal species is rapidly becoming one of the more attractive alternatives.
Cryopreservation in liquid nitrogen at -196ºC is also a promising alternative for both plant and animal species, although it is now largely experimental. The major advantage of cryopreservation over conventional techniques are an absence of complicated temperature and humidity controls, freedom from pest and pathogen damage, and indefinite viability with no genetic damage. For animal species, embryos and semen are used in cryopreservation. Seeds, embryos, or tissues may be used in plant cryopreservation. Cryopreservation may prove to be cheaper than the maintenance of growing cultures, since it will make long term, even indefinite, conservation possible.
Another emerging and very promising technique is the conservation of isolated DNA. Among its advantages is that only minute quantity of material are necessary for conservation and the possibility of reintroducing the material into related genotypes or species. It can be used for endangered or even extinct species by taking samples of material from hairs, bones, herbarium specimens or other material of the target species. However, at present this approach is even more experimental than cryopreservation and should be viewed only as a future option for the conservation of genetic diversity. Indeed, conservation of DNA at low or ultra-low temperatures is now a routine process, but regeneration of whole organisms or even expression of particular genes in related genotypes/ species is very difficult.
India has done commendably well as far as ex situ conservation of crop genetic resources is concerned. It has also taken up such work on livestock, poultry and fish genetic resources. However, there is need to develop facilities for long and medium term conservation through:
(i) Establishment of Genetic Enhancement Centres for producing good quality of seeds.
(ii) Enhancement in the existing zoos and botanical garden network.
(iii) Seed-gene banks.
(iv) Tissue culture gene banks
(v) Spore and pollen banks
(vi) Captive breeding in zoological gardens; and
(vii) In vivo and In vitro preservation
Linkages between biodiversity, technology and productivity:
Based on the occurrence of biodiversity and the status of technology the countries of the world can be divided into four groups:
(1) Biodiversity poor and biotechnology poor
(2) Biodiversity poor but biotechnology rich
(3) Biodiversity rich but biotechnology poor; and
(4) Biodiversity rich and biotechnology rich
The first group is represented by countries in West Asia like Saudi Arabia. The second group is represented by countries like United States of America, Japan, Germany, France, Sweden, and the United Kingdom; the third group comprises countries like Indonesia, India, China, Malaysia, Brazil, Mexico and others in the tropical-subtropical and arid or semi-arid belts. No country is represented by the fourth group. Presently there is flow of biodiversity from the third group to the second group. The extent and nature of the flow of biotechnology from the second group to the third group is not commensurate with the flow of biodiversity from the third group to the second group.
This is an unequal exchange and shall remain so till such time as the countries of the third group become self-reliant in biotechnology. An important factor underlying this exchange is that while some countries (like India and China) do have the capability to enter the fourth group (rich in biodiversity and presently reasonably rich in biotechnology), the countries of the second group can not really make it to the fourth group as they do not have any worthwhile naturally occurring agro-biodiversity, although they do have excellent ex situ facilities in the form of field gene banks, seed banks, and other banks. The latter do not have the advantage of the particular type of long range ecological processes and organic evolution that operate under natural habitats and constantly refine and update biodiversity through mutation, recombination, and natural selection which are the three cardinal elements of the organic evolution.
The developing countries have developed basic gene pools with high diversity but low productivity whereas on the other hand, industrial countries improved cultivars with high bio-productivity but low biodiversity.
2. In situ conservation:
In situ conservation measures usually emphasize the protection and communities to avoid the loss of resident species. Here the conservation of genetic resources through their maintenance within natural or even human made ecosystem in which they occur is practiced. This type includes a system of protected areas of different categories, managed with different objectives to bring benefit to the society. Strict Nature Reserve/Wilderness Area, National Parks, National Monuments/Natural Landmark, Habitat/Species Management Area, Protected Landscapes and Seascapes, Managed Resource Protected Area, National Biotic Areas and Anthropological Reserves, Multiple Use Management Areas, Wildlife Sanctuaries and Biosphere Reserves belong to this type of conservation.
