BIODIVERSITY AND ITS CONSERVATION
INTRODUCTION
- Biodiversity is the occurrence of different types of ecosystem, different species of organisms with their biotypes and genes adapted to different climates, environments along with their interaction and processes.
- Biodiversity includes three interrelated hierarchical levels - genetic diversity, species diversity and ecological diversity.
- Genetic diversity : It refers to variations of genes within the species. The difference could be in alleles or in chromosomal structure.
- Genetic variation shown by the medicinal plant Rauwolfia vomitoria growing in different Himalayan ranges might be in terms of the potency and concentration of the active chemical (reserpine) that the plant produces. India has more than 50,000 genetically different strains of rice, and 1,000 varieties of mango.
- The amount of genetic variation is the basis of speciation. It plays an important role in the maintenance of diversity at the species and community levels.
- Species diversity: The variety in the number and richness of the species of a region is called species diversity.
For example, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats.
- Ecological diversity: Ecological diversity describes the number of niches, trophic levels, and various ecological processes that sustain energy flow, food webs and the recycling of nutrients.
PATTERNS OF BIODIVERSITY
LATITUDINAL GRADIENTS
- The diversity of plants and animals is not uniform throughout the world but shows a rather uneven distribution.
- For many groups of animals or plants, there are interesting patterns in diversity, the most well- known being the latitudinal gradient in diversity.
- In general, species diversity decreases as we move away from the equator towards the poles. With very few exceptions, tropics (latitudinal range of 23.5° N to 23.5° S) harbour more species than temperate or polar areas.
NOTES
Biologists are engaged in the identification and naming of species for the last 250 years. Still, they are able to name and describe for less number of species than the actual number present. Presently, the known and described number of species of all organisms on the earth is between 1.7 and 1.8 million, which is fewer than 15% of the actual number. It is predicted that the number of total species varies from 5 to 50 million. Approximately 61% of the known species are insects. About 2,70,000 species of plants and only 4650 species of mammals are known to science. Only fragmentary information is available about bacteria, viruses, protists and Archaea. The major area where numerous species are believed to be unknown to science are tropics and coral reefs.
SPECIES-AREA RELATIONSHIPS
- During his pioneering and extensive explorations in the wilderness of South American jungles, the great German naturalist and geographer Alexander von Humboldt observed that within a region species richness increased with increasing explored area, but only up to a limit.
- In fact, the relation between species richness and area for a wide variety of taxa (angiospermic plants, birds, bats, freshwater fishes) turns out to be a rectangular hyperbola. On a logarithmic scale, the relationship is a straight line described by the equation.
log S = log C + Z log A
Fig. : Showing species area relationship
Note that on log scale the relationship becomes linear
where S = Species richness,
A= Area
Z = slope of the line (regression coefficient)
C = Y-intercept
- Ecologists have discovered that the value of Z lies in the range of 0.1 to 0.2, regardless of the taxonomic group or the region.
ECOSYSTEM DIVERSITY
- Ecosystem diversity describes the number of niches, trophic levels and various ecological processes that sustain energy flow, food webs and the recycling of nutrients. It has focus on various biotic interactions and the role and function of keystone species (species determining the ability of a large number of other species to persist in the community).
- Diversity helps in producing more productive and stable ecosystems/communities which can tolerate various stresses like prolonged drought.
- There are three perspectives of diversity at the level of community. These are alpha diversity, beta diversity and gamma diversity.
- Alpha diversity (α-index diversity, within-community diversity) : It indicates diversity within the community. It refers to the diversity of organisms sharing the same community or habitat. A combination of species richness and equitability/evenness is used to represent diversity within a community or habitat.
- Beta diversity (β-index diversity, between-community diversity) : It is the biodiversity which appears in a range of communities due to replacement of species with the change in community/habitat due to the presence of different microhabitats, niches and differences in environmental conditions.
- Gamma diversity (γ-index diversity) : It refers to the diversity of habitats over the total landscape or geographical area.
LOSS OF BIODIVERSITY
- The colonisation of tropical Pacific Islands by humans is said to have led to the extinction of more than 2,000 species of native birds. The IUCN Red List (2004) documents the extinction of 784 species (including 338 vertebrates, 359 invertebrates and 87 plants) in the last 500 years. Some examples of recent extinctions include the dodo (Mauritius), quagga (Africa), thylacine (Australia), Steller’s Sea Cow (Russia) and three subspecies (Bali, Javan, Caspian) of tiger.
