-Jayapaul Azariah, Ph.D.
Dept. of Zoology, University of Madras - Guindy Campus
Madras 600025, INDIA
Tracing the history of the world, a rough estimate would indicate that about 5-50 billion species existed during the pre-Cambrian and Cambrian era. However, today we have only 5-50 million species (Raup 1991). The Russian botanist, Navilov, has identified 12 important centers of biodiversity, containing several unique fauna and flora, among which India is one. About 100,000 sq. km (3%) of India's geographic area has been declared as wild life sanctuaries (441) and national parks (80). According to a Govt. of India publication (G.O.I.,1987), it is estimated that about 45,000 species of plants occur in India, of which the flowering plants alone account for 15,000 species. Among them, about 5000 species (30%) of flowering plants are endemic to India. India is also rich in fauna, containing about 65,000 species. Among these, more than 50,000 species of insects, 4000 species of molluscs, 6500 species of other invertebrates, 2000 species of fish, 140 species of amphibians, 420 species of reptiles, 1200 species of birds and 340 species of mammals have been recorded in India (G.O.I. 1987)
Many volumes of red data books were published in an attempt to conserve existing biodiversity. The World Resource Institute predicted that about 5-15% of world's species may be extinct between 1990 and 2020. The species all over the world as of now, are classified into the following groups as outlined by IUCN (1982):
(1) Extinct. Species not definitely located in the wild during the past 50 years.
(2) Endangered. Taxa in danger of extinction or whose survival is unlikely if the causal factors continue operating. Taxa whose numbers 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. Taxa that are possibly already extinct but have definitely have definitely been seen in the wild in the past 50 years.
(3) Vulnerable. Taxa believed likely to move into the endangered category in the near future if the causal factors continue operating. Taxa of which most or all the populations are decreasing because of over-exploitation, extensive destruction of habitat or other environmental disturbances.
Taxa with populations that have been seriously depleted and whose ultimate security has not been assured and taxa with populations that are still abundant but are under threat from severe adverse factors throughout their range.
(4) Rare. Taxa with small world populations that are not at present 'endangered' or 'vulnerable' but are at risk. These taxa are usually localized within restricted geographical areas or habitats or are thinly scattered over a more extensive range.
(5) Indeterminate. Taxa known to be endangered, vulnerable or rare but where there is not enough information to say which of the three categories is appropriate.
(6) Out of danger. Taxa formerly included in one of the above categories, but which are now considered relatively scarce because effective conservative measures have been taken or the previous threat to their survival has been removed.
(7) Insufficiently known. Taxa that are suspected but not definitely known to belong to any of the above categories, because of lack of information.
(8) Critically endangered. Recently this new category has been introduced which comprises of taxa whose number of individuals in species has been lowered by more than 80% of the earlier count.
Within the first 6 categories, about 1.75 million species have been described on a scientific basis. The last category of insufficiently known or unknown taxa amounts to about 3.25 million. With the destruction of habitats for human developmental activities and over-harvesting of natural ecosystems of forests and global pollution, there may be further potential loss of species from the ecosystem. In an attempt to provide a stable taxonomic database of all known existing species of plants and animals, the International Union of Biological Sciences, Committee on Data for Science and Technology and International Union of Microbiological societies have organized the Species-2000 Program. Some of the taxa considered by this Program include fossil plants, cacti, palms, legumes, umbellifers, virus, fungi, bacteria, corals, molluscs, crustacea, diphtheria, ichimenon, wasps, moths, butterflies, beetles, fishes, birds and mammals. The problem of providing a comprehensive computer index system for unknown species is compounded by the lack of qualified and trained taxonomists whose number is dwindling as the emphasis in science is shifting towards technology.
