Conservation of Biodiversity Essay
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With all the existing knowledge, Earth is like no other place in the entire universe. For among the countless stars, moons, asteroids, and other bodies arrayed across the vastness of outer space, only our tiny planet is known to support life. And some form of life is everywhere: on the slopes of high mountains and on the floors of the oceans, in scorching deserts and at the frigid poles. Life in enormously different shapes and sizes, from the giant blue whales and redwoods to butterflies and microbes is present everywhere. This is what is known as the 'biodiversity'. Biodiversity measures the vast variety of life in the earth and it is an indicator of the overall health of our planet. Because if some forms of life fail to survive and become extinct, it is a pointer to the environment becoming hostile towards those forms of life. To date, scientists have identified and counted about 1.4 million species, only a small fraction of the number of species that may have existed once.
Organisms are inter-dependent. One organism can hardly survive without the helping hand from a host of others. For example, Man depends upon other organisms for its various needs and he shares the planet with all others. Without the diverse forms of life, man would not survive. Man gets his food directly or indirectly from plants, animals and other organisms. Man derives direct benefits of biodiversity from the harvest of domesticated or wild species for food, fibres, fuel, medicines and many other purposes. The biodiversity influences climate regulation, water purification, soil formation, flood prevention and nutrient recycling along with innumerable aesthetic and cultural impacts. Biodiversity is thus fundamental for maintaining current and future social and economic livelihoods. The number of species of plants, animals, and microorganisms, the enormous diversity of genes in these species, the different ecosystems on the planet (deserts, rainforests and coral reefs) is all parts of this biological diversity. Even without much scientific knowledge, people from time immemorial have recognized the importance of biological diversity and have learnt to live in harmony with the nature. Yet, knowingly and unknowingly, man has attacked the biodiversity during the last one hundred years or more and now a large number of species are under tremendous stress.
Species diversity is useful to man in a variety of ways. A large number of species of edible plants is equivalent to giving more variety of crops satisfying diverse food habits. Similarly, a large number of species of animals ensures an appropriately long food chain that sustains the ecosystem. However, human activities are spreading their wings causing massive extinctions species. The cost associated with this is very high and we seldom realize it. The threats to biodiversity can be lessened only through a new model of development that avoids losses to biological diversity. The diversity must be preserved at any cost for the benefit of our future generations and if we cannot do the same, our descendents will never forgive us.
The Biodiversity concept was globally conceived after the publication: Conserving the World's Biological Diversity brought out by IUCN (International Union for Conservation of Nature), WWF (World Wildlife Fund), World Research Institute and World Bank.
Biodiversity or biological diversity
The UN Convention on Biological Diversity (1992) defines biodiversity as: Biodiversity or Biological diversity means the variability among living organisms from all sources including terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part. Biodiversity is a term used to describe the whole of biological diversity, i.e., all living things: plants, animals, and microorganisms and all their interactions with each other and their environment. The term includes three levels of organization: In simple words Biodiversity means the number of species of plants, animals and micro-organisms occurring in a given habitat or a region, country, continent or the entire globe. Biodiversity includes diversity within species (Genetic diversity), between species (Species diversity) and of ecosystems (Ecosystem diversity).
Genes are carriers of hereditary characteristics and each species has a variation of genes. This is what is known as Genetic Diversity. If a species becomes extinct, the genes, which are responsible for the distinctive characters of the species, are also lost forever. The genes may be present in hundreds of different combinations giving rise to different characteristics for individuals within the same species. Thus, all humans belong to the same species 'homo sapiens', yet each man is different from every other man at least in some respects of his physical, psychological and behavioral build-up. These differences from one individual to another reflect different gene-combinations and therefore, a rich genetic diversity. If the number of individuals of a species is small, genetic variations are less, and eventually, this leads to extinction of the species.
Man has learnt to work with the genetic variations existing in nature. Thus, it has been possible to create high-yielding and newer varieties of rice and other crops, and also animals through suitable combinations of effective genes. Biotechnology and bioengineering have helped man to create these to meet the ever-increasing demand for food and other items. By appropriately mixing genes from wild and domesticated species together, new varieties have been created. Genetic diversity is very rich in nature and scientists have been able to create a 'gene pool' by collecting and preserving gene-combinations from various species
If one goes to a forest and lists all the different animals, birds and plants present, the rich diversity in species is easily observed. If he goes to another forest and does the same thing, the lists now he makes will be different from those made earlier. This represents species diversity from one location to another. Such diversity can be seen in all ecosystems. Any natural ecosystem possesses a much richer species diversity compared to an artificially created ecosystem. For example, a wild forest will have many species of animals and plants compared to a social forestry plantation. Areas where a very large number of different species are naturally found are known as ecological 'hot spots', which need to be conserved. India is recognized as one of 15 countries particularly rich in species diversity.