- The last twenty years alone have witnessed the disappearance of 27 species.
- Presently, 12 percent of all bird species, 23 percent of all mammal species, 32 percent of all amphibian species and 31percent of all gymnosperm species in the world face the threat of extinction.
- A species is considered to be ecologically extinct, if it persists at such reduced numbers that its effects on other species in its community are negligible. Extinction is a natural process.
TYPES OF EXTINCTION
Species become extinct through three types of extinction processes:
NATURAL EXTINCTION
It is the extinction of species slowly from the earth due to changes in environmental conditions. Some species disappear and the others which are more adapted to changed conditions, take their place.
Many species have been lost in the geological past by natural extinction. The extinction of species in the geological past is also called background extinction.
MASS EXTINCTION
It refers to the extinction of a large number of species due to catastrophe.
ANTHROPOGENIC EXTINCTION
They are extinctions abetted by human activities like settlements, hunting, over exploitation and habitat destruction.
The World Conservation Monitoring Centre has found out that since 1600 A.D., the earth has lost 533 animal species (mostly vertebrates) and 384 plant species (mostly flowering plants). 75% of these extinctions are caused by direct human interference. It has been documented that Dodo (Raphus cucullatus) and Taswania wolf (Thylacinus cynocephalus) have been hunted to extinction by humans.
CAUSES OF BIODIVERSITY LOSSES
HABITAT LOSS AND FRAGMENTATION
- Expanding population and development require more industrial area, extension of present towns and cities, more area for agriculture, new roads, canals, dams etc.
All these activities will result in the destruction of natural habitat or habitat loss. Destruction of habitat is the primary cause of extinction of species.
- Habitat fragmentation is the breaking of a large habitat into smaller patches due to the development of agriculture, water body and other changes.
OVER-EXPLOITATION
Over exploitation of any particular species reduces the size of its population so that it becomes vulnerable to extinctions, e.g., hunting of animals, collection of medicinal plants.
ALIEN SPECIES INVASIONS
Any new species entering in a geographical region are known as exotic or alien species.
It may cause disappearance of native species through changed biotic interaction, like - Nile perch, where a large predator fish was introduced in Lake Victoria of South Africa. It begins to threaten the entire freshwater ecosystem by feeding on small herbivorous and carnivorous cichlid fish species which were endemic to the aquatic system.
Water hyacinth (Eichhornia crassipes) clogs rivers and lakes and threatens the survival of many aquatic species in lake and river flood plains in several tropical countries, including India. Lantana Camara has become a serious weed which replaced many species in forests of UP and MP.
CO-EXTINCTIONS
When a species becomes extinct, the plant and animal species associated with it also become extinct. Example, in a coevolved plant-pollinator mutualism, extinction of one always leads to the extinction of the other.
BIODIVERSITY CONSERVATION
- Earth’s rich biodiversity is vital for the very survival of mankind.
- The reasons for conserving biodiversity are narrowly utilitarian, broadly utilitarian and ethical.
- Narrowly utilitarian reason for conserving biodiversity are fairly apparent. According to most people, biodiversity is a reservoir of resources for the manufacture of food, pharmaceutical and cosmetic products. This probably explains most fears of resources disappearance related to the erosion of the biodiversity. Biodiversity provides food, crops etc. and has a role in medication.
- Broadly utilitarian reveals that biodiversity plays a main role in many ecosystem services that nature provides. Biodiversity makes the environment a self sustaining and a self regulating system. Amazon forest produces 20% of the total oxygen in the earth's atmosphere through photosynthesis. Similarly, pollination is another service ecosystems provide through pollinator layers-bees, bumblebees, birds and bats etc.
- Ethical reasons relates to what we owe to millions of plant, animal and microbe species with whom we share this planet.
- Besides the direct benefits (food, fibre, firewood, pharmaceuticals, etc.), there are many indirect benefits we receive through ecosystem services such as pollination, pest control, climate moderation and flood control.
