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.
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