Ecosystem diversity represents differences in ecosystem from one geographical location to another. It is observed that each geographical unit (country, state, district, etc.) has its own distinctive ecosystem. One location differs from another with respect to landscape consisting of inhabited or uninhabited land, forests, agricultural land, grassland, rivers, lakes, hills and mountains; human settlements and other factors. Consequently, the ecosystem of one place will have differences from the ecosystem of any other place. Some areas may continue to have a natural ecosystem which has not been disturbed by various human activities while others may have artificial ecosystem such as a park, game sanctuary, etc., which have been built by men for their own pleasure. When natural ecosystems are destroyed by human activities such as through construction of a dam or reservoir, or through installation of an industry or a huge settlement, the ecosystem diversity is affected.
Number of species in the world
It is almost impossible to give the total number of different species living in the earth. We can see only some of the species and the large majority of the species are invisible to us. Again, we can see only those species which are in our close vicinity. Every state, every country has got its own species, both animals and plants and we can hardly expect to know the same. It is a favourite game in the schools to name as many animals as one can, prepare lists of birds and insects, name the vegetables, name the plants that grow in the locality, etc. Even if one aims to enlist all the species (animals - domestic and wild, cattle, pigs, sheep and goats, horses and camels, paultry, birds, insects, vegetables, fruits, plants - food and non-food species, medicinal plants, herbs, etc.), the lists will be very very big and other people will be able to add more to the lists. It shows the enormity of the number of species. When one takes a powerful microscope and looks at the microorganisms, their number will overwhelm the observer.
People also know that the same species cannot be seen all throughout the year. We can see different species in every season. The general idea is that thousands of species can be found in the different ecosystems of the world and any attempt to enlist all the species and give them names would be a stupendous task. The scientists tried to develop a system during the mid-eighteenth century for naming and classifying organisms. A number of explorers from Europe went on long voyages to discover more species in other areas. Two of the best known explorers of those times were Alfred Russell Wallace and Charles Darwin. Wallace and Darwin sailed through the seas and the islands in search hitherto undiscovered species and the people came to know of the unexplored areas and their flora and fauna. Wallace was a British naturalist, who went to South America and to Indonesia for collecting and describing plants and animals not found in Europe. A British geologist, Charles Darwin sailed in a ship, H.M.S. Beagle to South America and collected numerous unknown species of plants and animals in their native habitats. The travels by the two men brought to the fore the rich diversity of life, with respect to both the number and variety of plants and animals on earth.
The explorers have shown that some species could be found only in certain specific locations and thus, the species found in a continent or a sub-continent differ from those found in another. There are many examples. The one-horn rhino can be found in Assam (India) while Africa has two-horn rhino. The llamas are found in South America, the orangutans in Southeast Asia, and the marine iguanas in the Galapagos Islands only. Some species outlive others and the principle of the survival of the fittest (the natural selection) determines which species dominate. Over the years, the lists of species have grown in length and more and more species have been discovered.
Scientists assume that up to 100 million species may be there in the earth - the large majority still unknown and undiscovered. Only about 1.8 million of the species have been identified, classified and documented so far. It is also possible that a large number of species will simply vanish from the earth without being identified. Humans are just one species out of the millions.
Each species has well-defined characteristics and this fact was recognized long ago by the founder of modern systematics, Carolus Linnaeus, in his magnum opus Systema Naturae (1758). The individual characteristics of the species help in their classification and documentation as a distinct species. Biologists today think of species as "groups of interbreeding organisms with distinct morphological, physiological, behavioral, and ecological characteristics, each created in geographic isolation from other similar populations through a long evolutionary process". This definition clearly shows that the species are dynamic in nature and they can change through time giving rise to hundreds of other forms, each evolving within a few generations.
Biogeographical classification of India
The scientific study of the geographic distribution of plants and animals is known as the Biogeography of a region. This distribution is dependent on geologic history of the region, the climate, soil composition, and the presence of forests, deserts, rivers and water bodies, seas and oceans, hills and mountains, etc. Other important factors are interactions among the species, co-evolutionary influences, and the reproductive and nutritional requirements of plants and animals, etc. A biogeographic region is a large, generally continuous part of the Earth's surface which has a distinctive biotic community. Biogeographic regions are usually defined separately for floral and faunal communities and are largely restricted to the terrestrial areas of the Earth.