- The International Union for Conservation of Nature and Natural Resources (IUCN), having its headquarters at Morgis in Switzerland, maintains a Red Data Book providing a record of animals and plants which are known to be in danger.
Table : Red list categories
Table : Threatened Animals of India
(T = Threatened, R = Rare, E = Endangered, V = Vulnerable).
- Conservation of biodiversity is the protection, upliftment and scientific management of biodiversity so as to maintain it at its optimum level and derive sustainable benefit for the present as well as future strategies.
- There are two basic strategies of biodiversity conservation - in-situ (on site) and ex-situ (off site).
Flow chart : The in-situ and ex-situ approaches of conserving biodiversity
IN-SITU CONSERVATION
- It is the protection and management of important components of biological diversity through a network of protected areas.
- In in-situ conservation, endangered species are protected in their natural habitat so that the entire ecosystem is protected. Recently, 34 ‘biodiversity hotspots’ in the world have been proposed for intensive conservation efforts. Of these, three (Western Ghats-Sri Lanka, Himalaya and Indo-Burma) cover India’s rich biodiversity regions.
- Protected areas are ecological / biogeographical areas where biological diversity along with natural and cultural resources are protected, maintained and managed through legal or other effective measures.
- National parks, wild life sanctuaries and biosphere reserves are the examples of protected areas.
- The World Conservation Monitoring Centre (WCMC) has recognised 37,000 protected areas around the world. As of September 2002, India has 581 protected areas (89 National parks and 492 Wildlife Sanctuaries). These areas cover 4.7 per cent of the land surface as against 10 per cent (internationally suggested norm).
NATIONAL PARKS
- National parks are reserves of land usually owned by governments that are protected from most human development and pollution. In national parks, both plants and animals are protected.
- There are 90 National Parks (in 2004) which occupy about 4.7% of the country's total geographical area.
- Cultivation, grazing, forestry and habitat manipulation are not allowed in the national parks.
Table : Famous National Parks of World Created for Specific Endangered Species
- Some Other Important National Parks
- Arunachal Pradesh - Namdapha National Park
- Assam - Manas National Park
- Bihar - Palamau National Park
- Kerala - Silent Valley National Park, Periyar National Park
- Madhya Pradesh - Pench National Park
- Meghalaya - Nokrek National Park
- Orissa - Simlipal National Park
- Rajasthan - Ranthambore National Park, Sariska National Park
- Sikkim - Keng Cheng Zong National Park (For Red Panda)
- Tamil Nadu - Marine National Park (Gulf of Mannar)
- Uttar Pradesh - Valley of Flowers National Park, Nanda Devi National Park
- Uttaranchal - Dudhwa National Park
- West Bengal - Buxa National Park
- The world's first National Park is Yellow Stone National Park.
- India's first National Park was set up in 1935 in the foothills of the Himalayas in UP and was known as Hailey National Park. It is now known as Jim Corbett National Park - Nainital (Uttaranchal).
- Smallest tiger reserve in India is Ranthambore National Park - Sawai Madhopur (Rajasthan). It is famous for Asiatic wild ass.
- Larger tiger reserve in India is Nagarjuna Sagar Srisailam Sanctuary. It is in Guntur, Andhra Pradesh.
- Nandan-Kanan zoo is known for white tiger.
WILD LIFE SANCTUARY
- Wild life sanctuary is a region which is made for the conservation of animals only. In this area, human activities like cutting wood, collection of small forest products etc. are allowed but without affecting animals.
- There are 448 wildlife sanctuaries (as on Sept. 2004) which occupy about 3.2% of the country's total geographical area.
NOTES
Thar and Sunderbans [W. Bengal] is also famous for tigers.
Table : Some Important Sanctuaries of India
- Some Other Important Sanctuaries of India
1.Andhra Pradesh - Pulicat (Lake) Sanctuary
2.Chandigarh - Sukhna Lake Sanctuary
3.Haryana - Sultanpur Lake bird Sanctuary
4.Himachal Pradesh - Govind Sagar bird Sanctuary
5.Karnataka - Ranganathittu bird Sanctuary (Mysore)
6.Tamil Nadu - Kalakad Sanctuary
Table : Important protected wildlife and associated protected areas.