Protected area is an area of land and/or sea especially dedicated to the protection and maintenance of biological diversity, and of natural and associated cultural resources, and managed through legal or other effective means. The IUCN (1994b) classifies Protected Areas under eight categories as follows:
I. Strict Nature Reserve/Wilderness Area : To protect nature and maintain natural processes in an undisturbed state in order to have ecologically representative examples of the natural environment for scientific study, environmental monitoring, education and maintenance of genetic resources in a dynamic and evolutionary state. There are two sub-categories: Ia It includes protected areas managed mainly for scientific research and monitoring. Ib It includes protected areas managed mainly for wilderness protection, subsistence and recreation.
II. National Parks: To protect outstanding natural and scenic areas of national or international significance for scientific, educational and recreational use. These are relatively large areas not materially altered by human activity and where extractive resources are not allowed.
III. National Monuments/Natural Landmark: To protect and preserve nationally significant natural features because of their special interest or unique characteristics. These are relatively small areas focused on the protection of specific features.
IV. Habitat/Species Management Area: To assure the natural conditions necessary to protect nationally significant species, groups of species, biotic communities or physical features of the environment where these may require specific human manipulation for their perpetuation. Controlled harvesting of some resources may be permitted.
V. Protected Landscapes and Seascapes: To maintain nationally significant natural landscapes that are characteristic of the harmonious interaction of man and land while providing opportunities for public enjoyment through recreation and tourism. These are mixed cultural/natural landscapes of high scenic value where traditional land uses are maintained.
VI. Managed Resource Protected Area: It is established for the long-term protection and maintenance of biological diversity, as well as providing for the sustainable flow of natural products and services to meet community needs. They are intended to be relatively large and predominately unmodified natural systems where traditional and sustainable resources are encouraged.
VII. National Biotic Areas and Anthropological Reserves: They permit traditional societies to continue to maintain their way of life without external inference. These people often hunt and extract resources for their own use.
VIII. Multiple Use Management Areas: They allow for the sustained production of natural resources like water, wildlife, grazing for livestock, timber, tourism, fishing etc. Protected Area Network in India
The protected area in India includes National Parks, Wildlife Sanctuaries and Biosphere Reserves.
These are the areas maintained by Government and reserved for the betterment of wildlife. Cultivation, grazing, forestry and habitat manipulation is not allowed. Tourism is permissible in National Park whereas research and scientific management is lacking. The boundaries of the National Parks are circumscribed by legislation. There are 89 National Parks in India, occupying nearly 1 per cent of the geographical area.
These are tracts of land with or without lake where wild animals/fauna take refuge without being habitat disturbance. Other activities like collection of forest products, harvesting of timber, private ownership of land, tilling of land etc. are allowed. Tourism is permissible however, no attention is given to research and scientific management and conservation practices as well. India has 500 wildlife sanctuaries occupying over 3.2 per cent of geographical area.
These are multipurpose protected areas which are meant for preserving genetic diversity in representative ecosystems by protecting wild populations, traditional life style of tribal and domesticated plant/animal genetic resources. Each biosphere reserve has following zones:
(1) Core zone: It includes the area where no human activity is allowed. It represents natural and minimally disturbed ecosystems
(2) Buffer zone: It includes the area of limited human activity.
(3) Manipulation (Forestry) zone: It includes the man-made forests and selected felling areas
(4) Manipulation (Tourism) zone: It includes areas earmarked for tourism, education and training.
(5) Manipulation (Agriculture) zone: It includes tribal settlements and other cultivated lands.
(6) Restoration zone: It includes degraded areas selected for restoration to natural or near natural form. There are 18 Biosphere Reserves in India, three of which i.e. Sunderbans, Gulf of Mannar and Agasthymalai Biosphere Reserves have been improved as World Biosphere Reserves by United Nations Educational, Scientific and Cultural Organization (UNESCO).
Biodiversity which represents the bedrock of human civilization is fast dwindling today chiefly due to destruction of habitat, habitat fragmentation, deforestation, over-grazing, environmental pollution, invasion of exotics, hunting and over-exploitation of biological resources. Therefore, it is the need of the hour to conserve the biodiversity to meet the need of food, fodder, fuel, fibre, timber and medicines and also for the improvement of existing crop varieties, maintenance of ecological balance, soil fertility, abatement of land degradation and environmental pollution, mitigation of natural disasters, breakdown and absorption of pollutants, and also for the hydrological cycle and enhancement of nutrient storage and its recycling.
Dr. Arvind Singh