India is the seventh largest country in the world and Asia's second largest nation with an area of 3,287,263 square km. The Indian mainland stretches from 8o 4' to 37o 6' N latitude and from 68o7' to 97o25' E longitude. It has a land frontier of some 15,200 km and a coastline of 7,516 km. India's northern frontiers is with Xizang (Tibet) in the Peoples Republic of China, Nepal and Bhutan. In the northwest, India borders with Pakistan; in the northeast, China and Burma; and in the east, Myanmar (Burma). Physically, the massive country is divided into four relatively well-defined regions - the Himalayan Mountains, the Gangetic river plains, the southern (Deccan) plateau, and the islands of Lakshadweep, Andaman and Nicobar. The Himalayas in the far north include some of the highest peaks in the world. The highest mountain in the Indian Himalayas is Kanchenjunga (8586 m), which is located in Sikkim on the border with Nepal. To the south of the main Himalayan massif lies the Lesser Himalaya, rising to 3,600- 4,600 m, and represented by the Pir Panjal in Kashmir and Dhaula dhar in Himachal Pradesh. Further south, flanking the Indo-Gangetic Plain, are the Siwaliks, which rise to 900-1,500 m. The southern peninsula extends into the tropical waters of the Indian Ocean with the Bay of Bengal lying to the southeast and the Arabian Sea to the southwest.
Biogeographically, India is divided into 10 regions as shown in Table 4.1. The biogeographicl zones of India along with their subdivisions are also shown in Fig. 4.1 (Source: "Conserving our Biological Wealth", WWF for Nature-India (modified) and Zoological Survey of India).
The values of biodiversity
People do not realize the true value of biodiversity till some species of plants and animals could no longer be found in his neighbourhood. For example, in a particular region, the coming of spring is associated with the cuckoo's singing. Then suddenly, people fail to hear the cuckoo as the bird has disappeared due to unfriendly environment and may have migrated to far-away regions. Now the people feel the absence of the bird and begin to understand the need for biodiversity.
There is a harmonious bonding between mankind and nature. When this bond is lost, biodiversity is also lost. Thus, biological diversity needs to be conserved by maintaining the appropriate conditions of habitat and physical environment, and by removing the threats against continuous existence of species. If we need some plant and animal species for our use, we must do it by following the principle of sustainable utilization. If a tree has to be cut, more trees are to be planted. For this, coordination between economic development, population, resources and environment is to be established and the linkages between production, living standards and eco-friendly environment are to be maintained. Conservation measures relate to a rational use of bioresources. The World Summit on Sustainable Development, 2002 (WSSD 2002), held in Johannesburg, South Africa has for the first time called for measures so that loss of biological diversity can be halted.
Protecting biodiversity is in the interest of the people and the world. Over the years, the human civilization has been built around the biological resources and these have acted as the pillars for consolidation, expansion and survival of civilization. The innumerable natural species (both plants and animals) have constituted the base for agriculture, cosmetics, pharmaceuticals, pulp and paper, horticulture, construction and also, waste elimination. The loss of biodiversity seriously affects the food supplies, medicines, conventional and non-conventional energy and reduces the scope for recreation and tourism.
Consumptive and productive values
The pleasure and satisfaction the people obtain through use of natural resources is immeasurable. This is the consumptive utilization of natural products or biodiversity, such as firewood, games, vegetables and poultry. A large number of goods are manufactured and from natural sources and are sold in the market - this is the productive value of biodiversity. Wild biological resources are domesticated through modern agriculture, are used in prevention of plant and animal diseases, etc. These impart productive value to the biodiversity. The consumptive and the productive uses of biodiversity have economic value.
The biodiversity has also non-consumptive value. A forest, a hill, a river add to the beauty of a place; flocks of birds returning to their nests in the evening gives an aesthetic value to the place. The animal voices in the night such as the foxes shouting remind the people of the wild nature and gives aesthetic pleasure. All these constitute the non-consumptive value of the biodiversity. There are various other values which we can neither see or realize; for example, the biodiversity of a place helps in maintaining the water resources, prevents water and soil loss, contributes to the genetic development and evolution of bio-system, contributes to climate adjustment and material recycling, etc.
Spiritual, ethical and existence values
These values of biodiversity are related to ethics and philosophy. For example, the people attach certain significance to some species of plants and animals and worship them in the belief that their continuous existence is required for man's survival. The people just attach special value to some species and environment which are not to be exploited at any cost because the next generation will benefit from them. Attaching such significance to nature and nature's objects in almost religious or spiritual manner gives similar values to the biodiversity. This type of value helps in building a strong bond between man and nature, and the people feel passion, concern and responsibility for the species.