BIOSPHERE RESERVES
- The Man and Biosphere (MAB) programme of UNESCO formulated the concept of biosphere in 1975, which deals with the conservation of ecosystems and genetic resources contained therein.
"The Biosphere reserves are a special category of protected areas of land/or coastal environments, wherein people are an integral component of the system''.
- These are representative examples of natural biomes and contain unique biological communities.
- There are 4 zones of Biosphere Reserve-
- Core Zone : It lies at the centre where no human activity is allowed.
- The Buffer zone : In this zone, limited human activity is allowed.
- Manipulative zone or transition zone: In this, a large number of human activities are allowed but ecology is not permitted to be disturbed.
- Restoration zone : These are the degraded areas for restoration to near natural form.
- 408 Biosphere reserves are located in 94 countries.
- In India, following 14 sites have been identified as potential biosphere reserves together with their locations:
Table : Biosphere Reserves of India
Table : Some special projects for endangered animal species
IMPORTANCE OF BIOSPHERE RESERVE
- Restoration : Biosphere reserves help in restoration of degraded ecosystems and habitats.
- Conservation : Biosphere reserves ensure the conservation of landscapes, ecosystems, species and genetic resources. These reserves also encourage the traditional resource use.
- Development : The biosphere reserves promote culturally, socially and ecologically sustainable economic development.
- Scientific research, monitoring and education : The biosphere reserves provide support for research monitoring, education and information exchange related to local, national and global issues of conservation and development.
SACRED GROOVES AND SACRED LAKES
- Sacred forest ( = Sacred grooves) are the forest patches protected by the tribal communities due to religious sanctity.
- They represent the most undisturbed forest patches without any human impact.
- They are found in several parts of India, e.g., Karnataka, Maharashtra, Kerala, Meghalaya etc.
- Bishnois of Rajasthan protect Prosopis cineraria and Black buck religiously.
- Similarly, some water bodies (sacred lakes) are also held sacred in certain places, e.g., Khecheopalri in Sikkim. Their aquatic flora and fauna are naturally preserved.
EX-SITU CONSERVATION
- It is the conservation of selected rare plants/animals in places outside their natural homes.
- Ex-situ conservation includes off-site collections and gene banks.
OFF-SITE COLLECTIONS
- They are live collections of wild and domesticated species in botanical gardens, zoos, arboreta, etc.
- Currently, there are more than 1500 botanical gardens and arboreta (gardens with trees and shrubs) having more than 80,000 species. Many of them have seed banks, tissue culture facilities and other ex-situ technologies.
- The number of zoos/zoological parks is more than 800. They have about 3000 species of mammals, birds, reptiles and amphibians. Most of them have well managed captive breeding programmes.
GENE BANKS
- A gene bank or germplasm bank is an institution where valuable plant material is preserved in a viable condition.
- These are stored either in the form of seeds or dormant vegetative organs or in the form of frozen gametes.
SEED BANKS
- Plant germplasm in live state is the viable seed. In a seed the embryo is present in a dormant state.
- The moisture content of seeds is kept low (5-15%) and they are stored at low temperatures (–10°C to –20°C) with supply of little oxygen. In these conditions, there is reduced enzyme activity and reduced respiration. From time to time at definite intervals these seeds are sown to produce new plants and fresh seeds are obtained. Such seeds are called orthodox seeds as they can withstand the reduction in moisture and prolonged exposure to low temperature.
- Seeds of trees and shrubs usually get killed on drying and freezing. Such seeds are called recalcitrant seeds, e.g., tea, litchi. In such cases, plants are kept in orchards and maintained through in-situ conservation.
- Plants with recalcitrant seeds are grown in orchards where all possible strains and varieties are maintained, e.g., litchi, oil palm, rubber tree, etc.
TISSUE CULTURE
- It is carried out through callus formation, embryoids, pollen grain culture and shoot tip culture for those plants which are either seedless, have recalcitrant seeds, variable seed progeny or where clone is to be maintained.
- This method is useful in maintaining a large number of genotypes in small area, rapid multiplication of even endangered species and for hybrid rescue.
- Shoot tip culture maintains virus free plants.
- It is used for international exchange of germplasm in vegetatively multiplied cultivars, e.g., banana, potato.
