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Vol. 2 No. 2 - April 1996

Biodiversity - A Challenge to Science and Society

By: J. K. Maheshwari,

Biodiversity or biological diversity - a collective term is used to describe the variety and variability among living organisms. It may be perceived as an interacting complex of plants, animals, and microorganisms in the physical environment. It is generally measured at genetic, species, and ecosystem levels. During the past two centuries, about 1.8 million species have been formally described and named; at least 5 million (or perhaps 30 million) remain to be catalogued. Tropical forests contain at least 50 percent of all terrestrial species in the entire world biota. The Antarctica, on the other hand, has few land species, although its oceans provide food for the krill, a shrimp-like creature, which in turn feeds whales, seals, fish, squid, and penguins.

The oceans cover 70 percent of the earth's surface and play a fundamental role in the regulation of the global environment through physical and biogeochemical processes that have made life possible on earth. It has been shown that they remain the greatest repository of the diversity of life at the level of orders and phyla. At least 43 out of approximately 70 phyla of all life forms are found in the oceans. Discoveries of marine biodiversity at the micron scale have shown that the diversity of life is probably greater than that found on land, but is far less documented. Using the more sophisticated microscopes and the flow cytometry technology to detect and describe the "invisible" biodiversity, scientists have discovered very small planktonic cells called "picoplankton" 0.2 to 2 microns in size, with live weights of the order of a picogram. The "picoplankton" (pico-eucaryotes, cyano-bateria and prochlorophytes) is recognized as the largest numerical component of the phytoplankton in the ocean and may play an important role as a sink for atmospheric carbon dioxide. Prochlorococcus, tiny precursor of green algae, a close relative of Cyanobacteria is considered to be the smallest prokaryote (0.6 microns) and most abundant photosynthetic organism on earth. A single milliliter of sea water may contain up to 100,000 Prochlorococcus.

The maintenance of a quality environment depends upon a myriad of complex natural systems composed of plants, animals, and microbial species, and the continued interaction of the flora and fauna with the environment. This point is better expressed by the example of a tripartite association observed between forest plants, fungi, and fungus-feeding mammals. Many forest fungi form intimate symbiotic associations (mycorrhiza) with the roots of a variety of shrubs and trees, and have an underground fruiting (hypogeal) habit, which limits the ways in which spore dispersal may be achieved. In southeastern mainland Australia, the most specialized of these fungus-feeders are small marsupial rat-kangaroos, called potoroos. At all times of the year, potoroos actively seek the fruiting bodies of atleast 40 species of hypogeal fungi. Spores, present in the fungal tissue consumed by the potoroos and other ground-dwelling mammals including bandicoots and rats, pass through the gut and are concentrated in the feces and deposited back to the forest floor by the animal at another location. In this way, fungus-feeding mammals such as potoroos play a vital role in the reestablishment of mycorrhizal fungal populations even after forest disturbances such as fire and logging, and hence in the regeneration of the forests. This interrelationship between plants, fungi and mammals serves as an example of why we should be trying to maintain all the components of biological diversity.

The rapid loss of biodiversity in developing countries has become the subject of national and international concern. The Harvard biologist, Edward O. Wilson, estimates that roughly 50,000 species per year - nearly 140 each day = are either extinguished or condemend to eventual extinction by the destruction of their habitiat. This catastrophic biological meltdown far exeeds anything the earth has seen since the extinction of the dinosaurs. The main causes of the loss of biodiversity are: habitat destruction and fragmentation; over-harvesting; pollution; and inappropriate introduction of exotic plants and animals, resulting in homogenization of the world's biota. The extinction of 'keystone' species (e.g. major predators, herbivores, or plants which are important food sources for animals) may lead to a chain of further extinctions, finally resulting in ecosystem collapse. The 1996 IUCN Red List of Threatened Plants is a massive document covering more than 30,000 species. The uniqueness of India's biological diversity and its role in bioindustrial development is significant. About 51,000 species of plants and approximately 81,000 species of animals are estimated to occur in the country. Their maintenance requires the application of different strategies, depending on particular circumstances. There are two main approaches to biodiversity conservation: in situ (on-sire) and ex situ (off=site). In situ conservation in biosphere reserves, national parks, wildlife sanctuaries, nature reserves, etc. is by far the more effective and cost-efficient, as a large range of species, habitats and ecological processes are able to co-exist with minimal pressures. Ex situ conservation methods include the use of botanic gardens, germplasm banks (for embryos, eggs, sperm, etc.), field gene banks, seed banks, aquaria, zoos as well as biotechnology applications through in vitro techniques, tissue cultures, cryopreservation and DNA library. A third approach - on-farm management or dynamic conservation of domesticated biodiversity has also been recommended to save crop genetic varieties. The goals of biodiversity come down to three simple words: save, study, and use. The International Union for Conservation of Nature and Natural Resources recognizes hat protecting individual species, or even individual sites, is not enough. It calls for a shift in conservation policy from species to habitats, from sites to ecosystems, and from national to international measures. In particular, it seems to reverse the fragmentation of habitats into small isolated 'islands' surrounded by land almost devoid of nature. The Convention of Biological Diversity signed by 174 countries including India, became international law on December 29, 1993. It marks a historic commitment by the nations of the world to conserve biological diversity and to ensure that biological resources are used sustainably and the benefits of such use are shared equitably. An open forum for continuing exploration and dialogue on biodiversity - how to save it, understand it and appreciate it, and how to use it wisely - is needed to enable citizens, governments, industries, NGOs, and rural communities to ensure that our biotic wealth is properly managed and conserved. Biodiversity, in all its forms, is the basis of the health of our planet and the wealth of our societies. It is a global asset of tremendous value to present and future generations.

This article has been reproduced from the archives of EnviroNews - Newsletter of ISEB India.

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