Each ecosystem serves some purpose and when the people realize the value of this service, it becomes the ecological value of biodiversity. When we have a large wetland in our neighbourhood, it serves to moderate waterlogging, filters the sediments, purify the water by taking away the excess nutrients and the contaminants, grows aquatic plants to be used as food and medicines, supports aquatic life including fish, etc. When the people realize that the wetland is giving them very important services, it is like attaching ecological value to the wetland which motivates the people to take steps for conservation. A wetland supports lots of biodiversity by acting as spawning and nursery grounds for fish and by providing a habitat to birds and animals. These are ecosystem values. Similarly, a huge forest serves to moderate water table, control extremes of weather, and generates oxygen for human consumption. These services give an ecological value to the forest.
The services that the biological diversity give to humans are:
- Provision of food, fuel and fiber
- Provision of shelter and building materials
- Purification of air and water
- Detoxification and decomposition of wastes
- Stabilization and moderation of the Earth's climate
- Moderation of floods, droughts, temperature extremes and the forces of wind
- Generation and renewal of soil fertility, including nutrient cycling
- Pollination of plants, including many crops
- Control of pests and diseases
- Maintenance of genetic resources as key inputs to crop varieties and
- Livestock breeds, medicines, and other products
- Ability to adapt to change
Each species is part of an ecosystem where it interacts with members of its own and also with other species. There are producers, consumers, decomposers, and many variations of these roles such as competitors, dispersers and pollinators, and more. A species that is seen as relatively unimportant may also have some important role which it is playing unknown to us.
The potential value of biodiversity is the value which is still not known to people. With the increased need for bio-resources and the decrease in supply, it may be found that some resources which might not have any use long ago may be very useful today or in future. The nature has immense potential to offer - some are already in use, others are in the process of discovery, and many more are yet to be discovered. Over the years, people have found a large number of cures, life-saving medicines from wild plants. In times of an epidemic or a pest outbreak threatening food crops, man has always turned towards nature for solutions, and found the remedies. It is like the diversity of plants and animals having infinite number of cires for our problems. The nature's potential is truly unlimited.
Scientific and Educational value
The nature and its intrinsic biodiversity is a limitless laboratory for scientific investigation and research. It has also tremendous learning resources. The uniqueness of each species, its life-cycle, etc. always fascinates the young and the old alike. People from different disciplines, botany, zoology, earth science, chemistry, sociology, anthropology, etc., find enough materials to do research. Everything in nature has also educational value. When one observes how the bees are collecting honey from different flowers and bring them to their home, and how systematically the bees do their work, is a great lesion in social behaviour, collective work, and discipline. When one looks at the ants line up one after another carrying small small food items to their home, it is a very interesting lesson on unity and strength. How the birds feed their young ones from their mouths have also many learning points. These are only a few examples. Everyone can learn from the nature and find out one hundred examples of how and why the nature is a great teacher.
All organisms strive (usually unconsciously and in an evolutionary sense) to achieve certain basic predetermined goals - to grow, to reach maturity and to reproduce. These are called intrinsic values. Intrinsic value of biodiversity is non-anthropocentric i.e. not related to man and his needs.
The social value is related to how the society is deriving different benefits from biodiversity. This value is varied in nature. Some people simply enjoy an interaction with the nature. For example, they like to spend some time in the bank of a river, or go in a safary to see animals in wild, do some fishing in a lake, or simply visit a naturally beautiful location in a picnic. The satisfaction behind such activities is the social value of biodiversity. Visits to a place of biological diversity have been associated with aesthetic, recreational, cultural and spiritual pleasures. Going for a swim in a river or a lake, or hitchhiking through hills and forests have immense health benefits and therefore, these activities are socially important. It is quite common to have different perceptions about the social values of biodiversity because the young and the old may have different views of nature, and similarly, the urban and the rural dwellers may look at species differently. The social value is therefore not fixed; it may have different meanings to different groups of people and may also change with time.
When biodiversity is measured in terms of some monetary value and a price is determined, it becomes the economic value of biodiversity. All the above values and the social, educational, recreational benefits drawn from biodiversity can be described in terms of a cost, direct or indirect, and together they will measure the economic value. It is not an easy task to calculate the economic value, but a reasonable estimate may be made in the following way:
- the intrinsic values of the plant species present in the system,
- the intrinsic values of fish and other eatable species which are part of the biodiversity,
- the reacreational value of the location including the animaland the birds species,
- the commercial value of any product that goes into the market for use as foodstuff, construction materials, etc.,
- the market value of any material that is used either directly as medicine or is used to manufacture medicines.
There may be many other items of economic value and their monetary values should be added to the above. Appropriate deduction should be made from the estimate to account for the restoration costs of various damages done to the system by human encroachment, flood and other natural damages, species extinction, etc.