CRYOPRESERVATION
- It is preservation at –196°C (liquid nitrogen) which can maintain tissue culture, embryos, animal cells/tissues, spermatozoa indefinitely.
- The cryopreserved material is revived through special technique when required.
HOTSPOTS OF BIODIVERSITY
- Hotspots are the areas with high density of biodiversity or megadiversity which are also the most threatened one.
- To designate priority areas for in situ conservation, Norman Myers developed the 'hot spots' concept in 1988.
- 'The hot spots are the richest and most threatened reservoirs of plant and animal life on earth'.
- Ecologically hot spots are determined by four factors:
- Number of species/species diversity.
- Degree of endemism.
- Degree of threat to habitat due to its degradation and fragmentation.
- Degree of exploitation.
- Over the world, 25 terrestrial hotspots have been identified for the conservation of biodiversity.
- The hot spots together occupy 1.4 percent of the earth's land area. About 20 percent of the human population lives in the hot spots.
- Out of the 25 hotspots of the world, two are found in India. These are Western Ghats and Eastern Himalayas, and these extend to the neighboring countries also. These areas show high degree of endemism and are inhabited by a wide variety of flowering plants, swallow tailed butterflies, amphibians, reptiles and mammals.
- Western Ghats : It lies parallel to the Western Coast of the Indian peninsula for almost 1600 km, spread over in Maharashtra, Karnataka, Tamil Nadu and Kerala. The evergreen forests are found at low elevation (i.e. 500 m above mean sea level), whereas semi-evergreen forests occur at 500-1500 m height. The two main centres of biological diversity are :
- the Agasthyamalai hills and Silent valley,
- the new Amarambalam Reserve.
- Eastern Himalaya : It extends to the north eastern India and Bhutan. Many deep and semi isolated valleys are found in this region. These valleys are exceptionally rich in endemic plant species. Temperate forests occur at altitudes of 1780 to 3500 m in this region. The eastern Himalaya is an active centre of evolution and exhibits a rich diversity of flowering plants. Numerous primitive angiosperm families (e.g., Magnoliaceae and Winteraceae) and primitive genera of plants like Magnolia and Betula and found in this region.
INTERNATIONAL EFFORTS FOR CONSERVING BIODIVERSITY
- Earth summit of Rio de Janeiro (1992), Brazil, promoted Convention of Biological Diversity (CBD) which was signed by 152 nations. Its recommendations came into effect on 29th Dec. 1993. India became a party to this Convention on Biological Diversity in May, 1994.
- The three key objectives of the convention are-
- conservation of biological diversity
- sustainable use of biodiversity
- fair and equitable sharing of benefits arising out of the utilization of genetic resources.
BIODIVERSITY CONSERVATION IN INDIA
- India is a home land of 167 cultivated species and 320 wild relatives of crop plants. It is a centre of diversity of animal species (e.g., zebu, mithun, chicken, water buffalo, camel); crop plants (e.g., edible dioscorea, alocasia, colocasia); species and condiments (e.g., cardamom, black pepper, ginger, turmeric), bamboos, brassicas and tree cotton.
India also represents a secondary centre of domestication for some animals (e.g., horse, goat, sheep, cattle, yak and donkey) and plants (e.g., tobacco, potato and maize).
- The National parks, Wildlife sanctuaries and other protected areas maintained by the Ministry of Environment and Forests provide in situ conservation of biodiversity.
The joint forest management systems involve forest departments and local communities to enable tribal and local people to have access to non-wood forest products (such as lac, silk, honey, wax, tendu leaves, etc.) and at the same time protect the forest resources.
- Major ex situ conservation of biodiversity is being managed by National Bureau of Plant, Animal and Fish Genetic Resources. There is an International Crop Research Institute for Semi-Arid Tropics (ICRISAT) in Hyderabad for conserving germplasm of Groundnut, Pigeon Pea, Chick Pea, Pearl Millet and Sorghum. A number of other centres in India are maintaining hundred and thousands of present and past varieties of crop plants. Thus, germplasms of plants and animals are being conserved in vitro in gene/seed banks, field gene banks, botanical gardens and zoological gardens. Being spread over different parts of the country, the various institutes are conserving regional variants of all types of important plants and animals.
Study Notes for NEET/AIIMS/JIPMER