It may be noted that there are 4630 mammalian species in the world, of which Indian mammals amount to 8.5%. Reduction in diversity of species has occurred over many geological time such as end of Ordovician, late Devonian, end of Permian and the K-T extinction which wiped out the dinosaurs and many other forms of marine life (Raup 1991). Recent progress in science and rapid human developmental activities have rapidly eroded the existing poor heritage of biological diversity. Pesticides like DDT, which are of man-made origin, besides leading to habitat loss, fragmentation and degradation of fertile fields, can also interfere with calcium metabolism to the extent that eggs are laid devoid of eggshells in birds. If this continues for 2-3 generations, then the entire birds species will be wiped out. The horns of rhinoceros and bones and other tissues of tigers are used in the manufacture of aphrodisiacs and drugs for kidney diseases and rheumatism. Hence they are sold for exorbitant prices to the neighboring countries, which if sustained could very well lead to the extinction of these species.
The results of a recent survey conducted by the Species Commission of the World Conservation Union is alarming. Of the total 4630 mammals belonging to 26 orders, about 25% (1096) have been classified as endangered, of which 169 species are critically endangered. On the global scene about 330 species of rodents, 231 species of birds, 151 species of rheas and moles, 651 species of carnivores including cats, raccoons, wild dogs, weasels, 96 primates and 70 even-toed ungulates (hippopotamus, pigs, deer, antelopes, goats and sheep) are listed as endangered. Similarly 11% of the world's bird population is endangered. About 253 reptiles, 124 amphibians, 734 fish and 1891 species of invertebrates mainly comprising crustaceans, insects and molluscs are endangered or threatened (vulnerable). In India alone, 75 species of mammals are in the endangered category. The time has now come to shift from a red book category to red list status.
The IUCN has brought out "The World Conservation Strategy: Living Resources Conservation Strategy for Sustainable Development", with emphasis on conservation for development. The strategy focuses on three main aspects (a) maintenance of essential ecological processes and life support systems, (b) preserve genetic diversity and, (c) to ensure sustainable utilization of species and ecosystem.
Among biological diversity, we can recognize two categories, (1) a small percentage of species which are abundant and (2) a large percentage of species which are rare. The biological inter-relationships between the species leads to stability. In the trophic niche, it is the large number of rare species that determine the species diversity of trophic groups and of whole communities, while the ecologically dominant group (category 1) controls the energy flow and affects the composition of other species (Odum 1971). The major ecological concept underlying biodiversity is that of the stability of ecosystem. Ecological processes such as mutualism, parasitism, commensalism, symbiosis, proto-co operation and competition control the length of food chain and increases the possibilities of constructing feed back systems to regulate population size and stability of the population. Therefore, existence of rich biodiversity reduces oscillations within a population, above and below equilibrium level, and increases stability.
Uncontrolled human population growth and economic development may lead to changes in the links in the food web. The major difference between man-made systems (clocks) and natural ecosystems is that in the former if one component is non-functional, then the entire system will collapse. Whereas in the latter, when one component is missing, another component will make connection with the other and the system will continue to work but at a different ecostability level. For instance, a herbivore (cow) which depends upon grass for its food, on conditions of scarcity of grass as in the city of Madras, is able to shift successfully its dietary habits to eat cinema and political posters pasted on brick walls. On several instances, veterinary doctors have found plastic throwaway bags from the stomach of ailing cattle. Such unsuccessful shifts of trophic status could lead towards faunal extinction.
The challenge of preserving biodiversity has been linked with the current system of science education. We need a change in our approach. It has been suggested that field research could offer excellent opportunities for first-hand scientific observation for science students and teachers, and could serve as a valuable learning device as well as generate useful inputs for decentralized management of natural resources at the panchayat and district level (Gadgil, 1996).
Gadgil, M. Documenting diversity: An experiment. Current Science 270 (1996), 36-44.
G.O.I. Biosphere Reserves. Government of India, Ministry of Environment and Forests, New Delhi, 1987.
Hajduch M and Pretova A (1996) The Environment in Slovakia and Biodiversity. EJAIB 6 (1996), 65-66.
IUCN. The IUCN Amphibia- Reptilia Red Data Book. IUCN , Switzerland 1982.
Odum EP Fundamentals of Ecology. W.B. Saunders & Co. New York 1971.
Raup (1991) Extinction: Bad genes or Bad luck. New Scientist (14 Sept. 1991), 46-49.