Position of Global Biodiversity
Apart from environmental factors, the species diversity depends on an appropriate reproduction rate. All individuals within a species have a finite life span and must die after the span is over. The survival of the species will be determined by the number of healthy offsprings each individual has been able to give birth to during its life span. If the reproduction rate is more than the death rate, the species will survive with ever-growing numbers. This is the case with man. However, if the reproduction rate comes down due to natural or environmental reasons, the particular species experience a decline in its numbers and is likely to become extinct in course of time. We have learnt so far that every species has some intrinsic value and provides some service to the ecosystem. If a species is no longer to be found, it means that some key service is lost and definitely, it will endanger human life too.
The World Conservation Monitoring Centre (WCMC), the biodiversity information and assessment wing of the United Nations Environment Programme (UNEP) has stated in 1992 that an estimate of 12.5 million species in the earth is quite reasonable. This estimate is shown in Table 4.3. 90 percent or more of these species are to be found in the moist tropical forests, comprising of about 8 per cent of the world's land surface. The biodiversity-rich regions of the world are Africa, Asia and the Pacific, and Latin America.
It is not known exactly how many species have become extinct over theyears. Many species must have perished even without being identified and enlisted. It is also difficult to assess whether the conservation measures adopted by different vountries have yielded any positive result. So far, two large groups of species, namely the mammals and the birds, have been comprehensively studied and according to an estimate of the International Union for Conservation of Nature (IUCN), 25 per cent of the world's approximately 4630 mammal species, and 11 per cent of the 9675 bird species can be stated as globally threatened species. This was the situation in 1996. These species are at significant risk of total extinction if no urgent measures are taken for their conservation.
It is found that the threatened and the vulnerable species are mostly terrestrial (land-based) and the principal reason for this is the destruction of their habitats by rapid decline in area under forests. However, freshwater species are equally under threat due to expansion of human activities and increasing use of rivers and lakes for recreation and other activities. Marine life is also threatened particularly in the coastal regions due to pollution, oil-spill and dumping of wastes.
One of the important areas of biodiversity is the large number of food plants existing in the wild - some known, the large number unknown. The ancient man used to take food from these plants directly, and then the most convenient food plants were domesticated, cultivated and grown in a regular way. A very large number still exists in the wild. Many of these are lost already with destruction of forests in the tropics.
The botanical families accounting for the world's main food plants are only a few: for example, Gramineae (grasses, including cereals) and Leguminosae (legumes, including peas, beans and lentils) constitute most of the food plants. People in different places cultivate a total of 200 plants for food - out of these, about 20 plants are of major interest. High yielding varities of almost all major crops have been prepared in the laboratories and released to the farmers. While people are engaged in the cultivation of these varities and in increasing production by use of fertilizer and pesticides, the wild varities have been mostly forgotten.
Timber from forests is a valuable resource - used in construction of houses, boats and ships, in making of door and window frames and panels, furniture and various fittings as well as decorative items, lamp posts, etc. Many different species are used and depending on their quality, they differ in prices. One tree needs several years of growth before it becomes fit for these needs. The timber is a declining commodiy and because of steady decline in markets, the price has gone up many times. This has also led to illegal felling of valuable trees by unscrupulous traders, black-marketing and cross-border illegal trade. With the growing market of plywood, a large number of trees have been quickly consumed by the plywood manuacturers. All these activities have led to disappearance of many timber-tree species from the forests or in a rapid decline in tree population. IUCN has estimated that out of about 10000 tree species, nearly 6000 have fallen into the threatened status, with 976 being Critically Endangered, 1319 as Endangered and 3609 as Vulnerable (Table 4.4).
Sometimes, existing species are also affected by introduction of exotic or new species willfully into the habitats. The new species because of the care taken for their survival in the new environment, multiply rapidly and soon the species existing already find competitors for food and habitat. This also leads to some species becoming extinct or endangered. Introduction of some rapidly growing fish species from other places has resulted in extinction of local species in many countries.
Environmental pollution is a major contributor to biodiversity loss in many countries. It is already known that pesticide residues particularly arising from large scale use of DDT for malaria control are responsible for reduction in population of many bird species and other organisms. Air and water pollution put ecosystems under huge stress and reduce populations of sensitive species, especially in coastal zones and wetlands. Rapid environmental change, such as the El Niño event, can also have significant impacts on natural habitats. Global warming and the accompanying climate change has been responsible for many species migrating northward in search of cooler climate and has caused reduction in species population. Extreme climate events such as high flood and long-lasting drought have put immense stress on many species, both animal and plant, and biodiversity is affected. Huge forest fires such as the ones occurring in Indonesia a few years ago destroyed many species along with their habitat.
Although biodiversity is often talked about, there are little concerted efforts to save biodiversity. Short-term and piecemeal economic, political and social measures are less effective in conservation of biodiversity. The measures are to be long-term, well planned and scientific; these will have to be built into all development activities. The countries will have to give adequate attention to the measures suggested under such international conventions as the Convention on Biological Diversity (CBD), Ramsar Convention, World Heritage Convention, etc.
The other important measure that every country should take is to carefully document biodiversity data region-wise and maintain a database with regular updating. This database will be very useful in national-level decision making related to development planning and will be of immense use to the scieniic community. International convention authorities like CBD, CITES, RAMSAR, etc., UN organizations like UNEP, UNDP, UNESCO, FAO, etc., and International environmental and conservation groups like IUCN, WWF, Conservation International, etc., could also use the database for various purposes. Such database exists already in some countries and has been put to good use.
The species diversity worldwide has two distinctive patterns: (i) the number of species increases in a regular fashion with the size of the habitat and (ii) there are more species of plants and animals in tropical regions than in temperate and Polar Regions.
Most biodiversity data are available for the terrestrial ecosystems primarily because of the lack of structural diversity with respect to marine and freshwater vegetation. The major terrestrial biomes of the world include arctic tundra, northern coniferous forest, temperate forest, tropical rainforest, tropical seasonal forest, temperate grassland, tropical savanna, grassland and scrub, desert, Mediterranean vegetation and mountains.
Information about global biodiversity can be obtained from various sources. A few of the organizations that provide information in this regard are:
- Bird Life International
- Botanic Gardens Conservation International
- Conservation International
- Consultative Group on International Agricultural Research
- Convention on Biological Diversity
- European Environment Agency
- Food and Agriculture Organization of the United Nations
- International Council of Scientific Unions
- International Centre for Living Aquatic Resources Management
- International Plant Genetic Resources Institute
- International Species Information System
- IUCN - The World Conservation Union
- National Oceanic and Atmospheric Administration
- The Nature Conservancy
- UNEP Global Resource Information Database
- UNEP International Environmental Information System
- United Nations Educational, Scientific and Cultural Organization, UNESCO
- United Nations Statistical Division: UNSTAT
- United States Geological Survey
- Wetland International
- World Conservation Monitoring Centre
The distribution of life on earth has evolved through time, climate, geographical regions, and interactions with other organisms. Humans have dominated all other creatures and their need and greed govern the way the workd is run. Expansion of human activities has driven many species to extinction or near-extinction. For recreation and other purposes, humans have introduced species alien to a particular region's climate and physical conditions thus trying to change whole ecosystems. Humans often do not recognize the existence of thousands of other species and think that they can exist without the help of other species. This line of thinking has proved to be completely erroneous today.
Fish constitute the oldest group of vertebrates that originated some 400 million years ago. There are known to be 24,600 fish species in the world divided into 3 classes (Fig. 4.2): (a) jawless vertebrates (lampreys and hagfishes), with many characteristics of the ancestral vertebrates, include about 80 species; (b) Chondrichthyes or cartilaginous fish (sharks, rays, skates, and relatives) represented by about 830 species; and (c) Osteichthyes, or bony fishes (perch, catfish, bass, trout, and relatives) the most diverse group with around 23,700+ species. 58% of the fish are only marine despite the oceans covering 70% of the Earth's surface and containing 97% of the Earth's water. The rest are fresh water species of the lakes and streams.
Amphibians, like frogs, toads, and salamanders, depend on water for reproduction but are otherwise quasi-terrestrial and live part of their life on land. They are thought to have descended from fish about 350 million years ago and today, their number is estimated at about 9800 species.
Reptiles (snakes, lizards, and turtles) have evolved from their amphibian ancestors and are thought to be the first truly terrestrial vertebrates. Some like the marine tortoises are found in the sea. During the Mesozoic period (210-65 million years ago), the Dinosaurs were supposed to have dominated the earth. Today, it is estimated that there are approximately 6,300 species of reptiles.
Birds are thought to have evolved from reptilian ancestors about 150 million years ago. There are now approximately 9,100 species of birds well-adapted for their largely aerial existence. A few species like ostriches, rheas, etc., however have lost their powers to fly and have completely adapted to terrestrial existence. The penguins, on the other hand, lead an aquatic life.
Humans (Homo sapiens) and other mammals have arisen during the Triassic Period, over 200 million years ago. Mammals range from very small (like shrews and house bats weighing less than 4 g) to very large creatures (the blue whale weighs over 160,000 kg). Mammals can be aerial (bats), marine (whales, dolphins, porpoises), and terrestrial (apes, monkeys, men). There are approximately 4 700 species of mammals in the world.
Fig. 4.2. Examples of the diversity of fish. On the upper right is a hagfish, which lacks jaws. Below the hagfish is a cowshark, a 4 m-long representative of the evolutionary line of cartilaginous fish. The evolutionary line of bony fish is represented by the Australian lungfish (top center), and seahorse, moray eel, deep-sea anglerfish, and Sacramento perch (bottom, left to right).
Distribution of Vertebrates
There seems to be an interesting trend of distribution of the vertebrates over the earth. It is seen that species diversity is highest near the equator and lowest near the poles. This latitudinal pattern was recognized by Wallace in as early as 1876. The polar region, consisting of areas greater than 67o (north and south) latitudes, the temperate region, between 23o and 67o (north and south) latitudes; and the tropical region, between the equator and 23o (north and south) latitude show distinct patterns of species distribution.
Vertebrates of the Polar Regions
The polar region consisting of the arctic and the continent of Antarctica are extremely cold, windswept, and inhospitable. Much of the land in the Arctic is covered with vegetation, traversed by rivers, and dotted with lakes and ponds. Even then, the animals have to bear the brunt of the long arctic winter, and have to adapt to the sub-freezing temperatures in total darkness for several months. It is very difficult to find food and for survival, they should be able to survive for months without eating. It is obvious that very few animals can survive the drastic conditions. As a result, most of the vertebrates living in the polar region (mainly the arctic) are migratory in nature, and whenever they find the conditions to be extremely unfavourable, they simply move to warmer regions.
A prerequisite for survival in the extreme winter at high latitudes is the capacity to regulate body temperature alog with changes in season, because if such self-regulation is not possible, the species cannot survive in the freezing cold. It is for this reason that reptiles and amphibians are not found in the polar region. Since many fish species have good adaptability to temperature extremes, marine fish are abundant in the Polar Regions. The blackfish is a very good example of true adaptability. It is a small (up to 20 cm) fat fish that lives in shallow water. This fish can survive for long periods even under partially frozen conditions.
The entire Arctic marine fish fauna consist of about 125 species, a large number of these species are also found at lower latitudes indicating that the species are not endemic to the Arctic. The Antarctic, on the other hand, has about 100 species of marine fish and more than 90% of them are endemic. In the brief polar summer, food organisms become abundant and the small number of species becomes abundant. During the summer, the whales come to the Polar Regions in search of food but leave quickly with the onset of the winter.
The Antarctic is much known for the penguins. Penguins, however, are not restricted to the polar region alone; the Galapagos penguin is found at the equator. The arctic is not known for any particular group of birds, but migratory species find temporary habitat in the arctic and breed there.
Similarly to the birds, no family of mammals is found to be endemic to the arctic areas and no terrestrial mammal is also known to inhabit the Antarctic. However, terrestrial species like the musk ox, polar bear, and arctic hare (all exclusively arctic) and marine mammals such as the walrus, beluga, and narwhal (in the arctic) and Weddell, crab eater, and leopard seal (in the Antarctic) are well known.
Vertebrates of the Temperate Regions
The temperate zones (between 23o and 67o latitudes, in both northern and southern hemispheres) have a large number of endemic species. For example, the Mississippi-Missouri River system alone has about 300 freshwater fish species endemic to the area. Similarly, Europe along with former Soviet Russia can boast of about 420 endemic species of freshwater fish.
Amphibians, who cannot tolerate the extreme conditions of the arctic, are abundantly present in the temperate region. Reptiles (lizards and snakes) also have more species in the temperate latitudes. Most of the world's deserts exist between 15o and 30o latitudes, and therefore, in these latitudes, species diversity is slightly less.
Very large number of bird species can be found in the temperate regions. For example, at least 88 bird species can be found in the Labrador Peninsula of northern Canada (55o N.), 176 species in Maine (45o N.), and more than 300 species in Texas (31o N.) The total number of bird species in California exceeds 540; the total for all of North America is roughly 700.
The mammalian distribution is affected by land elevation and it is found that mountainous regions have more species of mammals than low lying lands.
Vertebrates of the Tropical Regions
The greatest diversity of life can be observed in the tropical regions, between 23o north and 23o south latitudes. The tropics harbour at least 75% of all species (plants, animals, microorganisms). However, differences exist with respect to species diversity in the tropical regions of Africa, Asia, and South America.
The tropical region of Africa is covered by the great Sahara desert spread over 7,770,000 square kilometers covering almost 25% of the continent. The desert is very much inhospitable to different species of animals and plants. The west central part of Africa is the Rain forest area covering less than 9% of the continent providing a habitat to the species found normally in a rain forest.
The tropics in Asia consist mostly of low land rain forests. The Southeast Asia is full of islands which isolate populations of species and facilitate formation of new species. The tropics of Central and South America consist of lowland wet and dry forests and ecosystems that range from high-elevation shrublands (paramo) to grasslands (puna). Rain forest covers about 32% and savanna about 38% of the South American continent.
The tropical waters contain the maximum number of fish species. In case of the marine species, it is found that about 30-40% of all marine fish species are associated with tropical reefs. A single large reef may support as many as 2,200 species. Similarly a large river system may be a habitat to a very large number of fish species.
The amphibians also have their greatest diversity in the tropical region because they can move from water to land and vice-versa easil due to small differences in temperature.
Bird diversity is the highest in the rain forests of the South American tropics. Here, as many as 86 families and over 2,700 species of birds are known to exist. A tiny Central American country, Costa Rica (50,700 km2) claims to have over 750 species of birds and Colombia has well over 1,500.
A large number of Mammalian species are also to be found in the tropics. For example, Venezuela has 304 species, Bolivia 327 species, East Africa 351 species, and Zaire (central Africa) 427 species. Much of this increase in diversity is due to the Chiroptera bats.
Biodiversity at national level
The Asia and the Pacific regions include parts of three of the world's eight biogeographic divisions, namely the Palaearctic, Indo-Malayan and Oceanian realms. The region has the world's highest mountain system (Himalayas), the second largest rain forest and more than half the world's coral reefs. The Southeast Asian sub-region is noted as the centre of diversity of wild and domestic cereals and fruit species.
Of the 12 'mega-diverse' countries, four are in this region, namely Australia, China, Indonesia and Malaysia. China is ranked third in the world for biodiversity with more than 30000 species of advanced plants and 6347 kinds of vertebrates, representing 10 and 14 per cent respectively of the world total. Australia has an estimated one million species of which about 85 per cent of flowering plants, 84 per cent of mammals, more than 45 per cent of birds, 89 per cent of reptiles, 93 per cent of frogs and 85 per cent of inshore, temperate-zone fish are endemic.
The rich biological resources of the region have long been exploited for international trade and to sustain the growing population. The direct harvesting and export of natural products, particularly timber and fish, the expansion of agriculture into primary forests, wetlands and grasslands, and the replacement of traditional native crops with high-yielding exotic species are having adverse effects on the biodiversity. The threats to biodiversity have increased due to rapid urbanization and industrialization, both responsible for destroying natural habitats of species. Pollution of water, air, and soil, mining activities, tourism and related recreational programmes have created further environmental stress. Forced introduction of new and exotic species, hunting, illegal trade in endangered species and their parts (for example, rhino horn) and the lack of proper management practices have taken their toll. In the past decade, demand on biological resources increased sharply due to rapid economic and population growth.
Habitat fragmentation and destruction due to deforestation in an unprecedented scale has not only caused a loss of biodiversity, it has created other types of problems as well. Thus, depletion of forest cover in Southeast Asia has resulted in disappearance of a wide variety of forest products used for food, medicine and fodder. This has direct impact on the economy of the indigenous people.
With the advent of high-yielding species of crops such as rice, and also use of modern tools, equipments, fertilizers, other chemicals in agriculture, the number of species being cultivated has come down drastically. Thus, being a rice-growing country traditionally, as many as 30000 varities of rice are known. However, India now gets 75 per cent of its rice output from just 10 varieties. Many varities have already been lost and the genetic diversity of rice crop is seriously threatened.
Hunting, poaching and illegal trade in endangered species are major challenges to biodiversity in India. Tiger and many other animal species have become threatened. Illegal harvesting and trade in medicinal plants has also become a major problem.
Commercial fishing, with the help of fish poison and blasts, has depleted fish resources in lakes, rivers and coastal seas. Pollution from industries as well as solid waste dumping has damaged the spawning grounds of fish and other aquatic species. The mangroves in the coasts have almost disappeared along with rich aquatic life.
It is estimated that about two-thirds of Asian wildlife habitats have already been destroyed and 70 per cent of the major vegetation types in the Indo-Malayan areas (South Asia, the Mekong basin and Southeast Asia) have been lost, with a possible associated loss of up to 15 per cent of terrestrial species. Dry and moist forests have suffered 73 and 69 per cent losses respectively, and wetlands, marsh and mangroves have been reduced in extent by 55 per cent. Overall habitat losses have been most acute in the Indian sub-continent, China, Viet Nam and Thailand.
Many species are threatened. Of the 640 species listed for protection under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), 156 are found in China and around 15 to 20 per cent of the country's fauna and flora species are endangered.
In the Southeast Asia, no country has a complete listing of species. As a result, the extent and the importance of biodiversity are poorly understood, and development programmes often ignore this important aspect.
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